Configuring the Brownout for when VDD3P3_RTC is fed 1.8v

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hassan789
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Configuring the Brownout for when VDD3P3_RTC is fed 1.8v

Postby hassan789 » Thu Jan 18, 2018 4:22 pm

ESP team,
I am developing a 1.8v ESP32-D2WD board. The entire digital domain: VDD3P3_RTC, VDD3P3_CPU, and VDD_SDIO are powered from 1.8v :twisted:
Looking into the menuconfig and the Technical Ref Manual 2.8, the brownout has a 3-bit (eight settings). However, it is centered around 2.5v. It is not clear on how to center this around 1.8v...

How can I trigger the brownout at ~1.7v?

Thanks
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brownout.JPG
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Last edited by hassan789 on Fri Jan 19, 2018 3:02 am, edited 1 time in total.

ESP_Angus
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Re: Configuring the Brownout for when VDD3P3_RTC is fed 1.8v

Postby ESP_Angus » Thu Jan 18, 2018 10:28 pm

hassan789 wrote:ESP team,
I am developing a 1.8v ESP32-D2WD board. The entire digital domain: VDD3P3_RTC, VDD3P3_CPU, and VDD_SDIO are powered from 1.8v :twisted:
Looking into the menuconfig and the Technical Ref Manual 2.8, the brownout has a 3-bit (eight settings). However, it is centered around 2.5v. It is not clean on how to center this around 1.8v...
Hi Hassan,

This is not possible because 2.3V is the minimum voltage for the digital domain VDD supplies (except for VDD_SDIO). Consult ESP32 datasheet section 5 Electrical Characteristics, first row in "Absolute Maximum Ratings" table.

For this reason the minimum configurable brownout detector voltage is ~2.43V. Anything lower is too risky (the voltage may dip a small amount very temporarily without triggering the brownout detector, hence the 0.13V of headroom).

If a chip seems to run (with brownout detector disabled) at 1.8V anyhow, be advised that some features will probably not work and you may get data corruption, glitched instructions, and other weird problems.

Sorry to be the bearer of bad news.


Angus

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hassan789
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Re: Configuring the Brownout for when VDD3P3_RTC is fed 1.8v

Postby hassan789 » Thu Jan 18, 2018 10:34 pm

ESP_Angus wrote: Hi Hassan,

This is not possible because 2.3V is the minimum voltage for the digital domain VDD supplies (except for VDD_SDIO). Consult ESP32 datasheet section 5 Electrical Characteristics, first row in "Absolute Maximum Ratings" table.

For this reason the minimum configurable brownout detector voltage is ~2.43V. Anything lower is too risky (the voltage may dip a small amount very temporarily without triggering the brownout detector, hence the 0.13V of headroom).

If a chip seems to run (with brownout detector disabled) at 1.8V anyhow, be advised that some features will probably not work and you may get data corruption, glitched instructions, and other weird problems.

Sorry to be the bearer of bad news.


Angus

Angus,
According to the datsheet, it says 1.8v is possible. Please see attached pic.
Also, I am using the chip already in 1.8v mode...
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esp32 at 1.8v.JPG
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ESP_Angus
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Re: Configuring the Brownout for when VDD3P3_RTC is fed 1.8v

Postby ESP_Angus » Fri Jan 19, 2018 12:32 am

I'm sorry, I think this is a mistake in the datasheet. As per the footnote 1 to table 5.1, this range is only valid for the VDD_SDIO pin & associated power domain.

I've asked my colleagues to confirm, will get back to you.

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hassan789
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Re: Configuring the Brownout for when VDD3P3_RTC is fed 1.8v

Postby hassan789 » Sun Jan 21, 2018 7:08 pm

Here is another excerpt for the latest Hardware Design Guidelines v2.1
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VDD3P3_RTC at 1.8v.JPG
VDD3P3_RTC at 1.8v.JPG (109.03 KiB) Viewed 9676 times

ESP_Angus
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Re: Configuring the Brownout for when VDD3P3_RTC is fed 1.8v

Postby ESP_Angus » Wed Jan 24, 2018 3:25 am

The hardware team has confirmed with me that they don't recommend running the other digital domain supplies below 2.3V. The lower voltages mentioned in the datasheet will be corrected to reflect this.

If you run these power domains at 1.8V then the ESP32 will probably appear to work but you may encounter very occasional memory corruption and also problems writing to efuse.

I'll let you know once the documents have been updated.

Sorry to be the bearer of bad news.

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hassan789
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Re: Configuring the Brownout for when VDD3P3_RTC is fed 1.8v

Postby hassan789 » Wed Jan 24, 2018 3:46 am

wow.. thanks for clearing that up.
anyway to minimize the effects of this? perhaps running at 80MHz would help?

ESP_Angus
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Re: Configuring the Brownout for when VDD3P3_RTC is fed 1.8v

Postby ESP_Angus » Thu May 24, 2018 11:46 pm

Hi hassan,

Thanks for your patience with this update.

A new ESP32 datasheet (V2.2) has been released which corrects the VDD3P3_RTC voltage range (2.3V to 3.6V, with a footnote - see section 5.2 in the datasheet). VDD3P3_CPU voltage range remains 1.8V to 3.6V. You can download the new datasheet from here.

Angus

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hassan789
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Re: Configuring the Brownout for when VDD3P3_RTC is fed 1.8v

Postby hassan789 » Sat Jun 02, 2018 2:44 am

thanks! will review this in detail :D

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