lm395-2.5 voltage ref troubleshoot ?

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rngd

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Hi,

For some reason my lm385-2.5 voltage reference only outputs 0.47V instead of the 2.5V. Current flowing is 0.35 :mu: A, the minimum operating current is 13 :mu: A.

Any idea on what I should check ?

Thank you.
 
rngd said:
Hi,

For some reason my lm385-2.5 voltage reference only outputs 0.47V instead of the 2.5V. Current flowing is 0.35 :mu: A, the minimum operating current is 13 :mu: A.

Any idea on what I should check ?

Thank you.

For example you connect a 9V battery as per attached diagram
 
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its connected to a 330khm: resistor which is connected to a 12V battery, kinda like in the pic.
 
rngd said:
its connected to a 330khm: resistor which is connected to a 12V battery, kinda like in the pic.

Please reduce it to 270K or even 220K will do. The minimum recommended current is 30 :mu: A
 
Datasheet clearly stated "operating from 20uA ~ 20mA", twice on the first page, under General Description and Features.

13uA typical on page 2 is just a typical value with no guarantee that it will always work.
 
Oh I see. I guess I shouldn't always jump straight to the tables when looking at datasheets. I'll increase the current and see if it works.

Thanks guys.
 
You must also use a digital meter(10M internal impedance) to measure the voltage. An analogue meter(only 100K impedance @20K/V range DC5V) will shunt most of the current from the LM385.
 
rngd said:
Oh I see. I guess I shouldn't always jump straight to the tables when looking at datasheets. I'll increase the current and see if it works.

Thanks guys.

Minimum Operating Current μA
LM385M3-2.5 20 [Tested] 30 [Design Limit] μA

"Note 6: Guaranteed, but not 100% production tested. These limits are not used to calculate average outgoing quality levels."
 
unless you're running some sort of micropower solar app, why deal in microamps at all? just feed the thing a generous milliamp or two.
 
justDIY said:
unless you're running some sort of micropower solar app, why deal in microamps at all? just feed the thing a generous milliamp or two.

My generousity would go further. I'd feed it with 1Amp to make it smile.
 
Guys, I increased the current to 15mA but the voltage is still not 2.5V. It is just increasing a little bit every time I increase the current, it is now at 0.8V.

Why else could be wrong ? The connection is correct.

to justDIY, actually, I am using it in a solar application (solar batt charger).
 

First you try to put a schematic of what you have done. Also check whether the device is connected properly without reversal. and that the device is not faulty or gone bad later while trying?
 
Ah, it turns out I did indeed connect the diode forward biased instead of reverse ..

Im so annoyed, I can't believe I made such a simple mistake . I checked the circuit connections many times but did not check the pin assignments ..

Thanks everyone.
 
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