Other Parts Discussed in Thread: TPS54KC23
Tool/software:
Hi TI Team,
The TPS546E25 datasheet states:
“Under split rail configuration, PVIN, VCC bias, and CTRL are the signals to enable the part. For the start-up sequence, TI recommends that the external bias is applied on the VCC/VDRV pin earlier than PVIN rail. A
practical start-up sequence example is the external 5V bias is applied first, then the 12V bus is applied on PVIN, and then CTRL signal goes high.”
In a product powered by a single 12V supply, a circuit that disconnects PVIN from the 12V source would be necessary to comply with this recommendation. Such a circuit is undesirable.
In our product, the 5V rail rises significantly later than the 12V rail (approximately 800 ms). In this case, can we assume that the TPS546E25 initially operates in single-rail mode when 12V is applied to PVIN, and then automatically switches to split-rail operation once the external 5V bias is applied?
The power-up sequence of our product is as follows:
12V is applied to PVIN → 5V is applied to VDRV/VCC → EN pin goes high.
We will add a Schottky barrier diode between the external 5V bias and the VDRV/VCC pin to prevent abnormal external current.
With these countermeasures in place, would it be acceptable to apply power in the order of PVIN → VDRV/VCC?
There is a similar description in the TPS54KC23 datasheet, and we believe that applying the same countermeasure would also be effective for this device. Is this correct?
Regards,
Ayumu
