LTC3562_技术文档

LTC3562

2

I C Quad Synchronous

Step-Down DC/DC Regulator

2 × 600mA, 2 × 400mA

DESCRIPTION

FEATURES

2

The LTC^®3562 is a quad high efﬁciency monolithic syn-

n

Four Independent I C Controllable Step-Down

2

Regulators (2 × 600mA, 2 × 400mA)

chronous step-down regulator with an I C interface. Two

2

n

Two I C Programmable Feedback Voltage

regulators are externally adjustable and can have their

feedback voltages programmed between 425mV and

800mV in 25mV steps (Type A). The other two regulators

are ﬁxed output regulators whose output voltages can be

Regulators (R600A, R400A): V 425mV to 800mV

FB

2

Two I C Programmable Output Voltage Regulators

(R600B, R400B): V

600mV to 3.775V

OUT

®

Programmable Modes: Pulse Skip, LDO, Burst Mode,

programmed between 600mV and 3.775V in 25mV steps

Forced Burst Mode Operation

(Type B). All four regulators operate independently and

can be put into pulse skip, LDO, Burst Mode operation,

Quiescent Current < 100μA (All Regulators Enabled

in LDO Mode)

2

or forced Burst Mode operation through I C control. The

Fixed 2.25MHz Switching Frequency (Pulse Skip

Mode)

Slew Limiting Reduces Switching Noise

Power-On Reset Output for Regulator R600A

Small, Thermally Enhanced, 20-Lead 3mm × 3mm

QFN Package

Type-A regulators have separate RUN pins that can be

2

enabled if I C control is unavailable.

n

The 2.85V to 5.5V input voltage range makes the LTC3562

ideally suited for single Li-Ion battery-powered applica-

tions. At low output load conditions, the regulators can

be switched into LDO, Burst Mode operation, or forced

Burst Mode operation, extending battery life in portable

systems. The quiescent current drops to under 100μA

with all regulators in LDO mode, and under 0.1μA when

all regulators are shut down.

APPLICATIONS

n

Miscellaneous Handheld Applications with Multiple

Supply Rails

n

Personal Information Appliances

Switching frequency is internally set to 2.25MHz, allowing

the use of small surface mount inductors and capacitors.

All regulators are internally compensated. The LTC3562 is

available in a low proﬁle 3mm × 3mm QFN package.

n

Wireless and DSL Modems

n

Digital Still Cameras

n

MP3 Players

n

Portable Instruments

L, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

TYPICAL APPLICATION

R600x Burst Mode Efﬁciency

High Efﬁciency Quad Step-Down Converter with I²C

and Power Loss vs Load Current

MICROPROCESSOR

100

10000

1000

100

10

V

= 3.3V

OUT

SDA

SCL

DV

+

Li-Ion/Polymer

3.4V TO 4.2V

90

10μF

V

OUT

2.5V

=

CC

V

= 1.2V

80

OUT

POR

V

IN

SCL SDA DV

CC

V

600A

100k

OUT

1.8V

70

V

OUT

1.8V

=

V

RUN400A

SW400A

OUT

4.7μH

475k

3.3μH

POR600A

SW600A

600mA

634k

60

50

400A

1.5V

LTC3562

10μF

10pF

10μF

400mA

FB600A

40

30

20

10

0

RUN600A

FB400A

499k

V

OUT

= 3.3V

V

= 1.2V,

536k

OUT

1.8V, 2.5V

1

4.7μH

3.3μH

V

400B

1.2V

V

600B

OUT

3.3V

600mA

V

= 3.8V

SW400B

OUT400B PGND AGND OUT600B

SW600B

IN

0.1

400mA

10μF

0.01

0.1

1

10

100

1000

3562 TA01

LOAD CURRENT (mA)

3562 TA01b

3562fa

1

LTC3562

ABSOLUTE MAXIMUM RATINGS

PIN CONFIGURATION

(Notes 1, 2)

TOP VIEW

V ...............................................................–0.3V to 6V

IN

RUN600A...................................... –0.3V to (V + 0.3V)

IN

RUN400A...................................... –0.3V to (V + 0.3V)

IN

20 19 18 17 16

FBx...............................................................–0.3V to 6V

SWx .............................................................–0.3V to 6V

OUTx............................................................–0.3V to 6V

POR600A

FB600A

OUT600B

SW600B

PGND

15

14

13

12

11

AGND

FB400A

OUT400B

SW400B

PGND

1

2

3

4

5

21

8

DV , POR600A, SDA, SCL .........................–0.3V to 6V

CC

SW400x

SW600x

I

(DC) ........................................................600mA

(DC) ........................................................850mA

6

7

9 10

Operating Temperature (Note 2)...............–40°C to 85°C

Storage Temperature Range...................–65°C to 125°C

Junction Temperature (Note 3) ............................. 125°C

UD PACKAGE

20-LEAD (3mm × 3mm) PLASTIC QFN

= 125°C, θ = 68°C/W

T

JMAX

JA

EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB

ORDER INFORMATION

LEAD FREE FINISH

TAPE AND REEL

PART MARKING

PACKAGE DESCRIPTION

20-Lead (3mm × 3mm) Plastic QFN

TEMPERATURE RANGE

–40°C to 85°C

LTC3562EUD#PBF

LTC3562EUD#TRPBF

LCPV

Consult LTC Marketing for parts speciﬁed with wider operating temperature ranges.

Consult LTC Marketing for information on non-standard lead based ﬁnish parts.

For more information on lead free part marking, go to: http://www.linear.com/leadfree/

For more information on tape and reel speciﬁcations, go to: http://www.linear.com/tapeandreel/

The l denotes the speciﬁcations which apply over the full operating

ELECTRICAL CHARACTERISTICS

temperature range, otherwise speciﬁcations are at T_A= 25°C, V_IN= 3.8V, unless otherwise noted.

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

l

V

Input Voltage Range

2.7

5.5

V

IN

Input Current (Per Regulator Enabled)

Pulse Skip Mode, I

= 0

OUT

220

35

μA

OUT

Burst Mode Operation, I

= 0

60

40

3

Forced Burst Mode Operation, I

= 0

25

OUT

LDO Mode, I

= 0

OUT

24

0.7

OUT

Shutdown Mode, I

= 0, DV = 1.8V

CC

V

Shutdown Current

All Regulators in Shutdown, DV = 0V

0.1

1

μA

V

IN

CC

l

RUN600A, RUN400A Input High Threshold

RUN600A, RUN400A Input Low Threshold

RUN600A, RUN400A Input High Current

RUN600A, RUN400A Input Low Current

POR600A Threshold

1.0

0.3

1

V

RUNx = V

–1

μA

%

Ω

IN

RUNx = 0V

1

Percentage of R600A’s Final Output Voltage

–8

16

POR600A On-Resistance

40

POR600A Delay

231

ms

3562fa

2

LTC3562

ELECTRICAL CHARACTERISTICS ^Thel denotes the speciﬁcations which apply over the full operating

temperature range, otherwise speciﬁcations are at T_A= 25°C, V_IN= 3.8V, unless otherwise noted.

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

2

I C Port

l

DV Operating Voltage

1.5

5.5

1

V

μA

V

CC

DV Operating Current

CC

DV = 1.8V, Serial Port Idle

CC

DV UVLO Threshold Voltage

CC

1

V

SDA, SCL (Low Level Input Voltage)

SDA, SCL (High Level Input Voltage)

SDA (Digital Output Low)

0.3 • DV

V

IL

CC

0.7 • DV

V

IH

OL

CC

I

= 3mA

0.08

V

PULLUP

Serial Port Timing (Note 4)

t

Clock Operating Frequency

Bus Free Time Between Stop and Start Conditions

Hold Time After (Repeated) Start Condition

Repeated Start Condition Setup Time

Stop Condition Setup Time

Data Hold Time

400

kHz

μs

ns

μs

ns

SCL

1.3

0.6

225

0

BUF

HD,STA

SU,STA

SU,STO

HD,DAT(OUT)

HD,DAT(IN)

SU,DAT

LOW

Input Data Hold Time

900

Data Setup Time

100

1.3

0.6

20

Clock Low Period

Clock High Period

HIGH

Clock Data Fall Time

300

f

Clock Data Rise Time

20

r

Spike Suppression Time

50

SP

The ldenotes the speciﬁcations which apply over the

BUCK DC/DC ELECTRICAL CHARACTERISTICS

full operating temperature range, otherwise speciﬁcations are at T_A= 25°C, V_IN= 3.8V, V_OUTx= 1.5V, unless otherwise noted.

PARAMETER

CONDITIONS

MIN

TYP

2.25

0.25

MAX

UNITS

Regulators R600A, R400A, R600B, R400B

f

1.91

100

2.59

MHz

%

OSC

Maximum Duty Cycle

Pulse Skip Mode

LDO Mode

Ω

LDO Mode Closed Loop R

OUT

Regulators R600A, R600B

PMOS Switch Current Limit

Pulse Skip Mode

850

1200

0.38

2.2

1500

mA

Ω

PMOS R

NMOS R

DS(ON)

Ω

LDO Mode Open Loop R

Available Output Current

LDO Mode

OUT

Forced Burst Mode

75

50

140

mA

LDO, V

= 1.2V

OUT

SW Pull-Down in Shutdown

Shutdown

2.5

kΩ

3562fa

3

LTC3562

ELECTRICAL CHARACTERISTICS ^Thel denotes the speciﬁcations which apply over the full operating

temperature range, otherwise speciﬁcations are at T_A= 25°C, V_IN= 3.8V, V_OUTx= 1.5V, unless otherwise noted.

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Regulators R400A, R400B

PMOS Switch Current Limit

Pulse Skip Mode

600

800

0.5

3

1000

mA

Ω

PMOS R

NMOS R

DS(ON)

Ω

LDO Mode Open Loop R

LDO Mode

OUT

SW Pull-Down in Shutdown

Available Output Current

Shutdown

2.5

100

kΩ

Forced Burst Mode

LDO Mode, V

50

mA

= 1.2V

OUT

Regulators R600A, R400A

l

V

DAC = XXX1111, Pulse Skip Mode

DAC = XXX0000, Pulse Skip Mode

0.776

0.412

0.800

0.425

25

0.824

0.438

V

FB(MAX)

FB(MIN)

FB(STEP)

(0 to 15)

mV

I

FB Input Current

DAC = XXX1111

FB

–50

0

50

nA

Regulators R600B, R400B

l

V

= 4V, DAC = 0000000, Pulse Skip Mode

= 4V, DAC = 1111111,

0.582

3.661

0.600

3.775

0.618

3.889

V

OUT(MIN)

OUT(MAX)

IN

V

Pulse Skip Mode

V

(0 to 127)

V

IN

= 4V

25

mV

OUT(STEP)

Note 1: Stresses beyond those listed under Absolute Maximum Ratings

may cause permanent damage to the device. Exposure to any Absolute

Maximum Rating condition for extended periods may affect device

reliability and lifetime.

Note 2: The LTC3562E is guaranteed to meet performance speciﬁcations

from 0°C to 85°C. Speciﬁcations over the –40°C to 85°C operating

temperature range are assured by design, characterization and correlation

with statistical process control.

Note 3: This IC includes overtemperature protection that is intended

to protect the device during momentary overload conditions.

Overtemperature protection is active when junction temperature exceeds

the maximum operating junction temperature. Continuous operation above

the speciﬁed maximum operating junction temperature may result in

device degradation or failure.

Note 4: The serial port is tested at rated operating frequency. Timing

parameters are tested and/or guaranteed by design.

3562fa

4

LTC3562

TYPICAL PERFORMANCE CHARACTERISTICS

Efﬁciency vs Load Current

100

90

100

90

100

90

FORCED

Burst Mode OPERATION

FORCED

Burst Mode OPERATION

FORCED

Burst Mode

OPERATION

80

Burst Mode

OPERATION

600mA

BUCKS

600mA

BUCKS

70

600mA

BUCKS

60

50

60

50

60

50

PULSE SKIP

Burst Mode

OPERATION

Burst Mode

OPERATION

40

30

20

10

0

40

30

20

10

0

40

30

20

10

0

PULSE SKIP

V

= 3.8V

= 1.2V

V

= 3.8V

= 2.5V

V

= 3.8V

= 1.8V

IN

OUT

IN

OUT

IN

OUT

0.01

0.1

1

I

10

(mA)

100

1000

0.01

0.1

1

I

10

(mA)

100 1000

0.01

0.1

1

I

10

(mA)

100

1000

OUT

3562 G01

3562 G03

3562 G02

Efﬁciency vs Input Voltage

Burst Mode Operation

Efﬁciency vs Input Voltage

Burst Mode Operation

Efﬁciency vs Load Current

100

90

100

90

80

70

60

50

40

30

20

10

0

100

90

80

70

60

50

40

30

20

10

0

V

= 1.8V

FORCED Burst Mode

OPERATION

V

= 1.2V

OUT

80

600mA

BUCKS

70

60

50

PULSE SKIP

Burst Mode

OPERATION

40

30

20

10

0

I

= 0.1mA

= 1mA

= 10mA

= 100mA

= 400mA

I

= 0.1mA

= 1mA

= 10mA

= 100mA

= 400mA

OUT

I

V

= 3.8V

= 3.3V

I

IN

OUT

I

OUT

0.01

0.1

1

10

(mA)

100

1000

2.5

3

4

4.5

5

5.5

3.5

2.5

3

4

4.5

5

5.5

3.5

INPUT VOLTAGE (V)

I

INPUT VOLTAGE (V)

OUT

3562 G04

3562 G06

3562 G05

Output Transient

Burst Mode Operation

Output Transient

Pulse Skip Mode

Start-Up Transient

Pulse Skip Mode

V

OUT400B

V

OUT600A

50mV/DIV

AC

50mV/DIV

AC

500mV/DIV

COUPLED

INDUCTOR

CURRENT

V

OUT400A

OUT600B

50mV/DIV

AC

50mV/DIV

AC

I

= 100mA/

DIV

L

COUPLED

300mA

5mA

300mA

5mA

I

OUT400B

RUN600A OFF

2V/DIV ON

3562 G07

3562 G08

3562 G09

50μs/DIV

V

I

= 1.2V

= 20mA

V

I

= 1.8V

= 1.2V

= 15mA

OUT400B

OUT400A

V

R

= 1.2V

OUT600A

LOAD

OUT400B

OUT600B

= 6Ω

3562fa

5

LTC3562

TYPICAL PERFORMANCE CHARACTERISTICS

R600A Feedback Voltage

vs Temperature

Oscillator Frequency

vs Temperature

Output Voltage

vs Load Current (B Version)

1.220

1.215

1.210

1.205

1.200

1.195

1.190

0.810

0.808

0.806

0.804

0.802

0.800

0.798

0.796

0.794

0.792

0.790

2.5

2.4

2.3

2.2

2.1

2.0

1.9

1.8

1.7

1.6

1.5

I

= 1mA

V

= 3.8V

OUT

IN

OUT

V

= 5.5V

= 1.2V (TYPE-B)

IN

V

= 3.8V

IN

V

= 3V

IN

V

= 2.7V

IN

PULSE SKIP

0

100

300

400

500

600

200

–50

–25

25

50

75

100

–50

–25

25

50

75

100

0

LOAD CURRENT (mA)

TEMPERATURE (°C)

3562 G12

3562 G10

3562 G11

Dynamic Supply Current

vs Input Voltage

Dynamic Supply Current

vs Input Voltage

Burst Mode Operation

45

40

35

30

25

20

6

5

4

3

2

1

0

I

= 0mA

I

= 0mA

= 1.2V

OUT

V

OUT600A

V

50mV/DIV

AC

COUPLED

Burst Mode OPERATION

SW

2V/DIV

INDUCTOR

CURRENT

= 100mA/

DIV

FORCED Burst Mode

OPERATION

I

L

3562 G15

2μs/DIV

LDO MODE

PULSE SKIP

OPERATION

PV = 3.8V

IN

LOAD = 50mA

4.5

5

2

2.5

3

3.5

4

5.5

3562 G14

6

2.7 3.1 3.5 3.9 4.3

4.7 5.1 5.5

VOLTAGE (V)

V

VOLTAGE (V)

IN

400mA – V

600mA – V

400mA – V

600mA – V

= 1.2V

= 1.8V

400mA – V

600mA – V

400mA – V

600mA – V

= 2.5V

OUT

3562 G13

OUT

= 2.5V

= 3.3V

OUT

Forced Burst Mode Operation

Output Voltage vs Load Current

Switch R_DS(ON)vs Input Voltage

700

600

500

400

300

200

100

0

V

1.22

1.21

1.20

1.19

1.18

1.17

1.16

1.15

1.14

1.13

1.12

OUT600A

50mV/DIV

AC

FORCED

Burst Mode

OPERATION

400mA PMOS

400mA NMOS

600mA PMOS

COUPLED

SW

2V/DIV

INDUCTOR

CURRENT

= 150mA/

DIV

LDO MODE

600mA NMOS

I

L

3562 G16

2μs/DIV

V

= 3.8V

IN

OUT

PV = 3.8V

IN

LOAD = 50mA

= 1.2V (TYPE-B)

20 60

LOAD CURRENT (mA)

2.7 3.1 3.5 3.9 4.3

VOLTAGE (V)

4.7 5.1 5.5

0

80 100 120 140

40

V

IN

3562 G17

3562 G18

3562fa

6

LTC3562

PIN FUNCTIONS

AGND (Pin 1): Analog Ground Pin. All small-signal com-

ponents should connect to this ground, which in turn

connects to PGND at one point.

OUT600B (Pin 13): Output Voltage Feedback Pin for

2

R600B. An I C programmable internal resistor divider

divides the output voltage down for comparison to the

internal reference voltage. This pin converges to 1 of

128 possible set-points based on the programmed value

FB400A (Pin 2): Feedback Pin for R400A. When the con-

trol loop is complete, this pin servos to 1 of 16 possible

2

from the I C serial port (see Tables 5 and 6). This node

2

set-points based on the programmed value from the I C

must be bypassed to GND with a 10μF or greater ceramic

capacitor.

serial port (see Table 4).

OUT400B (Pin 3): Output Voltage Feedback Pin for

FB600A (Pin 14): Feedback Pin for R600A. When the con-

2

R400B. An I C programmable internal resistor divider

trol loop is complete, this pin servos to 1 of 16 possible

divides the output voltage down for comparison to the

internal reference voltage. This pin converges to 1 of

128 possible set-points based on the programmed value

2

set-points based on the programmed value from the I C

serial port (see Table 4).

2

from the I C serial port (see Tables 5 and 6). This node

POR600A(Pin15):Power-OnResetforR600A.Thisopen-

drain output goes high impedance after a 230ms delay

after the output of R600A reaches 92% of its regulation

voltage. This output gets pulled to GND whenever R600A

falls below 92% of its regulation voltage.

must be bypassed to GND with a 10μF or greater ceramic

capacitor.

SW400B (Pin 4): Switch Node Connection to the Inductor

for R400B. This pin connects to the drains of the internal

power MOSFET switches of R400B.

RUN400A (Pin 16): Enable Pin for R400A, Active High.

Apply a voltage greater than 1V to enable this regulator.

PGND (Pins 5, 11): Power Ground Pin. Connect this pin

closely to the (–) terminal of C .

RUN600A (Pin 17): Enable Pin for R600A, Active Low.

Apply a voltage less than 0.3V to enable this regulator.

IN

SW400A (Pin 6): Switch Node Connection to the Inductor

for R400A. This pin connects to the drains of the internal

power MOSFET switches of R400A.

2

DV (Pin18):SupplyVoltageforI CLines.Thispinsetsthe

CC

logic reference level of the LTC3562. A UVLO circuit on the

DV pin forces all registers to a default setting whenever

CC

V

(Pins 7, 8, 9): Input Supply Pin. This pin must be

IN

DV is < 1V. Bypass to GND with a 0.1μF capacitor.

closely decoupled to GND with a 10μF or greater ceramic

2

capacitor.

SCL (Pin 19): I C Clock Input. Serial data is shifted one

bit per clock to control the LTC3562. The logic level for

SW600A(Pin10):SwitchNodeConnectiontotheInductor

for R600A. This pin connects to the drains of the internal

power MOSFET switches of R600A.

SCL is referenced to DV .

CC

2

SDA (Pin 20): I C Data Input. The logic level for SDA is

referenced to DV .

CC

SW600B(Pin12):SwitchNodeConnectiontotheInductor

for R600B. This pin connects to the drains of the internal

power MOSFET switches of R600B.

Exposed Pad (Pin 21): Ground. Must be soldered to

PCB ground for electrical contact and optimum thermal

performance.

3562fa

7

LTC3562

BLOCK DIAGRAM

17

RUN600A

16

RUN400A

DV

CC

V

IN

18

20

19

DV

CC

7, 8, 9

4

2

SDA

SCL

I C

EN

SDA

SCL

1

MODE DATA

R600A

2

7

4

REF600A

D/A

EN

SW600A

FB600A

10

14

0.425V-0.8V

REF

MODE

FB

R400A

4

REF400A

D/A

EN

SW400A

FB400A

6

2

0.425V-0.8V

REF

MODE

FB

R600B

AGND

1

7

EN

SW600B

OUT600B

12

13

0.6V

REF

MODE

FB

R400B

1

7

EN

SW400B

OUT400B

4

3

0.6V

REF

MODE

FB

POR600A

15

POWER GOOD

R600A

230ms Delay

PGND

5,11

3562 BD

3562fa

8

LTC3562

OPERATION

Introduction

2

Through I C control, V

can be programmed from

FBxA

800mV (full scale) down to 425mV in 25mV increments.

When the RUN pins (RUN600A and RUN400A) are used

to activate these regulators, the default feedback servo

voltage is set to 800mV.

The LTC3562 is a highly integrated power management

2

IC that contains four I C controllable, monolithic, high ef-

ﬁciency step-down regulators. Two regulators provide up

to 600mA of output current and the other two regulators

produce up to 400mA. All four regulators are 2.25MHz,

constant-frequency,currentmodeswitchingregulatorsthat

LTC3562

L

2

SWxA

can be independently controlled through I C. All regula-

C

O

R1

R2

FB

tors are internally compensated eliminating the need for

external compensation components.

FBxA

425mV to 800mV

The LTC3562 offers two different types of adjustable

step-downregulators. ThetwoType-Aregulators(R600A,

R400A) can have the feedback voltages adjusted through

GND

3562 F01

2

I C from 425mV to 800mV in 25mV increments. The two

Figure 1. Type-A Regulator Application Circuit

Type-B regulators (R600B, R400B) can have the output

2

voltages adjusted through I C control from 600mV to

Typical values for R2 are in the range of 40k to 1MΩ. The

capacitor C cancels the pole created by the feedback

3.775V in 25mV increments.

FB

resistors and the input capacitance of the FB pin and also

helps to improve transient response for output voltages

much greater than 0.8V. A variety of capacitor sizes can be

All four converters support 100% duty cycle operation

(low dropout mode) when their input voltage drops very

close to their output voltage. To suit a variety of applica-

tions, four selectable mode functions are available on

the LTC3562’s step-down regulators to trade-off noise

for efﬁciency.

used for C but a value of 10pF is recommended for most

FB

applications.Experimentationwithcapacitorsizesbetween

2pF and 22pF may yield improved transient response.

Regulators R600A and R400A have individual RUN pins

At moderate to heavy loads, the constant-frequency pulse

skipmodeprovidesthelowestoutputswitchingnoisesolu-

tion. At lighter loads, either Burst Mode operation, forced

Burst Mode operation or LDO mode may be selected to

optimize efﬁciency. The switching regulators also include

soft-start to limit inrush current when powering on, short-

circuit current protection, and switch node slew limiting

circuitrytoreduceradiatedEMI.Noexternalcompensation

components are required.

2

that can enable the regulators without accessing the I C

port. The RUN600A and RUN400A pins are OR’ed with the

2

enable signals coming from the I C port (refer to the Block

Diagram) such that regulators R600A and R400A can be

2

enabled if the I C port is unavailable. The RUN600A pin is

active low and the RUN400A pin is active high.

When the RUN pins are activated, the Type-A regulators

are enabled in a default setting. The default mode for the

regulators is pulse skip mode and the default feedback

servo voltage setting is 800mV. Once enabled with these

default settings, the settings can always be changed on

V

Adjustable (Type-A) Regulators

FB

ThetwoType-Astep-downregulators(R600AandR400A)

haveindividualprogrammablefeedbackservovoltagesvia

2

the ﬂy through I C once the I C terminal is available.

2

I C control. Given a particular feedback servo voltage, the

ThemaximumoperatingoutputcurrentofregulatorsR600A

and R400A are 600mA and 400mA, respectively.

outputvoltageisprogrammedusingaresistordividerfrom

the switching regulator output connected to the feedback

pins(Figure1).Theoutputvoltageisrelatedtothefeedback

servo voltage by the following equation:

R1

R2

ꢀ

ꢃ

ꢄ

V_OUTxA= V

+1

ꢅ

ꢂ

^FBxAꢁ

3562fa

9

LTC3562

OPERATION

V

Adjustable (Type-B) Regulators

thepeakinductorcurrenttotheoutputofanerrorampliﬁer.

The output of the current comparator resets the internal

latch which causes the main P-channel MOSFET switch to

turn off and the N-channel MOSFET synchronous rectiﬁer

to turn on. The N-channel MOSFET synchronous rectiﬁer

turns off at the end of the 2.25MHz cycle or if the current

through the N-channel MOSFET synchronous rectiﬁer

drops to zero. Using this method of operation, the error

ampliﬁer adjusts the peak inductor current to deliver the

required output power. All necessary compensation is

internal to the switching regulator requiring only a single

ceramic output capacitor for stability. At light loads in

pulse skip mode, the inductor current may reach zero

on each pulse which will turn off the N-channel MOSFET

synchronous rectiﬁer. In this case, the switch node (SW)

goes high impedance and the switch node voltage will

“ring.” This is discontinuous mode operation, and is

normal behavior for a switching regulator. At very light

loads in pulse skip mode, the switching regulators will

automatically skip pulses as needed to maintain output

OUT

Unlike the Type-A regulators, the two Type-B regulators

do not require an external resistor divider network to

program its output voltage. Regulators R600B and R400B

havefeedbackresistornetworksinternaltothechipwhose

2

values can be adjusted through I C control. These inter-

nal feedback resistors can be conﬁgured such that the

output voltages can be programmed directly. The output

voltages can be programmed from 600mV to 3.775V in

25mV increments.

Pins OUT600B and OUT400B are feedback sense pins that

connecttothetopoftheinternalresistordividernetworks.

These output pins should sense the output voltages of

the regulators right at the output capacitor C (after the

inductor), as illustrated in Figure 2.

O

ThemaximumoperatingcurrentforregulatorsR600Band

R400B are 600mA and 400mA, respectively. The Type-B

regulatorsdonothaveindividualrunpinsasdotheType-A

regulators. Thus regulators R600B and R400B can only

2

be enabled through control of the I C port. When the

regulation. At high duty cycle (V

> V /2) it is possible

OUT

IN

part initially powers up, the Type-B regulators default to

shutdown mode and remain disabled until programmed

for the inductor current to reverse at light loads, causing

thestep-downswitchingregulatortooperatecontinuously.

When operating continuously, regulation and low noise

outputvoltagearemaintained, butinputoperatingcurrent

will increase to a couple mA.

2

through I C.

Regulator Operating Modes

All of the LTC3562’s switching regulators include four

possible operating modes to meet the noise/power needs

of a variety of applications.

In forced Burst Mode operation, the switching regulators

use a constant-current algorithm to control the inductor

current. By controlling the inductor current directly and

using a hysteretic control loop, both noise and switch-

ing losses are minimized. In this mode output power is

limited. While operating in forced Burst Mode operation,

In pulse skip mode, an internal latch is set at the start of

every cycle which turns on the main P-channel MOSFET

switch.Duringeachcycle,acurrentcomparatorcompares

LTC3562

L

600mV to 3.775V

SWxB

C

O

OUTxB

GND

3562 F02

Figure 2. Type-B Regular Application Circuit

3562fa

10

LTC3562

OPERATION

the output capacitor is charged to a voltage slightly higher

than the regulation point. The step-down converter then

goes into sleep mode, during which the output capacitor

provides the load current. In sleep mode, most of the

regulator’s circuitry is powered down, helping conserve

battery power and increase efﬁciency. When the output

voltage drops below a predetermined value, the switching

regulator circuitry is powered on and another burst cycle

begins. The duration for which the regulator operates in

sleep mode depends on the load current. The sleep time

decreasesastheloadcurrentincreases.ForcedBurstMode

operation has a maximum deliverable output current of

about 140mA for the 600mA regulators and 100mA for

the 400mA regulators. Beyond the maximum deliverable

output current, the step-down switching regulator will not

enter sleep mode and the output will drop out of regula-

tion. Forced Burst Mode operation provides a signiﬁcant

improvement in efﬁciency at light loads at the expense of

higher output ripple when compared to pulse skip mode.

For many noise-sensitive systems, forced Burst Mode

operation might be undesirable at certain times (i.e.,

during a transmit or receive cycle of a wireless device),

but highly desirable at others (i.e., when the device is in

Dropout Operation

It is possible for V to approach a switching regulator’s

IN

programmedoutputvoltage(e.g.,abatteryvoltageof3.4V

with a programmed output voltage of 3.3V). When this

happens, the PMOS switch duty cycle increases until it is

turned on continuously at 100%. In this dropout condi-

tion, the respective output voltage equals the regulator’s

input voltage minus the voltage drops across the internal

P-channel MOSFET and the inductor.

Soft-Start Operation

Soft-start is accomplished by gradually increasing the

peak inductor current for each switching regulator over

a 500μs period. This allows each output to rise slowly,

helping minimize the battery in-rush current. A soft-

start cycle occurs whenever a given switching regula-

tor is enabled, or after a fault condition has occurred

(thermal shutdown). A soft-start cycle is not triggered

by changing operating modes. This allows seamless

output operation when transitioning between Burst

Mode operation, forced Burst Mode operation, pulse

skip mode or LDO mode.

2

low power standby mode). The I C port can be used to

Switching Slew Rate Control

enableordisableforcedBurstModeoperationatanytime,

offering both low noise and low power operation when

they are needed.

The step-down switching regulators contain new pat-

ent pending circuitry to limit the slew rate of the switch

node (SWx). This new circuitry is designed to transition

the switch node over a period of a couple nanoseconds,

signiﬁcantly reducing radiated EMI and conducted supply

noise, while keeping efﬁciency high.

InBurstModeoperation,theswitchingregulatorautomati-

callyswitchesbetweenﬁxedfrequencypulseskipoperation

and hysteretic control as a function of the load current. At

light loads the regulators operate in hysteretic mode and

at heavy loads they operate in constant-frequency mode.

The constant-frequency mode provides the same output

ripple and efﬁciency as pulse skip mode while hysteretic

mode provides slightly lower output ripple than forced

Burst Mode operation at the expense of slightly lower

efﬁciency.

Step-Down Switching Regulator in Shutdown

Thestep-downswitchingregulatorsareinshutdownwhen

not enabled for operation. In shutdown, all circuitry in

the step-down switching regulator is disconnected from

the switching regulator input supply, leaving only a few

nano-amps of leakage current. The step-down switch-

ing regulator outputs are individually pulled to ground

through a 2k resistor on the switch pin (SWx) when in

shutdown.

Finally, the switching regulators have an LDO mode that

gives a DC option for regulating their output voltages. In

LDOmode,theswitchingregulatorsareconvertedtolinear

regulators and deliver continuous power from their SWx

pins through their respective inductors. This mode gives

the lowest possible output noise as well as low quiescent

current at light loads.

3562fa

11

LTC3562

OPERATION

I C Interface

2

Acknowledge

TheLTC3562maycommunicatewithahost(master)using

The Acknowledge signal is used for handshaking between

the master and the slave. An Acknowledge (active LOW)

generated by the slave (LTC3562) lets the master know

that the latest byte of information was received. The

Acknowledge-related clock pulse is generated by the

master. The master releases the SDA line (HIGH) during

theAcknowledgeclockcycle.Theslave-receivermustpull

down the SDA line during the Acknowledge clock pulse

so that it remains a stable low during the high period of

this clock pulse.

2

the standard I C 2-wire interface. The Timing Diagram in

Figure 4 shows the timing relationship of the signals on

the bus. The two bus lines, SDA and SCL, must be high

when the bus is not in use. External pull-up resistors or

current sources, such as the LTC1694 SMBus Accelerator,

are required on these lines. The LTC3562 is a receive-only

2

(slave) device. The I C control signals, SDA and SCL are

scaled internally to the DV supply. DV should be con-

CC

nected to the same power supply as the microcontroller

2

generating the I C signals.

Slave Address Byte

2

The I C port has an undervoltage lockout on the DV

CC

2

pin. When DV is below approximately 1V, the I C serial

The LTC3562 responds to only one 7-bit address which

has been factory programmed to 11001010. The eighth

bit of the address byte (R/W) must be 0 for the LTC3562

to recognize the address since it is a write-only device.

This effectively forces the address to be 8 bits long where

the least signiﬁcant bit of the address is 0. If the correct

7-bit address is given but the R/W bit is 1, the LTC3562

will not respond.

CC

port is cleared and the two switching Type-A regulators

are set to full scale.

Bus Speed

2

The I C port is designed to be operated at speeds of up

to 400kHz. It has built-in timing delays to ensure correct

2

operation when addressed from an I C compliant master

device. It also contains input ﬁlters designed to suppress

glitches should the bus become corrupted.

Sub-Address Byte

The sub-address byte uses bits A7 through A4 to specify

the regulator(s) being programmed by that particular

three-bytesequence(refertoTable2). Aspeciﬁcregulator

gets programmed if its corresponding sub-address bit is

high, whereas the regulator ignores the 3-byte sequence

if its sub-address bit is low. Note that multiple regulators

can be programmed by the same 3-byte sequence if more

than one of the sub-address bits are high. Bits A1 and A0

ofthesub-addressbyteareusedtoprogramtheoperating

mode (Table 3). Bits A3 and A2 of the sub-address byte

are not used.

START and STOP Conditions

A bus master signals the beginning of a communication

to a slave device by transmitting a start condition. A start

condition is generated by transitioning SDA from high

to low while SCL is high. When the master has ﬁnished

communicating with the slave, it issues a stop condition

by transitioning SDA from low to high while SCL is high.

2

The bus is then free for communication with another I C

device.

Byte Format

Data Byte

Each byte sent to the LTC3562 must be 8 bits long fol-

lowed by an extra clock cycle for the Acknowledge bit to

be returned by the LTC3562. The data should be sent to

the LTC3562 most signiﬁcant bit (MSB) ﬁrst.

The data byte only affects the regulators that are speciﬁed

to be programmed by the sub-address byte. The MSB

of the data byte (B7) is used to enable or disable the

regulator(s) being programmed. A high B7 indicates an

enable command, whereas a low B7 indicates a shutdown

command.

3562fa

12

LTC3562

OPERATION

SUB-ADDRESS

DATA BYTE

ADDRESS

WR

0

1

0

1

0

1

A7

A6

A5

A4

A3

A2

A1

A0

B7

B6

B5

B4

B3

B2

B1

B0

START

STOP

SDA

SCL

1

2

0

3

0

4

1

5

0

6

1

7

0

8

ACK

9

A7

1

A6

2

A5

3

A4

4

A3

5

A2

6

A1

7

A0 ACK

ACK

9

7

1

6

2

5

3

4

3

5

2

6

1

7

0

8

9

3562 F03

Figure 3. Bit Assignments

SDA

SCL

t

BUF

SU, DAT

SU, STA

t

LOW

HD, STA

SU, STO

HD, DAT

3562 F04

t

HIGH

t

SP

HD, STA

START

CONDITION

REPEATED START

CONDITION

STOP

CONDITION

START

CONDITION

t

f

r

Figure 4. Timing Parameters

Table 1. Write Word Protocol Used by the LTC3562

1

7

1

8

1

8

1

S

Slave Address

WR

A

*Sub-Address

A

Data Byte

A

P**

S = Start Condition, WR = Write Bit = 0, A = Acknowledge, P = Stop Condition

* The sub-address uses only the ﬁrst four most signiﬁcant bits, A7, A6, A5, and A4, for sub-addressing. The two least signiﬁcant bits, A1 and A0, are

used to program the regulator operating mode.

**Stop can be delayed until all of the data registers have been written.

Table 2. Sub-Address and Data Byte Mapping

SUB-ADDRESS BYTE

A5 A4

PROGRAM PROGRAM PROGRAM PROGRAM

R600A R400A R600B R400B

DATA BYTE

A7

A6

A3

A2

A1

A0

B7

B6

B5

B4

B3

DAC CODE

(See Tables 4, 5 and 6)

B2

B1

B0

NOT USED

REGULATOR

OPERATING REGULATOR

MODE

ENABLE

(SEE TABLE 3)

3562fa

13

LTC3562

OPERATION

If a Type-A regulator is being programmed, then bits B3

through B0 program the DAC that controls the regulator’s

feedback servo voltage. This 4-bit sequence programs the

feedback voltage from 425mV to 800mV in 25mV incre-

ments (Table 4). Bits B6 through B4 are not used when

programming a Type-A regulator.

will ignore this stop condition and will not respond until a

new start condition, correct address, new set of data and

stop condition are transmitted.

Likewise, with only one exception, if the LTC3562 was

previously addressed and sent valid data but not updated

with a Stop, it will respond to any Stop that appears on

the bus, independent of the number of Repeat-Starts that

have occurred. If a Repeat-Start is given and the LTC3562

successfully acknowledges its address, it will not respond

to a Stop until all three bytes of the new data have been

received and acknowledged.

If a Type-B regulator is being programmed, then bits B6

through B0 program the DAC that controls the regulator’s

output voltage. This 7-bit sequence programs the output

voltage from 600mV to 3.775V in 25mV increments

(Tables 5 and 6).

2

I C Examples

Bus Write Operation

To program R600A in forced Burst Mode operation with

its feedback servo voltage set to 600mV:

ThemasterinitiatescommunicationwiththeLTC3562with

a start condition and a 7-bit address followed by the write

bit R/W = 0. If the address matches that of the LTC3562,

the LTC3562 returns an Acknowledge. The master should

then deliver the sub-address byte for the regulator(s)

being programmed. Again the LTC3562 acknowledges

and then the data byte is delivered starting with the most

signiﬁcant bit. The data byte and the two mode bits in the

sub-address byte are transferred to an internal holding

latch for each programmed regulator upon the return

of an Acknowledge. After the sub-address byte and data

byte have been transferred to the LTC3562, the master

may terminate the communication with a stop condition.

Alternatively, a repeat-start condition can be initiated by

the master and the entire sequence can be repeated, this

time accessing a different sub-address code to program

another regulator. Likewise, the master can also initiate a

Sub-Address Byte – 1000XX10

Data Byte – 1XXX0111

To program R600B and R400B in LDO mode with their

output voltages set to 1.250V:

Sub-Address Byte – 0011XX01

Data Byte – 10011010

To put the entire chip in shutdown and disable all regula-

tors:

Sub-Address Byte – 1111XXXX

Data Byte – 0XXXXXXX

2

Disabling the I C Port

2

The I C serial port can be disabled by grounding the DV

CC

2

Repeat-Start so that another chip on the I C bus can be

pin.Inthismode,regulatorsR600AandR400Acanonlybe

addressed. This cycle can continue indeﬁnitely and the

LTC3562’s regulators will remember the last input of valid

data that it received. Once all chips on the bus have been

addressed and sent valid data, a global stop condition can

be sent and the LTC3562 will update its regulators with

the data that it had received.

activated through the individual logic input pins RUN600A

2

and RUN400A. Disabling the I C port also resets the feed-

back servo voltages to the default setting of 0.8V.

2

Note that if the I C port gets disabled while a Type-A

regulator is enabled and its RUN pin is activated, the

regulator will remain enabled and its feedback voltage will

immediately be reset to the default setting of 0.8V. If the

2

In certain circumstances the data on the I C bus may

2

become corrupted. In these cases the LTC3562 responds

appropriately by preserving only the last set of complete

datathatithasreceived.Forexample,assumetheLTC3562

has been successfully addressed and is receiving data

when a stop condition mistakenly occurs. The LTC3562

I C port gets disabled and the RUN pins are not activated,

then the regulators will immediately go into shutdown

mode. Since regulators R600B and R400B do not have

RUN pins, they immediately go into shutdown once the

2

I C port gets disabled.

3562fa

14

LTC3562

OPERATION

Table 5. Type-B Regulator Base Output Voltage Programming

TYPE-B REGULATOR

Table 3. Regulator Operating Modes

A1

0

A0

0

REGULATOR MODE

Pulse Skip Mode

B6

0

1

B5

0

1

0

1

B4

0

1

0

1

0

1

0

1

B3

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

B2

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

BASE OUTPUT VOLTAGE

0.600

0

1

LDO Mode

0.700

1

0

Forced Burst Mode Operation

Burst Mode Operation

0.800

1

0.900

1.000

Table 4. Type-A Regulator Servo Voltage Programming

TYPE-A REGULATOR

1.100

1.200

B3

0

1

B2

0

1

0

1

B1

0

1

0

1

0

1

0

1

B0

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

SERVO (FEEDBACK) VOLTAGE

1.300

0.425

0.450

0.475

0.500

0.525

0.550

0.575

0.600

0.625

0.650

0.675

0.700

0.725

0.750

0.775

0.800

1.400

1.500

1.600

1.700

1.800

1.900

2.000

2.100

2.200

2.300

2.400

2.500

2.600

2.700

2.800

2.900

POR600A Pin

3.000

3.100

The POR600A pin is an open-drain output used to indicate

that regulator R600A has been enabled and has reached

its ﬁnal voltage. POR600A remains low impedance until

regulator R600A reaches 92% of its regulation value. A

230msdelayisincludedtoallowasystemmicrocontroller

ample time to reset itself. POR600A may be used as a

power on reset to the microprocessor powered by regula-

tor R600A or may be used to enable regulator R400A for

supply sequencing. POR600A is an open drain output and

requiresapull-upresistortotheoutputvoltageofregulator

R600A or another appropriate power source.

3.200

3.300

3.400

3.500

3.600

3.700

Table 6. Type-B Regulator Incremental Output Voltage Programming

B1

0

B0

0

TYPE-B REGULATOR INCREMENTAL OUTPUT VOLTAGE

+0.000

+0.025

+0.050

0

1

0

1

+0.075

3562fa

15

LTC3562

APPLICATIONS INFORMATION

Inductor Selection

Table 7 shows several inductors that work well with the

LTC3562’sgeneralpurposeregulators.Theseinductorsof-

feragoodcompromiseincurrentrating,DCRandphysical

size. Consult each manufacturer for detailed information

on their entire selection of inductors.

Many different sizes and shapes of inductors are avail-

able from numerous manufacturers. Choosing the right

inductor from such a large selection of devices can be

overwhelming, but following a few basic guidelines will

make the selection process much simpler.

Table 7. Recommended Inductors

MAX

DCR

(Ω)

SIZE

(mm)

Thestep-downconvertersaredesignedtoworkwithinduc-

tors in the range of 2.2μH to 10μH. For most applications a

4.7μHinductorissuggestedforthelowerpowerswitching

regulators R400A and R400B and 3.3μH is recommended

for the more powerful switching regulators R600A and

R600B.Largervalueinductorsreduceripplecurrentwhich

improves output ripple voltage. Lower value inductors

result in higher ripple current and improved transient re-

sponse time, but will reduce the available output current.

To maximize efﬁciency, choose an inductor with a low DC

resistance. For a 1.2V output, efﬁciency is reduced about

2% for 100mΩ series resist-ance at 400mA load current,

and about 2% for 300mΩ series resistance at 100mA load

current. Choose an inductor with a DC current rating at

least 1.5 times larger than the maximum load current to

ensure that the inductor does not saturate during normal

operation. If output short circuit is a possible condition,

the inductor should be rated to handle the maximum peak

current speciﬁed for the step-down converters.

INDUCTOR

TYPE

L

I

DC

(μH) (A)

(L ×W ×H)

MANUFACTURER

DB318C

4.7 1.07

3.3 1.20

4.7 0.79

3.3 0.90

4.7 1.15

3.3 1.37 0.105* 3.0 × 2.8 × 1.2

4.7 1.25 0.072* 3.0 × 2.8 × 1.8

3.3 1.45 0.052* 3.0 × 2.8 × 1.8

0.1

3.8 × 3.8 × 1.8

3.6 × 3.6 × 1.2

Toko

www.toko.com

0.07

0.24

0.20

D312C

DE2812C

DE2818C

0.13* 3.0 × 2.8 × 1.2

CDRH3D16 4.7

0.9

1.1

0.5

0.6

0.11

0.085

0.17

4 × 4 × 1.8

3.2 × 3.2 × 1.2

Sumida

www.sumida.com

3.3

CDRH2D11 4.7

3.3

0.123 3.2 × 3.2 × 1.2

0.19

CLS4D09

4.7 0.75

4.7 1.3

3.3 1.59

4.7 0.8

3.3 0.97

4.7 1.29 0.117* 5.2 × 5.2 × 1.2

3.3 1.42 0.104* 5.2 × 5.2 × 1.2

4.7 1.08 0.153* 5.2 × 5.2 × 1.0

3.3 1.31 0.108* 5.2 × 5.2 × 1.0

4.9 × 4.9 × 1

SD3118

0.162 3.1 × 3.1 × 1.8

Cooper

0.113 3.1 × 3.1 × 1.8 www.cooperet.com

0.246 3.1 × 3.1 × 1.2

SD3112

SD12

0.165 3.1 × 3.1 × 1.2

SD10

LPS3015

4.7

3.3

1.1

1.3

0.2

0.13

3.0 × 3.0 × 1.5

3.0 × 3.0 × 1.5 www.coilcraft.com

Coil Craft

Differentcorematerialsandshapeswillchangethesize/cur-

rent and price/current relationship of an inductor. Toroid

or shielded pot cores in ferrite or Permalloy™ materials

are small and do not radiate much energy, but generally

cost more than powdered iron core inductors with similar

electrical characteristics. Inductors that are very thin or

have a very small volume typically have much higher core

and DCR losses, and will not give the best efﬁciency. The

choice of which style inductor to use often depends more

on the price versus size, performance, and any radiated

EMI requirements than on what the LTC3562 requires to

operate.

* Typical DCR

Input/Output Capacitor Selection

LowESR(equivalentseriesresistance)ceramiccapacitors

should be used at the switching regulator outputs as well

as the input supply. Only X5R or X7R ceramic capacitors

should be used because they retain their capacitance

over wider voltage and temperature ranges than other

ceramic types. A 10μF output capacitor is sufﬁcient for

most applications. For good transient response and sta-

bility the output capacitor should retain at least 4μF of

capacitance over operating temperature and bias voltage.

The input supply should be bypassed with a 10μF capaci-

tor, or greater. Consult with capacitor manufacturers for

detailed information on their selection and speciﬁcations

of ceramic capacitors. Many manufacturers now offer

The inductor value also has an effect on Burst Mode and

forced Burst Mode operations. Lower inductor values will

cause the Burst Mode and forced Burst Mode switching

frequencies to increase.

3562fa

16

LTC3562

APPLICATIONS INFORMATION

very thin (<1mm tall) ceramic capacitors ideal for use in

height-restricted designs. Table 8 shows a list of several

ceramic capacitor manufacturers.

result in higher thermal resistances.

Furthermore, duetoitshighfrequencyswitchingcircuitry,

it is imperative that the input capacitors, inductors, and

output capacitors be as close to the LTC3562 as possible

and that there be an unbroken ground plane under the

LTC3562 and all of its external high frequency compo-

nents. High frequency currents on the LTC3562 tend to

ﬁnd their way along the ground plane in a myriad of paths

ranging from directly back to a mirror path beneath the

incident path on the top of the board. If there are slits or

cuts in the ground plane due to other traces on that layer,

the current will be forced to go around the slits. If high

frequency currents are not allowed to ﬂow back through

their natural least-area path, excessive voltage will build

up and radiated emissions will occur. There should be a

group of vias directly under the grounded backside of the

packageleadingdirectlydowntoaninternalgroundplane.

Tominimizeparasiticinductance,thegroundplaneshould

be on the second layer of the PC board.

Table 8. Recommended Ceramic Capacitor Manufacturers

AVX

www.avxcorp.com

www.murata.com

www.t-yuden.com

www.vishay.com

www.tdk.com

Murata

Taiyo Yuden

Vishay Siliconix

TDK

Printed Circuit Board Layout Considerations

Todelivermaximumcurrentunderallconditions,itiscritical

thattheexposedmetalpadonthebacksideoftheLTC3562

package be soldered to the PC board ground. Correctly

2

soldered to a 2500mm double-sided 1oz. copper board,

the LTC3562 has a thermal resistance of less than 68°C/W.

Failure to make thermal contact between the exposed pad

on the backside of the package and the copper board will

3562 F05

Figure 5. High Frequency Ground Currents Follow Their Incident Path.

Slices in the Ground Cause High Voltage and Increased Emissions.

3562fa

17

LTC3562

TYPICAL APPLICATION

Quad Step-Down Converter with Push Button Control and Power Sequencing

100k

Li-Ion BATTERY

3.4V TO 4.2V

C5

10μF

V

SDA SCL DV

LTC3562

IN

CC

L3

R5

POR SCL SDA

V

600B

3.3V

3.3μH

V

600A

OUT

100k

SW600B

1.8V

600mA

L1

3.3μH

600mA

C3

POR600A

SW600A

OUT600B

10μF

V

CORE

I/O

CC

C6

C1

10μF

R1

FB600A

CC

10pF

L4

4.7μH

634k

400B

RUN600A

OUT

MICROPROCESSOR

1.2V

SW400B

OUT400B

R2

400mA

C4

10μF

499k

V

400A

OUT

L2

4.7μH

RUN400A

SW400A

FB400A

2.5V

400mA

C7

10pF

C2

10μF

R3

1070k

PGND AGND

3562 TA02

R4

499k

3562fa

18

LTC3562

PACKAGE DESCRIPTION

UD Package

20-Lead Plastic QFN (3mm × 3mm)

(Reference LTC DWG # 05-08-1720 Rev Ø)

0.70 ±0.05

3.50 ± 0.05

(4 SIDES)

1.65 ± 0.05

2.10 ± 0.05

PACKAGE

OUTLINE

0.20 ±0.05

0.40 BSC

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED

BOTTOM VIEW—EXPOSED PAD

PIN 1 NOTCH

R = 0.20 TYP

OR 0.25 × 45°

CHAMFER

R = 0.115

TYP

0.75 ± 0.05

3.00 ± 0.10

(4 SIDES)

R = 0.05

TYP

19 20

PIN 1

TOP MARK

(NOTE 6)

0.40 ± 0.10

1

2

1.65 ± 0.10

(4-SIDES)

(UD20) QFN 0306 REV A

0.200 REF

0.20 ± 0.05

0.00 – 0.05

0.40 BSC

NOTE:

1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE

2. DRAWING NOT TO SCALE

3. ALL DIMENSIONS ARE IN MILLIMETERS

4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE

MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE

5. EXPOSED PAD SHALL BE SOLDER PLATED

6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION

ON THE TOP AND BOTTOM OF PACKAGE

3562fa

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-

tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

19

LTC3562

RELATED PARTS

PART NUMBER

DESCRIPTION

COMMENTS

LTC3406/

LTC3406B

600mA I , 1.5MHz, Synchronous Step-Down

96% Efﬁciency, V

SD

= 2.5V, V

= 5.5V, V

= 0.6V, I = 20μA,

Q

OUT

IN(MIN)

< 1μA, ThinSOT™ Package

IN(MAX)

OUT(MIN)

DC/DC Converter

I

LTC3407/

LTC3407-2

Dual 600mA/800mA I , 1.5MHz/2.25MHz,

95% Efﬁciency, V

SD

= 2.5V, V

= 0.6V, I = 40μA,

Q

OUT

IN(MIN)

IN(MAX)

Synchronous Step-Down DC/DC Converter

I

< 1μA, MS10E and DFN Packages

LTC3410/

LTC3410B

300mA I , 2.25MHz, Synchronous Step-Down

95% Efﬁciency, V

SD

= 2.5V, V

= 0.8V, I = 26μA,

OUT

IN(MIN)

IN(MAX)

Q

DC/DC Converter

I

< 1μA, SC70 Package

LTC3531/LTC3531-3/ 200mA I , 1.5MHz, Synchronous Buck-Boost

LTC3531-3.3

95% Efﬁciency, V

= 1.8V, V

: 2V to 5V,

OUT

IN(MIN)

DC/DC Converter

I = 16μA, I < 1μA, ThinSOT and DFN Packages

Q SD

LTC3532

500mA I , 2MHz, Synchronous Buck-Boost

95% Efﬁciency, V

= 2.4V, V = 5.5V, V

IN(MAX)

: 2.4V to 5.25V,

OUT

IN(MIN)

DC/DC Converter

I = 35μA, I < 1μA, MS10 and DFN Packages

Q SD

LTC3542

500mA I , 2.25MHz, Synchronous Step-Down

95% Efﬁciency, V

SD

= 2.5V, V

= 5.5V, V

= 0.6V, I = 26μA,

Q

OUT

IN(MIN)

IN(MAX)

DC/DC Converter

I

< 1μA, 2mm × 2mm DFN Package

LTC3544/LTC3544B

Quad 300mA and 2 × 200mA and 100mA, 2.25MHz, 95% Efﬁciency, V

Synchronous Step-Down DC/DC Converter

= 2.5V, V

= 0.8V, I = 70μA,

Q

I

SD

< 1μA, 3mm × 3mm QFN Package

LTC3547/

LTC3547B

Dual 300mA, 2.25MHz, Synchronous Step-Down

DC/DC Converter

96% Efﬁciency, V

SD

= 2.5V, V

= 0.6V, I = 40μA,

Q

IN(MIN)

IN(MAX)

I

< 1μA, 2mm × 3mm DFN Package

LTC3548/LTC3548-1/ Dual 400mA and 800mA I , 2.25MHz,

LTC3548-2

95% Efﬁciency, V

= 2.5V, V

= 0.6V, I = 40μA,

Q

OUT

Synchronous Step-Down DC/DC Converter

I

SD

< 1μA, MS10E and DFN Packages

LTC3560

800mA I , 2.25MHz, Synchronous Step-Down

95% Efﬁciency, V

SD

= 2.5V, V

= 0.6V, I = 16μA,

Q

OUT

IN(MIN)

IN(MAX)

DC/DC Converter

I

< 1μA, ThinSOT Package

ThinSOT is a trademark of Linear Technology Corporation

3562fa

LT 1207 REV A • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

20

●

(408) 432-1900 FAX: (408) 434-0507 www.linear.com


型号：	LTC3562
厂家：	Linear
描述：	I2C Quad Synchronous Step-Down DC/DC Regulator 2 × 600mA, 2 × 400mA I2C四路同步降压型DC / DC稳压器2 × 600毫安， 2 × 400毫安稳压器
文件：	总20页 (文件大小：255K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LTC3562 [Linear]

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