Si501/2/3/4-EVB

Rev. 0.1

9

2. MCU

The Silicon Laboratories MCU, P/N C8051F380, is mounted on the back side of the board at U6. The MCU

provides the following functions:

3. Power Supply

The Si501/2/3/4-EVB can be powered from USB or from an external voltage supply. This is to support temperature

testing without a USB connection. The power supply consists of a Maxim MAX8869 adjustable voltage regulator

that steps down the USB +5 V or an external +5V power supply to one of a selectable 1.8, 2.5, or 3.3 V. VDD

selection is made via jumper P2. The supply voltage for all the device sites, both Si504 and eval sites, can be

adjusted to one of three settings: 3.3 V, 2.5gV, or 1.8 V by jumper P2. (Note that all four locations share the same

supply voltage, so any supply voltage change will affect all devices at sites U1, U2, U3, and U4.) The default

setting, connecting pins 2 and 3 as shown above, is 3.3 V. Moving the jumper to connect pins 1 and 2 results in

2.5 V. Removing the jumper altogether will result in 1.8 V supply voltage. The voltage regulator may be bypassed

by connecting VDD directly to the VDD P1 connection point.

4. LEDs

Two green indicator LEDs are driven by the on-board MCU. A "Ready" LED (D1) is illuminated to indicate the EVB

is recognized by the EVB GUI software and ready for use. A "USB" LED (D2) is illuminated whenever USB

communications are actively in progress.