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Customer requires three independent temperature sensors....

Question asked by mwfortner on Sep 6, 2012
Latest reply on Sep 7, 2012 by jtowey

Hello,

 

I have a customer that requires three I2C based independant temperature sensors within their application that will go down to -20C.

 

I explained to them that the ADT7516/ADT7517/ADT75191 combine a 10-bit temperature-to-digital converter, a 10-bit 4-channel ADC, and a quad 12-/10-/8-bit DAC.

 

Product Page: http://www.analog.com/static/imported-files/data_sheets/ADT7516_7517_7519.pdf

 

When I looked in the datasheet, I see that it states that there are four single-ended analog input channels on the ADT7516/ADT7517/ADT7519, AIN1 to AIN4.  AINx through AINx then appear to be multiplexed with external temperature sensor terminals (D+ and D−).

 

Bit C1 and Bit C2 of the Control Configuration 1 register (Address 0x18) are then used to select between AINx/AINx and the external temperature sensor.

 

I showed this to the customer and he stated that four independent ADC input without an AppNote explaining what transistor to use how to attach it, etc. is not the same as four D+/D- temperature channels (Maxim's MAX6648, 6646, 6647, 6649, and 6692 all support this, but do not go down to -20C). Based on his understanding, the current / voltage would vary between transistors and then so is the reading.  The Maxim parts above specifically state what transistor and how to run the signals into the four D+/D- temperature channels. 

He knows that he could use more than one chip for more than one D+/D- channel, but then he would have more chips + a more complex I2c configuration to manage, so he wants to find a single chip that will hanle the three channels independently.

 

Again, the Maxim temperature monitor chip(s) do not claim ‘four independent ADC channels’ like ours, but ‘xxx independent temperature channels.

 

Do we have any parts that can support this type of application in the same way the Maxim devices he found can ?

 

Thanks in advance for your help.

 

Mike

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