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RB-Pol-221

Step-Up / Step-Down Voltage Regulator S7V8A

Description

The S7V8A switching step-up/step-down regulator efficiently produces an adjustable output between

2.5 V to 8 V from input voltages between 2.7 V and 11.8 V. Its ability to convert both higher and lower

input voltages makes it useful for applications where the power supply voltage can vary greatly, as with

batteries that start above but discharge below the regulated voltage. The compact (0.45″ × 0.65″)

module has a typical efficiency of over 90% and can deliver 500 mA to 1 A across most combinations

of input and output voltages.

The Pololu step-up/step-down voltage regulator S7V8A is a switching regulator (also called a

switched-mode power supply (SMPS) or DC-to-DC converter) that uses a buck-boost topology. It takes

an input voltage from 2.7 V to 11.8 V and increases or decreases the voltage to a user-adjustable output

between 2.5 V and 8 V with a typical efficiency of over 90%. The input voltage can be higher than,

lower than, or equal to the set output voltage, and the voltage is regulated to achieve the set output

voltage.

Summary of content (6 pages)

PAGE 1
RB-Pol-221 Step-Up / Step-Down Voltage Regulator S7V8A Description The S7V8A switching step-up/step-down regulator efficiently produces an adjustable output between 2.5 V to 8 V from input voltages between 2.7 V and 11.8 V. Its ability to convert both higher and lower input voltages makes it useful for applications where the power supply voltage can vary greatly, as with batteries that start above but discharge below the regulated voltage. The compact (0.45″ × 0.
PAGE 2
This flexibility in input voltage is especially well-suited for battery-powered applications in which the battery voltage begins above the desired output voltage and drops below the target as the battery discharges. Without the typical restriction on the battery voltage staying above the required voltage throughout its life, new battery packs and form factors can be considered. For example: • A 4-cell battery holder, which might have a 6 V output with fresh alkalines or a 4.
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Connections The step-up/step-down regulator has four connections: shutdown (SHDN), input voltage (VIN), ground (GND), and output voltage (VOUT). The SHDN pin can be driven low (under 0.4 V) to power down the regulator and put it in a low-power state. The quiescent current in this sleep mode is dominated by the current in the 100k pull-up resistor from SHDN to VIN. With SHDN held low, this resistor will draw 10 µA per volt on VIN (for example, the sleep current with a 5 V input will be 50 µA).
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Setting the Output Voltage The output voltage can be measured using a multimeter. Turning the potentiometer clockwise increases the output voltage. The output voltage can be affected by a screwdriver touching the potentiometer, so the output measurement should be done with nothing touching the potentiometer. Please note that the output voltage can be set below 2.5 V at the low end of the potentiometer’s range and above 8 V at the high end.
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The maximum achievable output current of the board varies with the input voltage but also depends on other factors, including the ambient temperature, air flow, and heat sinking. The graph below shows output currents at which this voltage regulator’s over-temperature protection typically kicks in after a few seconds.