ML4771 Datasheet, PDF (1/8 Pages) Micro Linear Corporation – High Current Boost Regulator

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
s Guaranteed full load start-up and operation at
1.8V input
s Continuous conduction mode for high output current
s Very low supply current (20µA output referenced) for
micropower operation
s Pulse Frequency Modulation and Internal Synchronous
Rectification for high efficiency
s Maximum switching frequency > 200kHz
s Minimum external components
s Low ON resistance internal switching FETs
s Adjustable output voltage (3.0V to 5.5V)
BLOCK DIAGRAM
*CIN
VIN
2
VBAT
GND
3
(* Indicates Part is End Of Life as of July 1, 2000)
1
VL1
L1
6
VL2
BOOST
CONTROL
PWR GND
8
VOUT
5
R1
VOUT
COUT
SENSE
4
R2
*CFB
1