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LTM4633

4633f

For more information www.linear.com/LTM4633

operaTion

Power Module Description

The LTM4633 µModule regulator is a high performance

triple output nonisolated switching mode DC/DC power

supply. It can provide 10A per output with a few exter-

nal input and output capacitors. This module provides

precisely regulated output voltages programmable via

external resistors from 0.8V DC to 1.8V DC (VOUT1 and

VOUT2), and 0.8V DC to 5.5V DC (VOUT3) over a 2.375V

to 16V input range with control bias on the CNTL_PWR

pin, or 4.7V to 16V with control bias tied to VIN. When

applying control bias in the range from 4.7V to 5.5V, then

connect the bias to CNTL_PWR and INVTCC, otherwise

if >5.5V only bias the CNTL_PWR pin. The typical applica-

tion schematic is shown in Figure 16.

The LTM4633 has three integrated constant-frequency

current mode regulators, power MOSFETs, power induc-

tors, and other supporting discrete components. The

typical switching frequency is 750kHz. For switching

noise-sensitive applications, it can be externally syn-

chronized from 600kHz to 750kHz. See the Applications

Information section.

With current mode control and internal feedback loop

compensation, the LTM4633 module has sufficient stabil-

ity margins and good transient performance with a wide

range of output capacitors, even with all ceramic output

capacitors.

Current mode control provides cycle-by-cycle fast current

limit in an overcurrent condition. An internal overvolt-

age monitor protects the output voltages in the event

of an overvoltage >7.5%. The top MOSFET is turned off

and the bottom MOSFET is turned on until the output

overvoltage is cleared. There are two temperature moni-

tors in the LTM4633. TEMP1 monitors the close relative

temperature of channels 1 and 2, and TEMP2 monitors

the close relative temperature of channels 2 and 3. The

two diode connected PNP transistors are grounded in the

module and can be used as general purpose temperature

monitors using a device that is designed to monitor the

single-ended connection.

Pulling any of the RUN pins below 1.3V forces the cor-

responding regulator channel into a shutdown state. The

TK/SS pins are used for programming the output voltage

ramp and voltage tracking during start-up for each of the

channels. See the Applications Information section.

TheLTM4633isinternallycompensatedtobestableoverall

operatingconditions.Table5providesaguidelineforinput

and output capacitances for several operating conditions.

The LTpowerCAD™ software tool is provided for transient

and stability analysis. The VFB pin is used to program the

output voltage with a single external resistor to ground.

Each of the channels, operate with a 120° phase shift for

multiphase operation. VOUT1 and VOUT2 can be combined

to provide a single 20A output. The two channels will

not be operating 180° phase shift, but 120° phase when

combined for a 20A design. So the input RMS current

will be higher than a 180° phase shifted design. See the

Applications Information section.

High efficiency at light loads can be accomplished with

selectable Burst Mode operation using the MODE/PLLIN

pin. These light load features will accommodate battery

operation. Efficiency graphs are provided for light load op-

erationintheTypicalPerformanceCharacteristicssection.

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