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TPS55288: Not able to set output current using TPS55288.

Amol Punyarthi
Prodigy 20 points
Part Number: TPS55288

Tool/software:

Hi, I am working on a project which requires the device to output specified current and voltage configured by user.

For this purpose, I have selected TPS55288 because of its adjustable output voltage and programmable output current capability.

Currently I have TSP55288 EVM board on which I am testing program, connected to Orange pi using I2C.

I am able to set the output voltage to required levels using REF register.

Following are the issues faced by me.

1. While setting the output voltage, the voltage goes above the specified value.

For example, if I am setting 10V, then output voltage of TPS55288 is 12V.

These are the register values set by me 

ref_lsb_value = 52

ref_msb_value = 2

iout_limit_value = 255

vout_fs_value = 3

cdc_value = 224

mode_value = 161

2. Need a guidance on how to set output current at a specified level. For example, the output current can be 0.04A or 0.1 A or above that.

Kindly guide me in solving these issues.

Regards,

Amol.

  • 0
    TI__Mastermind 27750 points

    Hi Amol,

    1. I don't understand the values of registers you mentioned, what does '52' mean? Can you show it in binary code like below?

    2. If the internal feedback is selected, the output voltage is calculated by VREF/feedback Ratio which is in REF register and VOUT_FS register.

    3. To achieve constant output current output, the accuracy would not be good at light load, recommend to set FPWM mode. And you can program the output current value by programming the VISP-VISN value.

    BRs,

    Bryce

  • 0 in reply to Bryce Xun
    Prodigy 20 points

    Hi Bryce,

    1. Below is the breakdown of registers in binary code
    ref = 1000110100
    iout_limit = 10000010
    vout_sr = 00000001 #
    vout_fs = 00000011
    cdc = 11100000
    mode = 10101000

    2. I have selected internal feedback from VOUT_FS register, and it is at default value of 0.0564.

    3. I tried setting output current using VISP-VISN value but didn't get the result. I want to set the output current to 0.1A and maintain it throughout the process.
    What should be the register values to achieve the same.

  • 0 in reply to Amol Punyarthi
    TI__Mastermind 27750 points

    Hi Amol,

    I will look into this and reply to you next week.

    BRs,

    Bryce

  • 0 in reply to Bryce Xun
    Prodigy 20 points

    Hi Bryce,

    Any update??

  • 0 in reply to Amol Punyarthi
    TI__Mastermind 27750 points

    Hi Amol,

    Thanks for your patience.

    1. From your shared register values, the output voltage is set at 12.08V, Vref=681.756mV, feedback ratio=0.0564, Vout=Vref/ratio=12.08V.

    2. The VISP-VISN voltage is set at 1mV, which means the output current will be limited at 1mV/10mohm=0.1A. If the device is operating at PFM mode, it is difficult to realize the constant current output.

    3. From the MODE register values, the external VCC is selected, recommend to keep using internal VCC. Otherwise you will need to use one external 5V/100mA to supply VCC.

    BRs,

    Bryce