A slightly higher output voltage from a PIC - Electronic Circuits Projects Diagrams Free

Richard S · 28th August 2009, 09:06 PM

I want to switch a chip (low current) which requires an off signal of under 4.5v, and an on signal of over 5.5v. I need to do this for eight pins.

The first thing I thought of was an ULN2803 with pullup resistors, but that takes up a lot of room, and makes the board very complex. Are there any chips which will do this without the use of pullup resistors? I would like a chip with 8 switchers in it, which eliminates MOSFET drivers etc (although these seem like a waste as it is low speed, low current).

Any ideas of chips?

Summary:
Input: 8 TTL inputs
Output: 8 low/high outputs, high being close to VCC.

There is 9V and 5V power rails currently.

Many thanks!

Richard

Electronworks · 28th August 2009, 09:45 PM

Unless I have missed something, what is wrong with powering an octal changeover analogue switch off the 9V rail and switching the logic inputs with your micro? Connect one side of the switch to your 9V, one side to ground and the common to the device you need to drive. Not sure if you can get octal changeovers, but 2 quads should be easy to get. take a look at Maxim or TI..

Richard S · 28th August 2009, 09:57 PM

That sounds like the solution - I just need to find one. Anyone got any suggestion (pref. Maxim)?

The device I want to control is two 4066s, running on 9v (so needing 5.5v for a logic 1).

Richard

blueroomelectronics · 28th August 2009, 10:01 PM

Then just use pullups and tris the output pin (portx = 0)

Richard S · 28th August 2009, 10:17 PM

I was hoping to find an IC with internal pullups = less wiring.

Richard

blueroomelectronics · 28th August 2009, 10:23 PM

Use a sip resistor.

Richard S · 28th August 2009, 10:25 PM

Good thinking.

I'm currently looking at Maxim's analogue switchers, instead of the 4066.

Richard

Richard S · 28th August 2009, 10:27 PM

I've chosen:

I'm going to go with MAX474-something. They are the same as the 4066, but can be driven directly from a PIC (1.8v is logic high).

Thanks for everyone's help!

Richard

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28th August 2009, 09:06 PM	#1
Richard S	A slightly higher output voltage from a PIC I want to switch a chip (low current) which requires an off signal of under 4.5v, and an on signal of over 5.5v. I need to do this for eight pins. The first thing I thought of was an ULN2803 with pullup resistors, but that takes up a lot of room, and makes the board very complex. Are there any chips which will do this without the use of pullup resistors? I would like a chip with 8 switchers in it, which eliminates MOSFET drivers etc (although these seem like a waste as it is low speed, low current). Any ideas of chips? Summary: Input: 8 TTL inputs Output: 8 low/high outputs, high being close to VCC. There is 9V and 5V power rails currently. Many thanks! Richard

28th August 2009, 09:45 PM	#2
Electronworks	Unless I have missed something, what is wrong with powering an octal changeover analogue switch off the 9V rail and switching the logic inputs with your micro? Connect one side of the switch to your 9V, one side to ground and the common to the device you need to drive. Not sure if you can get octal changeovers, but 2 quads should be easy to get. take a look at Maxim or TI.. __________________ Bill Naylor www.electronworks.co.uk Electronic Kits for Education and Fun

28th August 2009, 09:57 PM	#3
Richard S	That sounds like the solution - I just need to find one. Anyone got any suggestion (pref. Maxim)? The device I want to control is two 4066s, running on 9v (so needing 5.5v for a logic 1). Richard

28th August 2009, 10:01 PM	#4
blueroomelectronics	Then just use pullups and tris the output pin (portx = 0) __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com/

28th August 2009, 10:17 PM	#5
Richard S	I was hoping to find an IC with internal pullups = less wiring. Richard

28th August 2009, 10:23 PM	#6
blueroomelectronics	Use a sip resistor. __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com/

28th August 2009, 10:25 PM	#7
Richard S	Good thinking. I'm currently looking at Maxim's analogue switchers, instead of the 4066. Richard

28th August 2009, 10:27 PM	#8
Richard S	I've chosen: I'm going to go with MAX474-something. They are the same as the 4066, but can be driven directly from a PIC (1.8v is logic high). Thanks for everyone's help! Richard Last edited by Richard S; 28th August 2009 at 10:39 PM.