Power another IC from PIC internal LDO

[gabirelms]

Hi all,
Is it possible to power another components of my board from PIC internal LDO ?

I'm using PIC16F1459 with 3.7v battery (4.2v full) and I need to power another part of my board with 3.3v.

I was thinking to use Vusb3v3, is it a good idea ?


Edit: Mistyped, I mean PIC16F1459.

[Ttelmah]

No.

You don't have regulator.....

Yours is an LF device. On the LF device, _you_ have to supply VUSB externally.
Quote from the data sheet:
"On F devices, the regulator is powered by VDD. On LF devices, the VUSB3V3 pin should be externally connected to VDD."
_Externally connected_. Vdd has to be between 3, and 3.6v, and directly feed Vusb.

It's rather pointless using a USB capable chip, since you can't use USB with your supply voltage....

[gabirelms]

Sorry, I mistyped.
I mean PIC16F1459.
This one has internal LDO, and Vusb 3v3 has 3.3v output.

[temtronic]

What is the 'device' ? How much current does it draw under MAXIMUM load conditions ?

I doubt the LDO has enough current capacity though it's not in the datasheet( well, that I could find....)

Perhaps you can power the 'device' from an I/O pin ? Providing it doesn't draw too much current this could be a viable method.

hth
jay

[gabirelms]

It is a motion dection sensor. It consumes 70uA in stand-by and 500uA when it wakes up, only 2-3 seconds.

What another I/O can I use ?

[temtronic]

Any free I/O pin will easily supply 500uA all day long and it's controllable. The PIC program can turn it on/off when required.

Just do an output_high(pin_name); to turn it on, same as an LED .

hth
jay

[gabirelms]

Hi temtronic, thanks for your reply. Any pin the output will be 3.3v ?

By the way, this can be a good idea to completely OFF a SPI flash memory than consumes 5uA during sleep. what do you think ? doable ?

[temtronic]

just put a 10K r as the 'load' and then cut code to turn on the pin and measure the output voltage. It should be close to Vdd, well within say 90%+ of it.

I've done this with 5V PICs for decades..so it should work for 3V ones.

Learn by doing ! Nothing is a better teacher than hands on, bench level education !!

hth
jay

[gpsmikey]

And when the magic smoke comes out, don't do that again :-)

mikey
_________________
mikey
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