Microlinear ML4870 Technical data
July 2000
PRELIMINARY
ML4870*
High Current Boost Regulator with Load Disconnect
GENERAL DESCRIPTION
The ML4870 is a continuous conduction boost regulator
designed for DC to DC conversion in multiple cell battery
FEATURES
■ Guaranteed full load start-up and operation at
1.8V input
power systems. Continuous conduction allows the
regulator to maximize output current for a given inductor.
■ Continuous conduction mode for high output current
The maximum switching frequency can exceed 200kHz,
allowing the use of small, low cost inductors. The ML4870
is capable of start-up with input voltages as low as 1.8V,
■ Pulse Frequency Modulation and internal synchronous
rectification for high efficiency
and is available in 5V and 3.3V output versions with an
output voltage accuracy of ±3%.
An integrated synchronous rectifier eliminates the need
■ Isolates the load from the input during shutdown
■ Minimum external components
for an external Schottky diode and provides a lower
forward voltage drop, resulting in higher conversion
■ Low ON resistance internal switching FETs
efficiency. In addtion, low quiescent current and variable
frequency operation result in high efficiency even at light
■ Low supply current
loads. The ML4870 requires only a few external
components to build a very small regulator capable of
■ 5V and 3.3V output versions
achieving conversion efficiencies approaching 85%.
The SHDN input allows the user to stop the regulator from
switching, and provides complete isolation of the load
from the battery. *Some Packages Are Obsolete
BLOCK DIAGRAM
V
IN
2
+
–
V
L1
SHDN
1
START-UP
CONTROL
BOOST
PWR GND
6
V
L2
SYNCHRONOUS
RECTIFIER
CONTROL
+
–
2.4V
8
GND
SHUTDOWN
CONTROL
+
–
3
SHDN
V
OUT
4
5
1
ML4870
PIN CONFIGURATION
ML4870
8-Pin SOIC (S08)
PIN DESCRIPTION
PIN NAME FUNCTION
1V
2V
L1
IN
3 GND Ground
Boost inductor connection
Battery input voltage
V
L1
V
IN
GND
SHDN
1
2
3
4
TOP VIEW
8
7
6
5
PIN NAME FUNCTION
5V
6V
PWR GND
NC
V
L2
V
OUT
OUT
L2
Boost regulator output
Boost inductor connection
7 NC No connection
4 SHDN Pulling this pin to VIN shuts down the
regulator, isolating the load from the
input
8 PWR GND Return for the NMOS output transistor
2
ML4870
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
ML4870CS-X .............................................. 0°C to 70°C
ML4870ES-X ........................................... -20°C to 70°C
VIN Operating Range .......................1.8V to V
OUT
- 0.2V
Junction Temperature ..............................................150°C
Storage Temperature Range ..................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec) .....................260°C
Thermal Resistance (qJA).................................... 160°C/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
IN(Q)
I
OUT(Q)VOUT
PFM REGULATOR
VIN Quiescent Current VIN = V
VIN = SHDN = 2.4V, V
Quiescent Current SHDN = 0V 25 35 µA
V
= SHDN = 2.4V 14 20 µA
IN
V
OUT
- 0.2V, SHDN = 0V 3 6 µA
OUT
= 0V 0.3 1 µA
OUT
= V
OUT(NOM)
I
PEAKIL
V
OUT
SHUTDOWN
V
IL
V
IH
Note 1:
Limits are guaranteed by 100% testing, sampling, or correlation with worst case test conditions.
Peak Current 1.1 1.3 1.6 A
Output Voltage I
Load Regulation -3 Suffix, VIN = 2.4V, I
Input Low Voltage 0.5 V
Input High Voltage VIN - 0.5 V
Input Bias Current -100 100 nA
= 0 -3 Suffix 3.30 3.35 3.40 V
OUT
See Figure 1 -5 Suffix 4.95 5.05 5.15 V
= 400mA 3.20 3.25 3.40 V
OUT
-5 Suffix, VIN = 2.4V, I
= 220mA 4.85 4.95 5.15 V
OUT
3
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