Power reset (VCC) of some device from PIC OUTPUT PIN without using relay

Started by AMIT KAPOOR September 3, 2010
Hello Friends,

Good Morning!...

I needhelp/suggestion from you!

ActuallyI have a device which communicates with PIC using the serial
communication. but sometimes this device stops communicating.In this case , this
device needs VCC reset( POWER RESET)..So what i want is to reset this device
from PIC whenever it stops communicating ( basically disconnecting the VCC power
of this device by turning on some outputpin of PIC and after 1 or 2 seconds
again connecting it)...I don't want to use relay logic..so any suggestions
regarding the hardware interfacing circuit between PIC and this device which
stopd communicating and need Power reset. Current requirement of this device is
below 600 mA. and voltage VCC is same as PIC( +5V).

Thanks a lot!,

Best Regards,
Kaps
--- In p..., AMIT KAPOOR wrote:
>
> Hello Friends,
>
> Good Morning!...
>
> I needhelp/suggestion from you!
>
> ActuallyI have a device which communicates with PIC using the serial
> communication. but sometimes this device stops communicating.In this case , this
> device needs VCC reset( POWER RESET)..So what i want is to reset this device
> from PIC whenever it stops communicating ( basically disconnecting the VCC power
> of this device by turning on some outputpin of PIC and after 1 or 2 seconds
> again connecting it)...I don't want to use relay logic..so any suggestions
> regarding the hardware interfacing circuit between PIC and this device which
> stopd communicating and need Power reset. Current requirement of this device is
> below 600 mA. and voltage VCC is same as PIC( +5V).
>
> Thanks a lot!,
>
> Best Regards,
> Kaps
>

If you're doing a prototype or one-of-a-kind project you might look at the TI TPS2021 (specifically the 512-TPS2021P from Mouser for $2.15 USD each). The Fairchild FPF1103/FPF1104 power switch would be good too but it's only available in a surface mount package that's very difficult to use for prototyping.

Alternatively, you could make you own power switching circuit using bipolar transistors or MOSFETs. A Si4483EDY ($2.81 USD each at Mouser.com) would be the power switch with gate connected to +5V, drain connected to your switched device's Vcc/Vdd input, and the gate pulled up to +5V with 2.2K Ohm resistor. The microcontroller pulls the gate low to power the device and high to turn it off. Of course, you can add an NPN transistor inverter driver stage between the microcontroller and the pMOSFET gate to get the logic sense you wanted. The Si4483EDY has an on resistance in the 15milliOhm area in this application so you won't lose any appreciable Vcc to your switched device even at 600mA of current.

If you're not experienced with these kinds of circuits I think the TPS2021P is your best bet.

Remember that after turning your switched device off, you may need to wait until any capacitance on the switched power rail is discharged to achieve an effective shut-down.

Coop, AA1WW



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> A Si4483EDY ($2.81 USD each at Mouser.com) would be the power switch
> with gate connected to +5V, drain connected to your switched device's
> Vcc/Vdd input, and the gate pulled up to +5V with 2.2K Ohm resistor.

Oops, I meant that the _source_ of the Si4483EDY is connected to +5V,
not the gate. The gate is pulled high as stated and driven as stated.
Sorry about the typo,

Coop, AA1WW

Kaps,

You can use a PNP transistor as a switch. You could use a 2N3906. Put a 4.7K
resistor from base to emitter. Connect the emitter to the 5V. Connect the
collector to the load. Connect a 10K resistor to the base of the PNP.
Connect the other end of the 10K resistor to a PIC programmable output pin.
Pull the line low to turn on the 5V. Raise the line high to turn off the 5V
to the load.

Virgil Stamps

From: p... [mailto:p...] On Behalf Of
AMIT KAPOOR
Sent: Thursday, September 02, 2010 10:01 PM
To: P...
Subject: [piclist] Power reset (VCC) of some device from PIC OUTPUT PIN
without using relay

Hello Friends,

Good Morning!...

I need help/suggestion from you!

Actually I have a device which communicates with PIC using the serial
communication. but sometimes this device stops communicating.In this case ,
this device needs VCC reset( POWER RESET)..So what i want is to reset this
device from PIC whenever it stops communicating ( basically disconnecting
the VCC power of this device by turning on some output pin of PIC and after
1 or 2 seconds again connecting it)...I don't want to use relay logic..so
any suggestions regarding the hardware interfacing circuit between PIC and
this device which stopd communicating and need Power reset. Current
requirement of this device is below 600 mA. and voltage VCC is same as PIC(
+5V).

Thanks a lot!,

Best Regards,

Kaps