LSF0204: when Vref_A open with pull-down resistor

Hiroshi Sato

Part Number: LSF0204

Hello,

Our customer facing a similar issue as below.

https://e2e.ti.com/support/interface/voltage_level/f/391/p/560507/2062303?tisearch=e2e-sitesearch&keymatch=lsf0204#2062303

The customer has added a 1k ohm pull-down resistor with Vref_A line, however, very low voltage still appears at Vref_A line, about 20 to 30mV.

To eliminate that voltage, please let us know the appropriate value for pull-down resistor.

Thank you,

Hiro

over 8 years ago

0 Emrys Maier over 8 years ago

TI__Guru* 97176 points

Hi Hiro-san,
I do not understand. Can you provide a schematic showing the application?

Also, I would recommend watching these videos so you will have a better understanding of the device: training.ti.com/LogicMinute

The LSF family of devices is complex to explain through text.

0 Hiroshi Sato over 8 years ago in reply to Emrys Maier

Expert 2590 points

LSF0204inquiry20171215.pptxHello Majer-san,

Thank you for your replying, Please see the attached file

Thanks and best regards,

Hiro.

0 Emrys Maier over 8 years ago in reply to Hiroshi Sato

TI__Guru* 97176 points

Hi Hiro-san,

The pull-down resistor is setting up a voltage divider with the 3.3V supply and the internal 200kohm through the diode-connected FET inside the device.

The best way to force the pin to 0V would be to use a low on-state resistance FET to short the pin to ground.

Another option would be to add a series load switch with Vref_A pin and disable the pin that way.

0 Hiroshi Sato over 8 years ago in reply to Emrys Maier

Expert 2590 points

Hello Maier-san,

Thank you for your explanation, I understand.

I'll tell that to the customer.

Thanks and best regards,

Hiro

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LSF0204: when Vref_A open with pull-down resistor