MIC4600 datasheet(10/26 Pages) MICROCHIP

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MIC4600

DS20005584A-page 10

 2016 Microchip Technology Inc.

4.0

FUNCTIONAL CHARACTERISTICS

4.1

Functional Diagram

FIGURE 4-1:

Functional Diagram.

4.2

Functional Description

The MIC4600 is a 28V half-bridge MOSFET driver with

integrated LDO. It is designed to independently drive

both high-side and low-side N-Channel MOSFETs. The

LDO eliminates the need for a second VDD supply

voltage by generating the gate drive voltage from the

input supply. The MIC4600 offers a wide 4.5V to 28V

operating supply range. Refer to the MIC4600 Block

Diagram above.

The high and low-side drivers contain an input buffer

with hysteresis and an output buffer. The high-side

output buffer includes a high-speed level-shifting circuit

that is referenced to the HS pin. An external diode is

used to supply VDD to the bootstrap circuit that provides

the drive voltage for the high-side output.

4.2.1

STARTUP AND UVLO

The UVLO circuit monitors VDD and inhibits both

drivers in a low state when the supply voltage is below

the UVLO threshold. Hysteresis in the UVLO circuit

prevents noise and circuit impedance from causing

chatter during turn-on.

4.2.2

ENABLE INPUT

A logic high on the enable pin (EN) allows normal

operation to occur. Conversely, when a logic low is

applied on the enable pin, the high and low-side driver

outputs turn-off and the driver enters a low supply

current shutdown mode. Do not leave floating.

4.2.3

DEAD-TIME DELAY

Shoot-through occurs in a half-bridge or synchronous

buck topology when both the high and low side

MOSFETs conduct at the same time. This condition is

caused by driver propagation delay variation and

MOSFET turn on/off times. Shoot-through causes an

increase in MOSFET power dissipation, circuit noise

and interference with power circuit operation. A resistor

on the DELAY pin sets the break-before-make delay

time between the high and low-side MOSFETs . See

the Applications section for additional information.

4.2.4

INPUT STAGE

Both the HSI and LSI pins are referenced to the AGND

pin. The voltage state of the input signal does not

change the quiescent current draw of the driver.

The MIC4600 has a TTL-compatible input range and

can be used with input signals with amplitude less than

or equal to the VDD voltage. A small amount of

hysteresis improves the noise immunity of the driver

inputs.

4.2.5

LOW-SIDE DRIVER

Figure 4-2 shows a block diagram of the low-side

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

(PGND pin) referenced N-channel MOSFET. The

low-side gate drive voltage equals VDD, which is

typically 5V.

A low driver impedance allows 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 MOSFET.

A high level applied to LSI pin causes the upper driver

MOSFET to turn on and VDD voltage is applied to the

gate of the external MOSFET. A low level on the LSI pin

turns off the upper driver and turns on the low side

driver to ground the gate of the external MOSFET.

FAULT

HSI

LSI

UVLO

MIC4600

LINEAR

REGULATOR

VIN

BST

AGND

DELAY

ANTI-SHOOT THRU

VDD

PGND

CONTROL

LOGIC

TIMER

AVDD

VDD

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