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TPS62147: How to adapt an existing TPS62135 PCB to use TPS62147/TPS62148?

AnBer
Mastermind 28890 points
Part Number: TPS62147
Other Parts Discussed in Thread: TPS62135

Team,

-Is it possible to use a TPS62147RGXR / TPS62148RGXR on an existing TPS62135RGXR PCB?
All 3 devices have the same VQFN-HR package. The main difference is pin 4 (FB2 on x35 and AGND on x47/x48).

-Is it 100% compatible if FB2 is not being used (ie connected to GND)?
-If FB2 is being used like on Fig 83 SLVSBH3B would the circuit at least work for the default voltage (ie with VSEL LOW)?

-For the LED power supply scenario (Fig 86 of SLVSBH3B and SLVSDR8):
What will happen if FSEL on TPS62147/48 is pulled low like VSEL on TPS62135?
Is it a must to have VSEL HIGH for the LED power use case of fig 86?

Thanks in advance!

A.

  • 0
    TI__Intellectual 1610 points

    A,

    Yes, this is possible, and you have correctly identified what needs to be taken into consideration in order to make this work.

     

    -Is it 100% compatible if FB2 is not being used (ie connected to GND)?

    Yes, as we actually specifically recommend tying the FB2 pin to GND when not in use.

     

    -If FB2 is being used like on Fig 83 SLVSBH3B would the circuit at least work for the default voltage (ie with VSEL LOW)?

    No, Fig 83 (tps62135) includes a resistor between FB2 (pin 4)  and FB (pin 5), and pin 4 (AGND) on the TPS62147 must be tied to GND for the device to work.

    -For the LED power supply scenario (Fig 86 of SLVSBH3B and SLVSDR8):
    What will happen if FSEL on TPS62147/48 is pulled low like VSEL on TPS62135?
    Is it a must to have VSEL HIGH for the LED power use case of fig 86?

    FSEL = low results in a 1.25MHz Fpwm

    FSEL does not have to be tied high as in figure 86.

    Please note that since Fpwm on the TPS62135 is 2.5Mhz, the inductor ripple currents will increase due to the switching frequency.  So, you may want to increase teh inductor value proportionally as shown in Figure 4 on the TPS62147 DS - SLVSDR8.

    Sincerely.

    -Matt