Keypad interfacing

Hi Jace
Thanks for your reply.
Actually, I don't need MCU. I already have an 8 bit MCU. I need an IC like shift register which can create interface between MCU and keypad using minimal number of digital pins.
I also need a solution to compensate debouncing affect of keypad.

Hi Clemens Ladisch
Thanks for your reply.
Do I need the debouncer part also if I use TCA8418  scanners?
I think TCA8418  will do the job that I am looking for.
Thanks

Thanks.
I noticed that TCA8418 is a 3.3V input supply device. Is there any 5V similar device available? I don't want to add step-down converter cost in the design because my product is USB operated.

 Our keypad scanners use lower voltage CMOS technology since these devices are typically used in battery applications where lower voltage saves power.

The TCA8418/TCA8418E is probably the device you are looking for but the absolute maximum voltage allowed on the pins is 4.6V.

If you're not willing to add an additional 3.3V line with a converter then the only option I could think of is to force the voltage to the pin and on the I2C lines lower with diodes going from 5V to the desired pins.

So in this example, if we assume the forward drop is about 1V each diode, then Vcc/SDA/SCL would see about 3V though Vforward is dependent on the current draw. The only major disadvantage I can think of with this set up is you'll have more wasted power consumption through the diodes. I'm not sure if this would be the best way to go about this but it's the only way I can think of without using a DC converter to step down the voltage.

-Bobby

I think If that is the case then I can use an LDO like TLV2217-33KVURG3 to make it work. Thanks for all your help.