TEA1993 or TEA1999 Vdrain min V with Vxv=0V

[Andrew-Lohmann]

My application is a 1-8W power SEPIC power supply running from rectified AC input 3Vrms-20Vrms.

300KHz operation.  5V output.  TEA1993TS operating high-side with Vxv=0V

From the datasheet, it looks as if the IC will operate from Vdrain=4.7V (same as Vxv) but other parts of the datasheets (TEA1993 or TEA1999) seem to suggest 8V or 12V?

I have also looked at the demo board documentation and I can not find any guidance on efficiency that would be a useful indication that I should pursue this over using another IC or using a Schottky diode.  Can you recommend an application note perhaps?

[Andrew-Lohmann · Accepted solution]

Thank you, Tomas,

I thought I should create a picture to explain what I was trying to say.  See attached, the input is 6Vrms rectified AC a from a bicycle dynamo so the input voltage varies 0V to 10V, in this case, it is part of a blog I am creating showing design steps https://blog.andrew-lohmann.me.uk/2020/09/electronics-design-project-bicycle.html

The point about using a high side switch is because of the better efficiency of a SEPIC converter capturing the power in the leakage inductance.  The efficiency particularly matters when the input voltage/power is low.

My thought about the choice between tea1993 and tea1998 is that the former has a higher voltage rating at little part cost difference. Circuit efficentcy does matter as I say so will I keep  your suggest. 

[TomasVaverka]

Hello Andrew,

Your question is not very clear to me, but if the concern is that the IC does not work well at low voltage, the TEA1998 provides the answer as it is intended for this type of application.

Best regards,

Tomas