LTC1986 datasheet(4/8 Pages) LINER

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LTC1986

1986fa

VOUT (Pin 1): Charge Pump Output. The VOUT voltage will

depend on the MODE pin input voltage. VOUT = 0V in

shutdown mode, VOUT = VIN in 3V mode and VOUT = 5V in

5V mode. The LTC1986 provides a 2.9V regulated output

when the part is in 3V mode and the VIN voltage is below

2.85V. This feature allows the input voltage to be below the

minimum voltage specification for 3V SIM cards without

violating the SIM VCC specification. Bypass the VOUT pin

with a

≥ 2.2µF low ESR capacitor to ground.

GND (Pin 2): Ground. Connect to a ground plane for best

performance.

MODE (Pin 3): MODE Input Pin. The voltage on this pin

determines the operating mode of the LTC1986. It oper-

ates in either shutdown mode, 3V mode or 5V mode

depending on the MODE pin voltage with respect to VIN.

PIN FUNCTIONS

The three different modes can be realized by using two

external resistors as shown in the typical application

circuit. If VMODE < VIN/2 – 0.1V, the part is in shutdown

mode.If VIN/2 + 0.1V < VMODE < VIN – 1V, the part is in 5V

mode. If VIN – 0.25V < VMODE, the part is in 3V mode. To

achieve the lowest possible shutdown current, the MODE

pin should be pulled to 0V, i.e., both the SHDN and 3/5

signals from the controller should be pulled low.

C1– (Pin 4): Charge Pump Flying Capacitor Negative

Terminal.

C1+ (Pin 5): Charge Pump Flying Capacitor Positive

Terminal.

VIN (Pin 6): Input Supply Voltage. Bypass VIN with a

≥ 0.1µF low ESR capacitor to ground.

PLIFIED BLOCK DIAGRA

SHDN

–

MODE

VIN

VOUT

VIN – 0.6V

VIN/2

1.25V

LOGIC

UVLO/

THERMAL

SHDN

CHARGE

PUMP

900kHz

OSC

2.9V BOOST

3V MODE

SOFT START

Ω

5V MODE

C1–

C1+

1.25V

REF

SHDN

GND

1986 BD

LTC1986

2.5

Ω

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