MCU 30 Volt INTERFACE 2

[torque]

I am trying to source an interface IC to buffer 8 input lines on an MCU operating at 3 Volts. I need to detect when a DC voltage of 12 to 30 Volts appears on any of the lines (automotive application). Also needs EMC/ESD protection. Optocouplers not suitable, we have a discrete solution but the component count is high for the size of pcb. Anybody know of an octal IC interface?
Regards
Torque

 

[nbucska]

can U send spec's and more info?

<nbucska@pcperipherals.com>

 

[Whalco]

I think if you check out the Spague IC's numbered ULN2803,you may find what you want. There is also a ULN2003, but I think it may only be 7 inputs.
There is a series of these for different input voltages. The parts are also sourced by other manufacturers.

 

[Warpdrive]

Torque,

Your discrete solution probably looks like this (x8) --

Tap the 12-30V line into a low wattage resistor (1/8 W, 16 Kohm or larger is fine), placing its output on the cathode of a 3V zener diode, with the zener's anode to ground. The zener diode will regulate its cathode to its specified voltage whenever the higher voltage line is ON. Tie the zener cathode to the IC input buffer.

This could be done with nine surface mount components -- a resistor array and eight zeners each in a SOD-323 package. The total circuit board space consumed would be about that of a comparable IC (and cheaper, too).

Cheers,

Warpdrive

 

[felixc]

To add upon Warpdrive's suggestion, I just had to do what you're looking for. Do a web search for the part number SM1603. Two or three companies do make this part. One of them is Protek Devices. It is an SO16 IC made of eight 3 volt avalanche diodes. Then you can use resistor networks that come in packs or 4 resistors per pack within the size of a 1206 resistor. This would even protect you against reverse connections.