TINA/Spice/TPL7407L: Input resistance not 1Meg?

electronicjohn

Part Number: TPL7407L
Other Parts Discussed in Thread: TINA-TI,

Tool/software: TINA-TI or Spice Models

Hello,

I've been modeling this part and noticed the input pull-downs were pulling more current than I was expecting. After running some simulations to investigate, the model seems pretty clear that each input channel has 300kOhm of resistance. The datasheet only shows there is a 1Meg resistance to ground. Is this a modeling error?

tpl7407l_input_resistance.TSC

over 7 years ago

0 John Miller - Sensing over 7 years ago

TI__Mastermind 40295 points

John,

Thank you for the inquiry and for uploading your circuit.
I will look at the behavior you described and get back to you next week.

Regards,
John

0 John Miller - Sensing over 7 years ago in reply to John Miller - Sensing

TI__Mastermind 40295 points

John,
The 1MEG pull-down resistor does not reflect all of the elements that affect input current.
Notice the datasheet specs a MAX/ON input current of 10uA for an input voltage range of 1.5V to 5.0V.
We could interpret this as an equivalent MIN input resistance of 150k to 500k which would include the total effects of the 1MEG pull-down resistor, the 50k resistor, Zener diode and MOS gate.
The 300k pull-down resistor used in the model is intended to reflect the typical behavior of the device's input current.
I hope this helps. Please let me know if you have any more questions.
Regards,
John

0 electronicjohn over 7 years ago in reply to John Miller - Sensing

Intellectual 330 points

OK that makes sense, thanks for the response!

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TINA/Spice/TPL7407L: Input resistance not 1Meg?