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Registered: ‎01-04-2019

QSPI Flash IO voltage levels during READ - zynq 7010

I am verifying the interface between the qspi flash, S25FL512S, to zynq 7010 on HW level.

zynq 7010 PS is VCCO_MIO is 1.8V

The VCC_IO of qspi flash is 1.8V

I am measuring the voltages of the nodes for read and write to the flash. 

nCS and SCK are measured to have a high voltage of about 1.8V for both read and write, which is correct.

for IO(3-0), high voltage of about 1.8V is also measured for write operation. No problem here as well


But for read operation, a high voltage if about 2.6V is measured on IO(3-0). 

2.6V is higher than the absolute maximum DC rating of PS_MIO of VCCO_MIO +0.55V = 1.8+0.55 = 2.35V

2.6V does not appear to be an overshoot. AC voltage Overshoot requirement, according to DS187 Table 4, VCCO +0.80 ==> 2.15% of UI (about 50 ns), is also not met, it is consistently 2.6V. 


On the Pg 25 datasheet of S25FL512S QSPI Flash Datasheet: during voltage transitions, inputs or I/Os may overshoot VSS to –2.0V or overshoot to VIO +2.0V, for periods up to 20 ns. - I am not sure if there is any overshoot in my measurement.



What is the cause of the high voltage of IO(3-0) during the read operation?

How can I reduce this voltage?

Can this voltage is acceptable?










QSPI Flash.png
Page 25 of S25FL512S QSPI Flash Datasheet on Signal Overshoot.png
1 Reply
Registered: ‎02-01-2013

Re: QSPI Flash IO voltage levels during READ - zynq 7010

First, confirm that the QSPI device on your board is NOT the part listed in your schematic.

The part in the schematic has a "SAGBHI210" suffix. According to the data sheet for the S25F512S, the "2" model does not have VIO support; its IO will be controlled by the VCC rail, which is 3.3V. You need to use a model that has VIO support. 


-Joe G.


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