MC33730 linear regulators

[alessandrocorti]

Hello all,

I'm going to use the MC3370 chip in an environment where I need only the 5V and the 3.3V voltages.

I don't need to use any stand by supplies, I know the VKAM is always active (also with the chip in sleep mode) and this is ok for me, I want to use VDDL as 3.3V source and I don't need more.

To save power in stand by, I want to program the VDD3 regulator as 3.3V, not stand by regulator, but I don't need it because I use the VDDL regulator as 3.3V source, here my question, have I to add the external pass NPN transistor and bypass capacitors to the VDD3 circuitry (VDD3_B and VDD3), or can I simply left open these two pins (VDD3_B and VDD3)?

Thanks a lot,

Regards.

Alessandro

[alessandrocorti]

Thank you G.w. Sun,

so there isn't at all the risk to damage the linear regulator or may be the entire chip?, I mean, the stage that should drive the external pass transistor (may be an op amp?) works always in saturation because of the absence of the feedback voltage, I think..

Regards,

Alessandro

[guoweisun]

HI Alessandro

After discussed ,to be on safe consider please add the external pass NPN transistor and bypass capacitors to the VDD3 circuitry (VDD3_B and VDD3) if unused this LDO