TMP112 - PoR threshold , I2C momentary pull down

Ryuji

Guru 20090 points

Hello,

(1) I2C state at POR
Could you please let me know the recommended state of I2C pins when PoR?
Is this Low? Or there is no recommendation?

(2) Momentary pull down
I knew that there is a possibility that TMP112 will momentarily pull down the SDA pin during power-on from the following E2E post.
https://e2e.ti.com/support/sensor/temperature_sensors/f/243/t/492828

Could you please let me know the resistance value of this pull down?

(3) PoR threshold
Could you please let me know the PoR threshold from ON to OFF, OFF to ON?

Best Regards,
Ryuji Asaka

over 9 years ago

0 Ren Schackmann over 9 years ago

TI__Mastermind 44245 points

I am looking into this and will get back to you soon.

Ren

0 Ryuji over 9 years ago in reply to Ren Schackmann

Guru 20090 points

Hi Ren san,

Any update on this?
Thank you for your support in advance.

Best Regards,
Ryuji Asaka

0 Ren Schackmann over 9 years ago

TI__Mastermind 44245 points

Hi Ryuji-san,

1) SDA should idle at logic high when not in use. During power on, SDA level should be equal to Vcc level.
2) The drive strength of SDA is specified at 3mA as part of the VOL spec. See page 5 of the data sheet.
3) I need more time to find this information.

Ren

0 Ryuji over 9 years ago in reply to Ren Schackmann

Guru 20090 points

Hello Ren san,

Thank you for your reply.
I'm looking forward to the reply for (3).

Best Regards,
Ryuji Asaka

0 Ren Schackmann over 9 years ago in reply to Ryuji

TI__Mastermind 44245 points

The Power-On-Reset voltage is around 0.9V for both turn-on and turn-off.

Ren

0 Ryuji over 9 years ago in reply to Ren Schackmann

Guru 20090 points

Hello Ren san,

Sorry again.
The momentarily pull down at the SDA pin may be occurred during around 0.9V to 1.4V.
Thus , we must not access the I2C during this period.
Is my understanding correct?

Best Regards,
Ryuji Asaka

0 Ren Schackmann over 9 years ago in reply to Ryuji

TI__Mastermind 44245 points

Yes, this is correct.

Ren

0 NAOKI AOYAMA over 9 years ago in reply to Ren Schackmann

Guru 11215 points

Hello,

Could you tell me how long "momentary" is ?
Is it several usec? several msec?

Regards,
Naoki Aoyama

0 Ren Schackmann over 9 years ago in reply to NAOKI AOYAMA

TI__Mastermind 44245 points

On my sample, the momentary pull down is 24us long. It takes my supply about 800us to ramp up to it's final supply voltage. Regardless of final supply voltage, the glitch begins at about 0.8V and has completed by the time the supply has reached 1V. The glitch should always begin around 0.9V and last around 24us, but there will be device-to-device variation.

Ren

0 NAOKI AOYAMA over 9 years ago in reply to Ren Schackmann

Guru 11215 points

Hello Ren,

Thank you for your reply.

Thanks,
Naoki Aoyama

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TMP112 - PoR threshold , I2C momentary pull down