A nonlinear trim circuit in a relaxation oscillator

Abstract

The present invention discloses a nonlinear trim circuit in a relaxation oscillator, belonging to the technical field of relaxation oscillator design. The nonlinear trim circuit includes a variable resistor R0 and a resistor R1 connected in series. The variable resistor R0 and the resistor R1 work together to complete the nonlinear trim circuit in the relaxation oscillator, so as to adjust a suitable resistance value when the manufacturing process of the relaxation oscillator changes. The variable resistor R0 includes 16 resistors R01-R016 connected in series, and the resistors R01-R016 connected in series use tap switches S1-S16 connected in series for signal control. The resistors R01-R016 connected in series take resistors R01-R04=0.8×r, resistors R05-R012=r, and resistors R013-R016=1.4×r from bottom to top. The present invention adopts three types of unit resistors to ensure the trimming accuracy of the resistors under all process angles without increasing the trimming bit and sacrificing the trimming range.

Description

Technical Field

[0001] The invention belongs to the technical field of relaxation oscillator design, and in particular relates to a nonlinear trim circuit in a relaxation oscillator. Background Art

[0002] TRIM is widely used in analog circuits. In the relaxation oscillator, the resistor R and the capacitor C determine the oscillation frequency (f=1 / RC). When manufacturing chips, there is uncertainty in the process corners of R and C. The resistance value will change with the process corner, and the range of change is related to the process. Here, 25% is taken. A resistor has a resistance of R0 in the TT corner, a resistor of the same size has a resistance of 1.25×R0 in the SS corner, and a resistance of 0.75×R0 in the FF corner. In order to correct this change in resistance, TRIM is used. In conventional trim technology, the Trimming bit is set to n, which can control 2n resistors, the unit resistance is r, and the TRIM range is 2n×r. However, in the SS corner, the unit resistance becomes 1.25×r, which makes the adjustment accuracy worse. If the same accuracy is to be maintained, the unit resistance must be reduced, which means that the trimming bit (n) must be increased while the TRIM range remains unchanged. At the same time, designers need to make a trade-off between trimming bits and accuracy. Summary of the invention

[0003] The purpose of the present invention is to provide a nonlinear trim circuit in a relaxation oscillator, which can maintain similar accuracy in all process corners without increasing the trimming bit while keeping the TRIM range unchanged; this TRIM method can be used not only in oscillators, but also in other resistor TRIM circuits to solve the problems raised in the above background technology.

[0004] To achieve the above object, the present invention provides the following technical solutions: a nonlinear trim circuit in a relaxation oscillator, the nonlinear trim circuit comprising a variable resistor R0 and a resistor R1 connected in series, the variable resistor R0 and the resistor R1 working together to complete the nonlinear trim circuit in the relaxation oscillator, so as to adjust a suitable resistance value when the manufacturing process of the relaxation oscillator changes;

[0005] The variable resistor R0 includes 16 resistors R01 to R016 connected in series, and the resistors R01 to R016 connected in series are controlled by signals using tap switches S1 to S16 connected in series;

[0006] The aforementioned series-connected resistors R01~R016 are respectively R01~R04=0.8×r, R05~R012=r, and R013~R016=1.4×r from bottom to top; wherein r is the resistance value of the unit resistor;

[0007] Take resistors R05~R012 as the middle resistors; at the same time, take the middle resistors as the default resistor values ;

[0008] .

[0009] Preferably, the nonlinear trim circuit is designed to include unit resistors in three regions, namely, TT corner resistors, SS corner resistors and FF corner resistors.

[0010] Preferably, when the unit resistor is a TT corner resistor, the manufacturing error of the relaxation oscillator is corrected by adding or subtracting a unit resistor having a resistance value of r.

[0011] Preferably, when the unit resistor is an SS corner resistor, its actual resistance is 125% of the designed value. Adjustment nearby is not enough to compensate for the resistance deviation. In this case, the resistance is adjusted to around R1+(R01+R02). Since the unit resistance of R01~R04 is 0.8×r, the adjustment step is 0.8×r×125%=r. At this time, under the SS corner resistance, the accuracy of the resistor trim is still r.

[0012] Preferably, when the unit resistor is a FF corner resistor, its actual resistance is 75% of the designed value. Adjustment near the resistance value is not enough to compensate for the resistance deviation. In this case, adjust the resistance to Nearby, the adjustment accuracy is 1.4×r×75%=1.05r; at this time, under the FF corner resistance, the resistor trim accuracy is still close to r.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] The present invention adopts three types of unit resistors to ensure the trimming accuracy of the resistor under all process angles without increasing the trimming bit and sacrificing the trimming range. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a circuit structure diagram of the relaxation oscillator of the present invention.

[0016] Figure 2 FIG. 4 is a TRIM circuit diagram of a relaxation oscillator of the present invention. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] This embodiment provides a nonlinear trim circuit in a relaxation oscillator, the nonlinear trim circuit comprising a variable resistor R0 and a resistor R1 connected in series, the variable resistor R0 and the resistor R1 work together to complete the nonlinear trim circuit in the relaxation oscillator, so as to adjust a suitable resistance value when the manufacturing process of the relaxation oscillator changes;

[0019] The variable resistor R0 includes 16 resistors R01 to R016 connected in series, and the resistors R01 to R016 connected in series are controlled by signals using tap switches S1 to S16 connected in series;

[0020] The aforementioned series resistors R01~R016 are respectively R01~R04=0.8×r, R05~R012=r, and R013~R016=1.4×r from bottom to top; wherein r is the resistance value of the unit resistor;

[0021] Take resistors R05~R012 as the middle resistors; at the same time, take the middle resistors as the default resistor values ;

[0022] .

[0023] As a specific manner of this embodiment, the nonlinear trim circuit is designed to include unit resistors in three regions, namely, a TT corner resistor, a SS corner resistor, and a FF corner resistor.

[0024] As a specific method of this embodiment, when the unit resistor is a TT corner resistor, the manufacturing error of the relaxation oscillator is corrected by adding or subtracting a unit resistor with a resistance value of r. For example, if the actual manufactured resistance is slightly larger than expected, the resistance can be adjusted to , still greater than expected, continued to adjust to .

[0025] As a specific method of this embodiment, when the unit resistor is an SS corner resistor, its actual resistance is 125% of the designed value. Adjustment nearby is not enough to compensate for the resistance deviation. In this case, the resistance is adjusted to around R1+(R01+R02). Since the unit resistance of R01~R04 is 0.8×r, the adjustment step is 0.8×r×125%=r. At this time, under the SS corner resistance, the accuracy of the resistor trim is still r.

[0026] As a specific method of this embodiment, when the unit resistor is a FF corner resistor, its actual resistance is 75% of the designed value. Adjustment near the resistance value is not enough to compensate for the resistance deviation. In this case, adjust the resistance to Nearby, the adjustment accuracy is 1.4×r×75%=1.05r; at this time, under the FF corner resistance, the resistor trim accuracy is still close to r.

[0027] This nonlinear trimming method not only ensures the accuracy of the resistor in all corners, but also does not sacrifice the trimming range under TT. This example takes a 4-bit circuit as an example. In fact, this design is also applicable to high-precision trimming circuits such as 7-bit and 8-bit.

[0028] The relaxation oscillator structure of the present invention is as follows Figure 1 As shown; wherein, the reference voltage VR is generated at Figure 2 VR=I0×(R1+R0), regardless of the change in current, the accuracy of VR depends on R1+R0. Here the target resistance is 27 KΩ, R1=20 KΩ, R01~R04 resistance is 0.8 KΩ, R05~R012 resistance is 1 KΩ, R013~R016 resistance is 1.4 KΩ. The middle resistor is taken as the default resistance value, S8 is selected to be turned on, If the resistor is a TT resistor, the actual resistance value manufactured is close to the design value, and the adjustment step is 1KΩ. If the resistor is an SS resistor, if S8 is still selected to be turned on, the actual resistance value manufactured is about 27.2×125%=34 KΩ, which is greater than the design target value of 27 KΩ. Next, reduce the number of resistor strings and select S2 to be turned on. The resistance value at this time is (20+0.8×2)×125%=27 KΩ, which is close to the target resistance value. At this time, the adjustment step is 0.8*125%=1KΩ. If the resistor is a FF resistor and S9 is still selected to be turned on, the actual resistance value manufactured is about 27.2×75%=20.4 KΩ, which is less than the design target value of 27 KΩ. The number of resistor strings is increased and S15 is turned on. The resistance value at this time is (20+0.8×4+1×8+1.4×3)×75%=26.55 KΩ, which is close to the target resistance value. The adjustment step size is 1.4×70%=1.05 KΩ.

[0029] In the present invention, by adopting three types of unit resistors, the trimming accuracy of the resistor under all process angles is guaranteed without increasing the trimming bit and sacrificing the trimming range.

[0030] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0031] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A nonlinear trim circuit in a relaxation oscillator, characterized in that: The nonlinear trim circuit includes a variable resistor R0 and a resistor R1 connected in series. The variable resistor R0 and the resistor R1 work together to complete the nonlinear trim circuit in the relaxation oscillator, so as to adjust the appropriate resistance value when the manufacturing process of the relaxation oscillator changes. The variable resistor R0 includes 16 resistors R01 to R016 connected in series, and the resistors R01 to R016 connected in series are controlled by signals using tap switches S1 to S16 connected in series; The aforementioned series-connected resistors R01~R016 are respectively R01~R04=0.8×r, R05~R012=r, and R013~R016=1.4×r from bottom to top; wherein r is the resistance value of the unit resistor; Take resistors R05~R012 as the middle resistors; at the same time, take the middle resistors as the default resistor values ; 。 2. The nonlinear trim circuit in a relaxation oscillator according to claim 1, characterized in that: The nonlinear trim circuit is designed to include unit resistors in three regions, namely TT corner resistors, SS corner resistors and FF corner resistors.

3. The nonlinear trim circuit in a relaxation oscillator according to claim 2, characterized in that: When the unit resistor is a TT corner resistor, the manufacturing error of the relaxation oscillator is corrected by adding or subtracting a unit resistor with a resistance value of r.

4. The nonlinear trim circuit in a relaxation oscillator according to claim 2, characterized in that: When the unit resistor is an SS corner resistor, its actual resistance is 125% of the designed value. Adjustment nearby is not enough to compensate for the resistance deviation. In this case, the resistance is adjusted to around R1+(R01+R02). Since the unit resistance of R01~R04 is 0.8×r, the adjustment step is 0.8×r×125%=r. At this time, under the SS corner resistance, the accuracy of the resistor trim is still r.

5. The nonlinear trim circuit in a relaxation oscillator according to claim 2, characterized in that: When the unit resistor is a FF corner resistor, its actual resistance is 75% of the designed value. Adjustment near the resistance value is not enough to compensate for the resistance deviation. In this case, adjust the resistance to Nearby, the adjustment accuracy is 1.4×r×75%=1.05r.

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