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Part: ML4775
Category:
Power Management
-> Regulators
Description: Adjustable Output Low Voltage Boost Regulator With Shutdown
Company: Micro Linear
Datasheet: Download ML4775 datasheet File size : 5795 kB
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Datasheet text preview:
August 2000
ML4775 Adjustable Output Low Voltage Boost Regulator with Shutdown
GENERAL DESCRIPTION
The ML4775 is a boost regulator designed for DC to DC conversion in 1 to 3 cell battery powered systems. The combination of BiCMOS process technology, internal synchronous rectification, variable frequency operation, and low supply current make the ML4775 ideal for 1 cell applications. The ML4775 is capable of start-up with input voltages as low as 1V, and the output voltage can be set anywhere between 2.5V and 5.5V by an external resistor divider connected to the SENSE pin. Unlike regulators using external Schottky diodes, the ML4775 isolates the load from the battery when the SHDN pin is high. This is accomplished by an integrated synchronous rectifier which 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 ML4775 requires a minimum number of external components to build a very small regulator circuit capable of achieving conversion efficiencies in excess of 90%.
FEATURES
s s s s s s s
Guaranteed start-up and operation at 1V input Pulse Frequency Modulation and Internal Synchronous Rectification for high efficiency Isolates the load from the input during shutdown Minimum external components Low ON resistance internal switching FETs Micropower operation Adjustable output voltage (2.5V to 5.5V)
BLOCK DIAGRAM
L1 CFF* VOUT
PWR GND
8
VL
6
5 VOUT
VIN 1
R1
*CIN
VBAT
BOOST CONTROL
FEEDBACK SENSE
4 COUT R2
GND 3
REGULATION & SHUTDOWN CONTROL
SHDN 2 FROM POWER MANAGEMENT
*Optional
1
ML4775
PIN CONNECTION
ML4775 8-Pin SOIC (S08)
VOUT COMP VREF BURST 1 2 3 4 8 7 6 5 GND VL BURST VIN
TOP VIEW
PIN DESCRIPTION
PIN NO. PIN NO.
NAME
FUNCTION
NAME
FUNCTION
1 2
VIN SHDN
Battery input voltage Pulling this pin high shuts down the regulator, isolating the load from the input Analog signal ground Programming pin is for setting the output voltage
5 6 7 8
VOUT VL N/C
Boost regulator output Boost inductor connection No connection
3 4
GND SENSE
PWR GND Return for the NMOS output t ra n s i s t o r
2
ML4775
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. VOUT ........ 7V Voltage on any other pin ..... GND 0.3V to VOUT +0.3V Peak Switch Current, I(PEAK) ... 1.5A Average Switch Current, I(AVG) .... 300mA 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
OPERATING CONDITIONS
Temperature Range ML4775CS ...... 0°C to 70°C ML4775ES ........... 20°C to 70°C VIN Operating Range ML4775CS .......... 1.0V to VOUT 0.2V ML4775ES .......... 1.1V to VOUT 0.2V
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, VIN = Operating Voltage Range, TA = Operating Temperature Range (Note 1).
PARAMETER SUPPLY VIN Quiescent Current VIN = VOUT 0.2 V VIN = 4.8V, SHDN = VIN VOUT Quiescent Current VL Quiescent Current PFM REGULATOR Pulse Width (TON) SENSE Comparator Threshold Voltage (VSENSE) Load Regulation See Figure 1 VIN = 1.2V, IOUT - 20mA VIN = 2.4V, IOUT - 105mA 8.9 194 10 200 11.1 206 µs mV 55 20 8 65 30 12 1 µA µA µA µA CONDITIONS MIN TYP. MAX UNITS
4.85 4.85
5.0 5.0 0.85
5.15 5.15 1
V V V
Undervoltage Lockout Threshold SHUTDOWN Input Bias Current Shutdown Threshold Shutdown Hysteresis
Note 1: Limits are guaranteed by 100% testing, sampling or correlation with worst case test conditions.
100 180 200 50
100 220 70
nA mV mV
3
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