Questions about the replacement of LTC2444

Question

Hi, 
 I have already started mass production with LTC2444, but due to the difficulty in availability, I'm considering a running change 
 to LTC2448 or LTC2445. Then I have two questions. 
 1: I will not use the analog input pins (8,9,11,12,15,16,19,20,23 pins) of LTC2448. In this case, is it OK to leave these pins unconnected? 
 2: The MUXOUT and ADCIN pins of LTC2445 will not be connected, is there any way to connect the output of the multiplexer and the input to the AD converter inside LTC2445? 
 Regards, 
 Kazu

andreialejandro · Accepted Answer

Hi Kazu, 
 1. When you replace the LTC2444 with LTC2448, multiple pins will be left floating such as the pins you mentioned above and the channel number assignment will be different from the previous one. But these changes can be adjusted through the software and the unused pins can be left floating without affecting the performance of the ADC. 
 2. You have mentioned that the mass production with LTC2444 has already started so I assume that there is no possibility to change the traces of the PCB. So replacing the LTC2444 with LTC2445 needs a lot of changes to the board such as adding external buffers and there is no option to connect the ADCIN with the MUXOUT internally. It is also not recommended to short the ADCIN pins with the MUXOUT pins as it will not give you the optimum performance of the ADC. 
 I recommend using the LTC2448 as a replacement. 
 Regards, 
 Andrei)

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Questions about the replacement of LTC2444