LM5085 Datasheet, PDF (1/23 Pages) National Semiconductor (TI) – 75V Constant On-Time PFET Buck Switching Controller

LM5085
May 8, 2012
75V Constant On-Time PFET Buck Switching Controller
General Description
The LM5085 is a high efficiency PFET switching regulator
controller that can be used to quickly and easily develop a
small, efficient buck regulator for a wide range of applications.
This high voltage controller contains a PFET gate driver and
a high voltage bias regulator which operates over a wide 4.5V
to 75V input range. The constant on-time regulation principle
requires no loop compensation, simplifies circuit implemen-
tation, and results in ultrafast load transient response. The
operating frequency remains nearly constant with line and
load variations due to the inverse relationship between the
input voltage and the on-time. The PFET architecture allows
100% duty cycle operation for a low dropout voltage. Either
the R_DS(ON) of the PFET or an external sense resistor can be
used to sense current for over-current detection.
Features
■ ^{LM5085Q is an Automotive Grade product that is AEC-}
Q100 grade 1 qualified (-40°C to 125°C operating junction
temperature)
■ ^{Wide 4.5V to 75V input voltage range}
■ ^{Adjustable current limit using R}_DS(ON) ^{or a current sense}
resistor
■ ^{Programmable switching frequency to 1MHz}
■ ^{No loop compensation required}
■ ^{Ultra-Fast transient response}
■ ^{Nearly constant operating frequency with line and load}
variations
■ ^{Adjustable output voltage from 1.25V}
■ ^{Precision ±2% feedback reference}
■ ^{Capable of 100% duty cycle operation}
■ ^{Internal soft-start timer}
■ ^{Integrated high voltage bias regulator}
■ ^{Thermal shutdown}
Package
■ ^MSOP-8EP
■ ^MSOP-8
■ ^{LLP-8 (3mm x 3mm)}
Typical Application, Basic Step Down Controller
© 2012 Texas Instruments Incorporated 300577 SNVS565E
30057701
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