AN709 Datasheet, PDF (1/7 Pages) Vishay Siliconix – Designing with the Si9976DY N-Channel Half-Bridge Driver

AN709
Vishay Siliconix
Designing with the Si9976DY N-Channel Half-Bridge Driver and
LITTLE FOOTR Dual MOSFETs
Wharton McDaniel
INTRODUCTION
The Si9976DY is a fully integrated half-bridge driver IC which
was designed to work with the LITTLE FOOT family of power
MOSFET products in 20- to 40-V systems. The Si9976DY
provides the gate drive for both the low- and high-side MOSFETs
while the Si9945 (SO-8, 3.3 A) or Si4946EY (SO-8, 4.5 A) dual
n-channel LITTLE FOOT MOSFETs provide power handling
capability without the need of a heatsink. All of these devices are
supplied in surface-mount packages. The combination of the
Si9976DY and one of the dual n-channel MOSFETs creates a
powerful and flexible solution for power switching in dc motor
drives.
SI9976DY OVERVIEW
The Si9976DY is an integrated driver for an n-channel
MOSFET half-bridge (see Figure 1). Schmitt trigger inputs
provide logic signal compatibility and hysteresis for noise
immunity. Low impedance outputs are provided to drive both
the low- and high-side MOSFETs of the half-bridge. The
addition of a bootstrap capacitor allows the internal circuitry to
level shift both the power supply and the logic signals that are
required for the high-side n-channel MOSFET gate drive. A
charge pump has been included to replace the leakage current
in the high-side driver, which allows static (dc) operation.
A separate voltage input, V_CC, powers the FAULT output to
allow easy interfacing to the user’s system. Protection circuits
include an undervoltage lockout to assure safe gate-drive
levels, timing delays to prevent cross-conduction, and a
monitor for short circuits on the half-bridge output (S1). An
internal voltage regulator drops the input voltage (V+) to a
nominal 16 V for the low-side circuitry, which allows the
Si9976DY to operate over an input voltage range of 20 to 40 V.
The device is specified over the industrial temperature range
(–40_ to +85_C).
V+
Bootstrap
V+3
Regulator
V_DD4
Low Voltage
Regulator
V_{CC 7}
8
FAULT
Under Voltage
Lockout 2
Charge
Pump
Short Ckt &
UVL Detect
V_DD
Under Voltage
Lockout 1
IN ₅
0.01 mF
EN 6
10
GND
R
S
Q
Enable Latch
Substrate
250 ns
Delay
300 ns
Delay
2 ^CAP
C_Boot
12 ^G1
13 ^S1
Half-Bridge
Output
9 ^G2
Document Number: 70582
15-Jun-00
Figure 1. Si9976DY Functional Block Diagram
GND
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