nige said:
muldersun said:
As I know, the common bandgap circuit need trimming circuit.
The circuit offset, layout mismatch, process variation, these factors can affect the precision of bandgap voltage.
would u please give me more details about trimming circuits?
thanks
Attached file is simple principle circuit. It is only for trim-up.
Original value is lower than you want.
Example: The bandgap voltage is 1.25V, the original value maybe 1.15v.
Red rectangle is trim PAD. Red line is top-level metal we called burned-fuse.
Burning the fuse between 1 and 2, you can get one step value.
If you set one step value is 25mV. Now the bandgap voltage is 1.15v+25mV.
Following this method, you can get 2^3 case.
The maximum bandgap voltage is 1.15v+7*25mV.
The step value & trimming-case should be depend on your accuracy.
If you add another trim PAD, you can get 2^4=16 case. So, you can reduce the step value or increase your range.
This is the common use circuit. Of course, you can use trim-up & trim-down circuit.
Or the trim PAD is isolated from the resistors.