Cirrus Logic CS42L42 Manual page 44

Output Level
–4 dB
–4.5 dB
–10 dB
–10.5 dB
–14 dB
–14.5 dB
Amplifier Rail
Voltage
+2.5 V
+VCP
+VCP
2
+VCP
3
–VCP
3
–VCP
2
–VCP
–2.5 V
4.6.3 Efficiency
As discussed in previous sections, amplifiers internal to the CS42L42 operate from one of four sets of rail voltages, based
on the needs of the signal being amplified.
provides details regarding the power supplied to 15- and 30-stereo loads versus the power drawn from the supply for
each Class H mode.
If rail voltages are set to ±2.5 V, the amplifiers operate in their least efficient mode for low-level signals. If they are held at
±VCP, ±VCP/2, or ±VCP/3, amplifiers operate more efficiently, but are clipped if required to amplify a full-scale signal.
The adapt-to-signal trace shows the benefit of four-mode Class H operation. At lower output levels, amplifier output is
represented by the ±VCP/3 or ±VCP/2 curve, depending on the signal level. At higher output levels, amplifier output is
represented by the ±VCP or ±2.5-V curve. The duration for which the amplifiers operate within any of the four curves
(±VCP/3, ±VCP/2, ±VCP, or ±2.5 V) depends on both the content and the output level of the material being amplified. The
highest efficiency operation results from maintaining an output level that is close to, without exceeding, the clip threshold
of the particular supply curve.
Note that the Adapt-to-Signal Mode trace in
VOL = 1 (–6 dB) due to a 15- stereo load.
DS1083F2
Figure 4-16. VCP_FILT Hysteresis—Headphone Output
Fig. 4-17 and Fig. 4-18
Fig. 4-17 shows that it never transitions to Mode 0, because FULL_SCALE_
5.5 s
5.5 s
show power curves for all modes of operation and
CS42L42
4.6 Class H Amplifier
5.5 s
Time
Time
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