MIC4605 Datasheet, PDF (13/25 Pages) Micrel Semiconductor – 85V Half-Bridge MOSFET Drivers

Micrel, Inc.
Functional Description
The MIC4605 is a non-inverting, 85V half-bridge
MOSFET driver designed to independently drive both
high-side and low-side N-Channel MOSFETs. The
MIC4605 offers a wide 5.5V to 16V operating supply
range with either dual TTL inputs (MIC4605-1) or a single
PWM input (MIC4605-2). Refer to the MIC4605 Top
Level Block Diagram.
Both drivers contain an input buffer with hysteresis, a
UVLO circuit, and an output buffer. The high-side output
buffer includes a high-speed level-shifting circuit that is
referenced to the HS pin. An internal diode is used as
part of a bootstrap circuit to provide the drive voltage for
the high-side output.
Startup and UVLO
The UVLO circuit forces the driver output 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 circuit monitors the
voltage between the HB and HS pins. Hysteresis in the
UVLO circuit prevents noise and finite circuit impedance
from causing chatter during turn-on.
Enable Input
The 10-pin 2.5mm × 2.5mm TDFN package features an
enable pin for on/off control of the device. Logic high on
the enable pin (EN) allows for startup and normal
operation to occur. Conversely, when a logic low is
applied on the enable pin, the device enters shutdown
mode.
Input Stage
Both the HI/LI pins of the MIC4605-1 and the single PWM
input of the MIC4605-2 are referenced to the VSS pin.
The voltage state of the input signal(s) does not change
the quiescent current draw of the driver.
The MIC4605 has a TTL-compatible input range and can
be used with input signals with amplitude less than the
supply voltage. The threshold level is independent of the
VDD supply voltage and there is no dependence between
I_VDD and the input signal amplitude with the MIC4605.
This feature makes the MIC4605 an excellent level
translator that will drive high-threshold MOSFETs from a
low-voltage PWM IC.
Low-Side Driver
A block diagram of the low-side driver is shown in Figure
4. The low-side driver is designed to drive a ground (VSS
pin) referenced N-channel MOSFET.
MIC4605
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 R_DSON from the external
MOSFET.
A high level applied to LI 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 LI pin
turns off the upper driver and turns on the low side driver
to ground the gate of the external MOSFET.
Figure 4. Low-Side Driver Block Diagram
High-Side Driver and Bootstrap Circuit
A block diagram of the high-side driver and bootstrap
circuit is shown in Figure 5. This driver is designed to
drive a floating N-channel MOSFET, whose source
terminal is referenced to the HS pin.
Figure 5. High-Side Driver and Bootstrap Circuit
Block Diagram
November 11, 2013
13
Revision 1.0