ML4863 Datasheet, PDF (1/10 Pages) Micro Linear Corporation – High Efficiency Flyback Controller

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July 2000
ML4863*
High Efficiency Flyback Controller
GENERAL DESCRIPTION
The ML4863 is a flyback controller designed for use in
multi-cell battery powered systems such as PDAs and
notebook computers. The flyback topology is ideal for
systems where the battery voltage can be either above or
below the output voltage, and where multiple output
voltages are required.
The ML4863 uses the output voltage as the feedback
control signal to the current mode variable frequency
flyback controller. In addition, a synchronous rectifier
control output is supplied to provide the highest possible
conversion efficiency (greater than 85% efficiency over a
1mA to 1A load range).
The ML4863 has been designed to operate with a
minimum number of external components to optimize
space and cost.
FEATURES
s Variable frequency current mode control and
synchronous rectification for high efficiency
s Minimum external components
s Guaranteed start-up and operation over a wide input
voltage range (3.15V to 15V)
s High frequency operation (>200kHz) minimizes the
size of the magnetics
s Flyback topology allows multiple outputs in addition to
the regulated 5V
s Built-in overvoltage and current limit protection
*Some Packages Are Obsolete
BLOCK DIAGRAM
SHDN
3
VIN
1
VFB
4
4.5V
LDO
BIAS & UVLO
VCC
VFB
I
18mV
Rgm
18mV
CURRENT
COMPARATOR
+
COMP
–
RECTIFIER
COMPARATOR
–
COMP
+
SWITCHING
CONTROL
BLANKING
VCC
5
VREF
VCC
A1
VFB
GND
8
OUT 1
6
VCC
A2
CROSS-CONDUCTION
PROTECTION
OUT 2
7
SENSE
2
1