Re: Canon PowerShot A710 IS backlight
- From: Franc Zabkar <fzabkar@xxxxxxxxxxxxxxxxx>
- Date: Mon, 16 Jul 2007 17:08:03 +1000
On 15 Jul 2007 23:07:24 GMT, u_1061771155@xxxxxxx (Remove _ for valid
address) put finger to keyboard and composed:
The driver circuit is somewhat hard to trace. (Anyone know of
a source for a schematic... ;-) So far I've traced it back
to a SOT23 sized 5-pin thing:
'large'
_ _____ _ inductor
drive?->--|_| |_|b-------@@@@@-----+------->
| XH |_ _|_ backlight
| 6 |_|GND 'tiny' ___ ?-->
_| G4 |_ cap |
a|_|_____|_|Vcc GND
I think "a" connects to "b" under the chip.
Could "a" connect to the junction of the cap and inductor, in which
case the chip may be a self contained, fixed voltage, PWM regulator
with integrated MOSFET, flywheel diode, oscillator, and error amp. "A"
may be the feedback pin for the error amp, ie this pin may sense the
regulator's output voltage. The "drive" may be an on/off pin.
Do you measure a diode drop between GND and "b" (anode to GND)? If so,
then this could be an internal flywheel diode.
- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
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