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LX1672

Multiple Output LoadSHARE™ PWM

Microsemi Corporation 

LX1672

®

Multiple Output LoadSHARE™ PWM

TM

PRELIMINARY DATA SHEET

NAME

FB1

EOX

FB2

RF2

VCC

VCCL

LDFB

CSX

SSX

AGND

DGND

LDGD

PGX

HOX

LOX

VCX

LDDIS

VSX

DISX

PWGD

FUNCTIONAL PIN DESCRIPTION

DESCRIPTION

Bi-Phase Operation: Phase 1 and 2 Voltage Feedback

Single Phase Operation: Phase 1 Voltage Feedback – connected to the output through a resistor network to

set desired output voltage of Phase 1

Error Amplifier Output – Sets external compensation for the corresponding phase denoted by “X”.

Bi-phase Operation: Load Sharing Voltage Sense Feedback – Connect filtered phase 2 switching output (pre-

inductor) to FB2 to ensure proper current sharing between phase 1 and phase 2.

Single Phase Operation: Phase 2 Voltage Feedback – connected to the output through a resistor network (post

inductor) to set desired output voltage of Phase 2.

Bi-Phase Operation: Load Sharing Voltage Sense Feedback Reference – Sets reference for current sharing

control loop. Connecting filtered phase 1 switching output (pre-inductor) to REF2 forces average current in

phase 2 to be equal to phase 1.

Single Phase Operation: Phase 2 Voltage Reference – connected to SS2 pin as reference.

IC supply voltage (nominal 5V).

Power supply pin for all Low side drivers.

Low Dropout Regulator Voltage Feedback – Sets output voltage of external MOSFET via resistor network.

Over-Current Limit Set – Connecting a resistor between CS pin and the source of the high-side MOSFET sets the

current-limit threshold for the corresponding phase denoted by “X”. Exceeding the current-limit threshold forces

the corresponding phase into hiccup mode protection. A minimum of 1KΩ must be in series with this input.

Soft-start/Hiccup Capacitor Pin – During start-up, the voltage on this pin controls the output voltage of its

respective regulator. An internal 20kΩ resistor and the external capacitor set the time constant for soft-start

function. The Soft-start function does not initialize until the supply voltage exceeds the UVLO threshold. When

an over-current condition occurs, this capacitor is used for the timing of hiccup mode protection.

Analog ground reference.

Digital ground reference.

Low Dropout Regulator Gate Drive – Connects to gate of external N-Channel MOSFET for linear regulator

function.

Driver Power Ground. Connects to the source of the bottom N-channel MOSFETS of phase 1 where X=1, and

phase 2 where X=2 for the TSSOP. The MLPQ package has a common PG output .

High Side MOSFET Gate Driver – “X” denotes corresponding phase.

Low Side MOSFET Gate Driver – “X” denotes corresponding phase.

Phase High-Side MOSFET Gate Driver Supply – Connect to separate supply or boot strap supply to ensure

proper high-side gate driver supply voltage. “X” denotes corresponding phase. If the phase is not used connect to

VCC.

LDO Disable input. High disables the LDO output. This pin has a 100KΩ nominal pulldown resistor

Voltage reference for Current sense. This is also the supply pin for the Current Sense Comparator.

“X” denotes corresponding phase. This pin cannot be left floating, if the phase is not used connect to VCC

PWM Disable Input – High disables the PWM output. This pin has a nominal 80KΩ pulldown resistor. “X”

denotes corresponding phase.

Open drain output , high at end of Soft Start and no Fault. Pulls low if any Fault condition occurs.

This output is present on the MLP package only.

Copyright © 2000

Rev. 0.3m, 2005-04-12

Microsemi

Linfinity Microelectronics Division

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

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