uP1965S

4

uP1965S-DS-F0000, May. 2018

www.upi-semi.com

Functional Description

Enable Control

The EN pin controls PWM pin state and the MOSFET gate

driver output state. Logic input low to EN pin disables the

gate drivers. Both UGATE and LGATE will be kept low, and

PWM pin will be in high input impedance state. Logic input

high to EN pin enables the gate drivers after a delay time

T

PWM pin stays at high input impedance state, both UGATE

and LGATE outputs are kept low, and the internal control

circuit does not respond to the PWM input voltage. After

T

to the PWM input. This mechanism is specifically designed

for uPI’s PWM controller, which uses its PWM pin as a

multi-functional pin.

PWM

LGATE

UGATE

EN

Figure 1. Enable Control, EN

PWM Input

The PWM pin is a tri-state input. Logic high turns on the

high-side gate driver and turns off the low-side gate driver

once the POR of VCC is granted and EN is kept high.

Logic low turns off the high-side gate driver and turns on

the low-side gate driver. High impedance input at PWM pin

will keep both high-side and low-side gate drivers low and

turns off both MOSFETs. The PWM pin voltage is kept

around 1.6V by internal bias circuit when floating.

Refer to Figure 1, during T

are kept low, the PWM pin is in high-input impedance state,

and the PWM input will be ignored. For the PWM controller

uses its PWM pin as a multi-functional pin, a resistor will

be connected from PWM pin to GND to set parameter.

Note that this resistor must be greater than 15kΩ. Lower

resistor value will cause incorrect PWM voltage level at

the PWM pin when the PWM controller output is in tri-

state (high-impedance state).

Low-Side Driver

The low-side driver is designed to drive a ground referenced

N-channel MOSFET. The bias to the low-side driver is

internally connected to VCC supply and GND. The low-

side driver output is out of phase with the PWM input when

it is enabled. The low side driver is held low if the EN pin is

pulled low or high-impedance at PWM pin.

High-Side Driver

The high-side driver is designed to drive a floating N-channel

MOSFET. The bias voltage to the high-side driver is

internally connected to BOOT and PHASE pins. An

integrated bootstrap switch that is connected between

BOOT and VCC pins provides the bias current for the high

side gate driver.

The bootstrap capacitor C

PHASE pin is grounded by turning on the low-side

MOSFET. The PHASE rises to V

MOSFET is turned on, forcing the BOOT pin voltage to V

IN

+ V

on.

The high-side gate driver output is in phase with the PWM

input when it is enabled. The high-side driver is held low if

the EN pin is pulled low or high-impedance at PWM pin.

Shoot Through Protection

The shoot-through circuit prevents the high-side and low-

side MOSFETs from being turned on simultaneously and

conducting destructive large current. It is done by turning

on one MOSFET only after the other MOSFET is off already

with adequate delay time.

At the high-side off edge, UGATE and PHASE voltages

are monitored for anti-shoot-through protection. The low-

side driver will not begin to output high until both (V

V

high-side MOSFET is turned off completely.

At the low-side off edge, LGATE voltage is monitored for

anti-shoot-through protection. The high-side driver will not

begin to output high until V

sure the low-side MOSFET is turned off completely.