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TS5A3159: Signal Issue

Kuan Wei Chen (Kevin Chen)
Genius 9710 points
Part Number: TS5A3159

Dear Team,

1.Is it necessary the NC and NO output pin have 50ohm during layout?

2.When Ch1(pin:6 IN) high, CH2 (pin:4 COM low), the CH3(pin:3 NC) didn't go low.

Is it because CH1 high just mean disconnect the COM to NC?

If I want to NC pin go low need to have pull low resistor? Or how to deal with it?

3. The COM pin have 22NH series inductance(AL19)

When input RF bandwidth 40MHz it will have rising time 9.6us

When input RD bandwidth 20MHz it will have rising time 24.8us, which causes the signal issue.

Any ideas can solve the rising time?

BR

Kevin

  • 0
    TI__Genius 9710 points

    Dear Team,

    BTW, what will happen if NC and NO output pin don't have 50ohm during layout?

    BR

    Kevin

  • 0 in reply to Kuan Wei Chen (Kevin Chen)
    TI__Genius 9132 points

    Hi Kevin,

    Please see details to your questions below:

    1.Is it necessary the NC and NO output pin have 50ohm during layout?

    • The 50Ohm impedance is standard impedance used to maintain good signal integrity. For high frequency signals, it is recommended to match your source and load impedance to avoid signal reflections. The TS5A3159 supports low bandwidth of 100MHz  - you would need 50Ohm impedance matching for high speed (~GHz) signals

    2.When Ch1(pin:6 IN) high, CH2 (pin:4 COM low), the CH3(pin:3 NC) didn't go low.

    Is it because CH1 high just mean disconnect the COM to NC?

    • Correct , if you look at the device functional table, when "IN" is HIGH, NC to COM is high impedance.

    If I want to NC pin go low need to have pull low resistor? Or how to deal with it?

    • Yes, you can use a pull down resistor at NC

    3. The COM pin have 22NH series inductance(AL19), Any ideas can solve the rising time?

    • According to the equation, V = L * di/dt, a change in current over a short period of time, such as a switching event, will cause a voltage spike on the order of the parasitic inductance of the trace - In order to minimize the rise time, you need to lower the di/dt as there can be a large voltage generated across the inductor.

    Regards

    Saminah

  • 0 in reply to Saminah C
    TI__Genius 9710 points

    Dear Saminah,

    Thanks for the promptly response.

    1. What is the suggested value for pull down reistor at NC and NO?

    2.Any comments for the schematic design?

    BR

    Kevin

  • 0 in reply to Kuan Wei Chen (Kevin Chen)
    TI__Genius 9132 points

    Hi Kevin,

    1. For the pull down resistor, there is no standard value but you need to consider the following:

    a) What's the impedance of the input that NC pin is connected to. The pull-down resistor should be lower than that impedance. b). Lower pull-down may burn static current depending on the NC pin connection. c). How fast should the NC pin go down.
    2. The schematic looks ok - I don't see decoupling on the supply pin - Please refer to Power Supply Recommendations section in the datasheet and all voltages are within the recommended operating conditions.
    Regards
    Saminah