TMP103: TMP103 I2C pin status after power-down

user4760726

Part Number: TMP103

Team,

One of the customers is wondering about what the I2C pins status (i.e. pull-low, pull-high,or open drain) are if the device is powered off. Also, what pull-up resistor do you recommend to use? 4.7k ohms ok?

Best Regards,

Leroy

over 8 years ago

0 Jose Arteaga4 over 8 years ago

TI__Expert 5695 points

Hi Leroy,
As described on the section 8.2.1 (Design Requirements) for the data sheet:
"The TMP103 device requires pullup resistors on the SCL and SDA pins. The pullup resistor values must be
selected such that the maximum current sinking capability of I/O pins is not violated. TI recommends a 0.01-μF
bypass capacitor on the supply"

Taking in account supply value (V+) is easy to calculate the pull up value once you know the max current for i/o pins. 4.7k should be ok, however please in account that the higher the value of these resistors the lower the current that is "burned" there.

0 user4760726 over 8 years ago in reply to Jose Arteaga4

TI__Intellectual 1195 points

Jose,

Thanks for the quick response.

How about the pin status of I2C (B1 and B2)? When TMP103 is off, what is the status of these pins (pull-down, open drain, or high-z)?

0 Aaron Heng over 8 years ago in reply to user4760726

TI__Mastermind 34270 points

Hi Leroy,

Let me check into this, and get back to you.

Aaron

0 Aaron Heng over 8 years ago in reply to Aaron Heng

TI__Mastermind 34270 points

Hi Leroy,

According to the datasheet, these pins are open-drain. The pins is connected to the nmos internally pulling to low. If the device is powered down the nmos will not be able to drive the pin, the output state is undefined. So, it is high impedance.

Hope this helps. Please let me know if you have further question.

Aaron