Controller for Custom LCD Glass

Have you looked at the NXP (Philips ) PCF85xx series devices ?

-jg

Hello Jim,

The only chip that seems to have enough segment drivers is the PCF 8533, and this is available as uncased die only, if I looked correctly - very hard to use for us.

Heiner

Make your own with a PIC18F8390. It supports up to 4 commons by 48 segments.

There are bond-out houses around -- perhaps you could pay to have the die bonded into a package for you, if you didn't want them to just bond them out onto your PC board.

you can't get the hitachi controller from obsolete distributors? How many do you need?

steve schrieb:

Hi Steve,

We need a few thousand pieces, maybe ~5k. They are hard to find, but we have contacted a few companies that sell obsolete components, up to now, without result.

Heiner

Thank you for this info. We will look into this, I didn't know this part. We use more AVRs or 8051 clones than PICs usually.

Heiner

Have you actually costed doing a new LCD glass? You may find that being able to use a cheaper LCDC, and maybe choose a new LCD supplier could more than cover the tooling cost.

try typing your part number into this web page

and see if it turns up. 5K is pretty small quantity, if it was a widely used I would think plenty should be available, but maybe not.

As an alternative, we have use small micros to drive mux LCD glass directly, with just plain I/O pins and a handful of resistors, see (go to bottom of document)

the waveforms you have to generate are screwy, but it's just software, of course, the easiest is to find the original LCD driver chip you were using

In the meantime, we found another chip of the µPD family made by NEC that could be used - but we are currently trying to get info about long term availability from them, the chip also seems to be a pretty old design. It's a larger version of the well known µPD7225.

Heiner

try entering your part number into

alternatively we have driven mux LCD's directly from micro general I/O pins and a handful of resistors (to get the bias)

Actually, we are thinking about the same. But we are going to use 2 pins (four states) per common. So, our 12x4 needs only 20 I/O pins.

I disagree. Using more commons could even be cheaper. You don't have to stop at 4 commons either.

The quality of display contrast decreases and the visibility of "shadow" segments if you look from a steep angle increases on higher multiplex rates.

In extreme situations, a "9" digit, seen from a bottom angle of 30° to the glass, looks like a "8", for example.

Even the difference between 1:3 and 1:4 is clearly visible if you have both versions to compare them side by side.

How many old LCD panels are you trying to save? Unless you have many thousands, it might be better to look into new panels.

They also become more temperature-sensitive as the mux ratio increases.

Best regards, Spehro Pefhany

we

ow,

I think the NRE would overide the cost savings of new glass

How

t we

now,

Yes, it's basically a 2 bits DAC. We will have 4 of these plus another 8 bits DAC. We are looking into an op amp ASIC design.