Hello, this is Motsu.
I am going to write again about something that we often receive inquiries about from our customers.
This time, it is about IO Standard for power supplies.
It is an inquiry at the pin setting stage.
The inquiry is,
“We are using Stratix® V. Bank 8A, 8B and 8C are set to 3.0 V IO Standard and Bank 8D is set to 2.5 V IO Standard. Is there anything I should be aware of?”
I thought that ”Bank 8 should be supplied with the same voltage. But if there are 8A, 8B, 8C, and 8D, is it OK to use different voltages for each of them?”
Unsure, I first checked the handbook, the device bible, and the pin guideline documents.
Then, I found a curious section in the Stratix® V handbook.
It reads, "Use the Same VCCPD for All I/O Banks in a Group.
This part of the handbook says that the VCCPD determines the I/O Standard that can be set.
VCCPD is the power supply for the IO pre-driver to use the IO, and the VCCPD may be shared by multiple IO banks.
For example, Bank 3A and Bank 3B form one VCCPD group, and Bank 3C and Bank 3D form one VCCPD group.
On the other hand, the Pin-Out file listed the names of the VCCPDs as follows
Table 1: VCCPD Groups
VCCPD3AB means that Bank 3A and Bank 3B form one VCCPD group.
This means that the IO power supply (VCCIO) for Bank 3A and Bank 3B must be the same VCCPD (VCCPD3AB).
The following table summarizes the correspondence between VCCIO and VCCPD in the Stratix V GX device.
Table 2: Relationship between Bank, IO Power Supply and VCCPD
The VCCPD and VCCIO (IO standard voltage) voltage values are also well defined and are described in the VCCPD note in the device datasheet (see figure below).
As shown in the figure above, when VCCIO is 2.5 V or lower, VCCPD must be set to 2.5 V. When VCCIO is 3.0 V, VCCPD must be set to 3.0 V.
The table is summarized below.
Table 3: Relationship between VCCIO and VCCPD voltage values
These show that although IO voltages can be set individually for Banks 8A, 8B, 8C, and 8D, it is not possible to set IO voltages with different values of VCCPD.
Therefore, the answer to your query is:
"Bank 8 must use VCCIO with the same VCCPD voltage for 8A, 8B, 8C, and 8D (Table 2). If VCCIO is less than 2.5 V, VCCPD must be 2.5 V. If VCCIO is 3.0 V, VCCPD must be 3.0 V. (Table 3) Therefore, 2.5 V and 3.3 V cannot be placed simultaneously in Bank 8."
Summary
When changing the voltage of IO Standard for each Bank, it is necessary to pay attention to the VCCPD group!
I didn't pay attention to it during the production practice, or rather, I didn't have such a setup in the first place, so I learned a lot.
This time, I thought it was hard to understand only the text in the handbook and pin guidelines, so I summarized it in a table, but I hope everyone understood.
In addition to VCCPD, there are many other types of power supply pins, and I am interested in what role each power supply plays, so I would like to look into power supply pins next time.
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