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TPS62870: TPS62870 & TPS22990

Lara Yeh
Prodigy 10 points
Part Number: TPS62870
Other Parts Discussed in Thread: TPS22990

Tool/software:

Hi Teams.

I used the architecture of TPS62870 + TPS22990.

And have some question shown as below.

Q1. For TPS62870 if hold EN (active low), is i2c could be control? until I set the voltage which I need then release EN pin.

Q2. When the voltage setting is by the i2c to control, due to the output voltage has many variations, the output inductor has been fix. Will it have any impact?

Q3. For TPS62870 which soft-start ramp just 500us / 1ms/ 2ms/ 4ms. thus I use the load switch TPS22990 for more ramp time control.

       but as section 9.3.2 mentioned. the output voltage seems be 5V, 3.3V, 1.8V, 1.05V and 0.6V. as my architecture the TPS22990's input will be TPS62870 output.

       If i'd like to set the voltage 1.2V  & 1.8V for the TPS22990 and  the rise time would like to be 10ms and 100ms. how to set the Ct?

       

Thanks.

Best Regards

Lara

  • 0
    TI__Expert 4478 points

    Hello Lara,

    thanks for reaching out on E2E.

    Q1. The I2C interface is enabled as soon as the device has completed the initialization and is not affected by the state of the EN pin

    Q2.  That depends on your system requirements. You can only optimize the design for one Vout and other voltages will have a different performance. You can follow the calculations in chapter 10 of the datasheet to check for the impact of different Vout settings.

    Q3: If I understand your application correctly, the TPS62870 will only power the TPS22990, which will then control a longer rise time. In this case the rise time of the TPS62870 can be left at the default value.

    The TPS22990 will have different rise times depending on the voltage, but it will not be possible to set it to 1.2V = 10ms AND 1.8V = 100ms, as they require different capacitors.

    Also all example calculations are in the range <1ms, so I don't think this device is suited for such long rise times, but I am no expert on these devices.

    Regards, Werner

  • 0 in reply to Werner Lummer
    Prodigy 10 points

    Hi Werner,

    Thanks for your reply.

    For the Q3, I'm confused about the rise time of the TPS62870 can be left at the default value. is it mean if I set the TPS62870 rise tine as 1ms and then TPS22990 set as 1ms, that I total rise time will be 2ms?

    I have two sets TPS62870 + TPS22990 on my test board, one for 1.2V and another for 1.8V. Could you help to recommend the capacitors. for 1.2V 10ms and 100ms and 1.8V 10ms and 100ms. I could replace those capacitors when I test.

  • 0 in reply to Lara Yeh
    TI__Expert 4478 points

    Hi Lara,

    The TPS62870 will raise the output voltage with a set slope. Once the startup threshold for the TPS22990 is reached, it will start operation and after some delay will ramp as well. So the result will be somewhere between 1-2ms.

    As said, I am no expert on this device. I will assign this question to another team, who are supporting it.

    Regards, Werner

  • 0 in reply to Werner Lummer
    TI__Mastermind 26671 points

    Hello Lara,

    I am here to help you on TPS22990.

    100 mS rise time is not possible through CT pin.

    You can give the ON signal after 100 mS and turn on the load switch.

    Thanks 

    Amrit 

  • 0 in reply to Amrit Jit
    Prodigy 10 points

    Hi Amrit,

    Thanks for your reply.

    How about 10ms?

    is it possible through CT pin to control?

    Thanks.

    Best Regards

    Lara

  • 0 in reply to Lara Yeh
    TI__Mastermind 26671 points

    Hello Lara,

    10mS is not possible too solely based on CT pin.

  • 0 in reply to Amrit Jit
    Prodigy 10 points

    Hi Amrit,

    Thanks for your help.

    Best Regards

    Lara