Pololu 12v 1A Step-Down Voltage Regulator
The regulators feature short-circuit/over-current protection, and thermal shutdown helps prevent damage from overheating. The boards do not have reverse-voltage protection.
- Input voltage: [output voltage + dropout voltage] to 36 V (see below for more information on dropout voltage)
- Fixed 12 V output with 4% accuracy
- Maximum output current: 1 A
- Typical efficiency of 80% to 93%
- 500 kHz switching frequency (when not in power-save mode)
- 2 ms soft-start reduces in-rush current on power-up
- 200 μA typical no-load quiescent current
- Integrated over-temperature and over-current shutoff
- Small size: 0.7″ × 0.5″ × 0.14″ (18 mm × 13 mm × 3.5 mm)
Using the regulator
The buck regulator has five connections: power good (PG). shutdown (SHDN), input voltage (VIN), ground (GND), and output voltage (VOUT).
The “power good” indicator, PG, is an open-drain output that drives low when the regulator’s output voltage falls below 80% or rises above 120% of its target output voltage. This output is also actively held low for the duration of the regulator’s 2 ms soft-start period and while the regulator is being disabled by the SHDN input or by over-temperature or over-current fault conditions. An external pull-up resistor is generally required to use this pin.
The SHDN pin can be driven low (under 0.4 V) to turn off the output and put the board into a low-power state. There is a 100 kΩ pull-up resistor between the SHDN pin and VIN, so if you want to leave the board permanently enabled, the SHDN pin can be left disconnected. While the SHDN pin is being driven low, the current draw of the regulator is dominated by the current through the pull-up resistor and will be proportional to the input voltage. (At 36 V in it will draw about 360 μA.)
The input voltage, VIN, powers the regulator. Voltages between 3 V and 36 V can be applied to VIN, but the effective lower limit of VIN is VOUT plus the regulator’s dropout voltage, which varies approximately linearly with the load (see below for graphs of dropout voltages as a function of the load). Additionally, please be wary of destructive LC spikes.The five connections are labeled on the back side of the PCB and are arranged with a 0.1″ spacing along the edge of the board for compatibility with solderless breadboards, connectors, and other prototyping arrangements that use a 0.1″ grid. You can solder wires directly to the board or solder in either the 5×1 straight male header strip or the 5×1 right-angle male header strip that is included.
Typical dropout voltage
The dropout voltage of a step-down regulator is the minimum amount by which the input voltage must exceed the regulator’s target output voltage in order to ensure the target output can be achieved. For example, if a 5 V regulator has a 1 V dropout voltage, the input must be at least 6 V to ensure the output is the full 5 V. Generally speaking, the dropout voltage increases as the output current increases.