Design of Voltage

References

BMR and BGRBy

Gaurish Nadkarni

Honor Pledge:- I have neither given nor received any unauthorized help on this project

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Calculation of Threshold voltage

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HAND CALCULATIONS - BMR

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BASIC CIRCUIT - BMR

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Vref and Iref with Supply and Temperature Sweep - BMR

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Sensitivity of Vref to Supply Voltage and Temperature Variations - BMR

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What TC of Resistance can give a better TC for Vref?

For a resistor with TC=2000 ppm

For a resistor with TC=2150 ppm

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Start-Up and PSRR - BMR

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HAND CALCULATIONS - BGR

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BASIC CIRCUIT - BGR

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Vref and Iref with Supply and Temperature Sweep - BGR

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Sensitivity of Vref to Supply Voltage and Temperature Variations - BGR

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Start-Up and PSRR - BGR

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Conclusions

Process – AMI 0.5u Given Specs Achieved Specifications for BMR Achieved Specifications for BGR

Supply (V) 5 5 5

Vref (V) 1.26 1.2608 1.2608

Max Supply Sensitivity (ppm) within ±10% of VDD 500 138.888 ppm 357.143 ppm

Max Temp Sensitivity (ppm @ 'C) 25 @ 50 -3253.97 ppm @ 50 4.7619 ppm @ 50

Max Power consumption (uW) 3 1.2 uW 2.075 uW

Iref (uA) 0.1 0.117 uA 0.102 uA

DIref with DVTHn = 10% and DVTHp = 10% around nominal value 0.73 nA 9.3 pA

DIref with DR= 10% around nominal value 39.85 nA 20.621 nA

DIref with DVDD = 10% around nominal value 18.141 pA 13 pA

DVref with DVTHn = 10% and DVTHp = 10% around nominal value 0.1369 V 0.26 mV

DVref with DR= 10% around nominal value 73.38 mV 5.61 mV

DVref with DVDD = 10% around nominal value 33.63 uV 90 uV

Minumum/Maximum Supply Voltage that the circuit is still working Approx 2.9 V Approx. 4 V

TCIref (ppm) 671ppm/C (i.e. 33567.0513ppm) 1676ppm/C (i.e. 83803 ppm)

TCVref (ppm) -65.376ppm/C(i.e -3253.97 ppm) 0.0953ppm/C (i.e. 4.7619 ppm)

Total Power Consumption (uW) 1.2 uW 2.075

Resistor Value (Ohm) and TCR1 3.431meg/2400ppm 400k/1500ppm & 3.5222M/1500ppm

Vref and Iref within temp sweep (-20 to 100 'C) Refer the waveforms Refer the waveforms

Vref and Iref within supply sweep (10% to 150%) Refer the waveforms Refer the waveforms

Power Supply Rejection Ratio (PSRR) for Vref and Iref Approx. -40 dB Approx. -75 dB

Startup delay (Apply a square or step input waveform to VDD and show the

transent response for Vref and Iref) tr=tf=25u 750 usec 800 usec

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Challenges

BMR

• Achieving temperature sensitivity was very difficult.

• Probably a resistor made using a combination of resistors made of different materials might be useful to achieve better sensitivity

• Designing start-up circuit for low power was crucial. The capacitor helps to reduce the static current consumption thus reducing power

• Getting exact current of 0.1uA was difficult as the W/L ratio was not perfect match as required for the given current value

BGR

• Designing start up circuit for low power was crucial. Just like BMR the capacitor helps to reduce power consumption here as well.

• The sensitivity of Vref to supply variations was quiet poor and hence there was a need to add a third cascode stage to the PMOS current mirror. Since the supply voltage was 5 volts this was possible. Other possible methods could have been to use a differential amplifier instead of cascoding.

References• CMOS Circuit Design, Layout and Simulation 3rd Edition, R Jacob Baker

• Analysis and Design of Analog Integrated Circuits, 5th Edition Grey and Meyer

• Voltage References, Akio Kitagawa, Kanazawa University

• Design of Wide-Swing Cascode Beta Multiplier Current Reference, Bradley David Miser, University of Tennessee - Knoxville

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