How to read this diagram?

Discussion in 'General Electronics Chat' started by dante_clericuzzio, Jul 16, 2016.

  1. dante_clericuzzio

    Thread Starter Member

    Mar 28, 2016
    Last edited: Aug 1, 2016
  2. ScottWang


    Aug 23, 2012
    Please see my attached circuit.

    Please see my second attached circuit.

    That is a fixed resistor, please see my attached circuit.
    Unless you want a precisely resistor then you can using a 100K+VR20K, otherwise you can using a 120 K to replace 117K. (120K-117=3K, Pcnt_R1 = 3K/117K=2.56%)


    LM2371 Datasheet.

    LM2371_Boost ConvertersLedFlashControl ic.gif
    dante_clericuzzio likes this.
  3. ScottWang


    Aug 23, 2012
    It means that you can using SHDN pin to control the leds to be flashing as the second circuit, and set SHDN = High(1.5V) then the SHDN is in the flash enable situation, the leds will be flashing, set SHDN = Low(0V or gnd) and then the SHDN is in the flash disable situation, the leds can work in flashing function, if you don't want the SHDN function then you can connect it to Vin pin(5V).

    SHDN - shutdown, you can check the datasheet to see more information about SHDN.

    I don't have the ic in hand, so I can't try it, if you have this ic then you can try it.
    dante_clericuzzio likes this.
  4. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
    SHDN is a control signal input to the chip. With R3 installed, you can leave it floating and the chip will operate all the time. If you want to shut down the boost circuit electronically, pull the SHDN input to ground. The arrow indicates that that connection goes off to some other switch or circuit that generates the shutdown signal.

    The basic problem here is that the schematic in post #1 is very poor. It looks like someone copied a datasheet circuit, but

    1. their software did not make some of the connections; that's why some lines step around some component pins.

    2. the way they show reference designation and component value is inconsistent. R3 is done the right way, refdes and value on two separate lines, no confusion. The wrong way is the way R1 is done. A dash would be slightly better than a /, but both are confusing.