RTC HT 1380 POWER CKT?

[UroBoros]

Hai
I am using HT1380 RTC with PIC.

This chip has got only one Vdd pin.So how is the best arrangement for a battery backup for the chip with a lithium 3v cell?

Also please link me any assembly programes for PIC with this or dallas DS13XX rtc chip.(I have c driver for this from this board)

Thanks
Picstudent

 

[bobcat1]

Hi

Most of the RTC device connected to 3V source via a shotky diode and a small 1uF
Capacitor.

When the main supply is on the diode is cut off and when the power supply is down the diode fwd voltage to RTC chip



P.s learn to progrm in C language you will find it more easy the assembly.
All the best

Bobi

 

[techie]

I use a 3V lithium battery and simple 2 diode (1n4148) arrangement to battery back the HT1380. Works fine. The RTC needs about 2V to keep operating. The small current from battery causes a very small drop of <0.5v on VCC. No particular need for a schottky diode.

 

[Gorilla]

I use a 3V lithium battery and simple 2 diode (1n4148) arrangement to battery back the HT1380. Works fine. The RTC needs about 2V to keep operating. The small current from battery causes a very small drop of <0.5v on VCC. No particular need for a schottky diode.

I second that. Actually << 0.5 V.

You do absolutely need a 100 nF or larger capacitor on the power pins of the IC, otherwise the switch between battery and external power is problematic.

 

[techie]

Yes I use a 0.1uf ceramic cap directly on the power pins of HT1380. It is a must.