Dc power rail probe and measurement method

Abstract

A direct current (DC) power rail probe (105) includes a single-ended probe (105) tip and a dual-path circuit having an input coupled to the single-ended probe (105) tip and an output configured for connection to a measurement device such as an oscilloscope (110). The dual-path circuit includes an alternating current (AC) path in parallel with a feed forward (FF) path, the AC path including a capacitive element and the FF path including a series connection of an amplifier and at least one resistive element. The probe (105) tip and the dual-path circuit are selectively operable in a non-attenuated mode and an attenuated mode.

Description

BACKGROUND

[0001] The increased functionality, higher density, and higher frequency operation of many modern electronic products has driven the need for lower supply voltages. It is common in many today's designs to have DC power supplies as low as 1.1 volts, and each new generation of products is accompanied by tighter tolerances. Therefore, it has become an increasing challenge to provide design engineers with the tools needed to analyze DC power supply rails. This analysis often requires the use of an oscilloscope to look for transients, measure ripple, analyze coupling, etc. Oscilloscopes often do not have enough offset to center the DC power rail on the screen for the desired measurements. Even if the oscilloscope used has enough offset to center the supply on the screen, the oscilloscope can alter the behavior of the supply, resulting in inaccurate characterization. Placing a DC blocking capacitor in the signal path eliminates the offset problem, but also eliminates the relevant DC information such as DC supply compression or low frequency drift.

[0002] One solution to these challenges is to utilize a specially designed DC power rail probe so that the user makes power integrity measurements that require mV sensitivity when measuring noise, ripple, and transients on the DC power rail. A low noise measurement solution is critical to avoid confusing the noise of the probe and oscilloscope with the noise and ripple of the DC supply being measured. Using a probe with more than 1 : 1 attenuation (active or passive) can help with the offset difficulty, but will also reduce the signal to noise ratio and negatively impact the measurement accuracy. Using an oscilloscope 50 Ω input with a passive coaxial cable provides a probing method with a 1 : 1 attenuation ratio, but results in a higher than desired DC load on the measured supply and has the offset limitations mentioned previously. Ripple, noise, and transients on the DC supply are a major source of clock and date jitter in digital systems. Dynamic loading of the DC supply by processors, memory, or similar items occurs at clock frequencies and can produce high speed transients and noise on the DC supply that can easily have content above 1 GHz. Designers are increasingly needing high bandwidth tools to evaluate and understand high speed noise and transients on the DC power rail. SUMMARY

[0003] According to one aspect of the inventive concept, a direct current (DC) power rail probe is provided, the DC power rail probe comprising a single ended probe tip and a dual path circuit having an input coupled to the single ended probe tip and an output configured for connection to a measurement device. The dual path circuit comprises an alternating current (AC) path in parallel with a feed forward (FF) path, wherein the AC path comprises a capacitive element and the FF path comprises a series connection of an amplifier and at least one resistive element. The probe tip and the dual path circuit are selectively operable in a non-attenuation mode and an attenuation mode.

[0004] The DC power rail probe can further comprise a detachable tip resistor, the tip resistor being attached to the probe tip in the attenuation mode and detached from the probe tip in the non-attenuation mode.

[0005] The DC power rail probe can further comprise a resistive probe tip and a switch, the switch being configured to connect the single-ended probe tip to the dual-path circuit in the non-attenuation mode and to connect the resistive probe tip to the dual-path circuit in the attenuation mode.

[0006] The DC power rail probe can further comprise a blocking switch in the AC path of the dual-path circuit, wherein the blocking switch is closed in the non-attenuation mode and open in the attenuation mode.

[0007] The DC power rail probe can further comprise an attenuation circuit in series with the capacitive element in the AC path of the dual-path circuit and at least one bypass switch for selectively bypassing the attenuation circuit in the AC path. In this case, the attenuation circuit is operable to attenuate the AC path in the attenuation mode and the bypass switch bypasses the attenuation circuit in the AC path in the non-attenuation mode. The attenuation circuit can be a matching Pi attenuator and the resistance of the attenuation circuit can be 50 Ω.

[0008] The measurement device can be an oscilloscope and the output of the dual-path circuit can be configured for connection to a 50 Ω input of the oscilloscope.

[0009] According to another aspect of the present inventive concept, there is provided a measurement system comprising an oscilloscope and a single-ended DC power rail probe connected to an input of the oscilloscope. The single-ended DC power rail probe is configured to selectively operate in a non-attenuation mode and an attenuation mode.

[0010] The DC power rail probe of the measurement system can comprise a single-ended probe tip and a dual-path circuit having an input coupled to the single-ended probe tip and an output connected to an input of the oscilloscope. In this case, the dual-path circuit comprises an alternating current (AC) path in parallel with a feed forward (FF) path, wherein the AC path comprises a capacitive element and the FF path comprises a series connection of an amplifier and at least one resistive element.

[0011] The input of the oscilloscope can be a 50 Ω input.

[0012] The DC power rail probe of the measurement system can further comprise a detachable tip resistor that is attached to the single ended probe tip in the attenuated mode and detached from the single ended probe tip in the non-attenuated mode.

[0013] The DC power rail probe of the measurement system can further comprise a resistive probe tip and a switch, wherein the switch is configured to connect the single ended probe tip to the dual path circuit in the non-attenuated mode and to connect the resistive probe tip to the dual path circuit in the attenuated mode.

[0014] The DC power rail probe of the measurement system can further comprise a blocking switch in the AC path of the dual path circuit, wherein the blocking switch is open to block the AC path in the non-attenuated mode and closed in the attenuated mode.

[0015] The DC power rail probe of the measurement system can further comprise an attenuation circuit in series with the capacitive element in the AC path of the dual path circuit and a bypass switch for selectively bypassing the attenuation circuit in the AC path. In this case, the attenuation circuit is operable to attenuate the AC path in the attenuated mode and the bypass switch bypasses the attenuation circuit in the AC path in the non-attenuated mode. The attenuation circuit can be a matching Pi attenuator and can match an input resistance of an input of the oscilloscope. The resistance of the attenuation circuit can be 50 Ω.

[0016] According to yet another aspect of the inventive concept, there is provided a method of measuring a DC voltage, the method comprising attaching a single ended DC power rail probe to an input of an oscilloscope, changing attenuation of the single ended DC power rail probe from a non-attenuated mode to an attenuated mode, and contacting the DC power rail probe with a DC power rail in the attenuated mode to measure a voltage of the DC power rail.

[0017] The single ended DC power rail probe can comprise a dual path circuit having an input coupled to a probe tip and an output configured for connection to an input of the oscilloscope, the dual path circuit comprising an alternating current (AC) path in parallel with a feed forward (FF) path, wherein the AC path comprises a capacitive element and the FF path comprises a series connection of a resistive element and an amplifier. In this case, the single ended DC power rail probe is changed to the attenuated mode by adding a resistance in the AC path of the dual path circuit. BRIEF DESCRIPTION OF DRAWINGS

[0018] The above and other aspects and features of the present inventive concept will become apparent from the following detailed description with reference to the accompanying drawings, in which:

[0019] Figure 1 is a schematic diagram of a measurement system according to a representative embodiment;

[0020] Figure 2 is a block diagram of a measurement system including a device under test (DUT) according to a representative embodiment;

[0021] Figure 3 This is a circuit diagram used for reference in describing the associated DC power rail probe;

[0022] Figure 4 is a circuit diagram for reference in describing a DC power rail probe according to an embodiment of the present inventive concept;

[0023] Figure 5 is a circuit diagram for reference in describing a DC power rail probe according to another embodiment of the present inventive concept;

[0024] Figure 6 is a circuit diagram for reference in describing a DC power rail probe according to another embodiment of the present inventive concept;

[0025] Figure 7 is a circuit diagram for reference in describing a DC power rail probe according to another embodiment of the present inventive concept;

[0026] Figure 8 is a circuit diagram for reference in describing a DC power rail probe according to another embodiment of the present inventive concept;

[0027] Figure 9 is a circuit diagram for reference in describing a DC power rail probe according to another embodiment of the present inventive concept; and

[0028] Figure 10 is a flowchart for reference in describing a method of measuring a DC voltage according to an embodiment of the present inventive concept. DETAILED DESCRIPTION

[0029] The embodiments described herein generally relate to probes configured to detect a direct current (DC) voltage and supply the detected DC voltage to a measurement / analysis device, such as an oscilloscope. Specifically, these embodiments are directed to detecting a DC power supply voltage present on a DC power rail of an electronic device or circuit board. For this reason, the probes of these embodiments are referred to herein as DC power rail probes. However, these embodiments are not limited by the terminology of the DC power system being analyzed.

[0030] Figure 1is a schematic diagram of a measurement system 100 according to representative embodiments.

[0031] Referring to Figure 1 , the measurement system 100 of this example includes a single-ended DC rail probe 105 and an oscilloscope 110. During typical operation of the measurement system 100, a user applies the probe tip of the probe 105 to a test point of a device under test (DUT). Once contact is made with the test point, the probe 105 detects a voltage signal at the test point and transmits the voltage signal to the oscilloscope 110. The oscilloscope 110 then converts the signal into a waveform to be displayed on a display 115 of the oscilloscope 110.

[0032] The oscilloscope 110 receives the output signal of the probe 105 as an input signal and processes the received input signal. This processing can include amplification by an input amplifier and digitization by an analog-to-digital converter (ADC), for example. The digitization produces a stream of digital values to be rendered on the display 115. The input amplifier and / or ADC are typically configured to amplify and / or digitize the signal according to a range of values that can be rendered on the display 115. This range (also referred to as the "full screen range" of the display 115) is typically specified by the number of vertical divisions and the number of volts per division (V / div) of the display 115. This range can be adjusted, for example, by changing the attenuation of the oscilloscope probe 105 and / or the input amplifier. In typical implementations, the full screen range is slightly below the dynamic range of the input amplifier and ADC, so these components do not immediately saturate when the input voltage to the oscilloscope 110 exceeds the full screen range.

[0033] Figure 2 is a block diagram of a measurement system including a DUT according to representative embodiments. This diagram is presented as a simple illustration of the signal flow from the DUT 205 to the oscilloscope 110. Referring to Figure 2 , when the probe 105 is in contact with the DUT 205, a voltage signal is transmitted from the DUT 205 to the oscilloscope probe 105 along one or more signal paths. The signal is transmitted to the oscilloscope 110, where it is amplified, digitized, and rendered on the display 115.

[0034] Figure 3 is a simplified circuit diagram of a related DC rail probe.

[0035] Referring to Figure 3 , the related DC rail probe includes a probe tip connected to a coaxial cable (probe coaxial cable), which feeds a circuit with a capacitance C and a first resistance R 1A , an amplifier A A , and a second resistance R 2AThe probe tip can be a pin-like protrusion or a wire configured to be temporarily (e.g., manually or using a probe stand) brought into contact with the power rail of the DUT. Alternatively, the probe tip can be connected to the power rail by solder or the like.

[0036] The output of the probe circuit is fed to the input of the oscilloscope (e.g., the 50Ω input of the oscilloscope). This type of power rail probe is available from Keysight Technologies under the product name N7020A. The N7020A probe is a self-contained unit that connects directly to the oscilloscope and has a fixed attenuation of approximately 1 : 1. This low attenuation ratio provides excellent signal-to-noise ratio. The N7020A probe can measure voltages up to + / - 24V with an input voltage range of + / - 850mV. In addition, this probe has a large DC input impedance of 50kΩ (which minimizes the probe DC load of the rail it is probing) and a high bandwidth of 2GHz (which allows fast transients and noise caused by switching current within the system under test to be captured). As will be appreciated by those skilled in the art, this type of probe is a single-ended implementation with a single-ended probe tip as opposed to a differential implementation with a pair of differential probe tips.

[0037] Figure 3 The probe architecture of the N7020A is characterized by a 2-path design that includes a passive AC high-frequency path ("AC path") and an amplified low-frequency path (referred to as a feed-forward path ("FF path")). At high frequencies, the impedance of capacitor C is close to 0Ω, and thus the AC path effectively bypasses the FF path. On the other hand, at low frequencies, the impedance of capacitor C is close to ∞, thus effectively blocking the AC path. Because the AC path is passive, it is relatively easy to design. The FF path is also relatively easy to implement because it does not require high bandwidth and can be implemented with readily available operational amplifiers.

[0038] The N7020A probe has an advantageous capability in viewing fine details on a power rail, but it has the limitation that it cannot view power supply excursions greater than the + / - 850mV input range of the probe. Such excursions can occur, for example, when turning the power on and off for a DUT. The N7020A probe is good at measuring power supplies that are in a steady state, but cannot measure any power supply excursions greater than the input range of the probe. The implementation described later adds a selectable attenuation in the power rail probe architecture that allows it to measure large input voltage excursions.

[0039] As just mentioned, the N7020A architecture ( Figure 3One disadvantage of the FF probe is that it cannot measure wide input voltages (excluding DC offset voltage). To maintain a high-quality, high-frequency 50Ω path with minimal attenuation, the voltage divider resistor at the output of the FF path needs to be relatively large, and this is one of the main tradeoffs that limits the probe's input range.

[0040] Adding attenuation comes at two major tradeoffs: design complexity and noise. Adding attenuation to a probe inherently adds noise. Therefore, depending on the implementation, the attenuation is selectable, giving the user the option of 1:1 attenuation with a limited input voltage range or higher attenuation with a wider input range. Figure 4 to Figure 9 These embodiments are described in turn.

[0041] Figure 4 is a circuit diagram for reference in describing a DC power rail probe 400 according to an embodiment of the inventive concept.

[0042] Similar to Figure 3 The configuration of the relevant example is, Figure 4 The embodiment includes a capacitor C and a first resistor R 1B , Amplifier A B and the second resistor R 2B The circuit is composed of series and parallel connections. Therefore, Figure 4 The probe architecture of is characterized by the previously described 2-path design, which includes a passive AC high frequency path ("AC path") and an amplified low frequency path, referred to as a feed-forward path ("FF path") . Figure 4 The embodiment of the invention is also characterized by providing a detachable tip resistor. This allows the user to obtain two different physical connection modes for connecting to the DUT. These modes are referred to herein as non-attenuation mode and attenuation mode. In non-attenuation mode, the user establishes a direct connection (i.e., without a detachable tip resistor), thereby setting the attenuation to 1:1 (similar to the N7020A probe described above). On the other hand, in attenuation mode, the customer uses a tip resistor, in which case the gain of the AC path changes. When the oscilloscope knows this connection, it can reconfigure the FF path gain to match the AC path gain, thereby providing attenuation and a flat frequency response across the entire bandwidth.

[0043] Adding a tip resistor at the input of the probe cable creates a resistive divider and therefore an attenuator in the AC path. In other words, with a 50Ω input, the gain A in the AC path is AC becomes 50 / (R 尖端 +50), where R 尖端 is the resistance of the tip resistor. Since the tip resistor R 尖端The DC input resistance is typically small compared to the AC input resistance, so it has minimal impact on the FF gain, and thus can enable the switch to change the gain of the FF path. That is, the gain A B in the AC path can be changed to match the gain A AC Once the signal has been attenuated and the gain path adjusted, the input range of the probe is increased by the amount of attenuation, allowing for the measurement of larger input voltages.

[0044] In other embodiments, the probe is equipped with multiple detachable tip resistors having different resistance values, thus allowing for multiple different attenuations corresponding to different tip resistance values.

[0045] The use of tip resistors in differential, continuously attenuating probes is known. However, Figure 4 Embodiments of the present application deviate from this configuration by using tip resistors in a single-ended implementation with little attenuation when establishing a directional connection. Figure 4 Embodiments of the present application provide the advantage of a relatively simple design, and the AC path in the probe remains uncontacted, which simplifies design complexity and increases signal integrity and bandwidth. Also, because the tip resistor is included in the input impedance of the probe, the AC load is improved in the attenuated mode.

[0046] Figure 5 is a circuit diagram referenced in describing a DC power rail probe 500 according to another embodiment of the inventive concept.

[0047] Similar to the configuration of the embodiments of Figure 4 the probe architecture of Figure 5 Embodiments of the present application include a circuit consisting of a capacitor C in series with a first resistor R 1B , an amplifier A B , and a second resistor R 2B in parallel. Similar to the previous embodiments, Figure 4 The probe architecture of Figure 5The embodiment further features the provision of a switch SW1 coupled to the coaxial cable probe head cable. The switch SW1 of this embodiment has two positions for implementing two different physical connection modes to the DUT. Similar to the previous embodiments, these modes are referred to as the non-attenuation mode and the attenuation mode. In the non-attenuation mode, the switch SW1 is set to establish a direct connection (i.e., without a tip resistor), whereby the attenuation is set to 1 : 1 (similar to the N7020A probe). In the attenuation mode, the switch SW1 is set to connect the resistive probe tip to a two-path circuit, in which case the gain of the AC path is changed. As with the previous embodiments, when the oscilloscope knows this connection, it can reconfigure the FF path gain to match the AC path gain, thus providing an attenuation and flat frequency response over the entire bandwidth.

[0048] As with the previous embodiments, Figure 4 the operation of the switch SW1 adds the resistance of the resistive probe tip at the input end of the probe cable creates a resistive voltage divider and thus an attenuator on the AC path. As previously described, in the case of a 50 Ω input, the gain A AC in the AC path becomes 50 / (R 尖端 + 50), where R 尖端 is the resistance of the tip resistor. Because the tip resistance R 尖端 is typically small compared to the DC input resistance, it has minimal impact on the FF gain, and thus can enable the switch to change the gain of the FF path. That is, the gain A B in the FF path can be changed to match the gain A AC in the AC path. Once the signal has been attenuated and the gain path adjusted, the input range of the probe is increased by the amount of attenuation, allowing for the measurement of larger input voltages.

[0049] In an alternative embodiment, the probe is equipped with a multi-position switch for selectively adding any one of a plurality of resistive tip probes having different resistance values, thus allowing for a plurality of different attenuation modes corresponding to the different tip resistance values.

[0050] Figure 6 is a circuit diagram referenced in describing a DC power rail probe 600 according to another embodiment of the inventive concept.

[0051] Referring to Figure 6 , the DC power rail probe 600 of this embodiment includes a probe tip connected to a coaxial cable (probe coaxial cable), which feeds a circuit consisting of a series connection of a capacitor C, a first resistor R 1B , an amplifier A B , and a second resistor R 2B in parallel. As with the previous embodiments,Figure 6 The probe architecture of FIG. 1 is characterized as a 2-path design, which includes a passive AC high frequency path ("AC path") and an amplified low frequency path, referred to as a feed forward path ("FF path").

[0052] Figure 6 Embodiments of FIG. 1 are characterized by including a blocking switch SW2 in the AC path of the 2-path circuit. The blocking switch SW2 can be a radio frequency (RF) switch. The blocking switch SW2 is closed in the non-attenuation mode, in which case the probe 600 operates with 1 : 1 attenuation, similar to the prior art N7020A probe.

[0053] On the other hand, in the attenuation mode, the blocking switch SW2 is open, thus breaking the AC path. This greatly reduces the bandwidth of the probe, but it allows for the selection of attenuation in the probe circuit only by modifying the gain A B to attenuate large input voltages on the FF path. In the attenuation mode, the probe bandwidth is the FF path bandwidth, but it can be used to measure large input voltages. The "2-path" design becomes a "1 -path", where the FF path is the only circuit passing the signal. These are typically much slower in the case of voltage supply on and off, where the bandwidth requirements are properly within the bandwidth achievable in the FF path.

[0054] Figure 6 Embodiments of FIG. 1 have the ability to change the probe attenuation with the same physical connections to the DUT (e.g., no tip resistor), thus giving the probe the ability to make non-attenuation measurements and additionally to measure high input voltages in the attenuation mode. For the non-attenuation mode, the blocking switch SW2 is closed, and the gain A B is the same as that of the related probe of FIG. 1. In the attenuation mode, the blocking switch SW2 is open, and A A is modified to attenuate large input voltages on the FF path. Figure 3 B

[0055] Figure 7 is a circuit diagram referenced in describing a DC power rail probe 700 according to another embodiment of the inventive concept.

[0056] Referring to Figure 7 , the DC power rail probe 700 of this embodiment includes a probe tip connected to a coaxial cable (probe coaxial cable), which feeds the circuit consisting of a series connection of a capacitor C 1B , an amplifier A B , and a second resistor R 2B in parallel. As with the previous embodiments, Figure 7 ​​probe architecture of Agilent® is characterized by a 2-path design, which includes a passive AC high frequency path ("AC path") and an amplified low frequency path, referred to as a feed forward path ("FF path").

[0057] Figure 7 Embodiments of Agilent® further feature an attenuator circuit in the AC path of the 2-path circuit and a bypass switch SW3. The bypass switch SW3 can be an RF switch. As shown, the bypass switch SW3 is connected across the attenuator circuit to allow selective inclusion of the attenuator circuit in the AC path of the 2-path circuit. That is, referring to Figure 7 , when the bypass switch SW3 is in a closed state, the attenuator circuit is bypassed and the probe 700 operates in a 1 : 1 attenuation mode in a non-attenuation mode, similar to the Agilent® N7020A probe Figure 3 ).

[0058] On the other hand, when the bypass switch SW3 is open, the attenuator is included in the AC path to establish an attenuation mode of the probe 700. In addition, the gain of the FF path can be modified in a similar manner as described above in connection with the embodiments of Agilent®. Figure 6 This allows electronic control of the attenuation mode without the need to change the tip resistor. Also, the frequency response can be matched for both attenuation modes. In other words, full bandwidth can be achieved in attenuation while still maintaining high impedance (and thus low loading) and without the need for any physical probe tip changes.

[0059] In the case where the input of the oscilloscope is a 50Ω input, Figure 7 the attenuator circuit of Agilent® can be a 50Ω attenuator. There are many ways to incorporate the attenuator and each has tradeoffs, primarily associated with the FF path. The main tradeoffs are attenuation, FF amplifier output voltage, and FF amplifier bandwidth.

[0060] Figure 8 is a circuit diagram referenced in describing an example of a DC power rail probe 800 in which the attenuator circuit of Agilent® is implemented by a matching Pi attenuator. Figure 7

[0061] Referring to Figure 8 , the matching Pi attenuator includes resistive elements R 输入 , R s , and R 输出 as shown. In the embodiment of this example, the bypass switch SW3 is closed in a non-attenuation mode, as previously described. On the other hand, in an attenuation mode, the bypass switch SW3 is open to introduce the matching Pi attenuator into the AC path. Here, the gain A B can be set to match the AC gain. In this example, R 2B and R 输出 ​can be set so that their parallel combination equals R 输入 . R 输出 The value of can be chosen to maximize the ability of the FF amplifier to fully drive the output with appropriate attenuation. By minimizing the attenuation, the signal-to-noise ratio of the probe is maximized. Other cases with higher attenuation can be more easily implemented. In an alternative embodiment of a matched Pi attenuator, R 2B and R 输出 are combined to provide R 2B and R 输出 A single resistor serves both purposes.

[0062] Figure 9 is a circuit diagram for reference in describing a DC power rail probe 900 according to another embodiment of the inventive concept.

[0063] It may be preferable to add an attenuator circuit (e.g., Figure 8 Galvanic isolation of the matched Pi attenuator). Figure 9 An example of an AC path for achieving increased attenuator circuit isolation by providing a pair of bypass switches SW4a and SW4b is shown. In this example, the attenuator circuit is implemented with Figure 8 The matched Pi attenuator is similar to the matched Pi attenuator, including the resistor element R as shown in the figure 输入 、R s and R 输出 As mentioned above Figure 8 As mentioned, R 输出 Can be used with FF path R 2B Also in this example, the pair of bypass switches SW4a and SW4b are implemented by single-pole double-throw (SPDT) switches, which can be RF SPDT switches. In the non-attenuation mode, the SPDT switches SW4a and SW4b are in Figure 9 The switch position 1 shown hereby bypasses the attenuator circuit (e.g., a matched Pi attenuator) and electrically isolates the attenuator circuit from the AC path. In attenuation mode, the SPDT switches SW4a and SW4b are in Figure 9 The switch is in position 2, thereby introducing the attenuator circuit into the AC path. In this state, the circuit is as above combined Figure 7 and Figure 8 Operate as described.

[0064] Figure 10 1 is a flowchart for briefly describing a method for measuring a DC voltage having a power supply deviation greater than the normal (non-attenuated) input range of a probe according to an embodiment of the present inventive concept. It should be noted that the order of the processing steps is not limited to Figure 9 The order shown in .

[0065] First, a single-ended DC power rail probe is connected to an oscilloscope (SI 01). For example, a connection can be made to the 50 Ω input of the oscilloscope.

[0066] Then, the single-ended DC power rail probe is switched from a non-attenuated mode to an attenuated mode (S102). As explained previously, this can be achieved by adding an attenuation ( Figure 4 and Figure 5 ) at the probe tip, by blocking the AC path ( Figure 6 ), or by adding an attenuation ( Figure 7 , Figure 8 and Figure 9 ) in the AC path. Further, if needed, the FF path can be adjusted under control of the oscilloscope.

[0067] The DC voltage is then measured for display / analysis on the oscilloscope (SI 03). This is done with the probe tip in contact with the DC voltage power rail of the DUT.

[0068] While the application has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the application is not limited to the disclosed embodiments. Other variations of the disclosed embodiments can be understood and effected by those skilled in the art in practising the claimed application, from an study of the drawings, the disclosure, and the appended claims. While representative embodiments are disclosed herein, one of ordinary skill in the art will understand that many variations are possible under the present teachings and are still within the scope of the appended claims. Therefore, the application is not to be restricted except by the scope of the claims appended hereto.

[0069] In summary, the application comprises the following embodiments:

[0070] 1. A direct current (DC) power rail probe, comprising:

[0071] a single-ended probe tip; and

[0072] a dual-path circuit having an input coupled to the single-ended probe tip and an output configured for connection to a measurement device, the dual-path circuit comprising an alternating current (AC) path in parallel with a feed forward (FF) path, the AC path comprising a capacitive element, and the FF path comprising a series connection of an amplifier and at least one resistive element,

[0073] wherein the single-ended probe tip and the dual-path circuit are selectively operable in a non-attenuated mode and an attenuated mode.

[0074] 2. The DC power rail probe of clause 1, further comprising a detachable tip resistor, the tip resistor being attached to the single-ended probe tip in the attenuation mode and detached from the single-ended probe tip in the non-attenuation mode.

[0075] 3. The DC power rail probe of clause 1, further comprising a resistive probe tip and a switch configured to connect the single-ended probe tip to the dual-path circuit in the non-attenuation mode and to connect the resistive probe tip to the dual-path circuit in the attenuation mode.

[0076] 4. The DC power rail probe of clause 1, further comprising a blocking switch in an AC path of the dual-path circuit,

[0077] wherein the blocking switch is closed in the non-attenuation mode and open in the attenuation mode.

[0078] 5. The DC power rail probe of clause 1, further comprising an attenuation circuit in series with the capacitive element in the AC path of the dual-path circuit and at least one bypass switch for selectively bypassing the attenuation circuit in the AC path,

[0079] wherein the attenuation circuit is operable to attenuate the AC path in the attenuation mode and the at least one bypass switch bypasses the attenuation circuit in the AC path in the non-attenuation mode.

[0080] 6. The DC power rail probe of clause 5, wherein the attenuation circuit is a matched Pi attenuator.

[0081] 7. The DC power rail probe of clause 5, wherein a resistance of the attenuation circuit is 50 Ω.

[0082] 8. The DC power rail probe of clause 1, wherein the measurement device is an oscilloscope and the output of the dual-path circuit is configured for connection to a 50 Ω input of the oscilloscope.

[0083] 9. A measurement system, comprising:

[0084] an oscilloscope; and

[0085] a single-ended direct current (DC) power rail probe connected to an input of the oscilloscope and configured to selectively operate in a non-attenuation mode and an attenuation mode.

[0086] 10. The measurement system of clause 9, wherein the DC power rail probe comprises a single-ended probe tip, and

[0087] a dual-path circuit having an input coupled to the single-ended probe tip and an output connected to an input of the oscilloscope, the dual-path circuit including an alternating current (AC) path in parallel with a feed-forward (FF) path, the AC path including a capacitive element and the FF path including a series connection of a resistive element and an amplifier.

[0088] 11. The measurement system of clause 10, wherein the input of the oscilloscope is a 50 Ω input.

[0089] 12. The measurement system of clause 10, further comprising a separable tip resistor, the tip resistor being attached to the single-ended probe tip in the attenuation mode and separated from the single-ended probe tip in the non-attenuation mode.

[0090] 13. The measurement system of clause 10, further comprising a resistive probe tip and a switch configured to connect the single-ended probe tip to the dual-path circuit in the non-attenuation mode and to connect the resistive probe tip to the dual-path circuit in the attenuation mode.

[0091] 14. The measurement system of clause 10, further comprising a blocking switch in the AC path of the dual-path circuit,

[0092] wherein the blocking switch is open to block the AC path in the non-attenuation mode and is closed in the attenuation mode.

[0093] 15. The measurement system of clause 10, further comprising an attenuation circuit in series with the capacitive element in the AC path of the dual-path circuit and at least one bypass switch for selectively bypassing the attenuation circuit in the AC path,

[0094] wherein the attenuation circuit is operable to attenuate the AC path in the attenuation mode and the at least one bypass switch bypasses the attenuation circuit in the AC path in the non-attenuation mode.

[0095] 16. The measurement system of clause 15, wherein the attenuation circuit is a matched Pi attenuator.

[0096] 17. The measurement system of clause 15, wherein a resistance of the attenuation circuit matches an input resistance of the input of the oscilloscope.

[0097] 18. The measurement system of clause 17, wherein the resistance of the attenuation circuit is 50 Ω.

[0098] 19. A method of measuring a direct current (DC) voltage, comprising:

[0099] attaching a single ended DC power rail probe to an input of an oscilloscope;

[0100] changing an attenuation of the single ended DC power rail probe from a non-attenuation mode to an attenuation mode; and

[0101] contacting the DC power rail probe with a DC power rail in the attenuation mode to measure a voltage of the DC power rail.

[0102] 20. The method of clause 19, wherein the single ended DC power rail probe comprises a dual path circuit having an input coupled to a probe tip and an output configured for connection to an input of the oscilloscope, the dual path circuit comprising an alternating current (AC) path in parallel with a feed forward (FF) path, the AC path comprising a capacitive element and the FF path comprising a series connection of a resistive element and an amplifier,

[0103] wherein the single ended DC power rail probe is changed to the attenuation mode by adding a resistance in the AC path of the dual path circuit.

Claims

1. A direct current, DC, power rail probe, comprising: a single-ended probe tip; and a dual-path circuit having an input coupled to the single-ended probe tip and an output configured for connection to a measurement device, the dual-path circuit including an alternating current, AC, path in parallel with a feed-forward, FF, path, the AC path including a capacitive element and the FF path including a series connection of an amplifier and at least one resistive element, wherein the single-ended probe tip and the dual-path circuit are selectively operable in a non-attenuated mode and an attenuated mode, and wherein the DC power rail probe further includes a detachable tip resistor that is attached to the single-ended probe tip in the attenuated mode and detached from the single-ended probe tip in the non-attenuated mode.

2. The DC power rail probe of claim 1, further comprising a resistive probe tip and a switch configured to connect the single-ended probe tip to the dual-path circuit in the non-attenuated mode and to connect the resistive probe tip to the dual-path circuit in the attenuated mode.

3. The DC power rail probe of claim 1, further comprising a blocking switch in the AC path of the dual-path circuit, the blocking switch being closed in the non-attenuated mode and open in the attenuated mode. wherein 4. The DC power rail probe of claim 1, further comprising an attenuation circuit in the AC path of the dual-path circuit in series with the capacitive element and at least one bypass switch for selectively bypassing the attenuation circuit in the AC path, the attenuation circuit being operable to attenuate the AC path in the attenuated mode and the at least one bypass switch bypassing the attenuation circuit in the AC path in the non-attenuated mode. wherein, the attenuation circuit is a matching Pi attenuator.

5. The DC power rail probe of claim 4, wherein, the resistance of the attenuation circuit is 50 Ω.

6. The DC power rail probe of claim 4, wherein, the measurement device is an oscilloscope and the output of the dual-path circuit is configured for connection to a 50 Ω input of the oscilloscope.

7. The DC power rail probe of claim 1, wherein, 8. A measurement system, comprising: an oscilloscope; and a single-ended direct current, DC, power rail probe connected to an input of the oscilloscope and configured to be selectively operable in a non-attenuated mode and an attenuated mode; and wherein the DC power rail probe includes a single-ended probe tip, a dual-path circuit having an input coupled to the single-ended probe tip and an output connected to the input of the oscilloscope, the dual-path circuit including an alternating current, AC, path in parallel with a feed-forward, FF, path, the AC path including a capacitive element and the FF path including a series connection of a resistive element and an amplifier, and wherein the DC power rail probe further includes a detachable tip resistor that is attached to the single-ended probe tip in the attenuated mode and detached from the single-ended probe tip in the non-attenuated mode. the input of the oscilloscope is a 50 Ω input. ​ 9. The measurement system of claim 8, wherein, ​ 10. The measurement system of claim 8, further comprising a resistive probe tip and a switch configured to connect the single ended probe tip to the dual path circuit in the non-attenuation mode and to connect the resistive probe tip to the dual path circuit in the attenuation mode.

11. The measurement system of claim 8, further comprising a blocking switch in an AC path of the dual path circuit, wherein, the blocking switch being open to block the AC path in the non-attenuation mode and being closed in the attenuation mode.

12. The measurement system of claim 8, further comprising an attenuation circuit in the AC path of the dual path circuit in series with the capacitive element and at least one bypass switch for selectively bypassing the attenuation circuit in the AC path, wherein, the attenuation circuit being operable to attenuate the AC path in the attenuation mode and the at least one bypass switch bypassing the attenuation circuit in the AC path in the non-attenuation mode.

13. The measurement system of claim 12, wherein, the attenuation circuit is a matching Pi attenuator.

14. The measurement system of claim 12, wherein, the resistance of the attenuation circuit matches an input resistance of an input of the oscilloscope.

15. The measurement system of claim 14, wherein, the resistance of the attenuation circuit is 50 Ω.

16. A method of measuring a direct current, DC, voltage, comprising: attaching a single ended DC supply rail probe to an input of an oscilloscope; changing attenuation of the single ended DC supply rail probe from a non-attenuation mode to an attenuation mode, wherein the DC supply rail probe further comprises a detachable tip resistor, the tip resistor being attached to a single ended probe tip in the attenuation mode and being detached from the single ended probe tip in the non-attenuation mode; and contacting the DC supply rail probe with a DC supply rail in the attenuation mode to measure a voltage of the DC supply rail.

17. The method of claim 16, wherein, the single ended DC supply rail probe comprises a dual path circuit having an input coupled to a probe tip and an output configured for connection to an input of the oscilloscope, the dual path circuit comprising an alternating current, AC, path in parallel with a feed forward, FF, path, the AC path comprising a capacitive element and the FF path comprising a series connection of a resistive element and an amplifier, wherein the single ended DC supply rail probe is changed to the attenuation mode by adding a resistance in the AC path of the dual path circuit.

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