Help on Teac A-L700P using battery power

[HolyGhostFire20]

I am having a problem trying to seperate voltages to work with powering this amp. I plan on using two 12v sla batteries connected in series to power the main tripath chip at 24 volts. My problem is running the output and delay relays which requires 12v and the processor chip at 5v. Should I use two seperate voltage regulators off the 24v line for the 12v and 5v line? I want to use just one of the 12v batteries for the 12v line and 5v, but I have no idea how to produce 12v when it is connected to the other battery producing 24v. Thanks for your time in this matter.
Kevin

[N-Channel]

Kevin-

You can easily run the 12V and 5V stuff right off the 24V battery pile by using some switching voltage regulators. National Semiconductor and others make some really nice switchers for just your purpose.

National even calls theirs the SimpleSwitcher series of switching regulators. When designed properly, these regulators are low-noise, compact, and VERY efficient. Speaking of efficiency, this is a MUST if you're dropping from 24V to 5V or even 12V.

In their simplest form, the Simple Switcher chips use only 2 caps (input & output), a coil and a diode. That's it!

For using two chips in close proximity to each other, you can choose models that are synchronizable to eliminate beat frequencies between the two chips' oscillators. A few more parts, but well worth it. You won't be dissappointed.

Try looking at the LM2670 (3A) or the LM2677 (5A) chips from National. They both run at 260kHz and can be synchronized up to 400kHz. They are pretty robust chips. Versions include 7-pin TO-220 and 7-pin SMT. Available outputs are Fixed at 3.3V, 5.0V, 12V. The adjustable version uses two resistors at the feedback pin to sense voltage. Anyway, check out the two links:

http://cache.national.com/ds/LM/LM2670.pdf

http://cache.national.com/ds/LM/LM2677.pdf

I have used the 5-Amp LM2677S (surface-mount) in several CPU applications before, with good results. The only time the chip got warm was when I touched it and it picked up the heat from my finger!

Hope this helps!

Steve