I'm designing a PSU using LM317T/LM337T regs. The National Semiconductor datasheet states that the output voltage is calculated by:
Vout = 1.25 * (1 + (R2 / R1)) + (Iadj * R2)
where Iadj = 1.25 / R1
However, using this formula on the Typical Applications circuits, I cannot get anything like what voltage they say I should be getting.
This is further complicated by the LM337L datasheet stating that the output voltage is calculated by:
Vout = 1.25 * (1 + (R2 / R1))
Which gives apparantely correct results.
Only this datasheet has the formula in this way, the LM317L, LM317T and LM337T all have the formula as in the first case. The L suffix is TO92 package and the T suffix is TO220 package.
Has anybody actually got any proven formula or values I can try? I built one using L suffix parts and according to the second formula and it worked fine, but I want to use T suffix parts now.
Vout = 1.25 * (1 + (R2 / R1)) + (Iadj * R2)
where Iadj = 1.25 / R1
However, using this formula on the Typical Applications circuits, I cannot get anything like what voltage they say I should be getting.
This is further complicated by the LM337L datasheet stating that the output voltage is calculated by:
Vout = 1.25 * (1 + (R2 / R1))
Which gives apparantely correct results.
Only this datasheet has the formula in this way, the LM317L, LM317T and LM337T all have the formula as in the first case. The L suffix is TO92 package and the T suffix is TO220 package.
Has anybody actually got any proven formula or values I can try? I built one using L suffix parts and according to the second formula and it worked fine, but I want to use T suffix parts now.
Thanks guys.
I was slightly misreading the datasheet and confusing Iadj with the whole current flowing in the programming resistors.
I was slightly misreading the datasheet and confusing Iadj with the whole current flowing in the programming resistors.
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