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Part: ML4761IS
Category:
Power Management
Description: Adjustable Output Low Voltage Boost Regulator
Company: Micro Linear
Datasheet: Download ML4761IS datasheet File size : 5795 kB
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July 2000
ML4761* Adjustable Output Low Voltage Boost Regulator
GENERAL DESCRIPTION
The ML4761 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 ML4761 ideal for 1 cell applications. The ML4761 is capable of start-up with input voltages as low as 1V, and the output voltage can be set anywhere between 2.5V and 6V 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 battery current and variable frequency operation result in high efficiency even at light loads. The ML4761 requires a minimum number of external components to build a very small adjustable regulator circuit capable of achieving conversion efficiencies in excess of 90%. The circuit also contains a RESET output which goes low when the IC can no longer function due to low input voltage (UVLO). (* Indicates Part is End Of Life as of July 1, 2000)
FEATURES
s s s s s s
Guaranteed full load start-up and operation at 1V input Pulse Frequency Modulation and Internal Synchronous Rectification for high efficiency Minimum external components Low ON resistance internal switching FETs Micropower operation Adjustable output voltage (2.5V to 6V)
BLOCK DIAGRAM
L1
CIN*
1 VIN
6 VL VOUT 5
CFF*
+ R1
UVLO VREF + 2
+
BOOST CONTROL VREF
SENSE 4 COUT R2 PWR GND 8
GND 3 7 *OPTIONAL TO MICROPROCESSOR RESET
1
ML4761
PIN CONNECTION
ML4761 8-Pin SOIC (S08)
VIN VREF GND SENSE
1 2 3 4 8 7 6 5
PWR GND RESET VL VOUT
TOP VIEW
PIN DESCRIPTION
PIN NO. NAME FUNCTION PIN NO. NAME FUNCTION
1 2 3 4
VIN VREF GND SENSE
Battery input voltage 200mV reference output Analog signal ground Programming pin for setting the output voltage
5 6 7 8
V OUT VL RESET
Boost regulator output Boost inductor connection Output goes low when regulation cannot be achieved
PWR GND Return for the NMOS output transistor.
2
ML4761
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. Voltage on any pin ....... 7V Peak Switch Current, I(PEAK) ......... 2A Average Switch Current, I(AVG) ....... 500mA 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 ML4761CS ....... 0°C to 70°C ML4761ES .... 20°C to 70°C ML4761IS ..... 40°C to 85°C VIN Operating Range ML4761CS ... 1.0V to VOUT 0.2V ML4761ES, ML4761IS .......... 1.1V to VOUT 0.2V VOUT Operating Range ......... 2.5V to 6.0V
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, VIN = Operating Voltage Range, TA = Operating Temperature Range (Note 1)
PARAMETER Supply VIN Current VOUT Quiescent Current VL Quiescent Current Reference Output Voltage (VREF) PFM Regulator Pulse Width (TON) VIN = 2.4V C/E Suffix I Suffix SENSE Comparator Threshold Voltage (VSENSE) Load Regulation See Figure 1 VIN = 1.2V, IOUT - 25mA VIN = 2.4V, IOUT - 135mA C/E Suffix I Suffix RESET Comparator RESET Output High Voltage (VOH) RESET Output Low Voltage (VOL)
Note 1:
CONDITIONS
MIN
TYP.
MAX
UNITS
VIN = VOUT 0.2V
45 3
55 5 1
µA µA µA
0 < IPIN2 < 5µA
194
200
206
mV
9 8.5 190
10 10 200
11 11.5 210
µs µs mV
4.85 4.85
5.0 5.0 0.85 0.95
5.15 5.15 0.95 1.05
V V V V
Undervoltage Lockout Threshold
IOH = 100µA IOL = 100µA
VOUT 0.2 0.2
V V
Limits are guaranteed by 100% testing, sampling, or correlation with worst case test conditions.
3
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