LTC1555C データシートの表示（PDF） - Linear Technology

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LTC1555C

SIM Power Supply and Level Translator

Linear Technology 

LTC1555/LTC1556

PIN FUNCTIONS

LTC1556 Only

EN (Pin 5): Auxiliary LDO/Power Switch Enable Pin. A

logic high on this pin from the controller will enable the

auxiliary LDO output. When the LDO is disabled, the LDO

output will float or be pulled to ground by the load. If left

floating, the EN pin will be pulled down to GND by an

internal 1µA current source.

FB (Pin 6): Auxiliary LDO Feedback Pin. When FB is

connected to the LDO pin (Pin 17), the LDO output is

regulated to 4.3V (typ). If the FB pin is left open or tied to

ground, the regulator acts as a ≤ 30Ω switch between VCC

and LDO.

LDO (Pin 17): LDO Output Pin. This pin should be tied to

the FB pin for 4.3V LDO operation. The 4.3V LDO output

is usable only when VCC is 5V (or greater). It is not

available when VCC = 3V. The LDO output may also be

used as a ≤ 30Ω power switch if the FB pin is grounded

or left floating. When used as a regulator, LDO must be

bypassed to GND with a ≥ 3.3µF capacitor. The LDO

output current will subtract from available VCC current.

BLOCK DIAGRAM

VBATT

+

CIN

10µF

0.1µF

C1+

C1–

VIN

M1

M0

3V

SS

VCC

STEP-UP/

STEP-DOWN

CHARGE PUMP

DC/DC

CONVERTER

VCC

CONTROLLER

DVCC

RIN

CIN

20k

DATA

OPTIONAL

LTC1555/LTC1556

LTC1556 ONLY

1µA

DDRV

EN

1µA

–

1.23V

FB 153k

+

61k

RST

CLK

10k

I/O

GND

GND

LDO

VCC

COUT

10µF

RST

SIM

CLK

I/O

GND

4.3V

+

CLDO

10µF

FREQUENCY

SYNTHESIZER

POWER

1555/56 BD

6

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