Fairchild Semiconductor ML4865 Datasheet
www.fairchildsemi.com
ML4865
High Voltage High Current Boost Regulator
Features
• Guaranteed full load start-up and operation at 1.8V input
• Continuous conduction mode for high output current
• Very low quiescent current
• Pulse frequency modulation and internal synchronous
rectification for high efficiency
• Maximum switching frequency > 200kHz
• Minimum external components
• Low ON resistance internal switching FETs
• Fixed 12V output can be adjusted to lower output voltages
Block Diagram
4
V
L1
V
IN
3
General Description
The ML4865 is a high voltage, 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 ML4865 is
capable of start-up with input voltages as low as 1.8V and
generates a 12V output with output voltage accuracy of ±4%.
Unlike most boost regulators, the ML4865 isolates the load
from the battery when the SHDN pin is high. 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 ML4865
requires only one inductor and two capacitors to build a very
small regulator circuit capable of achieving conversion efficiencies approaching 90%.
6
V
L2
SHUTDOWN
CONTROL
SHDN
7
START-UP
+
–
SHDN
BOOST
CONTROL
PWR GND
5
SYNCHRONOUS
RECTIFIER
CONTROL
+
–
2.42V
+
–
FEEDBACK
CONTROL
GND
2
V
OUT
8
SENSE
1
REV. 1.0.2 8/10/01
ML4865 PRODUCT SPECIFICATION
Pin Configuration
ML4865
8-Pin SOIC (S08)
V
SENSE
GND
V
V
L1
IN
1
2
3
4
TOP VIEW
8
OUT
SHDN
7
V
6
L2
PWR GND
5
Pin Description
PIN NAME FUNCTION
1 SENSE Programming pin for setting the output to any value lower than the normal fixed
voltage.
2 GND Ground.
3VINBattery input voltage.
4VL1Boost inductor connection.
5 PWR GND Return for the internal power transistors.
6V
L2
7 SHDN Pulling this pin to V
8V
OUT
Boost inductor connection.
through an external resistor shuts down the regulator,
IN
isolating the load from the input.
Boost regulator output.
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.
Parameter Min. Max. Units
Voltage on any other Pin GND – 0.3 16.5 V
Peak Switch Current (I
Average Switch Current (I
) 2 A
PEAK
)1A
AVG
Junction Temperature 150 °C
Storage Temperature Range -65 150 °C
Lead Temperature (soldering, 10s) 150 °C
Thermal Resistance (θJA) 160 °C/W
Operating Conditions
Parameter Min. Max. Units
Temperature Range ML4865CS-2 0 70 °C
VIN Voltage Range
Without external rectifier
With external rectifier
1.8
1.8
10
6
V
V
2 REV. 1.0.2 8/10/01
PRODUCT SPECIFICATION ML4865
Electrical Characteristics
Unless otherwise specified, V
Symbol Parameter Conditions Min. Typ. Max. Units
Supply
I
IN
VIN Current SHDN = 0 or V
V
Quiescent Current V
OUT
VL Quiescent Current 0V < VL2 < V
PFM Regulator
I
L(PEAK)
V
OUT
IL Peak Current VIN = 5V 0.8 1.2 1.6 A
Output Voltage See Figure 1
Load Regulation See Figure 1
Feedback
Threshold Voltage 2.38 2.42 2.48 V
Input Bias Current -150 150 nA
Shutdown
Threshold Voltage V
Input Bias Current -150 150 nA
= Operating Voltage Range, TA = Operating Temperature Range (Note 1)
IN
IN
= V
OUT
OUT(MAX)
VIN = 5V, SENSE = Open, I
VIN = 2.4V, I
VIN = 5V, I
SHDN
OUT
= HIGH to LOW 0.4 0.8 1.6 V
+ 5% 20 30 µA
OUT
= 40mA
OUT
= 160mA
= 0 11.72 12.1 12.48 V
OUT
-1 1 µA
11.52
11.52
10 25 µA
12.0
12.0
V
V
Note:
1. Limits are guaranteed by 100% testing, sampling, or correlation with worst-case test conditions.
REV. 1.0.2 8/10/01 3
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