MCBXC167: MALFUNCTION WITH 6V POWER SUPPLY

Information in this article applies to:

• MCB-XC167 Evaluation Boards

QUESTION

My MCB-XC167 Board shows strange behaviour like sporadic or periodic Resets, indicated by the RSTOUT LED. This happens in most cases if the PLL is configured to frequencies above 20 MHz.

CAUSE

In early versions of the MCB-XC167 Evaluation Boards (both BAS and NET variants) the two resistors R26/R27 may drop too much voltage. This prevents the voltage regulator IC8 from producing a stable output voltage if the input voltage is below ~7.5V.

RESOLUTION

To solve this problem you can remove the resistors and bridge them with a jumper wire. This will provide a proper power supply for the CPU Core when using the recommended 6V power supply. In newer production runs the board is populated with two 22 Ohm resistors.

Last Reviewed: Monday, February 14, 2005