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Posts: 5
Registered: ‎12-02-2016

Si1147 schematic

Hello,

I'm trying to use the sensor SI1147, but I'm little confused. When the internal ledA is used the other pins led1, led2 and led3 shoud be left not connected?? in the datasheet the max voltage is 4.3V for led but in the schematics for reference designs the 5V voltage is always used, someone can clarify these points please

 

Thanks

Posts: 50
Registered: ‎04-09-2015

Re: Si1147 schematic

Hi,

 

We recommend you still connect LED1/2/3 to Vdd. LED3 must be connected to Vdd for proper operation.

 

You should follow the reference design and use 5V Vled. The 4.3V max in the datasheet assumes only 1V forward voltage of the irLED.

 

Regards,

Tony

Posts: 5
Registered: ‎12-02-2016

Re: Si1147 schematic

Thank you for you reply

 

Led1,2,3 need a pull up resistor or I can connect them directly?

 

what's the forward voltage of ledA? 

Have u any example to calculate the R aand C connected to ledA?

 

Thanks for your help

Posts: 8,068
Registered: ‎08-13-2003

Re: Si1147 schematic

Led1,2,3 need a pull up resistor or I can connect them directly?

 

you need a resistor (or blow chip and/or LED) AND a hefty defty cap (see reference design) or the whole thing will get a jolt when the LED turns on

erik
Posts: 50
Registered: ‎04-09-2015

Re: Si1147 schematic

Hi,

 

If you do not use LED1/2/3, you can connect them to Vdd directly. 

 

I think a typical value is 1.4V.

 

No, that's not a single equation. If you want to know more about the detail, I recommend you submit a support ticket in our system.

 

Regards,

Tony