LDK320M-R Linear Voltage Regulator: Adjustable pin configuration unclear on datasheet

[Mariku]

Hello,

I am using the LDK320M-R, Linear Voltage Regulator IC with Positive Adjustable Output, in one of my current projects. The data sheet states that the ADJ pin voltage range is from - 0.3 to 2V, but does not show how this voltage range configures the regulated output voltage. 

I have search on the LDK320 product line page on STM website and was not able to find any useful information regarding how to configure the ADJ for the desired output. 

My input voltage is 8V, the desired output voltage is 7V

My guess is to take the ADJ voltage range and divide it by the input voltage to get the steps I need for incremental steps of input voltage. Please help! 

Thanks,

Marco Jacome

[Peter BENSCH · Accepted solution]

Welcome @Mariku, to the community!

The value you gave for VADJ only refers to the abs Max and is of little relevance for normal operation.

The example circuit from the data sheet, fig 4, shows how it works: the output voltage is applied to VADJ via a voltage divider, as is usual with adjustable LDOs, and compared with the reference voltage of 1.185V. If there is a deviation from this, the LDO adjusts accordingly. I recommend reading up on the function of an LDO on Wikipedia, for example.

Hope that helps?

Regards
/Peter

[AScha.3]

from ds :

the Vadj is in ds. so some basic math is too much ?

[Mariku]

Thank you for taking the time to explain it to me. 

Much Appreciated.