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TS5A22362: Issue regarding TS5A22362 input terminal (NC & NO) kept open ended.

Prodigy 40 points

Replies: 4

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Part Number: TS5A22362

I am using TS5A22362 for switching analog input Voltages applied to differential ADC. Supply for TS5A22362 is 3.3V. Input signal is from -450 mv to
+450 mV.

I am facing problem when the input terminal (NC & NO) of TS5A22362 switch is kept open ended, lifted Distorted waveform is observed at COM1 & COM2
terminal of TS5A22362.

When input terminal (NC & NO) of TS5A22362 are closed with RL< 70 Ohm or Input is applied to (NC & NO) terminal then waveform at COM1 & COM2
terminal of TS5A22362 is found ok.

Please suggest what is going wrong with above configuration.

Please refer attached circuit & waveform for your reference.

  • Hi Avik,

    The TS5A22362 is a bidirectional passive FET switch.  When the NC or NO path is enabled the device ideally should look like a 0 Ohm wire from COM to NC/NO so that the signal on COM pin will pass to NO and NC with no distortion.  

    The maximum current allowed through the switch is stated in the absolute maximum specification table in the datasheet as the on state switch current 150mA.

      

    Few things you can check:

    1. It is possible that your drive current it not strong enough to drive the load attached to NO or NC?

    2. . You mentioned your input signal range is from -0.45V to 0.45V. At 3.3V supply, the recommended signal range as specified in the datasheet is MIN of  Vcc -5.5 (-2.2V) to MAX VCC (3.3V). Please make sure you are operating under the recommended operating conditions of the device as specified in the datasheet.

    Thanks

    Saminah

  • In reply to Saminah C:

    Thanks Saminah for your response.

    I have checked following points
    1.Max on state switch current is not exceeded. It is only 0.7uA as we are passing -450 mV to 450 mV to ADC terminal.
    2.The total Input Signal is within the operating range i.e -450mV to 450mV.
    3.We observed problem only when no input is given to NO/NC terminal i.e these pins are left open & COM1/COM2 are connected to Differential ADC input terminal.

    Regarding Circuit diagram, We have attached external Current Transformer with voltage output to NO/NC terminal of the TS5A22362. and COM1/COM2 Pins are connected to Differential ADC terminals. I am not using it for audio application instead using it as simple switch to transfer AC mV signal to ADC.  

    We observed problem only when the Current Transformer is disconnected from the NO/NC terminal of the TS5A22362 i.e kept open ended.

  • In reply to Avik Bhowmik:

    Hi Avik,

    Thank you for providing the details. 

    Make sure that the device is powered up with a supply voltage on VCC before a voltage can be applied to the signal paths NC and NO.

    Also, it is better not to keep the input pins floating as they will be in an un-defined state - as you mentioned when you use a pull-up/pull down resistor on the NC and NO pins, the distortion goes away - I would recommend to use a pull-up in your design to keep the inputs at a definite level.

    Thanks

    Saminah

  • In reply to Saminah C:

    Hi Saminah,

    Thank you for your suggestion.

    The problem is solved when I have pulled these pin to keep the inputs at a definite level. I have pulled down these pins to ground to resolved the problem.

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