irs2608d International Rectifier Corp., irs2608d Datasheet - Page 11

• Manufacturer Part Number: irs2608d
• Description: Half-bridge Driver
• Manufacturer: International Rectifier Corp.

Integrated Bootstrap Functionality
The IRS2608D embeds an integrated bootstrap FET that allows an alternative drive of the bootstrap supply for a wide
range of applications.
A bootstrap FET is connected between the floating supply V
The bootstrap FET is suitable for most PWM modulation schemes, including trapezoidal control, and can be used
either in parallel with the external bootstrap network (diode+ resistor) or as a replacement of it. The use of the
integrated bootstrap as a replacement of the external bootstrap network may have some limitations in the following
situations:
The summary for the bootstrap state follows:
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www.irf.com
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Bootstrap turns-off (immediately) or stays off when at least one of the following conditions are met:
Bootstrap turns-on when:
When the motor runs at a very low current (so that the negative phase voltage decay can be longer than
20us) and complementary PWM is not used.
At a very high PWM duty cycle due to the bootstrap FET equivalent resistance (R
1- HO goes/is high
2- V
1- LO is high (low side is on) AND V
2- LO and HO are low after a LIN transition from H to L (HB output is in tri-state) AND V
(<1.1*V
3- LO and HO are low after a HIN transition from H to L (HB output is in tri-state) AND V
(<1.1(V
VB goes high (>1.1V
B
goes/is high (> 1.1*V
CC
CC
)) before a retriggerable time of 20us. In this case the time counter is kept in reset state until
) before a fixed time of 20us.
CC
Figure 8: Semplified BootFET connection
). Please refer to the BootFET timing diagram for more details.
Vcc
CC
)
B
is low (< 1.1(V
BootFet
B
and V
CC
))
CC
(see Fig. 8).
Vb
BS
, see page 3).
IRS2608DSPbF
B
B
goes low
goes low
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