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TPS65023: DCDC1 Output Voltage issue.

Zentral Einkauf
Prodigy 40 points
Part Number: TPS65023
Other Parts Discussed in Thread: TPS650250

Hi,

we use all 3 DCDC Converters on the TPS65023 as follows:

Supply Voltage = 5V

------------------------------

DCDC1 = Should be 1.2V but is 2.0V

DCDC2 = 1.8V

DCDC3 = 3.3V

We're using Resistor dividers to set the required output. Which is working fine for DCDC2 / 3 but not for DCDC1.

DCDC1 is at 2.0V all the time. We even set DEFDCDC1 to GND which should defaults the output to 1.2V but it stays at 2.0V

There is no other source of 2.0V on the board so it´s unlikely a short-circuit or something.

So the question is.. why is DCDC1 2.0V ?

Edit 1: DCDC1 has 1V Threshold on DEFDCDC1 which should be 0.6 like DCDC2 and 3 ?

Edit 2: We read out the I2C registers and the chip is reporting that all voltages are within regulation which is not the case in reality.
Additionally, register address "0x05" Bit 6 (Core ADJ allowed) is set to "0" but the default is "1" ... we never set any bits there...

Edit 3: Mesurement of Power-On behaviour

  • 0
    TI__Expert 3350 points

    Zentral,

    If the Core ADJ bit has been set to 0, the PMIC is not going to default to the 1.2V for DCDC1 when DEFDCDC1 is pulled to GND. The output voltage may be "within regulation" dependent on what is set in the I2C register, which is what the PMIC will reference when bit 6 of 0x05 is set to 0. I suggest re-programming the I2C setting for DCDC1 or resetting the Core ADJ bit to 1 to fix this issue.

    Best,
    Emily 

  • 0 in reply to Emily Kong1
    Prodigy 40 points

    Hi Emily,

    we try that already. Voltage on DCDC1 does not change at all. Its always in range of 2.0Volts ...

    Do you have an explanation why DCDC1 is regulating to 1.0Volt Threshold instead of 0.6Volt if we use the Voltage dividers mentioned above ?

  • 0 in reply to Emily Kong1
    Prodigy 40 points

    Any advice ? Really stuck on this issue ...

  • 0 in reply to Zentral Einkauf
    TI__Expert 3350 points

    Zentral,

    This issue was not reproducible on our EVM and does not seem device-dependent because the TPS650250 has been involved in design-ins for quite some time now. I advise probing the SW and surrounding components to determine if there is something else connected in the system (whether or not exactly 2.0V). The datasheet and EVM user's guide provide suggestions for attached components for the PMIC to operate within specified conditions. Removing components one by one or disconnecting if in a subsystem is a good place to start. 

    Best,
    Emily