LM3914 Vcc Vs Vsig?

Thread Starter

tracecom

Joined Apr 16, 2010
3,944
I have found that the LM3914 works with a signal voltage that peaks at Vcc, which in my circuit is 3.3V. Am I misreading the datasheet or is this to be expected?

Thanks.
 

GopherT

Joined Nov 23, 2012
8,012
That is correct in general. If your input signal is greater than Vcc, you can attenuate it with a voltage divider (pair if resistors in series).


If your signal is smaller than Vcc, and you want to use the full scale, there is a reference pin that lets you select the max range t something less than Vcc.
 

Thread Starter

tracecom

Joined Apr 16, 2010
3,944
I haven't drawn a schematic yet, but have been working against the application drawing on page 2 of the TI datasheet. Essentially, I am using a pot connected to Vcc and ground with the wiper connected to the sig input of the LM3914 to light 10 leds proportionately to the pot setting. It seems to work, but I am surprised.
 

Lestraveled

Joined May 19, 2014
1,946
OK, per fig. 1 on page 2 of data sheet.
The reference is scaled for a voltage of 5 volts. Since the Vcc is only 3.3 volts, the results you are getting are reasonable.
 
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