ADL5513 temperature compensation with a single resistor

Question

Hello, 
 I am connecting Comm pin to ground. I would like to adjust the voltage of Tadj pin by connecting a single resistor to ground, which will divide Vinternal to an optimum value. What are the values of the internal top and bottom resistors at the Tadj pin? Or do you offer a table which is similar to the AD8317 datasheet (Table 4, recommended RTadj values)?

enash · Accepted Answer

Hello again Turker, 
 I managed to get my hands on an ADL5513 evaluation board. The resistance from TADJ to ground measured at 15.383 Kohms. I then powered up the board and measured the voltage on the Tadj pin with no components attached. That voltage came out at 0.8998 V. I cannot measure the resistance from Tadj to &ldquo;Vinternal&rdquo; because the Vinternal node is not accessible (I measured the resistance from Tadj to the supply and that came in at 649kohms so that is not relevant). My guess is that Vinternal is around 1.9V. that work make the resistance from Tadj to Vinternal also equal to around 15.3K. Based on this, I don't think that it's a good idea to try and set the Tadj voltage using an external resistor. Because the Tadj voltage is already very close to 0.9V, you would need to connect a very large external resistor to move it to its target value which ranges from 0.8V to 0.9V (Table 4). So I think that its better to use a resistor divider between supply and ground whose total resistance is around no more than around 3K (i.e. an order of magnitude smaller than the internal resistances). 
 Please let me know if this answers your question and if there are any more issues you need assistance with. 
 Best Regards 
 Eamon)

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ADL5513 temperature compensation with a single resistor

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