1174 データシートの表示（PDF） - Linear Technology

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1174

High Efficiency Step-Down and Inverting DC/DC Converter

Linear Technology 

LTC1174

LTC1174-3.3/LTC1174-5

PI FU CTIO S

VOUT (VFB) (Pin 1): For the LTC1174, this pin connects to the

main voltage comparator’s input. On the LTC1174-3.3 and

LTC1174-5 this pin goes to an internal resistive divider

which sets the output voltage.

LBOUT (Pin 2): Open Drain of an N-Channel Pull-Down. This

pin will sink current when Pin 3 (LBIN) goes below 1.25V.

During shutdown the state of this pin is indeterminate.

LBIN (Pin 3): The “–” Input of the Low-Battery Voltage

Comparator. The “+” input is connected to a reference

voltage of 1.25V.

GND (Pin 4): Ground Pin.

SW(Pin5): Drain of the P-Channel MOSFET Switch. Cathode

of Schottky diode must be closely connected to this pin.

VIN (Pin 6): Input Supply Voltage. It must be decoupled

close to ground Pin 4.

IPGM (Pin 7): Selects the Current Limit of the P-Channel

Switch. With IPGM = VIN, the current trip point is 600mA and

with IPGM = 0V, the current trip value is reduced to 340mA.

SHUTDOWN (Pin 8): Pulling this pin to ground keeps the

internal switch off and puts the LTC1174 in micropower

shutdown.

W

FU CTIO AL DIAGRA (Pin 1 connection shown for LTC1174-3.3 and LTC1174-5, changes create LTC1174)

VIN

6

+

VTH2

A5

–

SLEEP

VLIM1

VLIM2

IPGM

7

RSENSE

0.1Ω

A2

gmVFB

LBOUT 2

GND 4

–

A4

CT

+

VTH1

LBIN

3

A3

RESET

Q

SET

1.25V

REFERENCE

SHUTDOWN

8

* R1 = 51k FOR LTC1174-3.3

R1 = 93.5k FOR LTC1174-5

VOUT (VFB)

1

5

× SW

R1*

VFB

A1

31.5k

1174 BD

1174fe

6

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