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hollowman 14th January 2008 07:11 AM

TDA1545 Vref and Iref questions
Looking at the block diagram of the TDA1545 (Datasheet page 4) shows Vref connected to the positive input of the I/V opamps. How critical is this connection? My only connection to the I/V I'm running Rudolf Broertjes' SS I/V Gain Stage) is IOR, IOL and GND. Any clues here? FWIW, my implementation sounds good Vref connected to nothing (but the rest of the Iref "feedback" is being used as per Datasheet)

Also, what's the best way to decouple or bypass Vref? The Datasheet suggests a 1uF polarized cap from Vref to gnd. Would further close-to-chip bypassing help (e.g., for Vdd I use a 100uF + 15pF from pin 5 to 4)?

Schematics from commercial players/DACs using the TDA1545(A) may shed some light. Not sure which commercial CDPs and DACs use(d) the TDA1545, but if anyone can "loan" me a copy ;) of the schematics I'd be grateful.


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