LM34937 Datasheet, PDF (1/31 Pages) Texas Instruments – Wide Input Range Synchronous Buck Controller

LM34937/LM34937Q
May 23, 2012
Wide Input Range Synchronous Buck Controller
General Description
The LM34937 is a synchronous buck controller intended for
step-down regulator applications from a high voltage or widely
varying input supply. The control method is based upon cur-
rent mode control utilizing an emulated current ramp. Current
mode control provides inherent line feed-forward, cycle-by-
cycle current limiting and ease of loop compensation. The use
of an emulated control ramp reduces noise sensitivity of the
pulse-width modulation circuit, allowing reliable control of
very small duty cycles necessary in high input voltage appli-
cations.
The operating frequency is programmable from 50 kHz to 650
kHz. The LM34937 drives external high-side and low-side
NMOS power switches with adaptive dead-time control. A us-
er-selectable diode emulation mode enables discontinuous
mode operation for improved efficiency at light load condi-
tions. A high voltage bias regulator that allows external bias
supply further improves efficiency. Additional features include
thermal shutdown, frequency synchronization, hiccup mode
current limit and adjustable line under-voltage lockout.
Features
■ ^{LM34937Q is an Automotive Grade product that is AEC-}
Q100 grade 1 qualified (-40°C to +125°C operating
junction temperature)
■ ^{Emulated peak current mode control}
■ ^{Wide operating range from 4.5V to 42V}
■ ^{Free-run or synchronizable clock up to 650kHz}
■ ^{Optional diode emulation mode}
■ ^{Programmable output from 0.8V}
■ ^{Precision 1.5% voltage reference}
■ ^{Programmable current limit}
■ ^{Hiccup mode over current protection}
■ ^{Programmable soft-start and tracking}
■ ^{Programmable line under-voltage lockout}
■ ^{Thermal shutdown}
Packages
■ ^{TSSOP-20EP (Thermally enhanced)}
■ ^{LLP-24 (4mmx4mm)}
Typical Application
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