TPS2115: internal pull-up resistor at D0/D1 pin

Sho Ogane

Part Number: TPS2115

Hi all

There is a following explanation at the terminal functions table in the datasheet P7.
" Each pin has a 1-µA pullup resistor."

Please tell me the value of pull up resistor?

Best Regards,
Sho

over 8 years ago

0 Darwin Fernandez over 8 years ago

TI__Mastermind 41760 points

Hi Sho,

The 1uA is pulled up to the internal VDD which is the higher between IN1 or IN2. So the effective impedance will be (VIN1 or VIN2) / 1uA

0 K.Yaita over 8 years ago in reply to Darwin Fernandez

Guru 29720 points

Hi Darwin-san,

My customer wants to put pull-down resistor at D1/D0 to be controlled by MCU and not to be input Hi-Z when power supply of MCU is off.
Could you tell me recommended value of the pull-down resistor?

Best Regards,
Yaita

0 Darwin Fernandez over 8 years ago in reply to K.Yaita

TI__Mastermind 41760 points

Hi Yaita,

You should choose the pull down resistor such that the micro can drive Dx pin and the pull down resistor.

When there is no power to the micro and thus no power to the TPS2115, there will be no current flowing through divider and the voltage on Dx will be 0V.

0 K.Yaita over 8 years ago in reply to Darwin Fernandez

Guru 29720 points

Hi Darwin-san,

Thank you for your reply.
I believe less than 700kΩ for pull-down resistor is required because VIL is 0.7V (min).
* 1uA (internal current source of Dx pin) x 700kΩ = 0.7V

Is my understanding correct?
I assumed TPS2115 has power supply in this case.

Best Regards,
Yaita

0 K.Yaita over 8 years ago in reply to K.Yaita

Guru 29720 points

May I have your comments?
If you needs additional information or has something unclear, please let me know.

Best Regards,
Yaita

0 Darwin Fernandez over 8 years ago in reply to K.Yaita

TI__Mastermind 41760 points

If assuming the IC is being powered, then looking at the electrical characteristics table, the current is 5uA. The pull down should be set such that it is less than VIL with a 5uA current. <140k ohms

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TPS2115: internal pull-up resistor at D0/D1 pin