Zetex ZXSC310-component list

Wim Hertog · Oct 13, 2004

Hi,

I would like to build a Zetex 310 driver to power a Lux III @ 1A. The power source will be a 3.6V Li-Ion accu

Can someone give me the right values for the inductor (inductance and saturation current), the sense resistor and the schottky?

I took a look at the zetex application forms, but I would like to get some more info from you guys....:)

I´m working on a microcontroller based flashlight project at school. We would like to controll the zetex driver with an Atmel AtTiny (PWM signal->dimming). Is this possible?

Thanks,
Wim

koala · Oct 13, 2004

PWM controlled Zetex 310 dimming, sounds pretty good. I suggest the Atmel AtTiny13, heaps of features. Regarding the inductor, just follow the application sheets from Zetex. Or you can ditch the Zetex all together and make your own boost circuit controlled directly from the microprocessor, of course that means higher complexity of software design. That way, you can tweak the efficiency through software.

Here's abit of code to start you off, based on the Atmel AtTiny12v.

jamaica · Oct 14, 2004

Wim,
Assuming you're using Zetex's Luxeon III driver (Zetex DN 73,
http://www.zetex.com/appnotes/design/dn73.pdf,
I estimate approximately 18 milliohms for the sense
resistor to produce 1 Amp (average) at the LED.

The Zetex ZHCS1000 recommended in the Design Note is a
decent schottky for this application.

The inductor is not super critical -- values of 33uH and
higher will keep the inductor's ripple current reasonable.
The saturation current rating of this inductor should be
1 Amp minimum (higher is preferred); a d.c. resistance of
<< 100 milliohms will ensure decent efficiency (there will
be losses of about 1% per 10 milliohms).

The Zetex Design Note recommends 100uF -- rather high
values -- for C1 & C2, but lower values may be used.

PWM dimming: yes, this is possible.

Hope this helps,
--Jamaica

[ QUOTE ]
Wim Hertog said:
Hi,

I would like to build a Zetex 310 driver to power a Lux III @ 1A. The power source will be a 3.6V Li-Ion accu

Can someone give me the right values for the inductor (inductance and saturation current), the sense resistor and the schottky?

I took a look at the zetex application forms, but I would like to get some more info from you guys....:)

I´m working on a microcontroller based flashlight project at school. We would like to controll the zetex driver with an Atmel AtTiny (PWM signal->dimming). Is this possible?

Thanks,
Wim

[/ QUOTE ]

jamaica · Oct 14, 2004

Oops -- bad link ... sorry. Look for Design Note 73
here: http://www.zetex.com/3.0/3-8-2a.asp

--Jamaica

Wim Hertog · Oct 14, 2004

jamaica,

Is it possible to use the zetex 300 for PWM dimming? It doesn´t have a shutdown pin....

jamaica · Oct 14, 2004

Probably, but you'd have to try a bit harder than with
the ZXSC310. You might be able to PWM the ZXSC300's supply
pin with the microcomputer at some slow rate, such as 1KHz.

If you try this, I'd add a diode from the PWM signal to the
MOSFET gate to make sure the MOSFET doesn't get left 'ON'
when you've gated the ZXSC300 'OFF.'

Any reason not to use the '300? That one's already set up
and ready to go.

--Jamaica