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Power Management Circuits

Jeongjin Roh, Ph.D.jroh@hanyang.ac.kr

Hanyang University

Outline and References• Introduction

• Linear Voltage Regulators

• Charge Pumps

• Inductor-type Switching Converters

References

1. Power Management Techniques for Integrated Circuit Design, K.-H. Chen.

2. CMOS VLSI Design, fourth edition, Weste & Harris.

3. Fundamentals of Power Electronics, second edition, Erickson & Maksimovic.

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Introduction

3

PMIC (Power Management IC)

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LCD Bias

PMIC

Smart Phone

PMIC

LED

PMIC

Battery

PMIC

Provide stable output voltage for electronic equipment with high power efficiency

Great increase in market

General Structure of Power Management ICs

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PMIC – Display Applications

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LED backlight driver - Thin and light

- Simple circuit

- Mercury free

- Low voltage driving

- Low power consumption

- Low temperature operation

- Fast response: wide dimming range

- Easy channel balancing[ LED backlight driver ]

Electric Vehicles

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Vehicle is not mechanical product anymore- It is becoming electric/electronic product

[ LED backlight driver ]

PMIC – Mobile Applications

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Mobile system includes various functions even if its battery-based power system.

Multi-output voltages are necessary for various function blocks.

[ Smart PMIC block diagram ][ Mobile system block diagram ]

PMIC– Mobile Applications, cont’d

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“A highly integrated power management IC foradvanced mobile applications”, IEEE JSSC 2007.by Qualcomm

Power Management Units

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• Typical Linear Voltage Regulators

• Low Drop-Out Regulators

Linear Voltage Regulators

• Switched-Capacitor (or Charge Pump) Converters

• Inductor-Type Switching Converters

Switching Power Converters

Linear Voltage Regulators

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Linear Regulators

(a) Regulator with source follower output stage

12

_

+VREF

IBIAS ILOADC

M0

VIN

A0

VG

VOUT

VSS

(c) Common-source output stage

Linear Regulators

Output capacitor with equivalent series resistance (ESR)

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Linear Regulators

Pass transistor types. (a) NPN Darlington, (b) NPN, (c) PNP, (d) NMOS, (e) PMOS, (f) NMOS with charge pump

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Linear Regulators

각 pass transistor type 별장단점

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Linear Regulators

(a) 기본적인 LDO regulator 의회로도

(b) pole-splitting with Miller capacitance CGD. (no output capacitor)

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Linear Regulators

(a) Large output capacitor for sudden load current variation

(b) Root locus of poles due to the output capacitor

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Linear Regulators

주파수특성을좋게하기위한 buffer stage 추가

(Buffer 추가로 pass transistor 의 gate 단에서의저항성분감소목적)

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Linear Regulators

Buffer stage 의구현예 (기본적인 source follower 회로)

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Linear Regulators

향상된 buffer 회로예 (feedback 을통한 buffer 의 output resistance 감소)

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Charge Pumps

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Charge Pump 응용예 – Flash Memory 1

NAND Flash Memory (Toshiba 1989)

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64Gb NAND Flash Memory (Toshiba 2009)

Charge Pump 응용예 – Flash Memory 2

NAND Flash string.

(ssl: string select line, gsl: ground select line)

• word 신호들은 active low 신호임.

• 총 16개 word 신호들중선택된한개만 low, 나머지는모두 high.

• 각 bit line 들은 pull-up 되어있음.

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Floating gate NMOS transistor,

& Erase and Program operations

Charge Pump 회로예

Diode 를사용한회로예

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CMOS 회로구현예

Charge Pump 설계예

(잘못된설계예임. 수업시간토론목적.)

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Inductor-Type SwitchingConverters

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Inductor and Capacitor

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vL

iL1

CiCv 1

2

21 vCW

2

21

LiLW

dt

dt

(J)

(J)

C

iC

v

iL L

v

Current:

Energy:

Current:

Energy:

Converter

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+

v(t)

-

R

Vg(t)

+

vs(t)

-

DTs Ts t

Vs(t)

Vg

On Off

offon

on

TTTCycleDuty

ggss

T

ss

Tss DVVDTT

dttvT

vs

)(1)(10

Duty Cycle

SPDT switch and a load

Buck Converter

+

v(t)

-

C R

L

Vg

12

iL(t)

Switch1 Switch2

+

V(t)

-

C R

L

Vg

iL(t)+

V(t)

-

C R

L

Vg iL(t)

Buck Converter

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Buck Converter analysis

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Switch1

Inductor voltage and Capacitor current

Small ripple approximation :

)(tvvv gL

VVv gL

Switch2

Inductor voltage and Capacitor current

Small ripple approximation :

)(tvvL

VvL

Rtvii Lc /)(

RVIic /

Rtvii Lc /)(

RVIic /

Inductor volt-second balance: applied to inductor over one switching period

Equation to zero and collect terms

The voltage conversion ratio is therefore

ssg

Ts

L TDVDTVVdttv ')()()(0

0)'( DDVDVg gDVV

DVVDM

g

)(

Buck Converter analysis

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Voltage ripple

t

V

Actual waveform v(t)=V+Vripple(t)

DC component V

Actual output voltage

Waveform

In a well-designed converter, the output voltage ripple is small. Hence the waveform can be easily approximated by ignoring ripple

-> Small ripple approximation

VtvVv

tvVtv

ripple

ripple

)(,

)()(

Small Ripple Approximation

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Boost Converter

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Boost Converter

Switch1 Switch2

+

V

-

C R

L

Vg

)(tiL+

V(t)

-

C R

L

Vg

)(tiL

Boost Converter analysis

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Net volt-seconds applied to inductor over one switching period

Equation to zero and collect terms

The voltage conversion ratio is therefore

t

VL(t)

Vg

DTs D`Ts

Vg-V

sgsg

Ts

L TDVVDTVdttv ')()()(0

0')'( VDDDVg

DDVVDM

g

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'1)(

'DV

V g

Boost Converter analysis

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Switch1

Inductor voltage and Capacitor current

Small ripple approximation :

Switch2

Inductor voltage and Capacitor current

Small ripple approximation :

Rvivv cgL /

RViVv cgL /

Rviivvv LcgL /

RvIivVv cgL /

Boost Converter analysis

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Capacitor charge balance

Collect terms and equate to zero

Eliminate V to express in terms of Vg

ssTs

c TDRVIDT

RVdtti ')()()(

0

0')'( IDDDRV

RDVI'

RD

VI g

'2

t

iC(t)

-V/R

DTs D`Ts

I - V/R

Basic Buck Converter• Basic DC-DC converter without

protection circuits

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VoutL

CR1

R2

Rload

Vg

compensator

bufferand

deadtimecontroller

S-Rlatchsawtooth

wavegenerator

comparator

clock

error ampVFB

Vref

reset

S

R

Qclock

generator

Vc

Sawtooth Waveform

• Sawtooth waveform and clock generator

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Vb

VCC

Ib

M1

clock

Comparator

Vsawtooth

C

Buffer and Non-Overlapping Circuit

• Large power transistor requires buffer block• Non-overlapping to reduce shoot-through current in

power transistor

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Pdr_b

Ndr

VCC

VSS

VCC

VSS

PI Compensator

• OTA and external R-C components

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1C

1R2C

OTAVc

OTA Error Amplifier• Conventional Mirror OTA

– Load cap=10pF– Tail current=200uA, quiescent output current=400uA

• Cascoded output may be used for higher gain– Drawback: limited output swing

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VpVn

Vo

M1 M2

M3 M4

It

M0

M6

M8M7

M5

Vss414 1

Vb

High-Performance Error Amp.• Gain Boosting Technique

• Load cap=10pF• Tail current=200uA, quiescent output current=40uA

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VpVnVo

M1 M2

M3 M4

It

M0

M6

M8M7

M5

Vcc

Vss

M9 M10

M12M11

M13 M14

41814 1 8 1

Vb

Current Sense Schemes• Current sense resistor in series with power transistor

• Most accurate technique• Additional resistance causes higher power loss

• Use turn-on resistance of power transistor for current sense

• Turn-on resistance varies too much for process, temperature, etc.

• Current sense circuits• accurate• Circuit design is complicated• Extra quiescent current loss

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Current Sense Circuit• Current sense circuit for Buck converter

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MP2

R

CO

L1

_ +

MS2

MR

M2 M1

MP1

MS1

MN1

VC

IO

VO

I1I1

VB

VQ

IP1IP2

Isen

Vadd

VIN

VA

VIN

VQ

Thank you.

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