CN-114826157-B - RC oscillator circuit based on laser trimming

CN114826157BCN 114826157 BCN114826157 BCN 114826157BCN-114826157-B

Abstract

The invention belongs to the technical field of RC oscillators, and particularly provides an RC oscillator circuit based on laser trimming, which comprises a bias voltage generating circuit for generating a standard voltage VREF, an RC charge-discharge circuit, a comparator circuit and a clock dithering circuit for reducing clock dithering, wherein the input end of the clock dithering circuit is connected with a power supply, the output end of the clock dithering circuit is connected with one end of the RC charge-discharge circuit and then connected with the first input end of the comparator, the other end of the RC charge-discharge circuit is grounded, the second input end of the comparator is connected with the standard voltage VREF, and the output end of the comparator outputs an oscillating signal. The circuit adopts a structure that a comparator is added to charge and discharge of a capacitor by current, and compared with the traditional structure that the capacitor is charged and discharged and two comparators are added, the area of a chip is saved. And the calibration accuracy is 0.5%, and the circuit can be applied to any required circuit needing a clock. On the other hand, the clock jitter of the circuit output is small.

Inventors

XIA JIANBAO
CHEN ZHIMING
TIAN JIEFENG
Peng Hejin
CHEN SU
Zhong Xuheng

Assignees

厦门澎湃微电子有限公司
厦门澎湃微电子有限公司

Dates

Publication Date: 20260421
Application Date: 20220519
Priority Date: 20220519

Claims (5)

1. An RC oscillator circuit based on laser trimming, comprising: A bias voltage generating circuit for generating a standard voltage VREF, an RC charge-discharge circuit, a comparator circuit, and a clock jitter circuit for reducing clock jitter; the input end of the clock dithering circuit is connected with a power supply, the output end of the clock dithering circuit is connected with one end of the RC charge-discharge circuit and then connected to the first input end of the comparator, and the other end of the RC charge-discharge circuit is grounded; The second input end of the comparator is connected with a standard voltage VREF, and the output end of the comparator outputs an oscillating signal; The RC charge-discharge circuit further comprises a capacitor trimming circuit, wherein the capacitor trimming circuit comprises a fuse and a voltage-regulating MOS tube, one end of the capacitor is connected with the output end of the clock dithering circuit, the other end of the capacitor is connected with the drain end of the voltage-regulating MOS tube, the gate end of the voltage-regulating MOS tube is connected with a power supply through the fuse, and the source end of the voltage-regulating MOS tube is grounded; the capacitor trimming circuit is realized by adding a weak pull-down mode of a current mirror to the gate end of the MOS tube of the laser trimming fuse control capacitor.
2. The RC oscillator circuit based on laser trimming according to claim 1, wherein the RC oscillator circuit further comprises a first inverter and a second inverter connected in series, and the output end of the comparator circuit is sequentially connected with the first inverter and the second inverter; The clock dithering circuit comprises a MOS tube MP0 and a MOS tube MP1; The drain terminal of Mp0 and the drain terminal of Mp1 are commonly connected with a power supply, the gate terminal of Mp0 is connected with the output terminal of the second inverter, the gate terminal of Mp1 is connected with the output terminal of the first inverter, the source terminal of Mp0 is grounded, and the source terminal of Mp1 is connected with the first input terminal of the comparator.
3. The RC oscillator circuit based on laser trimming according to claim 2, wherein the RC charge-discharge circuit comprises a MOS transistor Mp2, a source terminal of the Mp1 is connected to a drain terminal of the Mp2, a gate terminal of the Mp2 is connected to an output terminal of the first inverter, and a source terminal of the Mp2 is grounded.
4. The RC oscillator circuit of claim 2, wherein the output of the first inverter is coupled in series with an inverter for output.
5. The RC oscillator circuit of claim 1, further comprising a buffer circuit, wherein the output of the comparator is coupled in series with the buffer circuit to output an oscillating signal.

Description

RC oscillator circuit based on laser trimming Technical Field The invention relates to the technical field of RC oscillators, in particular to an RC oscillator circuit based on laser trimming. Background Some application systems exist in the electronic product, besides a main CPU, clocks are needed inside some interface chips, and the clock frequency precision and stability are required, so that two schemes can be adopted, one scheme is that the interface chip is also externally provided with a crystal oscillator, so that high precision can be obtained, but the chip needs to be led out of two pins, and the cost of the application system is high; the other way is to use a built-in RC oscillator for the interface chip, the cost of the scheme is very low, the pin number is not increased, but the precision and stability of the RC oscillator are not high, the traditional method for improving the RC oscillation precision is to perform in-process measurement before packaging in the chip production process, and perform fine adjustment correction on R or C in a bare chip by using a laser photoetching method, the method requires in-process measurement in the chip production process and correction on chip by chip according to the test result, so the test cost is relatively high, the scheme is not acceptable for low-value chips, and the oscillator is needed in any way. The conventional RC oscillator has low absolute precision of oscillation frequency, because the variation of the resistance and capacitance in the chip along with the process is about 20%, or the calibration of clock frequency is needed during wafer CP (wafer test), and then the calibrated Trim value (voltage regulating value) is written into the memory cells such as FLASH, EEPROM or OTP, thus requiring special process support or additional MASK, increasing the cost and prolonging the manufacturing period. Disclosure of Invention The invention aims at the technical problem that the absolute precision of the oscillation frequency of the traditional RC oscillator is lower in the prior art. The invention provides an RC oscillator circuit based on laser trimming, which comprises: A bias voltage generating circuit for generating a standard voltage VREF, an RC charge-discharge circuit, a comparator circuit, and a clock jitter circuit for reducing clock jitter; the input end of the clock dithering circuit is connected with a power supply, the output end of the clock dithering circuit is connected with one end of the RC charge-discharge circuit and then connected to the first input end of the comparator, and the other end of the RC charge-discharge circuit is grounded; And a second input end of the comparator is connected with a standard voltage VREF, and an output end of the comparator outputs an oscillating signal. Preferably, the RC oscillator circuit further comprises a first inverter and a second inverter connected in series, and the output end of the comparator circuit is sequentially connected with the first inverter and the second inverter; The clock dithering circuit comprises a MOS tube MP0 and a MOS tube MP1; The drain terminal of Mp0 and the drain terminal of Mp1 are commonly connected with a power supply, the gate terminal of Mp0 is connected with the output terminal of the second inverter, the gate terminal of Mp1 is connected with the output terminal of the first inverter, the source terminal of Mp0 is grounded, and the source terminal of Mp1 is connected with the first input terminal of the comparator. Preferably, the RC charge-discharge circuit includes a MOS transistor Mp2, a source terminal of the Mp1 is connected to a drain terminal of the Mp2, a gate terminal of the Mp2 is connected to an output terminal of the first inverter, and a source terminal of the Mp2 is grounded. Preferably, the output end of the first inverter is connected in series with an inverter for output. Preferably, the RC oscillator circuit further includes a buffer circuit, and the output end of the comparator is connected in series with the buffer circuit and outputs an oscillating signal. Preferably, the RC charge-discharge circuit further comprises a capacitor trimming circuit, the capacitor trimming circuit comprises a fuse and a voltage-regulating MOS tube, one end of the capacitor is connected with the output end of the clock dithering circuit, the other end of the capacitor is connected with the drain end of the voltage-regulating MOS tube, the gate end of the voltage-regulating MOS tube is connected with a power supply through the fuse, and the source end of the voltage-regulating MOS tube is grounded. Preferably, one ends of the capacitors of the capacitor trimming circuits are connected in parallel and then connected with the output end of the clock dithering circuit. Preferably, the RC charge-discharge circuit further includes a capacitance trimming circuit, where the capacitance trimming circuit is implemented by adding a weak pull-down mode of a current mirror