LSF0204: Pull-up resistance

Yuta Nishie

Genius 4925 points

Part Number: LSF0204

Hi,

I have any questions.

No. 1: Why is there no pull-up resistance in the A4 and B3 and B4 lines in the data sheet schematics?

　　　Also, please tell me the difference between when pull-up resistance is needed and when it is not.

No. 2: For the A3-B3 line, if A3 is input at 1.8 V, what V is the output signal of B3's High?

Best Regards,

Nishie

over 3 years ago

+1 Clemens Ladisch over 3 years ago

Guru 316470 points

B3 and A4 do not need pull-up resistors because they are always used as inputs and driven by push/pull outputs.

B4 is an output and does need a pull-up resistor. It's possible that the GPIO has an internal pull-up resistor, but this looks like an error.

0 David Cananzi over 3 years ago in reply to Clemens Ladisch

Prodigy 120 points

Is it possible that since A4 to B4 goes to a 1.0 V input, and Vref A is 1.8 V; there must be a 0.8 V difference between the two. Then would the output drop to 1.0 V?

0 Clemens Ladisch over 3 years ago in reply to David Cananzi

Guru 316470 points

The voltages are clamped to Vref_A. So the B4 output signal is 1.8 V. This will work with a 1.0 V device only if it has an overvoltage-tolerant input.

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LSF0204: Pull-up resistance