Microlinear ML4872 Technical data
FEATURING
Extended Commercial Temperature Range
-20˚C to 70˚C
for Portable Handheld Equipment
查询ML4872供应商
High Current Boost Regulator with Shutdown
July 2000
ML4872
GENERAL DESCRIPTION
The ML4872 is a continuous conduction boost regulator
designed for DC to DC conversion in multiple cell battery
powered 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 ML4872
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 battery current and
variable frequency operation result in high efficiency
even at light loads. The ML4872 requires only one
inductor and two capacitors to build a very small
regulator circuit capable of achieving conversion
efficiencies approaching 90%.
The SHDN input allows the user to stop the regulator from
switching and powers down the control circuitry.
FEATURES
■ Guaranteed full load start-up and operation at
1.8V Input
■ Continuous conduction mode for high output current
■ Very low supply current (20µA output referenced) for
micropower operation
■ Pulse frequency modulation and internal synchronous
rectification for high efficiency
■ Maximum switching frequency > 200kHz
■ Minimum external components
■ Low ON resistance internal switching FETs
■ 5V and 3.3V output versions
BLOCK DIAGRAM
V
IN
2
+
–
SHDN
4
V
L1
1
START-UP
CONTROL
BOOST
PWR GND
6
V
L2
SYNCHRONOUS
RECTIFIER
CONTROL
+
–
1.25V
8
GND
V
OUT
+
–
3
5
1
ML4872
PIN CONFIGURATION
ML4872
8-Pin SOIC (S08)
V
L1
V
IN
GND
SHDN
PIN DESCRIPTION
PIN NAME FUNCTION
1V
2V
L1
IN
3 GND Ground
4 SHDN Pulling this pin to VIN causes the
Boost inductor connection
Battery input voltage
regulator to stop switching, and
powers down the control circuitry
1
2
3
4
TOP VIEW
8
7
6
5
5V
6V
PWR GND
NC
V
L2
V
OUT
PIN NAME FUNCTION
OUT
L2
Boost regulator output
Boost inductor connection
7 NC No connection
8 PWR GND Return for the NMOS output transistor
2
ML4872
ABSOLUTE MAXIMUM RATINGS
Absolute maximum ratings are those values beyond which
the device could be permanently damaged. Absolute
maximum ratings are stress ratings only and functional
device operation is not implied.
V
.......................................................................... 7V
OUT
Voltage on any other pin .....GND – 0.3V to V
Peak Switch Current (I
Average Switch Current (I
) ......................................... 2A
PEAK
).....................................1A
AVG
OUT
+ 0.3V
OPERATING CONDITIONS
Temperature Range
ML4872CS-X.............................................. 0ºC to 70ºC
ML4872ES-X ...........................................–20ºC to 70ºC
VIN Operating Range
ML4872CS-X................................ 1.8V to V
ML4872ES-X ................................ 2.0V to V
OUT
OUT
– 0.2V
– 0.2V
Junction Temperature .............................................. 150ºC
Storage Temperature Range ...................... –65ºC to 150ºC
Lead Temperature (Soldering 10 sec) ...................... 260ºC
Thermal Resistance (qJA).................................... 160ºC/W
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, VIN = Operating Voltage Range, TA = Operating Temperature Range (Note 1).
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
SUPPLY
I
I
OUT(Q)VOUT
I
L(Q)
PFM REGULATOR
V
OUT
SHUTDOWN
Note 1:
VIN Current VIN = V
IN
VL Quiescent Current 1µA
IL Peak Current 1.2 1.4 1.7 A
Output Voltage I
Load Regulation See Figure 1, -3 Suffix 3.20 3.25 3.40 V
Input Bias Current –100 100 nA
Shutdown Threshold V
Limits are guaranteed by 100% testing, sampling, or correlation with worst case test conditions.
– 0.2V 2 5 µA
OUT
Quiescent Current SHDN = 0V 25 35 µA
SHDN = V
L(PEAK)
VIN = 2.4V, I
See Figure 1, -5 Suffix 4.85 4.95 5.15 V
VIN = 2.4V, I
SHDN
IN
= 0 -3 Suffix 3.30 3.35 3.40 V
-5 Suffix 4.95 5.05 5.15 V
= 400mA
OUT
= 220mA
OUT
= high to low 0.4 0.6 1.1 V
15 22 µA
3
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