July 2000
ML4771*
High Current Boost Regulator
GENERAL DESCRIPTION
The ML4771 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 ML4771
is capable of start-up with input voltages as low as 1.8V,
and the output voltage can be set anywhere between 3.0V
and 5.5V by an external resistor divider connected to the
SENSE pin.
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 ML4771 requires a minimum number of
external components to build a very small regulator circuit
capable of achieving conversion efficiencies exceeding
85%.
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
Adjustable output voltage (3.0V to 5.5V)
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(* Indicates Part is End Of Life as of July 1, 2000)
BLOCK DIAGRAM
L1
1
VL1
VIN
2
*CIN
6
VL2
VOUT
5
VOUT
R1
VBAT
COUT
GND
3
BOOST
CONTROL
SENSE
4
R2
*CFB
PWR GND
8
1
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
