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TS5A23157-Q1: What is the internal impedance value for TS5A23157 PIN 6 & PIN 10

Part Number: TS5A23157-Q1
Other Parts Discussed in Thread: TS5A23157, PCA9306

Hello  TI engineers,

   In our PCB design, we found a BUG, when power on ,an abnormal  900mV voltage appears on the network connected to Pin 10 of the TS5A23157. In our design ,PIN 10 was pull high to 1V8 with 2.2kohm,It looks like the power supply has been dividered. Then we measure the impedance between PIN 10 and GND,and the value is 2.4Kohm。 Can you share the information about the internal impedance value for PIN 10 and PIN 6?

   

  • In addition, the green waveform in the oscilloscope is the PIN 10 network I mentioned, and the corresponding schematic design is CSI_AB_I2C0_CLK

  • Hello Yepeng,

    The internal impedance of TS5A23157 in pin6 and pin10 is 180Ω at 1.8V supply. 

    Regarding the issues you are facing. Can you please explain if pin 9 and pin 7 (NC1 and NC2) are floating? 

    Also what is the voltage level on NO1 and what is it connected to?

    Thanks,

    Nir 

  • Hello Nir,

     1. pin 9 and pin 7 (NC1 and NC2) are floating,no connected.

     2. the NO1 network has no pull-up resistor.,because we think  I1 was pull high,C1 will be connected to NO1, C1 net has pull high resistor.

     3. The picture below is a simple schematic diagram,please help us review this design,thanks!

  • Hello Yepeng,

    Understood, regarding the schematic I would recommend to ground the floating pins. Other than that it looks good.

    Thanks,

    Nir 

  • Hi Nir 

         Thanks for review,and I had try to make floating pin tie to GND today , but the pin6 and pin 10 still abnormal when power on.

          Can you explain why the voltage levels are abnormal on pin 6 and pin 10?As you can see the picture on the below ,when power on the voltage on pin 10 is 700mv~900mv,but we design is 1V8 ,after about 50ms then the voltage on pin 10 is normal (1V8). 

          Can you verify that in your lab? makesure in your side the pin 6  and pin 10 is OK when power on

  • Hello Yepeng,

    Can you please test the TS5A23157 isolated from the rest of your system?

    My theory of what might be causing this odd signal is that the SOC and the PCA9306 might be turning on at different times than the switch causing the signal to lag.

    Thanks,

    Nir 

  • Hi Nir,

       In our system,the VDD_1V8_HS is powerd on after   VDD_1V8_CAM,  so the pin 6 and 10 will be 1v8 before than pin 8 & 1&  5.

       In datasheet ,we didnt see any requirement about the power  sequence for the chip

  • Hello Yepeng,

    I might be misunderstanding your comment, but what I meant is the other devices in your system (highlighted below) might be causing the issue.

    I believe the SOC or/and the PCA9306 are powered on at a different time than the TS5A23157 which causes the signal lag.

    Can you please test the TS5A23157 disconnected from the other devices to make sure our device is causing the issue? I want to see if there is an issue in our device, or is caused by a different device in the system.

    Thanks,

    Nir

  • Hello Nir,

        When TS5A23157 disconnected from the other devices,the issue disappears. 

        Maybe I didn't make it clear, in our system, for TS5A23157 chip, pin 6 and 10 will have the voltage signal first, because VDD_1v8_CAM is powered on earlier than VDD_1V8_HS. In other words, Before the pin8 VCC is powered, the output ports pin6 and 10 will be 1V8 voltage level. Do you think there is a problem with this design?

           We think the power sequence is the cause of the problem, because when we set VDD_1V8_HS to power on before pin 6 and 10, the system is normal. 

          Can you share some information about internal block about TS5A23157?  We want to know why the voltage on pin 6 &10 will be abnormal when they power on before VCC

  • Hello Yepeng,

    I understand now, thank you for the clarification. 

    Having a voltage signal on pins 6 and 10 before the device is powered on is a design flaw. The device doesn't have powered off protection (the device might get damaged if there is a high enough voltage signal while the device is off). 

    "We think the power sequence is the cause of the problem, because when we set VDD_1V8_HS to power on before pin 6 and 10, the system is normal". 

    I agree with your thought this probably what causes the issue. I suggest to redesign your system so the TS5A23157 will be powered on before it receives a voltage signal on the I/O pins.

    Thanks,

    Nir  

  • Hello, Nir

       I see, thanks!