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FEATURIN
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July 2000
ML4872
High Current Boost Regulator with Shutdown
GENERAL DESCRIPTION
The ML4872 is a continuous conduction boost regulator
designed for DC to DC conversion in multiple cell battery
powered systems. Continuous conduction allows the
regulator to maximize output current for a given inductor.
The maximum switching frequency can exceed 200kHz,
allowing the use of small, low cost inductors. The ML4872
is capable of start-up with input voltages as low as 1.8V
and is available in 5V and 3.3V output versions with an
output voltage accuracy of ±3%.
An integrated synchronous rectifier eliminates the need
for an external Schottky diode and provides a lower
forward voltage drop, resulting in higher conversion
efficiency. In addition, low quiescent battery current and
variable frequency operation result in high efficiency
even at light loads. The ML4872 requires only one
inductor and two capacitors to build a very small
regulator circuit capable of achieving conversion
efficiencies approaching 90%.
The SHDN input allows the user to stop the regulator from
switching and powers down the control circuitry.
FEATURES
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Guaranteed full load start-up and operation at
1.8V Input
Continuous conduction mode for high output current
Very low supply current (20µA output referenced) for
micropower operation
Pulse frequency modulation and internal synchronous
rectification for high efficiency
Maximum switching frequency > 200kHz
Minimum external components
Low ON resistance internal switching FETs
5V and 3.3V output versions
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BLOCK DIAGRAM
1
VIN
2
VL1
6
VL2
START-UP
SYNCHRONOUS
RECTIFIER
CONTROL
VOUT
+
–
5
+
–
BOOST
CONTROL
+
–
1.25V
SHDN
4
PWR GND
8
GND
3
1
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
