MPM3834C – 6V, 3A, ULTRA-SMALL STEP-DOWN POWER MODULE

MPM3834C Rev. 1.01

MonolithicPower.com

13

6/14/2022

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OPERATION

The MPM3834C comes in a small surface-

mounted ECLGA-14 (2.5mmx2.5mmx1.2mm)

package. The MPM3834C

’s integrated inductor

simplifies the schematic and layout design.

Only FB resistors, input capacitors, and output

capacitors are required to complete the design.

The MPM3834C uses constant-on-time (COT)

control

with

input

voltage

feed-forward

to

stabilize the switching frequency (fSW) across

the full input range.

Constant-On-Time Control (COT)

Compared

to

fixed-frequency

pulse-width

modulation (PWM) control, COT control offers

the advantage of a simpler control loop and

faster

transient

response.

By

using

input

voltage feed-forward, the MPM3834C maintains

a nearly constant fSW across the input and

output voltage ranges. The on time of the

switching pulse can be estimated with Equation

(1):

OUT

ON

IN

V

t

0.833

μs

V

=

(1)

To prevent inductor current runaway during the

load

transition,

the

MPM3834C

fixes

the

minimum off time at 230ns. This minimum off

time limit does not affect operation during

steady state.

Forced PWM Operation

The

MPM3834C

works

in

continuous

conduction mode (CCM) to achieve a smaller

output voltage ripple, load regulation, and load

transient response across the full load range.

Enable (EN)

If the input voltage (VIN) exceeds the under-

voltage lockout (UVLO) threshold (typically

2.5V), the MPM3834C can be enabled by

pulling EN above 1.2V. Leave EN floating or

pull

EN

down

to

ground

to

disable

the

MPM3834C. There is an internal pull-down

resistor connected from EN to ground.

Soft Start and Soft Shutdown

The MPM3834C has a built-in soft start that

ramps up the output voltage at a controlled slew

rate to prevent overshoots during start-up. The

soft-start time is tSS-ON.

When disabled, the MPM3834C ramps down

the

internal

reference,

so

the

load

can

discharge

the

output

linearly.

The

soft-

shutdown time is tSS-OFF.

Power Good (PG) Indicator

The MPM3834C has an open-drain power good

(PG) indication pin with a pull-up resistor (RPG).

When FB is within PG_OV and PG_UV, PG is

pulled up to IN by the internal resistor. If the FB

voltage is out of this window, PG is pulled down

to

ground

by

an

internal

MOSFET.

The

MOSFET has a maximum RDS(ON) of 100Ω.

Current Limit

The MPM3834C

’s high-side MOSFET (HS-

FET) has a typical peak current limit, and the

low-side

MOSFET (LS-FET)

has

a valley

current limit. When the HS-FET reaches its

current limit, the HS-FET turns off, and the LS-

FET turns on. When the current drops to the

valley current limit threshold, the MPM3834C

turns on the HS-FET again.

If the HS-FET reaches the peak current limit or

the LS-FET reaches the valley current limit for

64 consecutive cycles, the MPM3834C initiates

hiccup mode. It remains in hiccup mode until

the

current

decreases.

This

prevents

the

inductor current from continuously rising and

damaging components.

Short-Circuit Protection (SCP) and Recovery

If the output is shorted to GND, the current limit

is triggered. If the current limit is triggered every

for 64 consecutive cycles, the MPM3834C

enters hiccup mode and disables the output

power stage. The MPM3834C discharges the

soft-start capacitor, then automatically attempts

to soft start again. If the short-circuit condition

remains after soft start ends, the MPM3834C

repeats this operation until the short circuit is

removed and the output rises back to the

regulation level.