MP5403

– CONFIGURABLE 2.7V-6V MINI PMIC WITH DUAL 2.5A/3.5A BUCK,

ONE LOAD SWITCH, AND INPUT POWER SUPERVISORY

MP5403 Rev. 1.0

www.MonolithicPower.com

18

9/20/2016

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

© 2016 MPS. All Rights Reserved.

Power Failure Indicator (PFL)

The power failure indicator (PFL) senses the

external voltage rails. When the input voltage is

below the programmed threshold, the PFL

open-drain output is pulled low immediately to

indicate the monitored power failure. This

function is enabled by pulling any of the EN

pins (EN1, EN2, or EN3) high and disabled by

pulling all of the EN pins low. For example, if all

EN pins are low, PFL is zero, even if VIN is

above the UVLO threshold and PFL_ADJ is

higher than 0.6V. Ensure that there is at least

one EN pin that is high before using it to control

the other pins.

PFL_ADJ is used to adjust the power failure

threshold voltage. A resistor divider is used to

monitor the voltage rail. When the PFL_ADJ

voltage is lower than 0.6V, PFL is pulled down

to indicate the sense power failure. When the

PFL_ADJ voltage is higher than the 0.6V

reference voltage, PFL is pulled high with the

s

μ

5

.

3

+

)

A

μ

(

I

62

.

0

×

)

pF

(

C

=

)

s

μ

(

T

DELAY

DELAY

DELAY

(1)

3.1µA).

Current Limit

The MP5403 has a high-side 5.6A current limit

for the first regulator and a 4.7A current limit for

the second regulator. When the high-side

switch reaches the current limit threshold, the

regulators shut down the high-side switch and

force the low-side switch on until the low-side

current drops to the low-side valley current

threshold (5A and 4A for the two regulators).

After the low-side current reaches the valley

current

threshold,

the

high-side

switch

is

allowed to turn on again. If the high load current

persists, the high side turns on again, and the

current limit mechanism repeats until the output

voltage drops to the short-circuit threshold. If

the high-load current does not persist, then the

regulator runs back to normal condition.

For the load switch, the current limit begins

working when the load switch current reaches

the current limit threshold. The gate is pulled

low to regulate the load switch current to the

current limit. The output voltage drops until

thermal shutdown occurs.

Short Circuit and Recovery

When CH1 or CH2 is in buck mode, the

MP5403 enters short-circuit protection (SCP)

mode when the inductor current reaches the

current limit for 300µs continuously or the

output

voltage

drops

below

50%

of

the

regulation voltage. In SCP mode, the MP5403

disables the output power stage, discharges the

soft-start

capacitor,

and

enters

latch-off

protection mode. The MP5403 restarts by

recycling the power.

Parallel Capability

By connecting SW1 and SW2 together and

connecting PG1 and PG2 together, the two

step-down regulators can run in parallel mode

to increase the output power capability. In this

mode, only FB1 is used to program the output

voltage. Keep FB2 floating.

Load-Switch Mode of Buck1/2

By pulling FB1 or FB2 to ground, the step-down

regulator 1 or 2 can enter load-switch mode

without having to install an inductor. The

MP5403 pulses a smaller current to the FB pins

before the system starts up. If a low impedance

is connected to the FB pins, the MP5403 enters

load-switch mode, where the high-side switch is

turned on gradually to achieve a soft start, and

short-circuit protection is equipped.