Power

• Vin / + (terminal block) - To power the board, give it 3V to 5V DC. The power input pin is broken out at the bottom edge of the board (Vin) and on the terminal block on the left side of the board (+).
• G / - (terminal block) - common ground. The ground pin is broken out at the bottom edge of the board (G) and on the terminal block on the left side of the board (-).

LED Constant Current Output

The TPS61169 increases the voltage being output until a set current is being drawn. That makes it excellent for LEDs that are specified in current, not voltage. Since it's a constant current output, it's not good when you need a fixed and stable voltage output like 5V.

• L+ / CC Out + (terminal block) - This is the output that connects to the anode/positive input on your LED. This pin is broken out at the bottom edge of the board (L+) and on the terminal block on the right side of the board (CC Out +). By default, it outputs 25 mA before adding additional current through the DIP switch.
• LED- / CC Out - (terminal block) - This is the output that connects to the cathode/negative input on your LED. This pin is broken out at the bottom edge of the board (LED-) and on the terminal block on the right side of the board (-).

To figure out the approximate current output you can achieve, use the formula:

• Iout = (Vin * 1.2A * 0.9 efficiency) / Vout

Current DIP Switch

In the center of the board is a four switch DIP switch. These switches let you select the constant current output. When all of the switches are "OFF", there is a default 25 mA available. The switch is selected/on when they are set to the left towards the ON label on the switch body. Each switch "adds" a different current value to the output, for up to 400 mA on top of the default 25 mA. They are labeled on the board silk:

• The top switch adds 25 mA
• The second from the top adds 50 mA
  
• The third from the top adds 100 mA
• The bottom switch adds 200 mA

For example, if you needed 250 mA out, you would turn the top and bottom switches on (default 25 mA + 25 mA + 200 mA).

PWM Pin

• PWM - This is the pulse width modulation input pin. You can dim the LEDs by sending a PWM signal, where the duty cycle determines the total output current. The datasheet provides this formula for calculating your PWM signal:
  
  VFB = Duty * 204 mV
  
  where Duty is the duty cycle of the PWM signal and 204mV is the internal reference voltage.
  • The datasheet recommends a PWM frequency between 5kHz to 100kHz. If the PWM frequency is lower than 5kHz, it is out of the low pass filter's range.