TLF51801ELV Datasheet, PDF (12/29 Pages) Infineon Technologies AG – 10 A synchronous DC/DC Step-Down Controller

TLF51801ELV
Regulator
5.5
Current Limitation
5.5.1 Rdson-configuration
To optimize the efficiency, the regulator is measuring the voltage (which is the current through the MOSFET
multiplied by the Rdson) over the high-side switch, if it should be too high the pulse will be cut off. By varying the
sense resistor between the pin sensehigh and the drain of the high-side MOSFET the current limit can be adjusted.
Senselow is connected to the source of the MOSFET.
Pow er current
flow
E xternal high side M O S
VS
R_SENSE
SENSEHIG H
SENSELOW
OVERCURRENT
COMPARATOR
(O VC)
BUO
BLANK
OVERCURRENT
LO G IC SIG NA L
Figure 8 Rdson-configuration for current limitation
The figure above shows the concept of the Rdson configuration for current limitation. The characteristics of the
external high-side MOSFET must be known, especially its thermal behavior. The current limitation might be
calculated with the following equation:
I _limit
= I _{OC _ lim, ref}
⋅
R _ SENSE
Rdson _ EXT _ MOS
Data sheet
12
Rev. 1.0.1, 2013-04-15