LA4485 Datasheet, PDF (17/20 Pages) Sanyo Semicon Device – 5 W, Two-channel Power Amplifier with Very Few External Parts

LA4485
BTL-mode Operation Notes
In BTL mode, channel 1 should be non-inverted and channel 2 should be inverted.
. _{Use the input capacitor CIN in the range 0.22 µF to 2.2 µF.}
. _{Use the standby supply capacitor in the range 0.22 µF to 1.0 µF.}
When the capacitor is 2.2 µF or more, the V_N trace for standby-off changes, and the switching noise increases significantly.
. _{The recommended DC (filter) capacitor is 100 µF or greater.}
. _{The BTL-mode coupling capacitor should be 2.2 µF.}
When this capacitor is decreased, the output power is decreased. However, when this capacitor is increased, speaker
. turn-ON transient noise is increased significantly.
In BTL mode, the ripple rejection ratio (SVRR) is approximately 40 dB.
This is because the output ripple portion of the noninverted side penetrates the BTL coupling end, so that ripple on the
inverted side is large. The following method is described as one external measure:
SS VCC
LS VCC
This measure yields an SVRR of approximately 50 dB. Note that the Rx loss voltage is approximately 1 V, and the P_O loss is
about 1.0 to 1.5 W (to the 15 W level).
. _{Example of minimum parts for BTL operation}
Non-
inverting
Inverting
No standby function
SVRR 6 40 dB
C_IN = 2.2 µF
C_BTL = 2.2 µF
(Three point method)
Dual-mode short-circuit
test circuit
1 Load short-circuit (to ground)
2 Output-to-supply short-circuit
3Output-to-ground short-ciruit
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