FAN7384 Datasheet, PDF (14/17 Pages) Fairchild Semiconductor – Half-Bridge Gate-Drive IC

Typical Application Information
1. Protection Function
1.1 Under-Voltage Lockout (UVLO)
The high- and low-side drivers include under-voltage
lockout (UVLO) protection circuitry that monitors the
supply voltage (V_DD) and bootstrap capacitor voltage
(V_BS) independently. It can be designed to prevent
malfunction when V_DD and V_BS are lower than the
specified threshold voltage. Moreover, the UVLO
hysteresis prevents chattering during power supply
transitions. If the supply voltage (V_DD) maintains an
under-voltage condition over under-voltage filtering times
(typically 16µs), the fault and soft-off circuits are
activated, as shown Figure 34.
LIN
HIN/LIN
LIN/HIN
HO/LO
Shoot-Through Prevent
After DT
LO/HO
FAN7384 Rev.01
Figure 36. Waveforms for Shoot-Through Prevention
V_DD
FO
t_UVFLT
t_CSCFO
UVLO+
UVLO-
t_FO
LO
t_CSCLO
90%
FAN7384 Rev.01
t₁
t₂
t₃
Figure 34. Waveforms for Under-Voltage Lockout
1.2 Shoot-Through Prevention Function
The FAN7384 has a shoot-through prevention circuitry
that monitors the high- and low-side inputs. It can be
designed to prevent outputs of high- and low-side turning
on at same time, as shown Figure 35 and 36.
1.3 Over-Current Protection Function
The FAN7384 has over-current detection circuitry that
monitors the current-by-current sensing resistor con-
nected from the low-side switch source (V_SL) to ground.
It is a built-in time-filler from the over-current event to
prevent malfunction from a noise source, such as lead-
ing-edge pulse in inductive load application, as shown
Figure 37.
The sensing current is calculated as follows:
I_CS
= ^VCSCREF
R_CS
[ A]
(1)
where,
V_CSCREF: Reference voltage of current sense
comparator
R_CS: Current sensing resistor
HIN/LIN
LIN/HIN
HO/LO
Shoot-Through Prevent
After DT
LO/HO
After DT
FAN7384 Rev.00
Figure 35. Waveforms for Shoot-Through Prevention
LIN
V_CSC
FO
LO
Low-Side Output
Disable
t_CSCFO
t_FO
t_CSCLO
0.5V
Soft-Off
Short-Circuit ^Operating
Detection Point
FAN7384 Rev.03
Figure 37. Waveforms for Short-Circuit Protection
© 2006 Fairchild Semiconductor Corporation
FAN7384 Rev. 1.0.3
14
www.fairchildsemi.com