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Part: ML4770
Category:
Power Management
-> Regulators
Description: 2 Cell, Adjustable Output, High Current Boost Regulator With Load Disconnect
Company: Micro Linear
Datasheet: Download ML4770 datasheet File size : 5795 kB
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Datasheet text preview:
July 2000 PRELIMINARY
ML4770* 2 Cell, Adjustable Output, High Current Boost Regulator with Load Disconnect
GENERAL DESCRIPTION
The ML4770 is a continuous conduction mode boost regulator designed for DC to DC conversion in multiple cell battery power 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 ML4770 is capable of start-up with input voltages as low as 1.8V. The output voltage can be set anywhere between 3.0V and 5.5V by an external resistor divider connected to the SENSE pin. 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 current and variable frequency operation result in high efficiency even at light loads. The ML4770 requires only a few external components to build a very small regulator capable of 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.
F E AT U R E S
s
Guaranteed full load start-up and operation at 1.8V input Continuous conduction mode for high output current 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 Low supply current Adjustable output voltage (3V to 5.5V)
s s
s s s s s
* Some Packages Are Obsolete
BLOCK DIAGRAM
1
6
VL1
VL2
SHUTDOWN CONTROL
SHDN 7
VIN
2
START-UP
SYNCHRONOUS RECTIFIER CONTROL
VOUT
+
5
+
SENSE
BOOST CONTROL
+
4
2.57V
SHDN
PWR GND 8
GND 3
1
ML4770
PIN CONFIGURATION
ML4770 8-Pin SOIC (S08)
VL1 VIN GND SENSE 1 2 3 4 TOP VIEW 8 7 6 5 PWR GND SHDN VL2 VOUT
PIN DESCRIPTION
PIN NAME FUNCTION PIN NAME FUNCTION
1 2 3 4
VL1 VIN GND SENSE
Boost inductor connection Battery input voltage Ground Programming pin for setting the output voltage
5 6 7
V OUT VL2 SHDN
Boost regulator output Boost inductor connection Pulling this pin to VIN shuts down the regulator, isolating the load from the input Return for the NMOS output transistor
8
PWR GND
2
ML4770
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 (IPEAK) ........ 2A Average Switch Current (IAVG) .... 1A Junction Temperature ............ 150ºC Storage Temperature Range ........... 65ºC to 150ºC Lead Temperature (Soldering, 10 sec) .......... 260ºC Thermal Resistance (qJA) .......... 160ºC/W
OPERATING CONDITIONS
Temperature Range ML4770CS-X ............ 0ºC to 70ºC ML4770ES-X .......... -20ºC to 70ºC VIN Operating Range ..... 1.8V to VOUT - 0.2V VOUT Operating Range ....... 3.0V to 5.5V
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, VIN = Operating Voltage Range, TA = Operating Temperature Range (Note 1)
SYMBOL SUPPLY I IN VIN Current VIN = VOUT - 0.2V, SHDN = 0V VIN = SHDN = 2.4V, VOUT = 0V IOUT(Q) VOUT Quiescent Current SHDN = 0V VIN = SHDN = 2.4V, VOUT = VOUT(NOM) PFM REGULATOR IPEAK VSENSE IL Peak Current SENSE Comparator Threshold Voltage Line Regulation Load Regulation SHUTDOWN V IL VIH Input Low Voltage Input High Voltage Input Bias Current
Note 1:
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
3 0.3 25 14
6 1 35 20
µA µA µA µA
1.1 2.52 IOUT = 0, See Figure 1 VIN = 2.4V, IOUT £ 220mA See Figure 1 4.95 4.85
1.3 2.57 5.05 4.95
1.6 2.62 5.15 5.15
A V V V
0.5 VIN - 0.5 -100 100
V V nA
Limits are guaranteed by 100% testing, sampling, or correlation with worst case test conditions.
3
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