120VAC to 5V chip

[dsicon]

am trying to find a chip that i am pretty sure was by ST, 120VAC to 5VDC, non isolated, inductorless

i had no luck on their web but i am pretty sure they make one

i think it operated by turning off the pass transistor during the valleys and could do maybe 50mA at maybe 50% efficiency

anybody know about this ?
Supertex has something but it needs an external IGBT which is pretty big

a cap drop circuit won't work for this app and a full blown offline buck is pretty involved even with the PI chips,
i only need maybe 5-10mA at 7.5-9V ideally, from that i will use a post reg ldo for a little 5V

[Melanie]

> a cap drop circuit won't work for this app

Why? You can steal up to 30mA from a properly sized Cap...

> am trying to find a chip that i am pretty sure was by ST, 120VAC to 5VDC, non isolated...

The item you refer to is the VB408 which was discontinued... try (as an example but unlikely it will handle your current requirements)...

http://www.supertex.com/pdf/datasheets/LR8.pdf

Several vendors still have stocks of the VB408... be careful, they were VERY fragile (in as much as the SLIGHTEST error on your part resulted in their - spectacular - destruction!).

[dsicon]

> a cap drop circuit won't work for this app

Why? You can steal up to 30mA from a properly sized Cap...

> am trying to find a chip that i am pretty sure was by ST, 120VAC to 5VDC, non isolated...

The item you refer to is the VB408 which was discontinued... try (as an example but unlikely it will handle your current requirements)...

http://www.supertex.com/pdf/datasheets/LR8.pdf

Several vendors still have stocks of the VB408... be careful, they were VERY fragile (in as much as the SLIGHTEST error on your part resulted in their - spectacular - destruction!).

thanks Melanie
the VB408 was what i was trying to find, but no good if not in production

no room for a cap of nec. size
next plan of attack is to get the current requirement way down

[Melanie]

I calculate a 470nF/250vAC Cap would give you 20mA from a 60Hz source... a 220nF just under 10mA... both of those have a footprint the same as a VB408 with a decent Heatsink... and remember the VB408 needed a DC input (so you would have had to rectify and smooth the AC supply) - whereas with a Cap, you're rectifying and smoothing at a much lower voltage - so you win in the size of all the other components. An X2 Cap will also fail safe... a VB408 removes your fingertips...