Micro Linear Corporation ML4871ES-3, ML4871ES-5, ML4871CS-5, ML4871CS-3 Datasheet
July 2000
FEATURING
Extended Commercial Temperature Range
-20˚C to 70˚C
for Portable Handheld Equipment
ML4871
High Current Boost Regulator
GENERAL DESCRIPTION
The ML4871 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 ML4871
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 ML4871 requires only one inductor and two
capacitors to build a very small regulator circuit capable
of achieving conversion efficiencies approaching 90%.
The circuit also contains a RESET output which goes low
when the DETECT input drops below 1.25V.
BLOCK DIAGRAM
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
V
L1
V
IN
2
+
–
1
DETECT
4
V
REF
START-UP
CONTROL
+
COMP
–
BOOST
7
RESET
PWR GND
6
V
L2
SYNCHRONOUS
RECTIFIER
CONTROL
+
–
1.25V
8
GND
V
OUT
+
–
3
5
1
ML4871
PIN CONFIGURATION
ML4871
8-Pin SOIC (S08)
V
L1
V
IN
GND
DETECT
PIN DESCRIPTION
NO. NAME FUNCTION
1V
2V
L1
IN
3 GND Ground
4 DETECT Pulling this pin below 1.25V causes
Boost inductor connection
Battery input voltage
the RESET pin to go low
1
2
3
4
TOP VIEW
8
7
6
5
5V
6V
PWR GND
RESET
V
L2
V
OUT
NO. NAME FUNCTION
OUT
L2
Boost regulator output
Boost inductor connection
7 RESET Output goes low when DETECT goes
below 1.25V
8 PWR GND Return for the NMOS output transistor
2
ML4871
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
ML4871CS-X ............................................. 0ºC to 70ºC
ML4871ES-X .......................................... –20ºC to 70ºC
VIN Operating Range
ML4871CS-X ................................ 1.8V to V
ML4871ES-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
RESET
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
COMPARATOR
DETECT Threshold 1.18 1.25 1.28 V
DETECT Hysteresis 25 35 45 mV
DETECT Bias Current –100 100 nA
RESET Output High Voltage I
RESET Output Low Voltage I
OUT
Quiescent Current DETECT = V
DETECT = 0V 25 35 µA
= 0 -3 Suffix 3.30 3.35 3.40 V
L(PEAK)
VIN = 2.4V, I
See Figure 1, -5 Suffix 4.85 4.95 5.15 V
VIN = 2.4V, I
= –200µA V
RESET
= 500µA 0.2 V
RESET
– 0.2V 2 5 µA
IN
OUT
OUT
£ 400mA
£ 220mA
-5 Suffix 4.95 5.05 5.15 V
– 0.2 V
OUT
30 40 µA
Note 1:
Limits are guaranteed by 100% testing, sampling, or correlation with worst case test conditions.
3
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