AR# 61712


Zynq-7000 SoC ZC706 Evaluation Kit - ZC706 Fan stops working when the Vadj voltage is set to 1.8V


ZC706 supports a range of VADJ voltages, including 1.8V.  

However, when the VADJ is modified from the default 2.5V to 1.8V, the fan onboard the ZC706 does not continue to spin.

The fan can recover if manually started (with a push) but spins with a slower speed (compared to when VADJ is set to 2.5V).  

Why is this?


The transistor used on the ZC706 board to switch on the fan has the max VGS of 2V, therefore the fan is not guaranteed to work at 1.8V.

The fan spins with manual assistance because the FET acts like a current limiting resistor when the VGS is lower than 2V - the fan requires a greater start up current initially, and once spinning it requires less current to continue spinning.

The fan spins more slowly as the FET resistance is also dropping the voltage.

Linked Answer Records

Master Answer Records

Answer Number Answer Title Version Found Version Resolved
51899 Zynq-7000 SoC ZC706 Evaluation Kit - Known Issues and Release Notes Master Answer Record N/A N/A
AR# 61712
Date 05/25/2018
Status Active
Type General Article
Boards & Kits
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