Datasheet description of CY8C5288LTI-LP090

[TeMa_2997106]

I want to use External Reference when using ADC.

However, there is no description of "SAR0 ExtRef" in the datasheet.

In PSoC Creator, P0 [4] is assigned as ExtRef.

And, In AN61290, P0 [4] is described as SAR0 ExtRef.

https://www.cypress.com/file/44581/download

Can I use this pin as a SAR0 ExtRef?

Thanks,

Tetsuo

[Len_CONSULTRON · Accepted solution]

Tetsuo,

Can I use this pin as a SAR0 ExtRef?

Yes.  The External Reference for the SAR is intended to allow the user to supply an external voltage reference (vref) source instead of the internal vrefs available.  P0.4 is used for SAR0 and P0.2 is used for SAR1.  It is also recommended to use a bypass cap on this external vref input.

The PSoC vref are very good and reasonably accurate and stable for most applications.  However, if you felt you needed a more accurate and/or stable vref for the SAR ADC, there are products in the market.

If you do use an external vref, make sure the vref voltage doesn't exceed VDDA.

Len

[TeMa_2997106]

Len-san,

Thank you for your support.

Table 11-20 can be found on p.78 of the data sheet.

It is stated that it supports 1MSPS with an external voltage reference and a bypass capacitor.

My understanding is that using an ADC without an external voltage reference will only speed up to 500kSPS.

Is it correct?

(If correct, I think an external reference voltage and a bypass capacitor have to use for 1MSPS operation.)

Thanks,

Tetsuo

[Len_CONSULTRON]

Tetsuo,

If you want you can use the internal vref (1.024V) @ 1Msps if you set the Reference: to Internal Vref, bypassed.  It uses P0.4 is used for SAR0 and P0.2 is used for SAR1 with the proper bypass cap on this pin.

If the internal vref is not good enough, you can use the same bypass cap and pin on the PSoC with an external vref source to achieve 1Msps.

Len

[TeMa_2997106]

Len-san,

Let me check again, just in case.

Is it possible to achieve 1MSPS with an internal reference and a bypass capacitor on P0[2] (external) ?

Thanks,

Tetsuo

[Len_CONSULTRON]

Tetsuo,

Yes.   When you select P0[2] as the bypass pin the Application Build will select the fixed function SAR1 block instead of SAR0.  It shouldn't be a problem.

The way to check this out is after selecting P0[2] and a successful Application Build look at the Analog Editor tab in the DWR.  You will find SAR1 is allocated for your project.

Len

[TeMa_2997106]

Len-san,

Thank you for your kind support.

I understand everything.

Tetsuo