C
ed C
to 70°
ent
Extend
–20°C held Equipm
and
table H
for Por
FE
ommercial Te
G
URIN
ure Range
AT
mperat
April 1997
ML4890
High Efficiency, Low Ripple Boost Regulator
GENERAL DESCRIPTION
The ML4890 is a high efficiency, PFM (Pulse Frequency
Modulation), boost switching regulator connected in
series with an integrated LDO (Low Dropout Regulator)
that incorporates “Silent Switcher™” technology. This
technique incorporates a patented tracking scheme to
minimize the voltage drop across the LDO and increase
the total efficiency of the regulator beyond that which can
be obtained by using a discrete external LDO regulator.
The ML4890 is designed to convert single or multiple cell
battery inputs to regulated output voltages for integrated
circuits and is ideal for portable communications
equipment that cannot tolerate the output voltage ripple
normally associated with switching regulators.
An integrated synchronous rectifier eliminates the need for
an external Schottky diode and provides a lower forward
voltage drop, resulting in higher conversion efficiency.
FEATURES
s
s
Incorporates “Silent Switcher™” technology to deliver
very low output voltage ripple (typically 5mV)
Guaranteed full load start-up and operation at 1.0V
input and low operating quiescent current (<100µA)
for extended battery life
Pulse Frequency Modulation and internal synchronous
rectification for high efficiency
Minimum external components
Low ON resistance internal switching MOSFETs
5V, 3.3V, and 3V output versions
s
s
s
s
BLOCK DIAGRAM
L1
*C
IN
V
IN
C2
1
V
L
6
5
V
BOOST
V
BAT
7
SHDN
V
OUT
4
BOOST
CONTROL
FEEDBACK
LDO
CONTROL
C1
V
OUT
+
2
V
REF
3
FROM
POWER
MANAGEMENT
GND
PWR
GND
8
–
Patent Pending
*Optional
1
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
