1. Low-Dropout Regulator with
modest ripple and rugged performance in 180nm

2. Presentation Outline INTRODUCTION LINEAR REGULATOR CONCEPTS
CIRCUIT IMPLEMENTATION
PERFORMANCE ANALYSIS
CONCLUSION

3. Solution for above mentioned problems is to use a power converter
INTRODUCTION
Supplying and conditioning power are the most fundamental functions of an electrical system.
A loading application cannot sustain itself without energy, and cannot fully perform its functions without a stable supply
Transformers, generators, batteries, and other off-line supplies incur substantial voltage and current variations across time and over a wide range of operating conditions
High frequency switching circuits CPU and DSP circuits utilized in an application usually load it.
Solution for above mentioned problems is to use a power converter
Low-Dropout Regulator with modest ripple and rugged performance in 180nm 1

4. CONCEPT OF LINEAR REGULATOR
to sense and generate
a correcting signal
(high voltage gain)
stable dc-bias voltage impervious to noise, temperature, and input-supply voltage variations
pass device to mediate and conduct whatever load current is required from the unregulated input supply to the regulated output
to sense the output
reacts to offset and cancel effects of load current, input voltage, temperature, and an array of other variations on the output 2
Low-Dropout Regulator with modest ripple and rugged performance in 180nm

5. Transient response of LDO
LINEAR REGULATOR
Transient response of LDO
LDO provide power to low-voltage digital circuits operating under different modes of operation --voltage transients-cannot be handled by digital circuits
Factors affecting transient response of an LDO
The internal compensation of the LDO
The amount of output capacitance
The parasitics of the output capacitor
The faster local feedback n/w responds quicker to load changes than more complicated regulator loop
The additional loop has negligible effects on dc accuracy as its low frequency gain is kept well below that of the regulator
The additional loop also demand little to no current to have less impact on operational life of battery
Low-Dropout Regulator with modest ripple and rugged performance in 180nm 3

6. REGULATING PERFORMANCE
LINEAR REGULATOR
REGULATING PERFORMANCE
LOAD REGULATION
Steady-state (dc) voltage variations in the output (ΔVOUT) resulting from dc changes in load current (ΔILOAD) define load regulation(LDR) performance
Systematic input-offset voltages, which result from asymmetric currents and volt-ages in the feedback error amplifier, further degrade load-regulation performance
Even if the LDO were symmetric, its widely variable load would cause considerable voltage swings at internal nodes, subjecting some of the devices to asymmetric conditions
LINE REGULATION
Line regulation(LNR) performance is a dc parameter and it refers to output voltage variations arising from dc changes in the input supply
Power-supply variations affect the regulator in two ways
Directly through its own supply
Indirectly via supply-induced variations in reference VREF
Low-Dropout Regulator with modest ripple and rugged performance in 180nm 4

7. PROCESS AND TEMPERATURE INDEPENDENT BIASING
LINEAR REGULATOR
PROCESS AND TEMPERATURE INDEPENDENT BIASING
The transconductance of MOSFETs determine performance parameters: small signal gain, speed and noise.
It is desirable to bias the transistors such that their transconductance is independent of process, supply voltage and temperature
Low-Dropout Regulator with modest ripple and rugged performance in 180nm 5

8. Circuit Implementation
LINEAR REGULATOR
Circuit Implementation
PASS TRANSISTOR
FEED BACK NETWORK
PROCESS AND TEMPERATURE INDEPENDENT BIASING
FEEDBACK NETWORK
ERROR AMPLIFIER
ERROR AMPLIFIER
FAST REACTING PATHS
FAST REACTING PATHS
Low-Dropout Regulator with modest ripple and rugged performance in 180nm 6

9. FIRST REACTING PATH Linear Regulator FIRST FAST REACTING PATH
Low-Dropout Regulator with modest ripple and rugged performance in 180nm 7

10. FIRST REACTING PATH Linear Regulator SECOND FAST REACTING PATH
When load current output voltage
The loop results in
of Vgs of Mf4
which is coupled through cm2 to input of M18
Its operation current
leads to in drive for Mp restoring output voltage to its
original value
Low-Dropout Regulator with modest ripple and rugged performance in 180nm 8

11. FIRST REACTING PATH Linear Regulator THIRD FAST REACTING PATH
Transistors Mf6-Mf9, Mp, and feedback resistors R1-R2 form the third self-reacting path
Transistors Mf6-Mf9 constitute an error amplifier
When load current the output voltage
The output voltage of error amplifier leading to drive for M18
Gate voltage of Mp thus restoring the output voltage
Low-Dropout Regulator with modest ripple and rugged performance in 180nm 9

12. means a stable LDO and enough gain for a high output voltage accuracy
Linear Regulator AC ANALYSIS
Parameter
Iload(0mA)
Iload(100mA)
Loop gain
62dB
72dB
Phase margin
92.61o
95.38o
The Phase Margin for this load current range is above 95O, loop-gain is about 72dB
means a stable LDO and enough gain for a high output voltage accuracy
Low-Dropout Regulator with modest ripple and rugged performance in 180nm 10

13. Parameter Measured units
Linear Regulator DC ANALYSIS
Parameter
Measured
units
Line Regulation 1
mV/V
Load Regulation
0.162
mV/mA
Low-Dropout Regulator with modest ripple and rugged performance in 180nm 11

14. For a load current pulse of 100mA step with 1s rise and fall times
Linear Regulator TRANSIENT ANALYSIS
Parameter
Measured
units
OVERSHOOT 97 mV
UNDERSHOOT
144
For a load current pulse of 100mA step with 1s rise and fall times
Low-Dropout Regulator with modest ripple and rugged performance in 180nm 12

15. means a stable LDO and It has ripple voltage equal to 0.9 mv
Linear Regulator RIPPLE IN OUTPUT VOLTAGE
It has ripple voltage equal to 0.9 mv
means a stable LDO and
high output voltage accuracy
Low-Dropout Regulator with modest ripple and rugged performance in 180nm 13

16. Linear Regulator PSRR (POWER SUPPLY REJECTION RATIO)
It has PSRR of
At low frequencies the PSRR is very high which results in high suppression of disturbances from the supply line. In the higher frequency area of > 1 MHz the PSRR gets very small and even reaches 0 dB at 6 MHz. This means that a 1 MHz signal would pass through the regulator without attenuation
Low-Dropout Regulator with modest ripple and rugged performance in 180nm 14

17. Parameter Measured Units Summary of measured performance
LINEAR REGULATORS MEASURED PERFORMANCE
Summary of measured performance
Parameter
Measured
Units
Technology
0.18 mM
Loop gain
@full load current
@zero load current 71 62 dB
Line regulation
0.989
mV/V
Load regulation
0.162
mV/mA 42
Δvout(Undershoot)
144 mV
Δvout(Overshoot)
Low-Dropout Regulator with modest ripple and rugged performance in 180nm 15

18. Conclusion LDO regulator targeted for SOC applications
(optimized design for performance, board area, and cost)
LDO is stable for output current in the complete range from 0 to 100 mA
LDO with high regulation accuracy and fast transient response
Low-Dropout Regulator with modest ripple and rugged performance in 180nm 16

19. REFERENCES
[1] Sai Kit Lau, K.N. Leung, and P.K.T. Mok,“Analysis of low-dropout regulatorTopologiesfor low-voltageregulation”,inIEEE Conference of Electron Devices and Solid-StateCircuits,December2003
[2] P.Hazucha,T.Karnik,B.A Bradley,C. Parsons,D.Finan,and S.Borkar,”area –efficient
linear regulator withultra fast load regulation,” IEEE J. Solid-StateCircuits, vol. 40,
no. 4, pp , Apr. 2005
[3] P. Y. Or and K. N. Leung, “An output-capacitorless low-dropout regulator with direct voltage-spike detection,” IEEE J. Solid-State Circuits, vol. 45, no. 2, pp , Feb
[4] T. Y. Man, K. N. Leung, C. Y. Leung, P. K. T. Mok, and M. Chan,“Development of single-transistor control LDO based on flipped voltage follower for SoC,” IEEE Trans.Circuits Sys. I, vol. 55, no. 5, pp , Jun
[5]Texas Instruments, “Fundamental theory of PMOS low-dropout voltage regulators”,TexasInstruments Inc., SLVA068, Dallas, TX, USA, April 1999.
[6]Chester Simpson, “Linear and switching voltage regulator fundamentals”, NationalSemiconductor Corporation, Santa Clara, CA, USA, 1995.
[7] Chia-Min Chen,Chung-Chih Hung, “A Fast Self-Reacting Capacitor-less Low-Dropout Regulator, ” IEEE Trans. Circuits Syst. I, pp , Sept. 2011
[8]Frederik Dostal, “How and when to use low dropout linear regulators”, Embedded ControlEurope Magazine, pp March 2004 Issue.
[9]R. J. Milliken, J. Silva-Martinez and E. Sanchez- Sinencio, “Full onchipCMOS low-dropout voltage regulator,” IEEE Trans. Circuits Syst. I,vol. 54, no. 9, pp , Sept
[10]S. K. Lau, P. K. T. Mok, and K. N. Leung, “A low-dropout regulator forSoC with Q-reduction,” IEEE J. Solid-State Circuits, vol. 42, no. 3, pp , Mar
[11] D.A.Johns, K.Martin, “Analog Integrated Circuit Design,” John Wiley and Sons Inc, U.K., (1997)
Low-Dropout Regulator with modest ripple and rugged performance in 180nm 17

20. Queries?