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TPS51285B: Disable two buck controllers CH1 and CH2

Vito Liao
Intellectual 390 points
Part Number: TPS51285B


Hi Sir,

Our customer needs high input voltage 3V LDO and 5V LDO for his application. He wants to use TPS51285B's VREG3, VREG5 and disable dual buck controllers. Can you please guide us how to deal with CH1's pins and CH2's pins?

Best regards,

Vito

  • 0
    TI__Expert 5745 points
    What's the input and load of the LDO he wants? If the input voltage is bigger than the LDO output and the load is heavy, don't use the LDO because of the high power loss. BUck is better than LDO in this application.
    For disable the CH1 and CH2, just pull the EN pin to the GND
  • 0 in reply to Vental Mao
    Intellectual 390 points
    Hi Vental,

    Thank you for your reply.
    I am sorry I would like to know how to deal with these pins (EN1, EN2, VCLK, VBST1, DRVH1, SW1, DRVL1, VO1, FB1, CS1, VBST2, DRVH2, SW2, DRVL2, FB2, CS2) if CH1 and CH2 are not used.
    I learn from below link. How to treat CH2’s terminals when only CH1 is used => I can leave VBST2, DRVH2 and DRVL2 open and connect SW2, CS2, VFB2 and EN2 to ground through 1K ohm resistor.
    e2e.ti.com/.../323471
    Should I treat CH1's pins similar to CH2's pins? How about VO1?

    Thanks!
  • 0 in reply to Vito Liao
    TI__Expert 6425 points

    Hi, Vito,

    Yes, you can refer the data you provide. CH1's pins si similar to CH2's pins. And VO1 connects to ground through 1k-ohm.

    Please pay attention, 5V LDO and 3.3V LDO only support 100mA. And if you disable the CH1 and CH2, the VREG5 pin switchover function is disabled. so the LDO efficiency is low.

  • 0 in reply to Vito Liao
    TI__Expert 5745 points
    You can refer to the suggestion in that forum. CH1 can similar to CH2. For the Vo1,connect to the GND with 1Kohm . If you don't want to use CH1 and CH2 which means you also can't use the Vclk.
  • 0 in reply to Vental Mao
    Intellectual 390 points
    Hi Edwin, Vental,

    Thank you so much for your prompt reply.
    I will leave VBST1, DRVH1, DRVL1, VBST2, DRVH2 and DRVL2 open, connect VO1, SW1, CS1, VFB1, EN1, SW2, CS2, VFB2 and EN2 to ground through 1K ohm resistor and connect VCLK to ground through a 200 ohm resistor (refer to datasheet page 15).

    Thanks!