FEATURING
Extended Commercial Temperature Range
-20˚C to 70˚C
for Portable Handheld Equipment
ML4851*
Low Current, Voltage Boost Regulator
GENERAL DESCRIPTION
The ML4851 is a low power boost regulator designed for
DC to DC conversion in 1 to 3 cell battery powered
systems. The maximum switching frequency can exceed
100kHz, allowing the use of small, low cost inductors.
The combination of BiCMOS process technology, internal
synchronous rectification, variable frequency operation,
and low supply current make the ML4851 ideal for 1 cell
applications. The ML4851 is capable of start-up with input
voltages as low as 1V and is available in 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 ML4851 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
n
Guaranteed full load start-up and operation at 1V input
n
Maximum switching frequency > 100kHz
n
Pulse Frequency Modulation (PFM) and internal
synchronous rectification for high efficiency
n
Minimum external components
n
Low ON resistance internal switching FETs
n
Micropower operation
n
5V and 3.3V output versions
*Some Packages Are Obsolete
BLOCK DIAGRAM
7
DETECT
4
VREF
VIN
+
–
COMP
6
VL
RESET
1
START-UP
VOUT
+
–
5
S
R
Q
Q
5µs
ONE SHOT
PWR
GND
8
–
+
VREF
REFERENCE
VREF
GND
3
VREF
2
July, 2000
DATASHEET
1
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
