LYT7503 / 04 Feedback Pin

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Hi

I have a customer who two technical queries on the :

Part: LYT7503 / 04

1. Can he run these parts on pure DC (140Vdc) ?
Application: they going to use this part in an Emergency Backup Light Application, so a switcher over from mains to DC -> will it work without being damaged?

2. Can he use the feedback pin in such a way what he wishes to use it to implement On/Off control without negative effects to the chip?
ie Can he switch it off completely using the FB pin?

Regards
Shane
Avnet - South Africa
shane.padayachee@avnet.com

Hi Shane,
Hope you're doing fine and thanks for choosing Power Integrations. Here are my answer for your query's.

1. Can he run these parts on pure DC (140Vdc) ?
Application: they going to use this part in an Emergency Backup Light Application, so a switcher over from mains to DC -> will it work without being damaged?
Ans: Yes, it will work on pure 140V DC input but power factor will too low.
2. Can he use the feedback pin in such a way what he wishes to use it to implement On/Off control without negative effects to the chip?
ie Can he switch it off completely using the FB pin?
Ans: No. It is not recommended to use FB pin for remote on/off control. FB pin voltage is a voltage sensitive pin with pin voltage ranging from -273mV to -285mV. Connecting external circuit on this pin might affect the output current and probably will cause shimmer. For remote on/off control function, You can try using the BP pin by connecting an optocoupler (C-E terminal) from BP pin to Source pin. Turning on the Optocoupler CE will pull down the BP voltage which will cause LYTSwitch device to turn off. Likewise when you turn off the Optocoupler CE(Open) BP voltage will goes high again turning on the IC.

Best regards,
MARTOK

Hi Shane,
Goo day . For your Question on using pure 140VDC as emergency back up supply for LYT7503, The device is expected to over deliver output power causing it to heat up. Output current is also expected to increase that might cause the LED to get damage. So using 140VDC is not recommended for this particular device. I recommend to use LYTSwitch-5 for this particular application.

Best Regards,
MARTOK

thanks Martok!