TXB0104: Input waveform always keep high when VCCA and OE are valid

daniel

Genius 5095 points

Part Number: TXB0104

Hi Expert,

The test situation is sample only, so there are no other effect concern.

1. We input 3.3V square wave on B3 pin, but the high level can not reach 3.3V on B3 pin.

After input V3P3_A on VCCB, the high level can reach 3.3V on B3 pin. Is this normal?

2. Then we input V1P8_A (VCCA and OE are valid), the waveform become always high on both A3/B3 pin.

It should be 3.3V square wave on B3 pin, and 1.8V square wave on A3 pin, right?

3. We try to add a 3.92K pull down resister on B3 pin, then we can get 2.5V square wave on B3 pin, and 1.4V square wave on A3 pin.

Do you have this kind experience? Please help

Thanks

over 7 years ago

0 Emrys Maier over 7 years ago

TI__Guru* 96591 points

Hi Daniel,

I have notified the appropriate engineer; he will get back to you today.

0 aozer over 7 years ago

TI__Mastermind 23855 points

Hello Daniel,

Can you provide us with oscilloscope shots of you input and output waveforms?

0 daniel over 7 years ago in reply to aozer

Genius 5095 points

Dear Aozer,

The abnormal waveform always keep high.

Please help

Thanks

0 aozer over 7 years ago in reply to daniel

TI__Mastermind 23855 points

Hello Daniel,

It looks like the issue is with your device that is driving the inputs. The input is not switching either, which leads me to believe that whatever is driving the inputs is not able to sink enough current to pull the input down, hence why the pull-down resistor allows the input to switch. If you refer to the TXB0104 datasheet, it specifies that the driver must be able to source/sink at least 2mA of current for proper operation. Does you driver meet this spec?

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TXB0104: Input waveform always keep high when VCCA and OE are valid