LTC1159CS datasheet(5/20 Pages) LINER

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LTC1159

LTC1159-3.3/LTC1159-5

PI FU CTIO S

SENSE+: The (+) Input for the Current Comparator. A built-

in offset between the SENSE+ and SENSE– pins, in conjunc-

tion with RSENSE, sets the current trip threshold.

N-Gate: High Current Drive for the Bottom N-Channel

MOSFET. The N-Gate pin swings from ground to VCC.

P-Gate: Level-Shifted Gate Drive Signal for the Top

P-Channel MOSFET. The voltage swing at the P-gate pin is

from VIN to VIN – VCC.

P-Drive: High Current Gate Drive for the Top P-Channel

MOSFET. The P-drive pin(s) swing(s) from VCC to ground.

CAP: Charge Compensation Pin. A capacitor to VCC pro-

vides charge required by the P-gate level-shift capacitor

during supply transitions.

The charge compensation ca-

pacitor must be larger than the gate drive capacitor.

SHDN1: This pin shuts down the control circuitry only (VCC

is not affected). Taking SHDN1 pin high turns off the

control circuitry and holds both MOSFETs off. This pin

must be at ground potential for normal operation.

SHDN2: Master Shutdown Pin. Taking SHDN2 high shuts

down VCC and all control circuitry.

VIN: Main Supply Input Pin.

SGND: Small-Signal Ground. Must be routed separately

from other grounds to the (–) terminal of COUT.

PGND: Driver Power Grounds. Connect to source of N-

channel MOSFET and the (–) terminal of CIN.

VCC: Outputs of internal 4.5V linear regulator, EXTVCC

switch, and supply inputs for driver and control circuits.

The driver and control circuits are powered from the higher

of the 4.5V regulator or EXTVCC voltage. Must be closely

decoupled to power ground.

CT: External capacitor CT from this pin to ground sets the

operating frequency. (The frequency is also dependent on

the ratio VOUT/VIN.)

ITH: Gain Amplifier Decoupling Point. The current com-

parator threshold increases with the ITH pin voltage.

VFB: For the LTC1159 adjustable version, the VFB pin

receives the feedback voltage from an external resistive

divider used to set the output voltage.

SENSE–: Connects to internal resistive divider which sets

the output voltage in fixed output versions. The SENSE– pin

is also the (–) input of the current comparator.

EXTVCC Switch Drop

Current Sense Threshold Voltage

Off-Time vs VOUT

SWITCH CURRENT (mA)

100

200

300

400

500

600

510

LTC1159 • TPC07

OUTPUT VOLTAGE (V)

LTC1159 • TPC08

LTC1159-5

LTC1159-3.3

TEMPERATURE (

°C)

100

120

100

LTC1159 • TPC09

160

140

MAXIMUM

THRESHOLD

MINIMUM

THRESHOLD

TYPICAL PERFOR A CE CHARACTERISTICS

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