ML4869 Datasheet, PDF (1/8 Pages) Micro Linear Corporation – Medium Current Boost Regulator with Load Disconnect

July 2000
PRELIMINARY
ML4869
Medium Current Boost Regulator
with Load Disconnect
GENERAL DESCRIPTION
The ML4869 is a continuous conduction boost regulator
designed for DC to DC conversion in multiple cell battery
power 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 ML4869
is capable of start-up with input voltages as low as 1.8V,
and is available in 5V and 3.3V output versions with an
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 current and variable
frequency operation result in high efficiency even at light
loads. The ML4869 requires only a few external
components to build a very small regulator capable of
achieving conversion efficiencies approaching 85%.
The SHDN input allows the user to stop the regulator from
switching, and provides complete isolation of the load
from the battery.
FEATURES
s Guaranteed full load start-up and operation at
1.8V input
s Continuous conduction mode for high output current
s Pulse Frequency Modulation and internal synchronous
rectification for high efficiency
s Isolates the load from the input during shutdown
s Minimum external components
s Low ON resistance internal switching FETs
s Low supply current
s 5V and 3.3V output versions
s Shutdown current = 1µA MAX
BLOCK DIAGRAM
VIN
2
1
VL1
START-UP
6
VL2
SYNCHRONOUS
RECTIFIER
CONTROL
SHUTDOWN
CONTROL
SHDN
4
VOUT
5
+
–
BOOST
SHDN
CONTROL
2.4V
PWR GND
8
GND
3
1