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TRS3122E: RS232 Transceiver power consumption

Lex Hsiao
Prodigy 80 points
Part Number: TRS3122E

Hi,

Could anyone help to provide the information regarding the current consumption performance under Static and Off mode?

The datasheet shows the number of it but our TEST CONDITIONS are different, e.g. the /FORCEOFF and the FORCEON pin.

And our test result is 4.4mA at idle mode and became 0.3mA 30 seconds later.

Could anyone help to clarify it?

Thanks.

Our schematic is below.

From the datasheet

  • 0
    TI__Mastermind 23843 points

    Hi Lex,

    ICC (Static) is when the transceiver is powered up, but not driving any signal across no load.

    ICC (off) is when the device is powered on, but /FORCEOFF = GND, turning off the internal driving/receiving circuitry to save power. 

    These datasheet parameters are defined this way. When you change test conditions of these parameters, you are no longer testing the parameter as listed in the datasheet. 

    Lex Hsiao said:
    And our test result is 4.4mA at idle mode and became 0.3mA 30 seconds later.

    At idle (static) and when VCC = 3.0V ~ 3.6V, ICC is typically 0.7mA at no load. Do we know the load present on the DOUT pins of the transceiver? During idle state, the transceiver will output HIGH or LOW signal depending on the idle input of the UART. This keeps the transceiver out of the indeterminate region, but will also consume current since a load is present on DOUT. Only when 30 seconds have passed will the driver outputs enter High-Z state, reducing over all current consumption. 

    0.3mA >> 0.4uA typical ICC(off) current, but test conditions for your setup are different. The datasheet does not have test cases for ICC(off) current when using automatic powerdown plus mode. Therefore, you can test the device by following the /FORCEOFF conditions setting /FORCEOFF = GND, to see if you measure  <10uA through ICC.

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Prodigy 80 points

    Hi Tyler,

    Thanks for your reply.

    We will double confirm whether the load is present or not.

    Another question for you is, could you help to explain the below statement from the datasheet?

    It says the current will reduce to 0.5uA after 30s automatically shut down the charge pump under the same test condition as our design.

    But we got 0.3mA after 30s.

  • 0 in reply to Lex Hsiao
    TI__Mastermind 23843 points

    Hi Lex,

    What exact test setup are you using to measure supply current during automatic powerdown? 

    Regards,

    Tyler