July 2000
ML4866*
3.3V Output DC–DC Step-Down Converter
GENERAL DESCRIPTION
The ML4866 is a high efficiency pulse width modulated
(PWM) buck regulator designed for use in 5V systems or
portable equipment that need a compact, efficienct 3.3V
supply. It has a switching frequency of 120kHz and uses
synchronous rectification to optimize power conversion
efficiency. Unlike other solutions, the ML4866 requires no
external diodes or FETs.
The ML4866 can provide up to 500mA of output current,
and operates over an input voltage range of 3.5V to 6.5V
(3 to 4 cells or a 5 VDC supply). A complete switched
mode power converter can be quickly and easily
implemented with few external components. Thanks to a
built-in autoburst mode, power conversion efficiency of
this DC–DC converter can exceed 90% over more than 2
decades of output load current.
Stability and fast loop response are provided by current
programming and a current sense circuit. The ML4866
also has a
SHDN
pin for use in systems which have power
management control. Undervoltage lockout and soft start
are also built in.
FEATURES
s
High power conversion efficiency over 2 decades of
load current
No external FETs or diodes; minimum external
components
3.5V to 6.5V input voltage range
Significantly extends battery life over linear regulator
based solutions
Micropower operation
Low shutdown mode quiescent current
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s
s
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(* Indicates Part is End Of Life as of July 1, 2000)
BLOCK DIAGRAM
5
VIN
CURRENT
SENSE
7
VL
1
VOUT
UVLO/
SHUTDOWN
OSC
BUCK
CONTROL
REFERENCE
SLOPE
COMPENSATION
–
ERROR
AMPLIFIER
–
+
BURST
+
VREF
SHDN
6
3
VREF
BURST
4
2
COMP
8
GND
1
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
