LTM4643 datasheet(9/32 Pages) LINER

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LTM4643

4643fb

For more information www.linear.com/LTM4643

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

CIN

External Input Capacitor Requirement

(VIN = 4V to 20V, VOUT = 1.5V)

IOUT = 3A

4.7

µF

COUT

External Output Capacitor Requirement

(VIN = 4V to 20V, VOUT = 1.5V)

IOUT = 3A

µF

DECOUPLING REQUIREMENTS

OPERATION

The LTM4643 is a quad output standalone non-isolated

switch mode DC/DC power supply in 9mm × 15mm

× 1.82mm ultrathin package. It has four separate regula-

tor channels with each of them capable of delivering up

to 3A continuous output current with few external input

and output capacitors. Each regulator provides precisely

regulated output voltage programmable from 0.6V to

3.3V via a single external resistor over 4V to 20V input

voltage range. With an external bias voltage, this module

can operate from an input voltage as low as 2.375V. The

typical application schematic is shown in Figure 29.

TheLTM4643integratesfourseparateconstantfrequency

controlled on-time valley current mode regulators, power

MOSFETs, inductors, and other supporting discrete com-

ponents. The typical switching frequency is set to 1.2MHz.

For switching noise-sensitive applications, the µModule

regulator can be externally synchronized to a clock from

850kHz to 1.5MHz. See the Applications Information

section.

With current mode control and internal feedback loop

compensation, the LTM4643 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 the flexibility of paralleling

any of the separate regulator channels with accurate cur-

rent sharing. With a built-in clock interleaving between

regulator channels, the LTM4643 can easily be configured

for 2+2, 3+1 or 4 channels parallel operation providing

more design flexibility for multirail POL applications. Fur-

thermore, the LTM4643 has CLKIN and CLKOUT pins for

frequencysynchronizationorpolyphasingmultipledevices

whichallowupto8phasescascadedtorunsimultaneously.

Current mode control also provides cycle-by-cycle fast

current monitoring. Foldback current limiting is provided

in an overcurrent condition to reduce the inductor valley

current to approximately 40% of the original value when

VFB drops. An internal overvoltage and undervoltage

comparators pull the open-drain PGOOD output low if

the output feedback voltage exits a ±10% window around

the regulation point. Continuous conduction mode (CCM)

operation is forced during OV and UV conditions except

during start-up when the TRACK pin is ramping up to 0.6V.

Pulling the RUN pin below 1.1V forces the controller into

its shutdown state, turning off both power MOSFETs and

most of the internal control circuitry. At light load cur-

rents, discontinuous conduction mode (DCM) operation

can be enabled to achieve higher efficiency compared to

continuous conduction mode (CCM) by setting the MODE

pin to SGND. The TRACK/SS pin is used for power supply

trackingandsoft-startprogramming.SeetheApplications

Information section.

Atemperaturediodeisincludedinsidethemoduletomoni-

tor the temperature of the module. See the Applications

Information section for details.

(per Channel)

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