Onkyo HTP-420

APPLICATION SUGGESTIONS (see Test and Application Circuits of the Fig. 1)
The recommended values of the external components are those shown on the application circuit of Fig-
ure 1. Different values can be used; the following table can help the designer.
COMPONENTS SUGGESTED VALUE PURPOSE
LARGER THAN
SUGGESTED
SMALLER THAN
SUGGESTED
R1 (*) 22k INPUT RESISTANCE INCREASE INPUT
IMPEDANCE
DECREASE INPUT
IMPEDANCE
R2 680
Ω
CLOSED LOOP GAIN
SET TO 30dB (**)
DECREASE OF GAIN INCREASE OF GAIN
R3 (*) 22k INCREASE OF GAIN DECREASE OF GAIN
R4 22k ST-BY TIME
CONSTANT
LARGER ST-BY
ON/OFF TIME
SMALLER ST-BY
ON/OFF TIME;
POP NOISE
R5 10k MUTE TIME
CONSTANT
LARGER MUTE
ON/OFF TIME
SMALLER MUTE
ON/OFF TIME
C1 0.47
µ
F INPUT DC
DECOUPLING
HIGHER LOW
FREQUENCY
CUTOFF
C2 22
µ
F FEEDBACK DC
DECOUPLING
HIGHER LOW
FREQUENCY
CUTOFF
C3 10
µ
F MUTE TIME
CONSTANT
LARGER MUTE
ON/OFF TIME
SMALLER MUTE
ON/OFF TIME
C4 10
µ
F ST-BY TIME
CONSTANT
LARGER ST-BY
ON/OFF TIME
SMALLER ST-BY
ON/OFF TIME;
POP NOISE
C5 22
µ
FXN (***) BOOTSTRAPPING SIGNAL
DEGRADATION AT
LOW FREQUENCY
C6, C8 1000
µ
F SUPPLY VOLTAGE
BYPASS
C7, C9 0.1
µ
F SUPPLY VOLTAGE
BYPASS
DANGER OF
OSCILLATION
(*) R1 = R3 for pop optimization
(**) Closed Loop Gain has to be
≥
26dB
(***) Multiplay this value for the number of modular part connected
MASTER
UNDEFINED
SLAVE
-V
S
+3V
-V
S
+1V
-V
S
D98AU821
Slave function: pin 4 (Ref to pin 8 -V
S
)
Note:
If in the application, the speakers are connected
via long wires, it is a good rule to add between
the output and GND, a Boucherot Cell, in order to
avoid dangerous spurious oscillations when the
speakers terminal are shorted.
The suggested Boucherot Resistor is 3.9Ω/2W
and the capacitor is 1µF.
TDA7293
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