i.MX6 ZQ pull-down calibration.

[takayuki_ishii]

Hello community,

I have a question about method of ZQ automatic pull-down calibration.

In ZQ automatic Pull-up calibration(section 44.11.2.1.1), it say that

 "The MMDC drives zq_pu_pd_sel to "1"for indication of pull-up calibration"

From Figure 44-8 in Reference manual, It will connect between internal pull-up and external pull-down

register and calibrate a ZQPAD voltage to Vdd/2.

In ZQ automatic Pull-down calibration(44.11.2.1.2), it say that

"The MMDC drives zq_pu_pd_sel to "0" for indication of pull-down calibration"

In Figure 44-8, it seems that detach internal pull-up register and attach internal pull-down register

to external register.

It seems that both internal and external register are pull-down so ZQPAD keep GND level.

So we think that in pull-down zq calibration, internal pull-up and internal pull-down register

will attached to the comparator and detach external register.

Is it correct understanding?

Best regards,

Ishii.

[Yuri · Accepted solution]

Hello,

  Generally You are right:

The internal pull-up resistor calibration is done using the 1% external resistor.

The internal pull-down resistor calibration is done versus the internal pull-up resistor.

Have a great day,
Yuri

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[takayuki_ishii]

Hello Yuri,

Thank you for your quick response.

I will answer it to my customer.

Best regards,

Ishii.