SNVS219K – JUNE 2003 – REVISED APRIL 2013
LM5642/LM5642X High Voltage, Dual Synchronous Buck Converter with Oscillator
Synchronization
Check for Samples:
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FEATURES
Two Synchronous Buck Regulators
180° Out of Phase Operation
200 kHz Fixed Nominal Frequency: LM5642
375 kHz Fixed Nominal Frequency: LM5642X
Synchronizable Switching Frequency from 150
kHz to 250 kHz for the LM5642 and 200 kHz to
500 kHz for the LM5642X
4.5V to 36V Input Range
50 µA Shutdown Current
Adjustable Output from 1.3V to 90% of Vin
0.04% (Typical) Line and Load Regulation
Accuracy
Current Mode Control with or without a Sense
Resistor
Independent Enable/Soft-start Pins Allow
Simple Sequential Startup Configuration.
Configurable for Single Output Parallel
Operation. (See
Adjustable Cycle-by-cycle Current Limit
Input Under-voltage Lockout
Output Over-voltage Latch Protection
Output Under-voltage Protection with Delay
Thermal Shutdown
Self Discharge of Output Capacitors when the
Regulator is OFF
TSSOP and HTSSOP (Exposed PAD) Packages
DESCRIPTION
The LM5642 series consists of two current mode
synchronous buck regulator controllers operating
180° out of phase with each other at a normal
switching frequency of 200kHz for the LM5642 and at
375kHz for the LM5642X.
Out of phase operation reduces the input RMS ripple
current, thereby significantly reducing the required
input capacitance. The switching frequency can be
synchronized to an external clock between 150 kHz
and 250 kHz for the LM5642 and between 200 kHz
and 500 kHz for the LM5642X. The two switching
regulator outputs can also be paralleled to operate as
a dual-phase, single output regulator.
The output of each channel can be independently
adjusted from 1.3V to 90% of Vin. An internal 5V rail
is also available externally for driving bootstrap
circuitry.
Current-mode feedback control assures excellent line
and load regulation and wide loop bandwidth for
excellent response to fast load transients. Current is
sensed across either the Vds of the top FET or
across an external current-sense resistor connected
in series with the drain of the top FET.
The LM5642 features analog soft-start circuitry that is
independent of the output load and output
capacitance making the soft-start behavior more
predictable and controllable than traditional soft-start
circuits.
Over-voltage protection is available for both outputs.
A UV-Delay pin is also available to allow delayed shut
off time for the IC during an output under-voltage
event.
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APPLICATIONS
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Embedded Computer Systems
Navigation Systems
Telecom Systems
Set-Top Boxes
WebPAD
Point Of Load Power Architectures
Typical Application Circuit
V
IN
4.5V - 36V
UV_Delay
Vout1
1.3V-0.9V
IN
SYNC
LM5642/LM5642X
SS/ON1
SS/ON2
Vout2
1.3V-0.9V
IN
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Copyright © 2003–2013, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
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