REF43 Trim pin function

Question

The simplified schematic in the REF43 datasheet shows a resistor divider between the VOUT pin and GROUND pin. There is also a resistance from the TRIM pin to the middle of the resistor divider. 
 I want to calculate the worst case output voltage range when the TRIM pin is connected to the VOUT pin however the datasheet only specifies the output voltage range when the TRIM pin is left open. 
 In order to calculate the worst case output voltage range I need to know the variation of the resistances of the resistor divider and the TRIM pin resistance. Does anyone know a good rule of thumb to use for the variation of the resistances?

FormerMember · Accepted Answer

Paul, 
 The REF43 came out in 1988 and the product folder is a little skimpy. All available public 
 data is on the data sheet. The resistor divider is trimmed, so it could be trimmed up or down. 
 The untrimmed resistor tolerance is probably 10-20%, so you can't calculate the max swing 
 for the trim pin. The spec has a typical of 95 mV which is huge. The trim pin goes directly 
 into the heart of the bandgap, so the more you move the output voltage, the worse 
 the tempco gets. I would not trim more than 5mV, which would take out any intial offset on 
 the G grade part. As shown, you can move at least 15 times that.. 
 Harry)

EZAdministrator · Answer

This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

Thank you,
EZ Admin

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REF43 Trim pin function