Data Sheet

program the board over USB. The USB connection can also provide power to the P-Star.

The board also has five pins arranged so that they can be directly plugged into a standard In-Circuit Serial

Programming (ICSP) connector, such as the one found on the PICkit 3. More information about programming

with the PICkit 3 can be found in Section 7. The five pins are: MCLR, VDD, GND, RB7, and RB6. The MCLR

pin is pin 1.

Power

The P-Star 25K50 Micro can either be powered directly from the USB 5 V supply or from a separate source on

the VIN pin. The board features a power selection circuit that allows both USB and VIN to be connected at the

same time; if this is done, the P-Star will draw power from VIN.

USB power input: The P-Star can be powered from the USB 5 V bus voltage (VBUS) if it is connected to a

USB cable. It will draw power from USB only if VIN is disconnected. A resettable PTC fuse on VBUS makes

it less likely for the P-Star (and the connected computer or other device) to be damaged if too much current is

drawn from the USB connection.

VIN power input: The P-Star can be powered from VIN if you connect a 5.5 V to 15 V power supply (such as

a battery or wall power adapter) to the VIN and GND pins, with the positive terminal connected to VIN.

VDD: This pin provides access to the board’s 5 V supply, which comes from either the USB 5 V bus voltage or a

low-dropout (LDO) regulator on VIN, depending on which power source is connected. The regulator can supply

up to 100 mA, although some of this is used by the board itself or used to provide current for the GPIO pins.

To ensure that VDD is a stable 5 V, you must either disconnect VIN and use USB to power the board or supply

a VIN of at least 5.5 V. When VIN drops below 5.5 V, VDD will fall (even with USB connected). However, the

P-Star will continue to run with VDD below 5 V, and it can operate from VIN alone with VIN as low as 3.2 V to

3.8 V, depending on the load and temperature. With USB connected, VDD will drop at worst to about 4.5 V, and

the P-star will continue operating no matter how low VIN is.

When the P-Star 25K50 Micro is being powered through VIN, regardless of whether USB is connected, the sum

of the 5V output current, GPIO output current, and current used by the board itself (typically about 18 mA)

should not exceed the 100 mA that the regulator can provide.

3. Pinout and components Page 7 of 38