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PCF8576 question

Question asked by Ron Joyce on Dec 13, 2016

Hi, has the silicon changed in the PCF8576 LCD driver?


We use two versions (>2k pieces p.a.): a) PCF8576CT and b) PCF8576T (datasheets attached).


Monitoring the 'CLK' pin (pin 4), the PCF8567CT runs at about 200kHz and the backplane signals run at ~68Hz which agrees with the datasheet.


On the other hand, the PCF8576T runs at ~600kHz with the backplanes running at 225Hz i.e. ~3x the stated frequency!


By changing the value of a resistor connected between the 'OSC' pin (pin 6) and GND, the clock frequency of the PCF8576T can be altered over a wide range to bring it down to the 200kHz specified in the datasheet and beyond.


However, changing the resistor value, even up to 500k on the PCF8576CT has no affect on the clock frequency??!!


The PFC8576CT's frequency, although it is more in tune with the datasheet does however produce a flickering display while the 600kHz PCF8567T does not.


Has one version become obsolete, if so which? If not, do you intend to continue to produce two wildly different versions?


Thank you.

Regards, Ron