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TPS650250: TPS650250 Design

Part Number: TPS650250
Other Parts Discussed in Thread: LM3880, LM3881, TPS65023B

Dears, 

I am now using TPS650250 . 

Here has an timing sequencer requirement. 

I need three output (1.0V, 1.2V, 1.8V)

Setup: 1.0v -->1.2v -->1.8V  

Shut down:  1.8V-->1.2V-->1.0V

At least: 1.0V setup and shut down first. 1.2V and 1.8V setup and shut down after 1.0V operated. 

Does this function can be achieve by using TPS650250. 

  • Hello Zhengqing,

    TPS650250 uses external EN signals, so you can achieve any sequence you need by setting the EN pins high in the correct order, and setting them low in the correct order.

    You can see an example of a sequencing circuit in Figure 1 of this user's guide:
    www.ti.com/.../slvu731

    This is a 3-step sequence, and you can change the RC values to change the delay timing for each step. So I think you could implement this same circuit, just changing the order of the rails to match your requirements.

    If you want more precise timing, you could use a discrete sequencer IC, or GPIOs from a microcontroller, to control the power-up and power-down sequencing.

    Regards,
    Karl
  • Dear Karl,

    Many thanks for your reply. I read this reference design already. 

    Here is the problem, for setup setting, I need a 1V first to trigger other relative high voltage enable. (1.2V or 1.8V)

    In slvu731, 1.8V goes first and it 's enough to trigger next step voltage. 

    In my design, 1V NEED GO FIRST. As a result, the voltage is not highly enough to trigger next step circuit.

    Is there any method to do this IF I ONLY USE some discrete sequencer IC to achieve this?

    I know I can use a microcontroller or other programmable PMIC to do this. But due to some reason I can ONLY use this chip to achieve this. 

    I know is hard, but please help this case. 

    Many thanks,

    BR.

     

  • SLVU731 also uses 1V to trigger the PWRFAIL_SNS input to drive nPWRFAIL output at the end of the sequence.

    You can use your first rail (1V) to trigger PWRFAIL_SNS input comparator, then  wire nPWRFAIL output to the EN pin of your 1.2V and 1.8V rails.

    In order to make sure 1.8V rail turns on last, you can modify RC delay for 1.8V rail ENable pin. Change resistor to large value (100k or 1MOhm) and the delay can be as long as 0.1-1 seconds.

    This discrete sequencing circuit can be modified in any way you want to meet the needs of your application. Karl was using it as an example.

    If you do not want to modify sequencing circuit, you can use sequencer IC such as LM3880 or LM3881.

  • Thanks for your reply.

    I know that PWRFAIL_SNS can be used to trigger nPWRFAIL. But in my design, nPWRFAIL is used in other function.(To symbol that all output has set correctly. )
    Is there any way to achieve this sequence? This case need me only use this PMIC to achieve this sequence and I can't use nPWRFAIL to trigger 1.8V. There has no other voltage supply.

    How can achieve my sequence only use this chip? Please help.
    Many thanks.
  • Yes, you can use the TPS65023B instead of TPS650250.

    The TPS65023B has same number DC-DC converters and LDOs with different VRTC voltage and additional features (GPIO, I2C).

    You can use the LOWBAT_SNS input and nLOW_BAT output. The functionality is identical to PWRFAIL_SNS/nPWR_FAIL but the name is different.