LTM4650-1 datasheet(10/36 Pages) LINER

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LTM4636

4636f

For more information www.linear.com/LTM4636

Decoupling requireMenTs

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

CIN

External Input Capacitor Requirement

(VIN = 4.70V to 16V, VOUT = 1.5V)

IOUT = 40A, 6 × 22µF Ceramic X7R Capacitors

(See Table 4)

100

µF

COUT

External Output Capacitor Requirement

(VIN = 4.70V to 16V, VOUT = 1.5V)

IOUT = 40A (See Table 4)

1000

µF

TA = 25°C. Use Figure 1 configuration.

Power Module Description

TheLTM4636isahighefficiencyregulatorthatcanprovide

a40Aoutputwithfewexternalinputandoutputcapacitors.

This module provides precisely regulated output voltages

programmable via external resistors from 0.6V DC to 3.3V

DC over a 4.70V to 15V input range. The Typical Applica-

tion schematic is shown in Figure 20.

The LTM4636 has an integrated constant-frequency cur-

rent mode regulator, power MOSFETs, 0.18µH inductor,

protection circuitry, 5V regulator and other supporting

discrete components. The switching frequency range is

from250kHzto770kHz,andthetypicaloperatingfrequency

is 400kHz. For switching noise-sensitive applications, it

can be externally synchronized from 250kHz to 800kHz,

subject to minimum on-time limitations and limiting the

inductor ripple current to less than 40% of maximum

output current.

A single resistor is used to program the frequency. See

the Applications Information section.

With current mode control and internal feedback loop

compensation, the LTM4636 module has sufficient stabil-

ity margins and good transient performance with a wide

range of output capacitors, even with all ceramic output

capacitors. An option has been provided for external loop

compensation. LTpowerCAD® can be used to optimize

the external compensation option. See the Applications

Information section.

Current mode control provides cycle-by-cycle fast current

limit in an overcurrent condition. An internal overvoltage

operaTion

monitor feedback pin referred will attempt to protect the

output voltage in the event of an overvoltage >10%. The

top MOSFET is turned off and the bottom MOSFET is

turned on until the output is cleared.

Pulling the RUNC pin below 1.1V forces the regulator con-

trollerintoashutdownstate.TheTRACK/SSpinisusedfor

programmingtheoutputvoltagerampandvoltagetracking

during start-up. See the Applications Information section.

The LTM4636 is internally compensated to be stable over

all operating conditions. Table 5 provides a guideline for

input and output capacitances for several operating condi-

tions. LTpowerCAD is available for transient and stability

analysis. This tool can be used to optimize the regulators

loop response.

Aremotesenseamplifierisprovidedforaccuratelysensing

output voltages at the load point.

Multiphase operation can be easily employed with the

internal clock source or a synchronization clock applied

to the MODE/PLLIN input using an external clock source,

and connecting the CLKOUT pins. See the Applications

Information section. Review Figure 4.

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.

A TEMP+ and TEMP– pins are provided to allow the internal

device temperature to be monitored using an onboard

diode connected NPN transistor.

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