MP1909

– 30V, HIGH-FREQUENCY HALF-BRIDGE GATE DRIVER

MP1909 Rev. 1.0

www.MonolithicPower.com

10

7/10/2020

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© 2020 MPS. All Rights Reserved.

OPERATION

Theory of Operation

The MP1909 can drive two N-channel MOSFETs

in a synchronous buck or boost converter

topology. It can work at a 12V gate drive voltage

to minimize the external MOSFET

’s RDS(ON) and

achieve higher efficiency. A single PWM input

signal can generate the well-controlled high-side

and low-side drivers.

100% Duty Cycle

The high-side driver can turn on with 100% duty

cycle as long as the difference between VCC and

VIN exceeds 3.4V.

Switch Shoot-Through Protection

Internal anti-shoot-through circuitry protects the

high-side and low-side MOSFETs from turning

on at the same time. Adaptive dead time control

greatly reduces the dead time and switching

power loss.

When the PWM input goes high, the DRVL pin

goes low. The time it takes for the low-side

MOSFET (LS-FET) to turn off is determined by

the total gate charge. The MP1909 monitors the

LS-

FET’s VGS and level shifts this voltage

information to the high-side driver. The high-side

driver does not turn on the high-side MOSFET

(HS-FET) until the LS-FET is completely turned

off.

Under-Voltage Lockout

When BST-SW goes below its under-voltage

lockout (UVLO) threshold, the DRVH

pin’s output

goes low to turn off the HS-FET.

When VCC falls below its UVLO threshold, both

the DRVH and DRVL outputs go low to turn off

the MOSFETs.

Table 1 lists the operation of the HS-FET and

LS-FET

under

different

PWM

and

UVLO

conditions.

Table 1: States of Driver Outputs under Different Conditions

EN

BST-SW Voltage

VCC Voltage

PWM

DRVH

DRVL

Operating

Conditions

0

X

X

X

250kΩ

pull-down

resistor

250kΩ

pull-down

resistor

X

1

Above UVLO

Above UVLO

1

1

0

Normal operation

Above UVLO

Above UVLO

0

0

1

Falls below UVLO

Above UVLO

1

0

0

Falls below UVLO

Above UVLO

0

0

1

Above UVLO

Falls below UVLO

X

0

0

Normal-to-tripped

transition

Below UVLO

Falls below UVLO

X

0

0

Note:

9)

“X” means not applicable.