I'm using MSP430G2553IN20
microcontroller(http://www.kynix.com/Detail/569447/MSP430G2553IN20.html)
on LaunchPad to drive an 4056 chip (HCF4056B to be precise) and a 7
segment display. The 4056 is set to sink current.
I've connected the port 2 pins, set as outputs, to the BCD and STROBE
input pins of the 4056. The board with 4056 and display has its own
separate power supply and the MSP430 is powered via the LaunchPad which
provides it around 3.6 V. The grounds of both supplies are connected and
I've set the other power supply as close as possible to 3.6 V.
I'm concerned that with this setup I could damage the chips. For
example, when the 4056 power is down, it and the display are still
getting some power from the MSP430 via the BCD and STROBE pins and the
display remains on, although sometimes it works incorrectly.
Right now, I'm using 220 Ω220 Ω resistors on the output pins of the
MSP430 to limit the output current, but I'm afraid that the setup isn't
safe enough.
So my question is: Is there a simple and safe way to connect the MSP430
to the 4056? For best results, I'd want to drive 4056 at higher voltage
than MSP430, but if that's too difficult I could settle for 3.6 V.
