October 1996
ML4961
Adjustable Output Low Voltage
Boost Regulator with Detect
GENERAL DESCRIPTION
The ML4961 is a boost regulator designed for DC to DC
conversion in 1 to 3 cell battery powered systems. The
combination of BiCMOS process technology, internal
synchronous rectification, variable frequency operation,
and low supply current make the ML4961 ideal for 1 cell
applications. The ML4961 is capable of start-up with input
voltages as low as 1V, and the output voltage can be set
anywhere between 2.5V and 6V 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 ML4961 requires a minimum number of
external components to build a very small adjustable
regulator circuit capable of achieving conversion
efficiencies in excess of 90%.
The circuit also contains a
RESET
output which goes low
when the IC can no longer function due to low input
voltage, or when the DETECT input drops below 200mV.
FEATURES
s
s
s
s
s
s
Guaranteed full load start-up and operation at 1V input
Pulse Frequency Modulation and Internal Synchronous
Rectification for high efficiency
Minimum external components
Low ON resistance internal switching FETs
Micropower operation
Adjustable output voltage (2.5V to 6V)
BLOCK DIAGRAM
L1
C
IN
*
1
V
IN
6
V
L
V
OUT
5
C
FF
*
+
R1
*R
A
DETECT
4
+
鈥?/div>
*R
B
+
鈥?/div>
UVLO
BOOST
CONTROL
V
REF
PWR
GND
8
RESET
7
SENSE
3
C
OUT
R2
GND
2
鈥?/div>
*OPTIONAL
TO MICROPROCESSOR
1
1
2
3
4
5
6
7
8
