em
mmercial T
xtended Co
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-20˚C to 70˚C uipment
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Handheld E
for Portable
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FEATURIN
erature Range
p
July 2000
ML4950*
Adjustable Output, Low Current
Single Cell Boost Regulator with Detect
GENERAL DESCRIPTION
The ML4950 is a low power boost regulator designed for
low voltage DC to DC conversion in single cell battery
powered systems. The maximum switching frequency can
exceed 100kHz, allowing the use of small, low cost
inductors.
The combination of integrated synchronous rectification,
variable frequency operation, and low supply current
make the ML4950 ideal for single cell applications. The
ML4950 is capable of start-up with input voltages as low
as 1V, and the output voltage can be set anywhere
between 2V and 3V.
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 ML4950 requires a minimum number of
external components and is 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
Guaranteed full load start-up and operation at 1V input
Pulse Frequency Modulation (PFM) and internal
synchronous rectification for high efficiency
Minimum external components
Low ON resistance internal switching FETs
Micropower operation
Adjustable output voltage (2V to 3V)
Low battery detect
s
s
s
s
s
*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
SENSE
–
+
3
VREF
REFERENCE
VREF
GND
2
1
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
