LTM4625Y(RevC) Просмотр технического описания (PDF) - Analog Devices

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LTM4625Y
(Rev.:RevC)

20VIN, 5A Step-Down DC/DC µModule Regulator

Analog Devices 

LTM4625

OPERATION

The LTM4625 is a standalone nonisolated switch mode DC/

DC power supply. It can deliver up to 5A DC output current

with few external input and output capacitors. This module

provides precisely regulated output voltage adjustable

between 0.6V to 5.5V via one external resistor over a 4V

to 20V input voltage range. With an external bias supply

above 4V connected to SVIN, this module operates with

an input voltage down to 2.375V. The typical application

schematic is shown in Figure 20.

The LTM4625 contains an integrated constant on-time

valley current mode regulator, power MOSFETs, inductor,

and other supporting discrete components. The default

switching frequency is 1MHz. For switching noise-sensitive

applications, the switching frequency can be adjusted

by external resistors and the μModule regulator can be

externally synchronized to a clock within ±30% of the set

frequency. See the Applications Information section.

With current mode control and internal feedback loop

compensation, the LTM4625 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 cur-

rent limiting. Foldback current limiting is provided in an

overcurrent condition indicated by a drop in VFB reducing

inductor valley current to approximately 40% of the origi-

nal value. Internal output 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 operation is forced during OV

and UV condition except during start-up when the TRACK

pin is ramping up to 0.6V.

Furthermore, in order to protect the internal power MOSFET

devices against transient voltage spikes, the LTM4625

constantly monitors the VIN pin for an overvoltage condi-

tion. When VIN rises above 23.5V, the regulator suspends

operation by shutting off both power MOSFETs. Once VIN

drops below 21.5V, the regulator immediately resumes

normal operation. The regulator does not execute its

soft-start function when exiting an overvoltage condition.

Multiphase operation can be easily employed with the

synchronization and phase mode controls. Up to 12 phases

can be cascaded to run simultaneously with respect to

each other by programming the PHMODE pin to different

levels. The LTM4625 has CLKIN and CLKOUT pins for

PolyPhase operation of multiple devices or frequency

synchronization.

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

currents, discontinuous mode (DCM) operation can be

enabled to achieve higher efficiency compared to continu-

ous mode (CCM) by pulling the MODE pin to SGND. The

TRACK/SS pin is used for power supply tracking and

soft-start programming. See the Applications Informa-

tion section.

Rev C

8

For more information www.analog.com

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