Problem after changing CM8888PI to MT8888CE DTMF IC

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jcding1980

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Hi

Anyone faces the same problem as I do? Previously my dialer project is working fine with CM8888PI DTMF transceiver. However due to the CM8888PI (from Calmicro) is not in production anymore so I have opted to use MT8888CE (from Zarlink) to replace it. After I change the chip, the project won't dial out. Anyone got any ideas? Or is there any difference between these two chips? I need help urgently.. Thanks.


regards.
 

Hi,

Comparing the two datasheets, zarlink use a 4.7meg resistor between OSC1 pin and Vss. Carlifornia Micro Device do not. Meabe the oscillator of the chip do not start. If you dont have this resistor on your board, try to add it.
 

Also check the timing of the MPU interface.
For instance, tAH is specified to a minimum of 10 ns for the CMD chip
and 26 ns for the Zarlink chip.

/Rambo
 

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