Process, voltage and temperature optimized asynchronous SAR ADC
A method of enhancing SAR ADC performance includes employing PVT processor to correct process, voltage and temperature (PVT) variation. The PVT processor senses process, supply voltage and temperature information then maximize the time for SAR binary search process. The PVT processor first applies coarse optimization to correct process and voltage variation then applies fine optimization to correct the temperature variation. The SAR ADC is operated at its optimized PVT condition and its performance is enhanced after PVT optimization.
1. A converter, comprising:
a Successive Approximation Register Analog-to-Digital Converter (SAR ADC); and
a Process, Voltage and Temperature (PVT) processor coupled with the SAR ADC to enhance asynchronous self-time ADC performance, wherein the processor performs coarse optimization and first sets a regulator voltage based on ADC supply voltage; then sets a coarse bit-test clock delay based on a process sensor, then decreases a supply voltage to deassert a done signal and then increases the supply voltage to assert the done signal to obtain an optimized time delay.
2. The converter of claim 1 , wherein PVT processor comprises a temperature sensor, a process sensor, a PVT optimization code, and voltage regulator, wherein the temperature sensor and the process sensor render information to the PVT optimization code to set variables to control voltage regulator and SAR ADC.
3. The converter of claim 1 , comprising a PVT optimization code that of adjusts the bit-test clock delay of self-time asynchronous SAR ADC and the supply voltage to maximize the time of binary search process to enhance DAC and Reference settling response.
4. The converter of claim 1 , comprising a PVT optimization code for coarse optimization and fine optimization, wherein the coarse optimization corrects process and supply voltage variation by adjusting coarse bit-test clock delay and supply voltage; and wherein the fine optimization corrects temperature variation by adjusting fine bit-test clock delay and supply voltage.
5. The converter of claim 1 , comprising a PVT optimization code that introduces a done signal to check the status of the binary search process, wherein the done signal check is repeated to avoid spontaneously erroneous result.
6. The converter of claim 4 , comprising a coarse optimization followed by a fine optimization to assure PVT optimization algorithm convergence, wherein a plurality of fine optimization are executed to maintain an optimization status of SAR ADC.
7. The converter of claim 4 , comprising a fine optimization that includes setting the fine bit-test clock delay based on temperature sensor; decreasing supply at fine step to deassert the done signal and then increasing the supply voltage at a fine step to assert done signal to obtain an optimized time delay.
8. The converter of claim 2 , wherein the process sensor comprises a series of delay elements and flip-flops, wherein the delay elements are coupled to flip-flops, the clock input of flip-flops are all coupled together, wherein a voltage pulse is asserted and the clock is asserted at the center of the delay elements time delay, the number of “1” and “0” of flip-flops outputs represents process delay information.
9. The converter of claim 2 , wherein temperature sensor comprises a series of resistor elements and comparators, a Proportional to Absolute Temperature (PTAT) current, and constant voltage inputs, wherein the PTAT current is coupled to the resistor elements and comparators, and the constant voltage is coupled to a second comparator input and a second comparator output is a thermometer code representing a temperature condition.
10. A method for data conversion, comprising:
applying a Process, Voltage and Temperature (PVT) processor and performing coarse optimization and fine coarse optimization,
wherein the coarse optimization first sets a regulator voltage based on ADC supply voltage; then sets a coarse bit-test clock delay based on a process sensor, then decreases a supply voltage to deassert a done signal and then increases the supply voltage to assert the done signal to obtain an optimized time delay;
adjusting a bit-test clock delay and supply voltage based on the optimization; and
performing Successive Approximation Register Analog to Digital Conversion (SAR ADC) with a predetermined ADC reference settling based on the adjusted bit-test clock delay and supply voltage.
11. The method of claim 10 , wherein PVT processor comprises a temperature sensor, a process sensor, a PVT optimization code, and a voltage regulator, comprising using the temperature sensor and the process sensor information to set variables to control the voltage regulator.
12. The method of claim 10 , comprising adjusting the bit-test clock delay of self-time asynchronous SAR ADC and the supply voltage to minimize a binary search time to enhance DAC and Reference settling response.
13. The method of claim 10 , comprising performing coarse optimization and fine optimization, wherein the coarse optimization corrects process and supply voltage variation by adjusting coarse bit-test clock delay and supply voltage.
14. The method of claim 10 , comprising controlling a done signal to check the status of the binary search process, wherein the done signal check is repeated to avoid spontaneously erroneous result.
15. The method of claim 10 , wherein the coarse optimization is applied first and followed by a fine optimization to assure PVT optimization convergence, wherein a plurality of fine optimization are executed to maintain an optimization status of SAR ADC.
16. The method of claim 10 , wherein the fine optimization comprises setting the fine bit-test clock delay based on temperature sensor; decreasing supply at fine step to deassert the done signal and then increasing the supply voltage at a fine step to assert done signal to obtain an optimized time delay.
17. The method of claim 11 , wherein the process sensor comprises a series of delay elements and flip-flops, wherein the delay elements are coupled to flip-flops, the clock input of flip-flops are all coupled together, wherein a voltage pulse is asserted and the clock is asserted at the center of the delay elements time delay, the number of “1” and “0” of flip-flops outputs represents process delay information.
18. The method of claim 11 , wherein temperature sensor comprises a series of resistor elements and comparators, a Proportional to Absolute Temperature (PTAT) current, and constant voltage inputs, wherein the PTAT current is coupled to the resistor elements and comparators, and the constant voltage is coupled to a second comparator input and a second comparator output is a thermometer code representing a temperature condition.