MP86905

– INTELLI-PHASE SOLUTION W/ INTEGRATED MOSFETS AND DRIVERS

MP86905 Rev. 1.1

www.MonolithicPower.com

10

8/31/2020

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

© 2020 MPS. All Rights Reserved.

APPLICATION INFORMATION

Operation

The MP86905 is a 50A, monolithic, half-bridge

driver with integrated MOSFETs and is ideally

suited for multi-phase buck regulators.

An external 3.3V supply is required to supply

both VDD and VDRV. When EN transitions

from low to high, and the VDD and VDRV

signals are both sufficiently high, operation

begins.

PWM

The PWM input is capable of a tri-state input.

When the PWM input signal is within the tri-

state threshold window for 50ns (tHT or tLT), the

HS-FET is turned off immediately, and the LS-

FET enters diode emulation mode, which is on

until zero-current detection. The tri-state PWM

input can come from a forced middle voltage

PWM signal or made by floating the PWM input

so the internal current source charges the

signal to a middle voltage. Please refer to the

PWM timing diagram on page 5 for the

propagation delay definition from PWM to the

SW node.

Diode Emulation Mode

In diode emulation mode, when PWM is either

low or in a tri-state input, the LS-FET is turned

on whenever the inductor current is positive.

The LS-FET turns off if the inductor current is

negative or after the inductor current crosses

zero current. Diode emulation mode can be

enabled by pulling SYNC low, driving PWM to

middle-state, or floating PWM.

Current Sense (CS)

CS

is

a

bi-directional

current

source

proportional to the inductor current. The current

sense gain is 9.7

μA/A (GCS). Generally, there is

a resistor (RCS) connected from CS to an

external voltage which is capable of sinking

small currents to provide enough of a voltage

level shift to meet the CS operating voltage.

The CS voltage range of 0.7V to 2.1V is

requ

ired to keep CS’s output current linearly

proportional to the inductor current.

A proper reference voltage, VCM, and RCS

values can be determined with Equation (1) and

Equation (2):

2.1V

V

R

I

0.7V

CM

CS

CS









(1)

CS

L

CS

I

I

G



(2)

Where VCM is a reference voltage connected to

RCS.

Intelli-

Phase’s current sense output can be

used by the controller to accurately monitor the

output

current.

The

cycle-by-cycle

current

information from CS can be used for phase-

current balancing, over-current protection, and

active

voltage

positioning

(output-voltage

droop).

Positive and Negative Inductor Current Limit

When HS-FET over-current is detected for four

consecutive cycles, the HS-FET latches off, and

FAULT# is asserted low. The LS-FET is turned

on until zero-current detection, and then is

turned off. Recycling VIN, VDD/VDRV, or

toggling EN releases the latch and restarts the

device.

When the LS-FET detects a -30A current, the

MP86905 turns off the LS-FET for 40ns to limit

the negative current. The LS-

FET’s negative

current limit will not trigger a fault report.

Over-Temperature Protection (OTP)

When the junction temperature reaches the

over-temperature threshold, the HS-FET is

latched off, FAULT# is asserted low, and the

LS-FET

is

turned

on

until

zero-current

detection.

Temperature Sense Output (VTEMP)

VTEMP

reports

the

junction

temperature.

VTEMP is a voltage proportional to the junction

temperature. The VTEMP output voltage is

10mV/°C

(GVTEMP)

with

a

-100mV

offset

(VTEMP_Offset) and can be calculated with

Equation (3):







TEMP

JUNCTION

VTEMP

V

T

G

VTEMP _ Offset (3)

For example, if the junction temperature is

100°C, then VTEMP is 0.9V. VTEMP = 0V for

junction temperatures below 10°C. In multi-

phase operation, VTEMP of every Intelli-Phase

can be connected to the temperature monitor

pin of the controller (see Figure 2).