LTC1438CG-ADJ View Datasheet(PDF) - Linear Technology

Part Name

Description

MFG CO.

LTC1438CG-ADJ

Dual High Efficiency, Low Noise, Synchronous Step-Down Switching Regulators

Linear Technology 

Prev 21 22 23 24 25 26 27 28 29 30 Next

LTC1438/LTC1439

APPLICATIONS INFORMATION

current, reducing the susceptibility to both the “loop”

radiated magnetic fields and the transformer or inductor

leakage fields.

The capacitor on INTVCC acts as a reservoir to supply the

high transient currents to the bottom gates and to re-

charge the boost capacitor. This capacitor should be a

4.7µF tantalum capacitor placed as close as possible to the

INTVCC and PGND pins of the IC. Peak current driving the

MOSFET gates exceeds 1A. The PGND pin of the IC,

connected to this capacitor, should connect directly to the

lower plates of the output capacitors to minimize the AC

ripple on the INTVCC IC power supply.

The previous instructions will yield a PC layout which has

three separate ground regions returning separately to the

bottom plates of the output capacitors: a signal ground, a

MOSFET gate/INTVCC ground and the ground from the

input capacitors, Schottky diode and synchronous

MOSFET. In practice, this may produce a long power

ground path from the input and output capacitors. A long,

low resistance path between the input and output capaci-

tor power grounds will not upset the operation of the

switching controllers as long as the signal and power

grounds from the IC pins does not “tap in” along this path.

TYPICAL APPLICATIONS

LTC1438 5V/3A, 3.3V/3.5A Regulator

0.1µF

1000pF

100Ω

100Ω

1N4148 1000pF

1 SENSE+ 1 RUN/SS1 28

2 SENSE– 1 BOOST 1 27

10Ω

+

0.1µF

22µF

35V

1000pF

10k

220pF

56pF

470pF

INTVCC

POR2

LBI

3

VPROG1

26

TGL1

4

ITH1

25

SW1

5

POR2

24

VIN

6

23

COSC

BG1

7

LTC1438

22

SGND

INTVCC

8

LBI

21

PGND

CMDSH-3

0.1µF + 4.7µF 16V

1000pF

10k

56pF

221k, 1%

392k, 1%

220pF

10Ω

0.1µF

LBO

9

LBO

20

BG2

1k

22pF

1000pF

1N4148

10Ω

10

SFB1

19

EXTVCC

VOUT1

11

ITH2

18

SW2

12

VOSENSE2

17

TGL2

13 SENSE– 2 BOOST 2 16

14 SENSE+ 2 RUN/SS2 15

CMDSH-3

0.1µF

+

22µF

35V

10µH

SUMIDA

M1 CDRH125-100MC

0.033Ω

+

M2

MBRS140T3

M4

MBRS140T3 +

220µF

10V

0.033Ω

10µH

M3 SUMIDA

CDRH125-100MC

+

22µF

35V

220µF

10V

+

22µF

35V

1438 TA01

VIN

5.2V

TO

28V

VOUT1

5V

3A

GND

VOUT2

3.3V

3.5A

VIN 5.2V TO 28V: SWITCHING FREQUENCY = 180kHz

5V, 3A/3.3V, 3.5A

M1 TO M4: Si4412ADY

INPUT CAPACITORS ARE AVX-TPS SERIES

OUTPUT CAPACITORS ARE AVX-TPSV LEVEL II SERIES

14389fb

25

Share Link: