FAN7888 Fairchild Semiconductor, FAN7888 Datasheet - Page 11

• Manufacturer Part Number: FAN7888
• Description: The FAN7888 is a monolithic three half-bridge gate-drive IC designed for high-voltage, high-speed driving MOSFETs and IGBTs operating up to +200V
• Manufacturer: Fairchild Semiconductor

© 2008 Fairchild Semiconductor Corporation
FAN7888 • Rev.1.0.0
Application Information
1. Protection Function
1.1 Under-Voltage Lockout (UVLO)
The high- and low-side drivers include under-voltage
lockout (UVLO) protection circuitry for each channel that
monitors the supply voltage (V
tor voltage (V
prevent malfunction when V
than the specified threshold voltage. The UVLO hystere-
sis prevent chattering during power supply transitions.
1.2 Shoot-Through Prevention Function
The FAN7888 has shoot-through prevention circuitry
monitoring the high- and low-side control inputs. It can
be designed to prevent outputs of high and low side from
turning on at same time, as shown Figure 27 and 28.
Figure 27. Waveforms for Shoot-Through Prevention
Figure 28. Waveforms for Shoot-Through Prevention
HIN1,2,3/LIN1,2,3
LIN1,2,3/HIN1,2,3
HO1,2,3/LO1,2,3
LO1,2,3/HO1,2,3
HIN1,2,3/LIN1,2,3
LIN1,2,3/HIN1,2,3
HO1,2,3/LO1,2,3
LO1,2,3/HO1,2,3
BS1,2,3
) independently. It can be designed
DD
DD
and V
) and bootstrap capaci-
After DT
Shoot-Through Prevent
After DT
BS1,2,3
FAN7888 Rev.00
FAN7888 Rev.00
Shoot-Through Prevent
are lower
After DT
11
2. Operational Notes
The FAN7888 is a three half-bridge gate driver with
internal typically 120ns dead-time for the three-phase
Brushless DC (BLDC) motor drive system, as shown in
Figure 1.
Figure 29 shows a switching sequence of 120° electrical
commutation for a three-phase BLDC motor drive system.
The waveforms are idealized: they assumed that the
generated back EMF waveforms are trapezoidal with flat
tops of sufficient width to produce constant torque when
the line currents are perfectly rectangular 120° electrical
degrees with the switching sequence as shown in Figure
29. The operating waveforms of the wey-connection
reveal that repeat every 60 electrical degrees, with each
60° segment being “commutated” to another phase, as
shown in Figure 29.
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