MIC4607 datasheet(20/42 Pages) MICROCHIP

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MIC4607

DS20005610A-page 20

 2016 Microchip Technology Inc.

5.0

FUNCTIONAL DESCRIPTION

The MIC4607 is a non-inverting, 85V three-phase

MOSFET driver designed to independently drive all six

N-Channel MOSFETs in a three-phase bridge. The

MIC4607 offers a wide 5.5V to 16V VDD operating

supply range with either six independent TTL inputs

(MIC4607-1) or three PWM inputs, one for each phase

(MIC4607-2). Refer to the Functional Diagram section.

The drivers contain input buffers with hysteresis, four

independent UVLO circuits (three high-side and one

low-side), and six output drivers. The high-side output

drivers utilize a high-speed level-shifting circuit that is

referenced to its HS pin. Each phase has an internal

diode that is used by the bootstrap circuits to provide

the drive voltages for each of the three high-side

outputs. A programmable overcurrent protection circuit

turns off all outputs during an overcurrent fault.

5.1

Startup and UVLO

The UVLO circuits force the driver’s outputs low until

the supply voltage exceeds the UVLO threshold. The

low-side UVLO circuit monitors the voltage between

the VDD and VSS pins. The high-side UVLO circuits

monitor the voltage between the xHB and xHS pins.

Hysteresis in the UVLO circuits prevent system noise

and finite circuit impedance from causing chatter during

turn-on.

5.2

Enable Inputs

There is one external enable pin that controls all three

phases. A logic high on the enable pin (EN) allows for

startup of all phases and normal operation. Conversely,

when a logic low is applied on the enable pin, all

phases turn-off and the device enters a low current

shutdown mode. All outputs (xHO and xLO) are pulled

low when EN is low. Do not leave the EN pin floating.

5.3

Input Stage

All input pins (xLI and xHI) are referenced to the VSS

pin. The MIC4607 has a TTL-compatible input range

and can be used with input signals with amplitude less

than the supply voltage. The threshold level is indepen-

dent of the VDD supply voltage and there is no depen-

dence between IVDD and the input signal amplitude.

This feature makes the MIC4607 an excellent level

translator that will drive high level gate threshold MOS-

FETs from a low-voltage PWM IC.

5.4

Low-Side Driver

The low-side driver is designed to drive a ground (VSS

pin) referenced N-channel MOSFET. Low driver

impedances allow the external MOSFET to be turned

on and off quickly. The rail-to-rail drive capability of the

output ensures a low RDSON from the external power

device. Refer to Figure 5-1.

A high level applied to the xLI pin causes VDD to be

applied to the gate of the external MOSFET. A low level

on the xLI pin grounds the gate of the external

MOSFET.

FIGURE 5-1:

Low-Side Driver Block

Diagram.

5.5

High-Side Driver and Bootstrap

Circuit

Figure 5-2 illustrates a block diagram of the high-side

driver and bootstrap circuit. This driver is designed to

drive a floating N-channel MOSFET, whose source ter-

minal is referenced to the HS pin.

FIGURE 5-2:

High-Side Driver and

Bootstrap-Circuit Block Diagram.

A low-power, high-speed, level-shifting circuit isolates

the low side (VSS pin) referenced circuitry from the

high-side (xHS pin) referenced driver. Power to the

high-side driver and UVLO circuit is supplied by the

bootstrap capacitor (CB) while the voltage level of the

xHS pin is shifted high.

The bootstrap circuit consists of an internal diode and

external capacitor, CB. In a typical application, such as

the motor driver shown in Figure 5-3 (only Phase A

illustrated), the AHS pin is at ground potential while the

low-side MOSFET is on. The internal diode charges

capacitor CB to VDD-VF during this time (where VF is

VSS

VDD

EXTERNAL

FET

MIC4607

SWITCH

NODE

EXTERNAL

FET

VDD

MIC4607

LEVEL

SHIFT

VIN

RHS

SWITCH

NODE

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