User manual

Explorer 8 Development Board User’s Guide
DS40001812A-page 28  2015 Microchip Technology Inc.
The Explorer 8 Development Board’s R20 and R19 resistors have their default values
of 1 kΩ and 330Ω, respectively. Without R102 and R101 being inserted in parallel on
the PIM board, V
OUT = 1.25V(1 + 1 kΩ/330Ω) = 5.04V.
To calculate a desired V
OUT:
1. Solve for R2, given R1 = R19 = 330Ω.
2. Now knowing R2 and R20, solve for R102.
3. Determine the nearest available resistor value for R102 and recalculate the
resulting V_VAR to make sure it does not exceed the maximum V
DD for the part
being used.
For devices that are not mounted on a PIM but need a supply voltage other than 5V or
3.3V, external resistors may be connected to the ADJ pin of J29. A resistor connected
between ADJ and ground is equivalent to R102 and a resistor connected between ADJ
and V_VAR is equivalent to R101. Calculate the resistor values using the equations
previously discussed in this section.