MP8847 – 6A, 2.7V-6V, HIGH-EFFICIENCY, SYNCHRONOUS

STEP-DOWN SWITCHER WITH I

MP8847 Rev. 1.02

www.MonolithicPower.com

17

12/28/2017

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

© 2017 MPS. All Rights Reserved.

OPERATION

The MP8847 is a low-voltage, 6A, synchronous,

interface. The MP8847 applies MPS’s patented

constant-frequency hysteretic control to utilize

fast transient response of the hysteretic control

and keep the switching frequency constant. No

compensation is required, which simplifies the

design procedure.

interface that allows transfers up to 3.4Mbps.

This communication interface can be used for

dynamic voltage scaling with voltage steps

down to 5mV with the output voltage from 0.6V

to 1.235V. The voltage transition slew rate can

be controlled as well.

Light-Load Operation

In light-load condition, the MP8847uses a

proprietary control scheme to save power and

improve efficiency. The MP8847 turns off the

low-side switch when the inductor current

begins reversing. The MP8847then works in

discontinuous

conduction

mode

(DCM)

operation.

Enable(EN)

When the input voltage is greater than the

under-voltage

lockout

(UVLO)

threshold

(typically 2.55V), the MP8847 can be enabled

by pulling EN above 1.8V. Pull EN down to

ground to disable the MP8847. The IC can also

be disabled by floating EN. There is an internal

1MΩ resistor from EN to ground.

Soft Start (SS)

The MP8847 has a built-in soft start that ramps

up the output voltage at a controlled slew rate,

preventing inrush current and output voltage

overshoot at start-up. The soft-start time is

about 1ms.

Power Good (PG) Indictor

The MP8847 has an open drain output for

power good (PG) indication. When the output

voltage is within ±10% of the regulation voltage,

PG is pulled up to VIN by the external resistor.

Current Limit

The MP8847 has a typical 9A current limit for

the high-side switch. When the high-side switch

reaches the current limit, the MP8847expands

the minimum off time until the current drops to

5.8A before the high-side switch is turned on for

the next switching cycle. This prevents the

inductor current from continuing to build up and

damaging the components.

Thermal Protection

The MP8847employs thermal shutdown by

monitoring the junction temperature of the IC

internally. If the junction temperature exceeds

the thermal warning threshold (around 130°C),

OTW is set. If there is no action or response

from the system, the junction temperature

continues rising until it exceeds the thermal

shutdown threshold (typically 150°C). After

thermal shutdown, a new power start-up cycle

is needed to turn on the MP8847 again.