November 1, 2007
36V, 2A PowerWise® Adjustable Frequency Synchronous
The LM20242 is a full featured 1MHz capable synchronous
buck regulator capable of delivering up to 2A of load current.
The current mode control loop is externally compensated with
only two external components, offering both high perfor-
mance and ease of use. The device is optimized to work over
the input voltage range of 4.5V to 36V making it well suited
for high voltage systems.
The device features internal Over Voltage Protection (OVP)
and Over Current Protection (OCP) circuits for increased sys-
tem reliability. A precision Enable pin and integrated UVLO
allows the turn on of the device to be tightly controlled and
sequenced. Startup inrush currents are limited by both an in-
ternally fixed and externally adjustable soft-start circuit. Fault
detection and supply sequencing are possible with the inte-
grated PGOOD circuit.
The LM20242 is designed to work well in multi-rail power
supply architectures. The output voltage of the device can be
configured to track a higher voltage rail using the SS/TRK pin.
If the output of the LM20242 is pre-biased at startup it will not
sink current to pull the output low until the internal soft-start
ramp exceeds the voltage at the feedback pin.
The LM20242 is offered in an exposed pad 20 pin TSSOP
package that can be soldered to the PCB, eliminating the
need for bulky heatsinks.
■ 2A Output Current, 3.7A peak current
■ 130 mΩ/110 mΩ integrated power MOSFETs
■ 1.5% output voltage accuracy
■ Current Mode Control, selectable compensation
■ Resistor programmed, 1MHz capable oscillator
■ Synchronous rectifier with diode emulation
■ Adjustable output voltage down to 0.8V
■ Compatible with pre-biased loads
■ Programmable soft-start with external capacitor
■ Precision enable pin with hysteresis
■ OVP, UVLO inputs and PGOOD output
■ Internally protected with peak current limit, thermal
shutdown and restart
■ Accurate current limit with frequency foldback
■ Non-linear current mode slope compensation
■ eTSSOP-20 exposed pad package
■ Simple to design, high efficiency point of load regulation
from a 4.5V to 36V bus
■ High Performance DSPs, FPGAs, ASICs and
■ Communications Infrastructure, Automotive
Simplified Application Circuit
PowerWise® is a registered trademark of National Semiconductor Corporation.
© 2007 National Semiconductor Corporation 300314