TLE6284G_07 Datasheet, PDF (10/16 Pages) Infineon Technologies AG – H-Bridge Driver IC Deactivation of dead time and shoot through protection possible

Data Sheet TLE6284G
Operation at different voltages for Vs, DH1 and DH2
If DH1 and DH2 are used with a voltage higher than Vs, a duty cycle of 100% can not be
guaranteed. In this case the driver is acting like a normal driver IC based on the bootstrap
principle. This means that after a maximum “On” time of the highside switch of more than
1ms a refresh pulse to charge the bootstrap capacitor of about 1µs is needed to avoid un-
dervoltage lock out of this output stage.
Operation at extreme duty cycle:
The integrated charge pump allows an operation at 100% duty cycle. The charge pump is
strong enough to replace leakage currents during “on”-phase of the highside switch. The
gate charge for fast switching of the highside switches is supplied by the bootstrap capaci-
tors. This means, that the bootstrap capacitor needs a minimum charging time of about 1µs,
if the highside switch is operated in PWM mode (e.g. with 20kHz a maximum duty cycle of
96% can be reached). The exact value for the upper limit is given by the RC time formed by
the impedance of the internal bootstrap diode and the capacitor formed by the external Mos-
fet (C_Mosfet=Q_Gate / V_GS). The size of the bootstrap capacitor has to be adapted to the external
MOSFET the driver IC has to drive. Usually the bootstrap capacitor is about 10-20 times big-
ger than C_Mosfet. External components at the Vs Pin have to be considered, too.
The charge pump is active when the highside switch is “ON” and the voltage level at the SHx
is higher than 4V. Only under these conditions the bootstrap capacitor is charged by the
charge pump.
Data Sheet
10
Rev 2.3 2007-01-11