MP86934 – 16V INTELLI-PHASE SOLUTION IN TQFN 3X4

MP86934 Rev.1.2

www.MonolithicPower.com

11

5/26/2021

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OPERATION

The MP86934 is a 25A monolithic half-bridge

driver with MOSFETs ideally suited for multi-

phase buck regulators.

When VIN, VCC and VBST signals are sufficiently

high, operation begins.

PWM

PWM input pin is capable to Tri-state input.

When the PWM input signal is within the tri-

state threshold window for 50ns (typical), THT or

TLT, the HSFET will be turned OFF immediately

and the LSFET will be in diode emulation mode

which is ON until zero current detection. The tri-

state PWM input can be from a forced middle

voltage PWM signal or made by floating PWM

input and the internal current source will charge

the signal to a middle voltage. Please refer to

the PWM timing diagram for the propagation

delay definition from PWM to SW node.

Standby Mode

When SYNC pin is floating or forced to middle

state voltage for 2us, MP86934 will enter to

standby mode. During standby mode, the part

shuts down and both CS and VTEMP/FLT

outputs are disabled. The fault latch will not be

reset by entering standby mode.

Diode Emulation mode

In diode emulation mode, when PWM is either

low or Tri-state input, the LSFET will be turned

ON whenever the inductor current is positive.

LSFET is off if the inductor current crossed zero

current. Diode emulation mode can be enabled

by:

1) Pull SYNC pin low

2) Drive PWM to middle state

3) Floating PWM pin.

Positive and Negative Inductor Current limit

When HSFET over current is detected for 4

consecutive cycles, HSFET will latch off,

VTEMP/FLT will be pull to 3.3V, LSFET will turn

on until zero current detection and then LSFET

will be turned off. Recycling VIN/VCC or toggling

EN will release the latch and restart the device.

When LSFET detects a -15A current, the part

will turn off LSFET for 40ns to limit the negative

current. LSFET’s negative current limit will not

trigger fault report.

Over Temperature Protection

When the junction temperature reaches the

Over Temperature Threshold, the HSFET will

be latched OFF, VTEMP/FLT will be 3.3V,

LSFET will turn on until zero current detection

and then LSFET will turn off.

Temperature Sense Output with Fault

indicator, VTEMP/FLT

VTEMP/FLT is a pin with dual functions.

1) Junction

Temperature

Sense:

VTEMP/FLT

is

a

voltage

output

proportional to junction temperature

whenever the VCC is higher than its

UVLO and in part is in active mode. The

gain is 10mV/°C and it has -100mV

offset

at

25°C.

i.e.

0V@TJ<10°C,

0.15V@TJ=25°C and 0.9V@TJ=100°C.

2) Fault function: When any fault occurred,

the VTEMP/FLT will be pulled to

3.3V_typ (3.0V_min) regardless the

temperature to report the fault event. It

monitors three fault events;

(a)

Over Current limit: A consecutive

4 times current limit fault. Once fault, the

part will latch OFF to turn OFF HSFET.

The LSFET will be turned OFF when the

inductor current reaches zero.

(b)

Over

Temperature

fault

at

TJ>160°C. Once fault, the part will latch

OFF to turn OFF HSFET. The LSFET

will be turned OFF when the inductor

current reaches zero.

(c)

SW to PGND shorted. Once fault,

the part will latch OFF to turn OFF

HSFET.

The fault latch will not be reset by

entering standby mode. The release of

fault latch can be done by either re-cycle

VIN or VCC.