April 30, 2008
LM5118
Wide Voltage Range Buck-Boost Controller
General Description
Features
The LM5118 wide voltage range Buck-Boost switching regu-
lator controller features all of the functions necessary to im-
plement a high performance, cost efficient Buck-Boost
regulator using a minimum of external components. The
Buck-Boost topology maintains output voltage regulation
when the input voltage is either less than or greater than the
output voltage making it especially suitable for automotive
applications. The LM5118 operates as a buck regulator while
the input voltage is sufficiently greater than the regulated out-
put voltage and gradually transitions to the buck-boost mode
as the input voltage approaches the output. This dual mode
approach maintains regulation over a wide range of input
voltages with optimal conversion efficiency in the buck mode
and a glitch-free output during mode transitions. This easy to
use controller includes drivers for the high side buck MOSFET
and the low side boost MOSFET. The regulator’s control
method is based upon current mode control utilizing an em-
ulated current ramp. Emulated current mode control reduces
noise sensitivity of the pulse-width modulation circuit, allow-
ing reliable control of the very small duty cycles necessary in
high input voltage applications. Additional protection features
include current limit, thermal shutdown and an enable input.
The device is available in a power enhanced TSSOP-20
package featuring an exposed die attach pad to aid thermal
dissipation.
Ultra-wide input voltage range from 3V to 75V
Emulated peak current mode control
Smooth transition between step-down and step- up modes
Switching frequency programmable to 500KHz
Oscillator synchronization capability
Internal high voltage bias regulator
Integrated high and low-side gate drivers
Programmable soft-start time
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Ultra low shutdown current
Enable input wide bandwidth error amplifier
1.5% feedback reference accuracy
Thermal shutdown
Package
TSSOP-20EP (Exposed pad)
Typical Application Circuit
30058501
© 2008 National Semiconductor Corporation
300585
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