Техническая Спецификация для Linear Technology LTM4613EV Demo Board: Ultralow EMI, 36V, 8A Step-down µModule Regulator DC1743A DC1743A

Модели

DC1743A

LTM4613

4613f

OPERATION

Power Module Description
The LTM4613 is a standalone nonisolated switch mode

DC/DC power supply. It can deliver 8A of DC output cur-

rent with minimal external input and output capacitors.

This module provides a precisely regulated output voltage

programmable via one external resistor from 3.3V

15V

over a wide 5V to 36V input voltage. The typical

application schematic is shown in Figure 18.
The LTM4613 has an integrated constant on-time current

mode regulator, ultralow R

DS(ON)

FETs with fast switching

speed and integrated Schottky diodes. The typical switching

frequency is 600kHz at full load at 12V output. With current

mode control and internal feedback loop compensation,

the LTM4613 module has sufficient stability margins and

good transient performance under a wide range of operat-

ing conditions and with a wide range of output capacitors,

even all ceramic output capacitors.
Current mode control provides cycle-by-cycle fast current

limiting. Moreover, foldback current limiting is provided in

an overcurrent condition when V

drops. Internal over-

voltage and undervoltage comparators pull the open-drain

PGOOD output low if the output feedback voltage exits a

±10% window around the regulation point. Furthermore,

in an overvoltage condition, internal top FET M1 is turned

off and bottom FET M2 is turned on and held on until the

overvoltage condition clears.
Input filter and noise cancellation circuitry reduce the

noise coupling to inputs and outputs, and ensure the

electromagnetic interference (EMI) meets the limits of

EN55022 Class B (see Figure 7).
Pulling the RUN pin below 1V forces the controller into

its shutdown state, turning off both M1 and M2. At light

load currents, discontinuous mode (DCM) operation can

be enabled to achieve higher efficiency compared to con-

tinuous mode (CCM) by setting FCB pin higher than 0.6V.
When the DRV

pin is connected to INTV

, an integrated

5V linear regulator powers the internal gate drivers. If a

5V external bias supply is applied on DRV

pin, then an

efficiency improvement will occur due to the reduced power

loss in the internal linear regulator. This is especially true

at the higher input voltage range.
The MPGM, MARG0, and MARG1 pins are used to sup-

port voltage margining, where the percentage of margin

is programmed by the MPGM pin, while the MARG0 and

MARG1 select positive or negative margining. The PLLIN

pin provides frequency synchronization of the device to

an external clock. The TRACK/SS pin is used for power

supply tracking and soft-start programming.

The typical LTM4613 application circuit is shown in Fig-

ure 18. External component selection is primarily deter-

mined by the input voltage, the maximum load current and

the output voltage. Refer to Table 2 for specific external

capacitor requirements for a particular application.

to V

OUT

Stepdown Ratios

There are restrictions in the maximum V

and V

OUT

step

down ratio that can be achieved for a given input voltage.

These constraints are shown in the Typical Performance

Characteristic curve labeled “V

to V

OUT

Step-Down

Ratio.” Note that additional thermal derating may be ap-

plied. See the Thermal Considerations and Output Current

Derating section in this data sheet.

APPLICATIONS INFORMATION

Output Voltage Programming and Margining
The PWM controller has an internal 0.6V reference volt-

age. As shown in the Block Diagram, a 100k 0.5% internal

feedback resistor connects the V

OUT

and V

pins together.

Adding a resistor, R

, from the V

pin to the SGND pin

programs the output voltage.

OUT

= 0.6V •

100k

or equivalently,

100k

OUT

0.6V

− 1