LTC6560

Question

How to check that LTC6560 is properly grounded via thermal pad? I put one pull down resistor-60Kohm to input (Din), but the voltage at this pin is still showing is 1.5 Volt !!! I am using this IC for APD with positive bias. (equal to Vref-pin of IC), please suggest.

Hooman · Answer

Hi visnu , 
 The LTC6560 input is biased to 1.5V nominal internally when Active: 
 
 So, you're measuring a valid input voltage. At least electrically, it seems like the exposed pad is properly grounded. 
 Also, from datasheet page 14: 
 "To maximize dynamic range, the LTC6560&rsquo;s input is limited to negative current pulses (current flowing out of the LTC6560). When using a negatively biased APD, the TIA input can be AC or DC coupled to the APD cathode. When using a positively biased APD, the input must be AC coupled to the APD&rsquo;s anode. " 
 Let me know if you have any quesitons. 
 Regards, 
 Hooman

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Products In This Thread

LTC6560