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

Presentation Outline INTRODUCTION LINEAR REGULATOR CONCEPTS CIRCUIT IMPLEMENTATION PERFORMANCE ANALYSIS CONCLUSION

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

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

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

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

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

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

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

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

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

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

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

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

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

Linear Regulator PSRR (POWER SUPPLY REJECTION RATIO) It has PSRR of 42dB @1Khz 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

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 PSRR@1KHZ 42 Δvout(Undershoot) 144 mV Δvout(Overshoot) Low-Dropout Regulator with modest ripple and rugged performance in 180nm 15

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

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