Multiplication digital-to-analog converter with increased multiplication bandwidth

Abstract

The multiplicative digital-to-analog converter (MDAC) (200) includes a first resistor (232) and a second resistor (236), the first resistor being configured to be selectively connected to a current output node (277) based on the first bit of a first portion of the input digital code, and the second resistor being configured to be selectively connected to a current output node (277) based on a second bit of the first portion of the input digital code. The resistance of the second resistor (236) is the resistance of the first resistor (232) scaled by a factor. The MDAC (200) further includes a first capacitor (306) and a second capacitor (308), the first capacitor being configured to be selectively connected to a current output node (277) based on the first bit of the first portion, and the second capacitor being configured to be selectively connected to a current output node (277) based on a second bit of the first portion. The capacitance of the second capacitor (308) is the capacitance of the first capacitor (306) scaled by the reciprocal of the factor.

Description

Background Technology

[0001] Digital-to-analog converters (DACs) are common components in many electronic devices. A DAC device receives an input digital code and outputs an analog signal based on that code. One type of DAC used today is the multiplying DAC (MDAC). MDACs use a resistor ladder to weigh the contribution of each bit of the input code to the output current based on its bit order. Due to the resistor ladder, higher-order bits of the code have a greater impact on the output current than lower-order bits. Such MDACs typically include or are connected to operational amplifiers to convert the output current into an output voltage. The output voltage (V) in an N-bit DAC is... OUT The relationship between the input code and the input code can be represented as follows: Where V REF This corresponds to the reference voltage received by the DAC.

[0002] A common application of MDACs is as variable attenuators, where the input signal is connected to the DAC's reference input and the DAC code is used to set the attenuation factor. In such applications, the multiplication bandwidth is defined as the frequency at which the DAC gain drops from the reference input to the OPAMP output to -3dB below the DAC gain at DC. The multiplication bandwidth is a function of the OPAMP bandwidth and the parasitic capacitance generated by the resistive ladder. In particular, switches included in such resistive ladders generate high parasitic capacitance. Additionally, there are further parasitic capacitances due to board traces and amplifier input capacitance. This parasitic capacitance degrades the stability of the OPAMP and can introduce peaks into the DAC's bandpass response, thus limiting the DAC's multiplication bandwidth. Summary of the Invention

[0003] A multiplicative digital-to-analog converter (MDAC) is disclosed, comprising a capacitor array scaled inversely to the resistors in the MDAC. Each capacitor in the capacitor array is selectively coupled to the output current node based on a portion of the MDAC node used to selectively couple a corresponding resistor to the output current node. This arrangement alters the transfer function of the MDAC, allowing for an increase in the multiplication bandwidth of the MDAC without increasing its power dissipation. Attached Figure Description

[0004] To provide a detailed description of the various examples, reference will now be made to the accompanying drawings, in which:

[0005] Figure 1 illustrates a prior art multiplication digital-to-analog converter (MDAC).

[0006] Figure 2 An MDAC is shown, comprising a capacitor array that scales inversely to the resistance in the DAC. Detailed Implementation

[0007] Referring to Figure 1, a prior art multiplication digital-to-analog converter (MDAC) 100 is shown. As shown, the prior art MDAC 100 includes a resistor section 102 configured to generate a DAC resistor at a current output node 106 based on the input digital node. The current output node 106 is connected to a first terminal of an operational amplifier (OPAMP) 104. A parasitic capacitance 110 is shown coupled to the first terminal of the OPAMP 104. This parasitic capacitance 110 is primarily generated by the switching in the resistor section 102, but also by board traces and the OPAMP input capacitance. In the illustrated example, a second terminal of the OPAMP 104 is connected to ground 108; in other embodiments, the second terminal of the OPAMP 104 is connected to a non-zero voltage. Accordingly, the OPAMP 104 is configured to output a voltage based on the resistance at the current output node 106. A feedback resistor 112 is connected to the output of the OPAMP 104 and to the current output node 106, establishing a feedback loop. The MDAC 100 includes a feedback capacitor 114 connected across the feedback resistor 112. The feedback capacitor 114 is used to improve the stability of the OPAMP 104 and achieve a flat bandpass response in the presence of the parasitic capacitance 110.

[0008] The Laplace transform function of the MDAC 100 at the all-digital input code is given by the following equation: Where V OUT Corresponding to the output voltage of OPAMP 104, V REF The reference voltage received by resistor section 102 corresponds to s, which corresponds to the Laplace transform complex frequency, and R FB Corresponding to the resistance of feedback resistor 112, C P Corresponding to the parasitic capacitance 110, and ω UGB This corresponds to the uniform gain bandwidth of OPAMP 104 in rad / s. This second-order transfer function can be derived by assuming... To simplify, we arrive at The function, where ω n This is the natural frequency of the second-order system and is approximately equal to the multiplication bandwidth of the MDAC 100. The damping factor ζ is equal to... For a flat bandpass response, a damping factor of 0.7 is chosen. By reducing R FB Or C FB To increase the multiplication bandwidth of the MDAC 100, it is important to maintain a damping factor of 0.7 to achieve a flat bandpass response. Accordingly, this can be achieved by adjusting the R value of the feedback resistor 112. FB Halve and ω of OPAMP104 UGB Double or by making R FB Multiply And the C of the feedback capacitor 114 FB Doubling the multiplication bandwidth of the MDAC 100 is achieved. However, the R value of the feedback resistor 112 is increased. FB Halve and ω of OPAMP 104 UGB Doubling the power dissipation of the MDAC 100 will double, the area of ​​the MDAC 100 will double, and the power of the OPAMP 104 will increase. Additionally, it will increase R... FB Multiply And the C of the feedback capacitor 114 FB Doubling the power dissipation would quadruple and increase the area of ​​the MDAC 100 by four times.

[0009] refer to Figure 2 The illustration shows a multiplication DAC (MDAC) 200 with increased multiplication bandwidth. The MDAC 200 includes a temperature-sensing RDAC segment 202, a binary-scaled RDAC segment 204, an R-2R DAC segment 205, and a capacitor array 289. In the illustrated example, the MDAC 200 corresponds to an 18-bit DAC configured to receive 18-bit digital codes and generate analog signals based on these codes. The temperature-sensing RDAC segment 202 is configured to operate on the four most significant bits of the 18-bit digital code, the R-2R DAC segment 205 is configured to operate on the ten least significant bits of the 18-bit digital code, and the binary-scaled RDAC segment 204 is configured to operate on the four bits between the four most significant bits and the ten least significant bits. The MDAC 200 can be arranged in alternative configurations operating on digital codes with more or fewer bits. Similarly, each of segments 202, 204, and 205 can operate on a different number of bits than those shown in the example.

[0010] Segments 202, 204, 205 and capacitor array 289 are connected to current output node I. OUT277, the current output node is received by the first terminal of operational amplifier (OPAMP) 282. In the illustrated example, the second terminal of OPAMP 282 receives ground 296. In other embodiments, the second terminal of OPAMP 282 receives a different DC potential. Each of segments 202, 204, and 205 includes a switch and a resistor. The resistors described herein may correspond to fixed resistors or variable resistors. Capacitor array 289 includes capacitors and switches. Each capacitor in capacitor array 289 corresponds to a resistor in thermometric RDAC segment 202 or binary-scale RDAC segment 204. Each capacitor has a capacitance based on the inverse resistance scale of the corresponding resistor. Although capacitors and resistors are described as a 1-1 correspondence, it should be noted that any resistor described herein may be replaced by multiple resistors, and any capacitor described herein may be replaced by multiple capacitors. The switches described herein may include mechanical switches, semiconductor devices (e.g., transistors), or combinations thereof. Additionally, R-2R DAC segment 205 may be replaced by different types of resistor ladder segments (e.g., a series resistor ladder network).

[0011] Although only four segments are shown for simplicity, the temperature-sensing RDAC segment 202 comprises 15 segments (e.g., segments for each decimal value other than zero, which can be represented by the four most significant bits). Each segment in the temperature-sensing RDAC segment 202 includes a resistor (with resistance R) and two switches. One terminal of the resistor is connected to VREF, and the other terminal is connected to I depending on the DAC code. OUT 277 or ground. Reference voltage source 201 can correspond to a DC voltage source or an AC voltage source. I OUT 277 is connected to the first terminal of operational amplifier 282. The sections of temperature-sensing RDAC segment 202 are arranged in parallel such that when the corresponding switch is switched to connect reference voltage source 201 to I... OUT The resistor in the 277 time segment is connected in parallel to the reference voltage source 201 and I. OUT Between 277. Accordingly, in the illustrated example, the conductivity of the temperature-sensing RDAC segment 202 varies between 0 and 15 / R. Figure 2The first segment 206, the second segment 208, and the third segment 210 of the temperature-measuring RDAC segment 202 are depicted. The first segment 206 corresponds to the first bit of the temperature-measuring (e.g., unary) code of the four most significant bits of the input digital code, the second segment 208 corresponds to the second bit of the temperature-measuring code, and the third segment 210 corresponds to the fifteenth bit of the temperature-measuring code. Although not depicted, the temperature-measuring RDAC segment 202 further includes segments corresponding to the third through fourteenth bits of the temperature-measuring code. Additionally, it should be noted that in embodiments where the temperature-measuring RDAC segment is configured to process different numbers of most significant bits (bits other than four) of the input digital code, the temperature-measuring RDAC segment may include different numbers of segments.

[0012] The first section 206 of the temperature-sensing RDAC segment 202 includes a first pair of switches 214 and a first resistor 212 connected to a reference voltage. The first pair of switches 214 are configured to switch one terminal of the resistor 212 to I based on the value of the first bit of the temperature-sensing code, which is one of the four most significant bits of the input digital code. OUT 277 or ground. The second section 208 of the temperature-sensing RDAC segment 202 includes a second resistor 216 and a second pair of switches 218. The second pair of switches 218 is configured to switch one terminal of the resistor 216 to I based on the second bit of the temperature-sensing code. OUT 277 or ground. The third section 210 of the temperature-sensing RDAC segment 202 includes a third resistor 220 and a third pair of switches 222. The third pair of switches 222 is configured to switch one terminal of the resistor 220 to I based on the fifteenth bit of the temperature-sensing code. OUT 277 or ground. The temperature measurement code for number N consists of N ones (or N zeros). For example, a four-bit binary number 0011 (e.g., 3 in decimal) can be encoded as 000000000000111 (or 111111111111000). Therefore, the temperature measurement RDAC segment 202 is configured to connect the reference voltage source 201 to I through a number of resistors equal to the number of decimal values ​​of the four most significant bits of the input digital code. OUT 277. In response to a value of 0, the temperature sensing RDAC segment 202 is configured to couple the corresponding resistor to ground. Due to this temperature sensing encoding, each segment of the temperature sensing RDAC segment 202 affects I based on the segment's position. OUT Total resistance at 277.

[0013] The binary-scale RDAC segment 204 includes a first segment 224, a second segment 226, a third segment 228, and a fourth segment 230. The first segment 224 corresponds to the fifth bit of the input digit code, the second segment 226 corresponds to the sixth bit of the input digit code, the third segment 228 corresponds to the seventh bit of the input digit code, and the fourth segment 230 corresponds to the eighth bit of the input digit code. It should be noted that in embodiments where the binary-scale RDAC segment 204 is configured to process different numbers of bits of the input digit code (e.g., bits other than four), the binary-scale RDAC segment 204 may include different numbers of segments.

[0014] The first segment of the scaling RDAC segment 204 includes a first pair of switches 234 and a first resistor 232 connected to a reference voltage. The first pair of switches 234 are configured to switch one terminal of the first resistor 232 to I based on the first bit of a portion of the input digital code processed by the scaling RDAC segment 204. OUT 277 or ground 296. The second segment 226 of the binary scale RDAC segment 204 includes a second pair of switches 238 and a second resistor 236. The second pair of switches 238 is configured to switch one terminal of the second resistor 236 to I based on the second bit of a portion of the input digital code processed by the scale RDAC segment 204. OUT 277 or ground 296. The third segment 210 of the scale RDAC segment 204 includes a third pair of switches 242 and a third resistor 240. The third pair of switches 242 is configured to switch one terminal of the third resistor 240 to I based on the third bit of the portion of the input digital code processed by the scale RDAC segment 204. OUT 277 or ground 296. The fourth segment of the scale RDAC segment 204 includes a fourth pair of switches 246 and a fourth resistor 244. The fourth pair of switches is configured to switch one terminal of the fourth resistor 244 to I based on the fourth bit of the portion of the input digital code processed by the scale RDAC segment 204. OUT 277 or ground 296. Resistors 232, 236, 240, and 244 of the binary-scaled RDAC segment 204 are all binary-scaled so that each segment has a resistance of 2. x The resistor R is the resistance of the temperature-sensing RDAC segment 202, and x is the position of the bit processed by this segment within the portion of the bit processed by the scaling RDAC segment 204. In the illustrated example, the first resistor 232 has 2R (e.g., 2...). 1 The second resistor 236 has a resistance of 4R (e.g., 2R). 2 The third resistor has a resistance of 8R (e.g., 2). 3 The fourth resistor 244 has a resistance of 16R (e.g., 2). 4The resistor (R) is used for the resistance. Because the resistor is binary-scaled, the bit position weighting is based on the bit-scaled RDAC segment 204, which processes each bit of I. OUT The influence of the total resistance at 277. Additionally, because the first segment 224 of the binary scale segment has a resistance (2R) twice that of the resistor in the temperature-sensing RDAC segment 202, the bit weighting relative to the temperature-sensing RDAC segment 202 is handled by the bit pair I processed by the binary scale RDAC segment 204. OUT The effect of the total resistance at 277.

[0015] The R-2R DAC segment 205 comprises eleven segments (e.g., one segment for each of the ten least significant bits of the input digital code processed by the R-2R DAC segment 205 and one termination segment). For ease of explanation, Figure 2 Four of the eleven segments are depicted. These four segments include segment 248, segment 250, segment 252, and segment 254. Segment 248 corresponds to the ninth bit of the input digit code, segment 250 corresponds to the tenth bit of the input digit code, segment 252 corresponds to the eighteenth bit of the input digit code, and segment 254 is a terminating resistor. Although not shown, R-2R DAC segment 205 further includes segments corresponding to the eleventh through seventeenth bits. It should be noted that in embodiments where R-2R DAC segment 205 is configured to process different numbers of bits of the input digit code (e.g., bits other than 10), R-2R DAC segment 205 may include different numbers of segments.

[0016] The first section 248 of the R-2R DAC segment 205 includes a first "ladder" resistor 256, a first branch resistor 258, and a first pair of switches 260. The first branch resistor 258 is connected in series with the first ladder resistor 256 and in parallel with resistors 212, 216, 220, 232, 236, 240, and 244 of the temperature-sensing RDAC segment 202 and the binary-scale RDAC segment 204, and is connected to a reference voltage source 201. The first pair of switches 260 is configured to switch one terminal of the first branch resistor 258 to I based on the ninth bit of the input digital code. OUT 277 or ground 296. The first-stage resistor 256 is a rescaled resistor and has an equal to (2 y -1) The resistance of R, where y is the number of bits processed by the binary-scale RDAC segment 204. This ensures that the input to the R-2R DAC segment 205 has 2 y The resistance of R. In the illustrated example, the first-stage resistor 256 has a resistance of 15R (e.g., (2 4-1)R). Accordingly, the effect of the R-2R DAC segment 205 on I is weighed relative to the bit processed by the binary scaling RDAC segment 204 and the temperature sensing RDAC segment 204 by the first ladder resistor 256 (e.g., a rescaling resistor). OUT The effect of the total resistance at 277. The first branch resistor 258 has a resistance of 2R.

[0017] The second section 250 of the R-2R DAC segment 205 includes a second step resistor 262, a second branch resistor 264, and a second pair of switches 266. The second branch resistor 264 is connected in series with the first step resistor 256 and the second step resistor 262, and in parallel with the first branch resistor 258 and resistors 212, 216, 220, 232, 236, 240, and 244 of the temperature-sensing RDAC segment 202 and the binary-scale RDAC segment 204, and is connected to a reference voltage source 201. The second pair of switches 266 is configured to switch one terminal of the second branch resistor 264 to I based on the tenth bit of the input digital code. OUT 277 or ground 296. The second step resistor 262 has a resistance R, and the second branch resistor 264 has a resistance of 2R. The R-2RDAC segment 205 between the second segment 250 and the third segment 252 each has step resistors, branch resistors, and switches arranged relative to the second segment 250 as shown.

[0018] The third section 252 of the R-2R DAC segment 205 includes a third ladder resistor 268, a third branch resistor 270, and a third pair of switches 272. The third branch resistor 270 is connected in series with the ladder resistors of the first ladder resistor 256, the second ladder resistor 262, the third ladder resistor 268, and the section between the second section 250 and the third section 252. It is also connected in parallel with the resistors 212, 216, 220, 232, 236, 240, and 244 of the first branch resistor 258, the second branch resistor 264, and the resistors 212, 216, 220, 232, 236, 240, and 244 of the temperature-sensing RDAC segment 202 and the binary-scale RDAC segment 204, and is connected to the reference voltage source 201. The third pair of switches 272 is configured to switch one terminal of the third branch resistor 270 to I based on the seventeenth bit of the input digital code. OUT 277 or ground 296. The third step resistor 262 has a resistance R, and the third branch resistor 270 has a resistance of 2R. The segments of the R-2R DAC segment 205 are arranged such that the step resistors are arranged in series and the branch resistors are arranged in parallel. The series connection of the step resistors results in a tradeoff between the switching of one of the segments of the R-2R DAC 205 based on the segment location (e.g., corresponding to the bit position associated with the segment) and the coupling of the reference voltage source 201 to I. OUT The impact of 277.

[0019] The fourth segment 254 includes a fourth branch resistor 274 and a fourth switch 276. The fourth branch resistor 274 is connected in parallel with the first step resistor 256, the second step resistor 262, the third step resistor 268, and the step resistors of the segment between the second segment 250 and the third segment 252. It is also connected in parallel with resistors 212, 216, 220, 232, 236, 240, and 244 of the first branch resistor 258, the second branch resistor 264, the third branch resistor 270, and the temperature-sensing RDAC segment 202 and the binary-scale RDAC segment 204, and is connected to the reference voltage source 201. In some embodiments, the fourth switch 276 is always closed and couples one end of the resistor 274 to ground 296. The fourth switch 276 can be replaced by a direct connection between the resistor 274 and ground 296. Capacitor array 289 is connected in parallel with segments 202, 204, and 205 and coupled to reference voltage source 201 and I. OUT Between 277. Capacitor array 289 includes a first plurality of capacitors corresponding to temperature sensing RDAC segment 202 and a second plurality of capacitors corresponding to scaling RDAC segment 204. Each of the first plurality of capacitors, with a corresponding digital code of a temperature sensing code configured based on the four most significant bits of the input digital code, selectively couples the capacitor to ground 298 or to I. OUT A pair of switches (or other switch configurations, such as a single switch) are associated with 277. In the illustrated example, the first switch in each pair of switches associated with the first plurality of capacitors is configured to selectively couple the corresponding capacitor to I based on a corresponding digital code of the temperature measurement code. OUT 277, and the second switch in the pair of switches is configured to selectively couple the corresponding capacitor to ground 298 based on the inverted type of the digital signal. Each of the second plurality of capacitors is configured to selectively couple the capacitor to ground 298 or I based on the corresponding bit in the bits processed by the scale RDAC segment 204. OUT A pair of switches (or other switch configurations, such as a single switch) are associated with 277. In the illustrated example, the first switch in each pair of switches associated with the second plurality of capacitors is configured to selectively couple the corresponding capacitor to I based on the corresponding bit of the input digital code. OUT 277, and the second switch in the pair of switches is configured to selectively couple the corresponding capacitor to ground 298 based on the inverted type of that bit. Each of the first plurality of capacitors has a capacitance of C. Each of the second plurality of capacitors has a capacitance scaled inversely based on the resistance scale corresponding to the resistor of the capacitor.

[0020] The first plurality of capacitors includes a first capacitor 300 corresponding to a first resistor 212 of the temperature measuring RDAC segment 202, a second capacitor 302 corresponding to a second resistor 216 of the temperature measuring RDAC segment 202, and a third capacitor 304 corresponding to a third resistor 220 of the temperature measuring RDAC segment 202.

[0021] The first capacitor 300 is connected to a first pair of switches 312, which are configured to selectively connect the first capacitor 300 to ground 298 or I based on the same digital code of the temperature measurement code received by the first switch 214 of the temperature measurement RDAC segment 202. OUT 277. Therefore, the first capacitor 300 and the first resistor 212 of the temperature sensing RDAC 202 are configured to be selectively coupled to I in response to the same conditions. OUT 277.

[0022] The second capacitor 302 is connected to a second pair of switches 314, which are configured to selectively connect the second capacitor 302 to ground 298 or I based on the same digital code of the temperature measurement code received by the second switch 218 of the temperature measurement RDAC segment 202. OUT 277. Therefore, the second capacitor 302 and the second resistor 216 of the temperature sensing RDAC 202 are configured to be selectively coupled to I in response to the same conditions. OUT 277.

[0023] The third capacitor 304 is connected to a third pair of switches 316, which are configured to selectively connect the third capacitor 304 to ground 298 or I based on the same digital code of the temperature measurement code received by the third switch 222 of the temperature measurement RDAC segment 202. OUT 277. Therefore, the third capacitor 304 and the third resistor 220 of the temperature sensing RDAC 202 are configured to be selectively coupled to I in response to the same conditions. OUT 277.

[0024] Although not illustrated, the first plurality of capacitors further includes capacitors and switch pairs corresponding to resistors (not illustrated) of the temperature-sensing RDAC segment 202. These unillustrated capacitors are similarly controlled by digital codes corresponding to the temperature-sensing codes of the resistors of the temperature-sensing RDAC segment 202.

[0025] The second plurality of capacitors includes a fourth capacitor 306 corresponding to a first resistor 232 of scale RDAC segment 204, a fifth capacitor 308 corresponding to a second resistor 236 of scale RDAC segment 204, and a sixth capacitor 310 corresponding to a third resistor 240 of scale RDAC segment 204. Although not illustrated, the second plurality of capacitors further includes a capacitor corresponding to a fourth resistor 244 of scale RDAC segment 204. Each capacitor in the second plurality of capacitors has a capacitance scaled inversely to the resistance of its corresponding resistor.

[0026] The fourth capacitor 306 is connected to a fourth pair of switches 318, which are configured to selectively connect the fourth capacitor 306 to ground 298 or I based on the same bit of the input digital code received by the first switch 234 of the binary scale RDAC segment 204. OUT 277. Therefore, the fourth capacitor 306 and the first resistor 232 of the binary scale RDAC segment 204 are configured to be selectively coupled to I in response to the same conditions. OUT 277. The capacitance of the fourth capacitor 306 is... The resistance of the first resistor 232 in the binary scale RDAC segment 204 is 2R. Therefore, the fourth capacitor 306 has a scale that is inversely proportional to the scale of the first resistor 232 in the binary scale RDAC segment 204.

[0027] The fifth capacitor 308 is connected to a fifth pair of switches 320, which are configured to selectively connect the fifth capacitor 308 to ground 298 or I based on the same bit of the input digital code received by the second switch 238 of the binary scale RDAC segment 204. OUT 277. Therefore, the fifth capacitor 308 and the second resistor 236 of the binary scale RDAC segment 204 are configured to be selectively coupled to I in response to the same conditions. OUT 277. The capacitance of the fifth capacitor 308 is... The resistance of the second resistor 236 in the binary scale RDAC segment 204 is 4R. Therefore, the fifth capacitor 308 has a scale that is inversely proportional to the scale of the second resistor 236 in the binary scale RDAC segment 204.

[0028] The sixth capacitor 310 is connected to a sixth pair of switches 322, which are configured to selectively connect the sixth capacitor 310 to ground 298 or I based on the same bit of the input digital code received by the third switch 242 of the binary scale RDAC segment 204. OUT 277. Therefore, the sixth capacitor 310 and the third resistor 240 of the binary scale RDAC segment 204 are configured to be selectively connected to I in response to the same conditions. OUT277. The capacitance of the sixth capacitor 310 is... The resistance of the third resistor 240 in the binary scale RDAC segment 204 is 8R. Therefore, the sixth capacitor 310 has a scale that is inversely proportional to the scale of the third resistor 240 in the binary scale RDAC segment 204.

[0029] Although not illustrated, the second plurality of capacitors further includes a capacitor and a switch pair corresponding to a fourth resistor 244 of the binary scale RDAC segment 204. This capacitor has the following characteristics: The capacitor, not illustrated, has a scale inversely proportional to the scale of the fourth resistor 244 of the binary scale RDAC segment 204. This unillustrated capacitor is controlled by bits of the input digital code that control the fourth switch 246.

[0030] Additionally, in some embodiments, capacitor array 289 further includes a third group of capacitors corresponding to one or more of the segments of R-2R DAC 205. Each capacitor in the third group of capacitors can be selectively coupled to I via a pair of switches, as described above with reference to the first and second plurality of capacitors. OUT 277. Each capacitor in the third group of capacitors can have a suitable capacitance to achieve a flat bandpass response. The parasitic capacitance 292 of the MDAC 200 is illustrated as being connected to ground 294. Besides being connected only to ground 294, the parasitic capacitance 292 can also be extended in several nodes. The parasitic capacitance 292 is caused by switches in segments 202, 204, and 205, and may not include a separate dedicated capacitor device. The parasitic capacitance 292 can also be caused by board traces, OPAMP input capacitors, etc.

[0031] The OPAMP 282 is configured to receive streams through I... OUT The current 277 is summed with the feedback current at the first terminal and configured to receive ground 296 at the second terminal. OPAMP 282 is configured to generate a voltage output based on the input received at the first and second terminals. The output of OPAMP 282 is connected to feedback resistor 282. OUT 277 is connected to the output of feedback resistor 284, making I OUT The current at 277 and the current from feedback resistor 284 are combined. Accordingly, a feedback loop is established between the output of OPAMP 282 and the input received at the first terminal. Feedback capacitor 290 is coupled across feedback resistor 284 to reduce the damping factor of MDAC 200 and flatten the bandpass response of MDAC 200. The value of the feedback capacitor is chosen such that R... FB *CFB =R*C, where R is the resistance of the temperature measuring section and C is the capacitance in the capacitor array 289 corresponding to the temperature measuring section.

[0032] In operation, MDAC 200 receives an input digital code (e.g., an input digital signal) comprising 18 bits. MDAC 200 converts the four most significant bits into a temperature measurement representation. For example, MDAC 200 may include temperature measurement logic (not shown) that may include hardware, software, or a combination thereof configured to convert binary numbers into temperature measurement representations. MDAC 200 applies each of the four most significant bits of the temperature measurement representation to a corresponding switch in the temperature measurement RDAC segment 202 and a corresponding switch pair associated with the first plurality of capacitors. MDAC 200 further applies each of the next four most significant bits to a corresponding switch in the binary scaling RDAC segment 204 and a corresponding switch pair associated with the second plurality of capacitors. Additionally, MDAC 200 applies each of the ten least significant bits to a corresponding switch in the R-2R DAC segment 205. The switches of MDAC 200 connect the reference voltage source 201 or ground 286 to I based on the received bits. OUT 277. Accordingly, I is set based on the input numeric code. OUT The resistors (and current) and capacitors of the MDAC 200 at position 277. As mentioned above, the trade-offs for each bit of I are based on the different structures of DAC segments 202, 204, and 205. OUT The effect of the resistance at 277. Correspondingly, I OUT The current generated at 277 is based on the input code. OPAMP 282 generates the output voltage based on the current and the feedback current received at the first terminal through the feedback resistor 284, and based on the ground 296 received at the second terminal.

[0033] Because each resistor in the temperature-sensing RDAC segment 202 and the binary-scale RDAC segment 204 is coupled to a corresponding inverse-scale capacitor, the capacitance of the MDAC 200 can be expressed by the equation... To approximate, where C DAC For the capacitors of the MDAC 200, C FB Here, is the capacitance of the feedback capacitor 290, code is the input digital code, and N is the number of bits in the input digital code. The resistance of the MDAC 200 can be approximated as... Where R DAC The resistor for the MDAC 200 and R FB This is the resistance of the feedback resistor 284. Accordingly, R DAC C DAC =R FB C FBTherefore, the Laplace transform function of the MDAC 200 in full code is: Where V OUT V is the output voltage of the OPAMP 282. REF ω is the reference voltage of reference voltage source 201. UGB Let be the uniform gain bandwidth of the OPAMP 282 in rad / s, and s be the Laplace transform complex frequency. Assume... Then the second-order transformation function can be simplified to the first-order transformation function. Accordingly, for the same MDAC and OPAMP parameters RFB, C P and ω UGB The MDAC 200's multiplication bandwidth is approximately twice that of the MDAC 100. Furthermore, the MDAC 200's multiplication bandwidth can be independent of R... FB Therefore, the multiplication bandwidth of the MDAC 200 can be increased without increasing the power dissipation of the MDAC 200.

[0034] It should be noted that the MDAC 200 can be implemented in alternative configurations. For example, the MDAC 200 can be configured to convert input digital codes comprising more than 18 bits. In such examples, segments 202, 204, and 205 may include additional resistors, and capacitor array 289 may include additional capacitors. Furthermore, as mentioned above, the resistors described herein can be replaced by multiple resistors, and the capacitors described herein can be replaced by multiple capacitors. Additionally, Figure 2 Some or all of the switch pairs illustrated can be replaced by a single switch.

[0035] Additionally, in some examples, R-2R DAC segment 205 is replaced by an R-2R DAC segment that does not include a rescaling resistor. This R-2R DAC segment may include a ladder resistor having a resistance equal to half the resistance of a resistor (e.g., fourth resistor 244) in the binary scale RDAC segment 204 associated with the least significant bit processed by the binary scale RDAC segment 204. Additionally, this R-2R DAC segment may include a branch resistor having a resistance equal to twice the resistance of a resistor in the binary scale RDAC segment 204 associated with the least significant bit processed by the binary scale RDAC segment 204. In some examples, MDAC 200 may not include R-2R DAC segment 205. In some examples, MDAC 200 may not include either the temperature-sensing RDAC segment 202 or the binary scale RDAC segment 204. Aspects of these alternative examples can be combined. For example, a sample MDAC may include a binary scale RDAC segment 204 and a capacitor array 289, but not a temperature-sensing RDAC segment 202 or an R-2R DAC segment 205.

[0036] Additionally, as described above, in some examples, capacitor array 289 includes one or more capacitors corresponding to segments of R-2R DAC 205. Each of these capacitors can be inversely scaled based on the total resistance of the corresponding segment of R-2R DAC segment 205. The capacitor responding to a bit of the input digital code corresponds to the DAC segment responding to the same bit.

[0037] The term "coupled" is used throughout this specification. The term may cover a connection, communication, or signaling path that achieves a functional relationship consistent with the description of this disclosure. For example, if device A generates a signal to control device B to perform an action, in a first example, device A is coupled to device B; or in a second example, if intermediate component C substantially does not alter the relationship between device A and device B, device A is coupled to device B via intermediate component C such that device B is controlled by device A via control signals generated by device A.

Claims

1. A multiplication digital-to-analog converter, i.e., an MDAC, comprising: A first resistor, the first resistor having a first resistance; The first pair of switches is configured to selectively connect or disconnect the first resistor to the current output or ground based on the first bit of the input digital code. A second resistor having a second resistance, the second resistance being scaled relative to the first resistor by a factor N, where N is an integer; The second pair of switches is configured to selectively connect or disconnect the second resistor from the current output or ground based on the second bit of the portion of the input digital code. A first capacitor, the first capacitor having a first capacitance; A third pair of switches is configured to selectively connect or disconnect the first capacitor from the current output or ground based on the first bit of the portion of the input digital code. A second capacitor, the second capacitor having a second capacitance, the second capacitance being scaled relative to the first capacitor by 1 / N; as well as A fourth pair of switches is configured to selectively connect or disconnect the second capacitor from the current output or ground based on the second bit of the portion of the input digital code.

2. The MDAC according to claim 1, wherein: The first pair of switches is configured to connect the first resistor to the current output in response to the first bit having a first binary value; The third pair of switches is configured to connect the first capacitor to the current output in response to the first bit having the first binary value; The second pair of switches is configured to connect the second resistor to the current output in response to the second bit having a second binary value; as well as The fourth pair of switches is configured to connect the second capacitor to the current output in response to the second bit having the second binary value.

3. The MDAC according to claim 1, further comprising: A third resistor, the third resistor having a third resistance, wherein the first resistance is scaled by N relative to the third resistance; The fifth switch is configured to connect the third resistor to the current output based on the first digit of the temperature measurement code of the second part of the input digital code; A fourth resistor, the fourth resistor having the third resistor; The sixth pair of switches is configured to connect the fourth resistor to the current output based on the second digit of the temperature measurement code; A third capacitor, the third capacitor having a third capacitance, wherein the first capacitance is scaled relative to the third resistor by 1 / N; The seventh pair of switches is configured to connect the third capacitor to the current output based on the first digit of the temperature measurement code; A fourth capacitor, wherein the fourth capacitor has the third capacitor; as well as An eighth pair of switches is configured to connect the fourth capacitor to the current output based on the second digital code of the temperature measurement code.

4. The MDAC of claim 1, further comprising a plurality of resistors arranged in an R-2R resistor ladder.

5. The MDAC of claim 4, further comprising a fifth capacitor configured to be selectively coupled to the current output and having a fifth capacitor with resistance scaling based on the resistor segment of the R-2R resistance ladder.

6. The MDAC of claim 1, wherein the first switch of the third pair of switches is configured to connect the first capacitor to the current output based on the first bit, and the second switch of the third pair of switches is configured to connect the first capacitor to ground based on the inverted form of the first bit.

7. The MDAC of claim 1, further comprising: An operational amplifier (OPAMP) includes a first terminal and a second terminal, wherein the first terminal is connected to the current output and the second terminal is connected to a DC voltage; and A feedback resistor is connected to the output of the OPAMP and to the first terminal of the OPAMP.

8. The MDAC of claim 7, further comprising a feedback capacitor coupled across the feedback resistor.

9. The MDAC of claim 1, wherein the first resistor, the second resistor, the first capacitor, and the second capacitor are connected in parallel to a reference voltage source.

10. A multiplication digital-to-analog converter, i.e., an MDAC, comprising: A plurality of resistors, the plurality of resistors comprising: A first resistor, configured to be selectively connected to a current output based on the first bit of a first portion of an input digital code; and A second resistor, configured to be selectively connected to the current output based on a second bit of the first portion of the input digital code, wherein the resistance of the second resistor is twice the resistance of the first resistor; and A plurality of capacitors, said plurality of capacitors including: A first capacitor, configured to be selectively connected to the current output based on the first bit of the first portion; and A second capacitor, configured to be selectively connected to the current output based on the second bit of the first portion, wherein the capacitance of the second capacitor is half the capacitance of the first capacitor.

11. The MDAC of claim 10, further comprising: The second plurality of resistors includes: A third resistor, configured to be connected to the current output based on a first digit of a temperature-measuring code derived from a second portion of the input digital code, wherein the third resistor has a resistance that is half the resistance of the first resistor; and A fourth resistor, configured to be connected to the current output based on a second digit of the temperature measurement code, wherein the fourth resistor has a resistance that is half the resistance of the first resistor; and The second plurality of capacitors includes: A third capacitor, configured to be connected to the current output based on the first digital code of the temperature measurement code, wherein the third capacitor has a capacitance twice that of the first capacitor; and A fourth capacitor having the third capacitor, the fourth capacitor being configured to be connected to the current output based on the second digital code of the temperature measurement code, wherein the fourth capacitor has a capacitance twice that of the first capacitor.

12. The MDAC of claim 11, wherein the second portion corresponds to a plurality of most significant bits of the input digit code.

13. The MDAC of claim 11, further comprising a third plurality of resistors arranged in an R-2R resistor ladder.

14. The MDAC of claim 10, further comprising an operational amplifier, namely an OPAMP, the operational amplifier including a first terminal and a second terminal, the first terminal being connected to the current output and the second terminal being connected to ground.

15. The MDAC of claim 14, further comprising a feedback resistor connected to the output of the OPAMP and connected to the first terminal of the OPAMP.

16. The MDAC of claim 15, further comprising a feedback capacitor coupled across the feedback resistor.

17. The MDAC of claim 10, wherein the first resistor, the second resistor, the first capacitor, and the second capacitor are connected in parallel to a reference voltage source.

18. A multiplication digital-to-analog converter, i.e., an MDAC, comprising: A first resistor, the first resistor having a first resistance; The first pair of switches is configured to selectively connect or disconnect the first resistor from the current output or ground based on the temperature-coded digital part of the input digital code. A second resistor having a second resistance, the second resistance being scaled relative to the first resistor by a factor N, where N is an integer; The second pair of switches is configured to selectively connect or disconnect the second resistor from the current output or ground based on a bit of the second part of the input digital code. A first capacitor, the first capacitor having a first capacitance; A third pair of switches is configured to selectively connect or disconnect the first capacitor from the current output or ground based on the digital code of the temperature measurement code. A second capacitor, the second capacitor having a second capacitance, the second capacitance being scaled relative to the first capacitor by 1 / N; as well as A fourth pair of switches is configured to selectively connect or disconnect the second capacitor from the current output or ground based on the bit of the second portion of the input digital code.

19. The MDAC of claim 18, further comprising an operational amplifier, namely an OPAMP, the operational amplifier including a first terminal and a second terminal, the first terminal being connected to the current output and the second terminal being connected to ground.

20. The MDAC of claim 19, further comprising: A feedback resistor, which is connected to the output of the OPAMP and to the first terminal of the OPAMP; as well as A feedback capacitor is coupled across the feedback resistor.

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