LTC1439IGW#PBF Datasheet LTC1438IG-ADJ#PBF, LTC1439IG#PBF, LTC1439CGW#PBF | P1-P3

LTC1438/LTC1439

1

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, LTC and LT are registered trademarks of Linear Technology Corporation. Adaptive

Power is a trademark of Linear Technology Corporation. All other trademarks are the prop-

erty of their respective owners. Protected by U.S. Patents including 5481178, 6304066,

5929620, 6580258, 5705919, 5731731.

The LTC

®

1438/LTC1439 are dual, synchronous step-

down switching regulator controllers which drive external

N-channel power MOSFETs in a phase-lockable fixed

frequency architecture. The Adaptive Power

TM

output stage

selectively drives two N-channel MOSFETs at frequencies

up to 400kHz while reducing switching losses to maintain

high efficiencies at low output currents.

An auxiliary 0.5A linear regulator using an external PNP

pass device provides a low noise, low dropout voltage

source. A secondary winding feedback control pin (SFB1)

guarantees regulation regardless of load on the main

output by forcing continuous operation.

An additional comparator is available for use as a low

battery detector. A power-on reset timer (POR) is included

which generates a signal delayed by 65536/f

CLK

(typ

300ms) after the output is within 5% of the regulated

output voltage. Internal resistive dividers provide pin

selectable output voltages with remote sense capability on

one of the two outputs.

The operating current levels are user-programmable via

external current sense resistors. Wide input supply range

allows operation from 3.5V to 30V (36V maximum).

■

Maintains Constant Frequency at Low Output

Currents

■

Dual N-Channel MOSFET Synchronous Drive

■

Programmable Fixed Frequency (PLL Lockable)

■

Wide V

IN

Range: 3.5V to 36V Operation

■

Ultrahigh Efficiency

■

Very Low Dropout Operation: 99% Duty Cycle

■

Low Dropout, 0.5A Linear Regulator for VPP

Generation or Low Noise Audio Supply

■

Built-In Power-On Reset Timer

■

Programmable Soft Start

■

Low-Battery Detector

■

Remote Output Voltage Sense

■

Foldback Current Limiting (Optional)

■

Pin Selectable Output Voltage

■

Logic-Controlled Micropower Shutdown: I

Q

< 30µA

■

Output Voltages from 1.19V to 9V

■

Available in 28- and 36-Lead SSOP Packages

APPLICATIO S

U

TYPICAL APPLICATIO

U

DESCRIPTIO

U

FEATURES

■

Notebook and Palmtop Computers, PDAs

■

Portable Instruments

■

Battery-Operated Devices

■

DC Power Distribution Systems

Dual High Efficiency,

Low Noise, Synchronous

Step-Down Switching Regulators

Figure 1. High Efficiency Dual 5V/3V Step-Down Converter

BOOST 2BOOST 1

TGL2

TGS2

SW2

BG2

SENSE

+

2

SENSE

–

2

V

OSENSE2

I

TH2

TGL1

M3*

M1

M2

TGS1

D1

MBR140T3

V

OUT1

5V

3.5A

V

OUT2

3.3V

3.5A

L1

10µH

SW1

BG1 LTC1439

SENSE

+

1

SENSE

–

1

C

SS1

0.1µF

C

C1

1000pF

C

OUT1

220µF

10V

R

SENSE1

0.03Ω

R

SENSE2

0.03Ω

C

OUT

220µF

10V

R

C1

10k

I

TH1

RUN/SS2PGNDSGNDV

PROG2

C

OSC

INTV

CC

D

B2

, CMDSH-3D

B1

, CMDSH-3

V

IN

V

PROG1

RUN/SS1

D2

MBR140T3

C

B1

0.1µF

C

B2

,

0.1µF

4.7µF

16V

M6*

1438 F01

M4

1000pF

C

OSC

56pF

C

SS2

0.1µF

C

C1A

220pF

M1, M2, M4, M5: Si4412ADY M3, M6: IRLML2803 *NOT REQUIRED FOR LTC1438

C

C2A

470pF

C

C2

1000pF

R

C2

10k

+

L2

10µH

V

IN

5.2V TO 28V

+

C

IN

22µF

35V

× 4

+

BOLD LINES INDICATE HIGH CURRENT PATHS

M5

LTC1438/LTC1439

2

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1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

TOP VIEW

GW PACKAGE

36-LEAD PLASTIC SSOP

G PACKAGE

36-LEAD PLASTIC SSOP

36

35

34

33

32

31

30

29

28

27

26

25

24

23

22

21

20

19

RUN/SS1

SENSE

+

1

SENSE

–

1

V

PROG1

I

TH1

POR2

C

OSC

SGND

LBI

LBO

SFB1

I

TH2

V

PROG2

V

OSENSE2

SENSE

–

2

SENSE

+

2

RUN/SS2

AUXDR

PLL LPF

PLLIN

BOOST 1

TGL1

SW1

TGS1

V

IN

BG1

INTV

CC

PGND

BG2

EXTV

CC

TGS2

SW2

TGL2

BOOST 2

AUXON

AUXFB

1

2

3

4

5

6

7

8

9

10

11

12

13

14

TOP VIEW

G PACKAGE

28-LEAD PLASTIC SSOP

28

27

26

25

24

23

22

21

20

19

18

17

16

15

SENSE

+

1

SENSE

–

1

V

PROG1

*

I

TH1

POR2**

C

OSC

SGND

LBI

LBO

SFB1

I

TH2

V

OSENSE2

SENSE

–

2

SENSE

+

2

RUN/SS1

BOOST 1

TGL1

SW1

V

IN

BG1

INTV

CC

PGND

BG2

EXTV

CC

SW2

TGL2

BOOST 2

RUN/SS2

V

OSENSE1

ON LTC1438-ADJ

NC ON THE LTC1438XCG

*

**

Input Supply Voltage (V

IN

)......................... 36V to –0.3V

Topside Driver Voltage (BOOST 1, 2) ........ 42V to –0.3V

Switch Voltage (SW1, 2) ....................... V

IN

+ 5V to –5V

EXTV

CC

Voltage......................................... 10V to –0.3V

POR2, LBO Voltages ................................. 12V to –0.3V

AUXFB Voltage ......................................... 20V to –0.3V

AUXDR Voltage......................................... 28V to –0.3V

SENSE

+

1, SENSE

+

2, SENSE

–

1, SENSE

–

2,

V

OSENSE2

Voltages ................. INTV

CC

+ 0.3V to –0.3V

V

PROG1

, V

PROG2

Voltages ..................... INTV

CC

to –0.3V

PLL LPF, I

TH1

, I

TH2

Voltages .................... 2.7V to –0.3V

ABSOLUTE AXI U RATI GS

W

WW

U

AUXON, PLLIN, SFB1,

RUN/SS1, RUN/SS2, LBI Voltages ....... 10V to –0.3V

Peak Output Current < 10µs (TGL1, 2, BG1, 2).......... 2A

Peak Output Current < 10µs (TGS1, 2) ............... 250mA

INTV

CC

Output Current ........................................ 50mA

Operating Ambient Temperature Range

Commercial ............................................ 0°C to 70°C

Extended (Note 7)............................... –40°C to 85°C

Industrial ............................................ –40°C to 85°C

Junction Temperature (Note 2)............................. 125°C

Storage Temperature Range .................. –65°C to 150°C

Lead Temperature (Soldering, 10 sec).................. 300°C

ORDER

PART NUMBER

LTC1439CG

LTC1439EG

LTC1439IG

LTC1439CGW

LTC1439IGW

ORDER

PART NUMBER

PACKAGE/ORDER INFORMATION

W

U

LTC1438CG

LTC1438CG-ADJ

LTC1438IG

LTC1438IG-ADJ

LTC1438XCG

T

JMAX

= 125°C, θ

JA

= 95°C/W

T

JMAX

= 125°C, θ

JA

= 95°C/W (G)

T

JMAX

= 125°C, θ

JA

= 85°C/W (GW)

(Note 1)

Consult factory for Military grade parts.

LTC1438/LTC1439

3

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The ● denotes the specifications which apply over the full operating

temperature range. T

A

= 25°C, V

IN

= 15V, V

RUN/SS1,2

= 5V unless otherwise noted.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

Main Control Loops

I

IN

V

OSENSE1,2

Feedback Current V

PROG1,

V

PROG2

Pins Open (Note 3) 10 50 nA

V

OUT1,2

Regulated Output Voltage (Note 3)

1.19V (Adjustable) Selected V

PROG1,

V

PROG2

Pins Open ● 1.178 1.19 1.202 V

3.3V Selected V

PROG1,

V

PROG2

= 0V ● 3.220 3.30 3.380 V

5V Selected V

PROG1,

V

PROG2

= INT V

CC

● 4.900 5.00 5.100 V

V

LINEREG1,2

Reference Voltage Line Regulation V

IN

= 3.6V to 20V (Note 3), V

PROG1,2

Pins Open 0.002 0.01 %/V

V

LOADREG1,2

Output Voltage Load Regulation I

TH1,2

Sinking 5µA (Note 3) ● 0.5 0.8 %

I

TH1,2

Sourcing 5µA ● –0.5 –0.8 %

V

SFB1

Secondary Feedback Threshold V

SFB1

Ramping Negative ● 1.16 1.19 1.22 V

I

SFB1

Secondary Feedback Current V

SFB1

= 1.5V –1 –2 µA

V

OVL

Output Overvoltage Lockout V

PROG1,2

, SENSE

–

1 and V

OSENSE1,2

Pins Open 1.24 1.28 1.32 V

I

PROG1,2

V

PROG1,2

Input Current 0.5V > V

PROG1,2

–3 –6 µA

INTV

CC

– 0.5V < V

PROG1,2

< INTV

CC

3 6 µA

I

Q

Input DC Supply Current EXTV

CC

= 5V (Note 4)

Normal Mode 3.6V < V

IN

< 30V, V

AUXON

= 0V 320 µA

Shutdown V

RUN/SS1,2

= 0V, 3.6V < V

IN

< 15V 16 30 µA

V

RUN/SS1,2

Run Pin Threshold ● 0.8 1.3 2 V

I

RUN/SS1,2

Soft Start Current Source V

RUN/SS1,2

= 0V 1.5 3 4.5 µA

∆V

SENSE(MAX)

Maximum Current Sense Threshold V

OSENSE1,2

= 0V, 5V V

PROG1,2

= Pins Open 130 150 180 mV

TGL1, 2 t

r

, t

f

TGL1, TGL2 Transition Time

Rise Time C

LOAD

= 3000pF 50 150 ns

Fall Time C

LOAD

= 3000pF 50 150 ns

TGS1, 2 t

r

, t

f

TGS1, TGS2 Transition Time

Rise Time C

LOAD

= 500pF 100 200 ns

Fall Time C

LOAD

= 500pF 50 150 ns

BG1, 2 t

r

, t

f

BG1, BG2 Transition Time

Rise Time C

LOAD

= 3000pF 50 150 ns

Fall Time C

LOAD

= 3000pF 50 150 ns

Internal V

CC

Regulator

V

INTVCC

Internal V

CC

Voltage 6V < V

IN

< 30V, V

EXTVCC

= 4V ● 4.8 5.0 5.2 V

V

LDO

INT INTV

CC

Load Regulation I

INTVCC

= 20mA, V

EXTVCC

= 4V –0.2 –1 %

V

LDO

EXT EXTV

CC

Voltage Drop I

INTVCC

= 20mA, V

EXTVCC

= 5V 170 300 mV

V

EXTVCC

EXTV

CC

Switchover Voltage I

INTVCC

= 20mA, EXTV

CC

Ramping Positive ● 4.5 4.7 V

Oscillator and Phase-Locked Loop

f

OSC

Oscillator Frequency C

OSC

= 100pF, LTC1439: PLL LPF = 0V (Note 5) 112 125 138 kHz

VCO High LTC1439, V

PLLLPF

= 2.4V 200 240 kHz

R

PLLIN

Input Resistance 50 kΩ

I

PLLLPF

Phase Detector Output Current LTC1439

Sinking Capability f

PLLIN

< f

OSC

10 15 20 µA

Sourcing Capability f

PLLIN

> f

OSC

10 15 20 µA

Power-On Reset

V

SATPOR2

POR2 Saturation Voltage I

POR2

= 1.6mA, V

OSENSE2

= 1V, 0.6 1 V

V

PROG2

Pin Open

I

LPOR2

POR2 Leakage V

POR2

= 12V, V

OSENSE2

= 1.2V, V

PROG2

Pin Open 0.2 1 µA

V

THPOR2

POR2 Trip Voltage V

PROG2

Pin Open % of V

REF

V

OSENSE2

Ramping Negative – 11 – 7.5 – 4 %

t

DPOR2

POR2 Delay V

PROG2

Pin Open 65536 Cycles

ELECTRICAL CHARACTERISTICS

LTC1439IGW#PBF

LTC1439IGW#PBF

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