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TCAN2451-Q1: How to understand the VCC1 pin sinking current capable related to SPI register VCC1_SINK and VCC1_SINK_DIS.

Shiyu Xia
Prodigy 130 points
Part Number: TCAN2451-Q1
Other Parts Discussed in Thread: TCAN24XXEVM

Tool/software:

"The VCC1 pin is capable of sinking either 10μA or 1000μA of current depending upon the register setting VCC1_SINK and is active by default. The current sink can be disabled by setting the register bit VCC1_SINK_DIS."

Yes, I understand the VCC1_SINK_DIS is a switch of VCC1 sinking current and VCC1_SINK is used to selected the max VCC1 sinking current 10uA or 1000uA.

My Question:

1. I keep the VCC1_SINK_DIS = enable and VCC1_SINK = 1000uA. What are the influences of this configuration?

2. What condition I need to change the VCC1_SINK from 1000uA to 10uA?

3. What condition I need to change the VCC1_SINK_DIS from enable to disable?

  • 0
    TI__Mastermind 26806 points

    Shiyu,

    Thanks for reaching out! Generally the purpose of the VCC1 sink is to help keep the VCC1 line in regulation if there is any risk of reverse-biasing the VCC1 line from another device on the rail. For example, if the VCC1 output is 3.3V, but there is another device on the rail that incorrectly has 5V applied to it from another source, it's possible for it to back-bias onto the VCC1 line. The sinking capability helps mitigate this risk.

    Shiyu Xia said:
    1. I keep the VCC1_SINK_DIS = enable and VCC1_SINK = 1000uA. What are the influences of this configuration?

    When you have these configurations, it means that the current sink is enabled on your VCC1, and it is capable of sinking up to 1000µA. This would only apply if you have some other source that would be feeding charge into the VCC1 line. If the VCC1 output is always supplying current, then this would not change the behavior of your design.

    Shiyu Xia said:
    2. What condition I need to change the VCC1_SINK from 1000uA to 10uA?

    This is very system-dependent, but mostly this depends on the other devices on the supply line. If there are no other devices that might inadvertently apply additional charge/bias to the line, then you might not need to have the additional current sinking capability.

    Shiyu Xia said:
    3. What condition I need to change the VCC1_SINK_DIS from enable to disable?

    You could consider doing this if you need to prevent any negative current flowing into the VCC1 line, particularly if there are other devices on the VCC1 rail that might be in contention with the output from the TCAN2451-Q1.

    Best,

    Danny

  • 0 in reply to Danny Bacic
    Prodigy 130 points

    Your answer is very official. 

    I actually want to know whether the configuration of these two registers (VCC1_SINK_DIS and VCC1_SINK) affect the output accuracy of VCC1. 

    And when the SBC go into standby mode or sleep mode, whether the configuration of these two registers (VCC1_SINK_DIS and VCC1_SINK) affect the quiescent current of SBC.

  • 0 in reply to Shiyu Xia
    Prodigy 130 points

    Or whether the configuration of these two registers (VCC1_SINK_DIS and VCC1_SINK) affect some other features of SBC.

    After all, the datasheet only describes these two registers in a very simple way, and does not mention any relationship between these two registers and other performance of SBC.

    At last, for the new SBC TCAN2451-Q1, do you have any application note or errate note? We have only datasheet. We want to get more technical data.

  • +1 in reply to Shiyu Xia
    TI__Mastermind 26806 points

    Shiyu,

    No, the configuration should not impact the regulation you'd see from the VCC1 output. The output range from the Power Supply Characteristics would apply regardless of the current sink setting.

    Additional documentation for the device will be publicly released in the next few months as the device approaches full release. Right now, the TCAN2451-Q1 is only in advanced release state. However, in the same MySecure folder as the device data sheet, you can find the TCAN24XXEVM user guide which might provide additional context as well.

    Best,

    Danny