June 2003
LM2727/LM2737
N-Channel FET Synchronous Buck Regulator Controller
for Low Output Voltages
General Description
The LM2727 and LM2737 are high-speed, synchronous,
switching regulator controllers. They are intended to control
currents of 0.7A to 20A with up to 95% conversion efficien-
cies. The LM2727 employs output over-voltage and under-
voltage latch-off. For applications where latch-off is not de-
sired, the LM2737 can be used. Power up and down
sequencing is achieved with the power-good flag, adjustable
soft-start and output enable features. The LM2737 and
LM2737 operate from a low-current 5V bias and can convert
from a 2.2V to 16V power rail. Both parts utilize a fixed-
frequency, voltage-mode, PWM control architecture and the
switching frequency is adjustable from 50kHz to 2MHz by
adjusting the value of an external resistor. Current limit is
achieved by monitoring the voltage drop across the on-
resistance of the low-side MOSFET, which enhances low
duty-cycle operation. The wide range of operating frequen-
cies gives the power supply designer the flexibility to fine-
tune component size, cost, noise and efficiency. The adap-
tive, non-overlapping MOSFET gate-drivers and high-side
bootstrap structure helps to further maximize efficiency. The
high-side power FET drain voltage can be from 2.2V to 16V
and the output voltage is adjustable down to 0.6V.
Features
n Input power from 2.2V to 16V
n Output voltage adjustable down to 0.6V
n Power Good flag, adjustable soft-start and output enable
for easy power sequencing
n Output over-voltage and under-voltage latch-off
(LM2727)
n Output over-voltage and under-voltage flag (LM2737)
n Reference Accuracy: 1.5% (0˚C - 125˚C)
n Current limit without sense resistor
n Soft start
n Switching frequency from 50 kHz to 2 MHz
n TSSOP-14 package
Applications
n Cable Modems
n Set-Top Boxes/ Home Gateways
n DDR Core Power
n High-Efficiency Distributed Power
n Local Regulation of Core Power
Typical Application
© 2003 National Semiconductor Corporation DS200494
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