TLF51801ELV Datasheet, PDF (11/29 Pages) Infineon Technologies AG – 10 A synchronous DC/DC Step-Down Controller

TLF51801ELV
Regulator
5.4
Bootstrap concept
The high-side MOSFET driver is supplied by the bootstrap concept. The capacitor at pin BTS and BUO must be
switched to GND to be charged by the internal LDO. A monitoring circuit controls the charge of the bootstrap
capacitor. If the charge is sufficient the driver will trigger the external high-side MOSFET. If a recharge is
necessary, the capacitor will be loaded using the integrated bootstrap diode by switching pin BUO to ground
forcing a proper PWM signal.
For very high duty-cycle and high input capacitance of the MOSFET, it may be necessary to consider use of an
external diode placed in parallel with the internal bootstrap diode to speed up the recharge of the bootstrap
capacitor. In addition, the small voltage drop across the external diode improves the overdrive of the gate of the
high-side MOSFET.
VS
Linear Regulator
EN
IVCC
Parts in grey are optional
Figure 7 Bootstrap concept
UV
CROSS
PWM CONDUCTION
SAFETY LOGIC
LS
UG
DRIVER
PHS
DETECT
V_LS
LG
DRIVER
BTS
CBTS
UG
BUO
LG
PGND
Data sheet
11
Rev. 1.0.1, 2013-04-15