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TPS62864: How to generate Vout=1.2V and Vout=1.5V at start-up (Vin=3.3V) without any I2C programming ?

Pekon Gupta1
Prodigy 25 points
Part Number: TPS62864
Other Parts Discussed in Thread: TPS62866

Hi,

We are using multiple TPS62864 (TPS628640A) in our design to generate following Voltage rails

  • Vout=1.2V, Vin=3.3, Iout=<4A
  • Vout=1.5V, Vin=3.3, Iout=<4A

Our use-case requires that regulator supplies above voltages after power-on, without requiring any programming from I2C.

Question-1: What will be the value of Resistor (E96 Series) at VSET/VID pin to achieve above voltages

Reference: Table 1. Start-up Output Voltage and I2C Slave Address Options

Question-2: What is the output Voltage "after" start-up, does it lower-down to 0.9V based on default value of Register VO1_SET=0x64 (900mV default value) ?

Regards, pekon

  • 0
    TI__Genius 14876 points

    Hello pekon,

    Question 1: The only resistor values/range you can use to program a startup output voltage are the ones detailed in the datasheet of TPS62866. 

    You will not be able to program startup voltage outside of [0.40 ; 1.15] V range. Resistor values above 249 kOhm will set a 1.15V startup output voltage.

    Question-2: After start-up and readout of the resistor value connected to the VSET pin. The Register VO1_Set is overwritten with the register readout value.

    If you connect a 249kOhm resistor, device startup at 1.15V and will stay at this until an I2C command modifies this value.

    Thank you,

    Dorian 

  • 0 in reply to Dorian Brillet de Cande
    TI__Genius 14876 points

    Hello pekon,

    I haven't heard back from you.

    Do you any follow up question son this topic?

    We have a TPS62864 spin version in QFN version in development which will be able to address the case you mentioned above.

    If this is of interest we can discuss via private message regarding the schedule of this device to see if it fits your timeline.

    Let me know.

    Thanks a lot!

    Regards,
    Dorian 

  • 0 in reply to Dorian Brillet de Cande
    Prodigy 25 points

    Hi Dorian,

    Thank You for answering my questions. Few more follow-up queries.

    1. Yes I'll be interested in learning about new version of TPS62864 and its availability. We wanted to use PG pin functionality available in TPS628640B, but it isn't available as of today.
    2. We have multiple rails in our design (both Digital and Analog), I2C is required only for debugging and bring-up purpose. Biggest challenge is the footprint. Our PCB has multiple rails but we cannot fit as many regulators. So we plan to derive Analog supplies from Digital rails using LDO to minimize the noise. Please suggest smallest form-factor LDO which can support upto 2A current and have good noise margin.
      1. Vin=3.3
      2. Vout= (0.8, 0.88, 1.2, 1.5, 2.5) @4A or less.
    3. If using TPS62864 for generating start-up voltage of 0.88V. please suggest the accurate value of R1 resistor on VID/VSET pin.
      • R1=68.1KOhm for Vout = 0.85
      • R1=?? for Vout = 0.88V
      • R1=86KOhm for Vout = 0.9V

    Regards, pekon

  • 0 in reply to Pekon Gupta1
    TI__Genius 14876 points

    Hello Pekon,

    1. I sent you a request so we can talk via private message about the spin version of TPS62864 and its availability.

    2. You would have to create a second regarding your LDO or after that we have looked at the Buck regulator question I will point you to an LDO specialist.

    3. Regarding the Vout=0.88V, the value you would need to use depends on your load specification on the supply rail. Then you would need to pick the resistor value accordingly. 

    Thank you!
    Regards,
    Dorian