Hello,
I have the question of LM3405A about RZI calculation.
Please see the attached file.
LM3405A_RZI.pdf
I simulated the LM3405A with some Vin value( Vin=9V, Vin=18V, Vin=9V~18V)
As a result the Rzi values as the following.
Vin=9V , Rzi=634ohm
Vin=18V, Rzi=2.05kohm
Vin=9V~18V, Rzi=2.05kohm
I could find the calculation of Rzi from the datasheet P.10 and figure 17.
I think that we should choose 634ohm for Vin=9V~18V.
The Rzi is used for charge current for zener and boost cap.
Thus, the Vin(min) is worst case of charge current.
Is my understanding correct?
Thus , if we use E24 resistor, should we use 620ohm of Rzi for Vin=9V~18V, Vout=3.4V, Iled=700mA application.
Best Regards,
Ryuji Asaka