ML4861 Datasheet, PDF (1/11 Pages) Micro Linear Corporation – Low Voltage Boost Regulator

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October 1996
ML4861*
Low Voltage Boost Regulator
GENERAL DESCRIPTION
The ML4861 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 ML4861 ideal for 1 cell
applications. The ML4861 is capable of start-up with input
voltages as low as 1V and is available in 6V, 5V, and 3.3V
output versions with 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 ML4861 requires only one
inductor and two capacitors to build a very small
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 Guaranteed full load start-up and operation at 1V input
s Pulse Frequency Modulation and Internal Synchronous
Rectification for high efficiency
s Minimum external components
s Low ON resistance internal switching FETs
s Micropower operation
s 6V, 5V, and 3.3V output versions
* Some Packages Are Obsolete
BLOCK DIAGRAM
C_IN*
*R_A
+
–
*R_B
DETECT
4
V_REF
2
GND
3
*OPTIONAL
L1
1
VIN
6
V_L
V_OUT
5
UVLO
+
BOOST
–
CONTROL
FEEDBACK
RESET
7
TO MICROPROCESSOR
PWR
GND
8
+
C_OUT
–
1