Pre-Production
WM8959
SPEAKER POWER DE-RATING CURVE
The speaker driver has been designed to drive a maximum of 1W into 8Ω with a 5V supply.
However, thermal restrictions defined by the W-CSP package ӨJA limit the amount of power that can
be safely dissipated in the device without exceeding the maximum operating junction temperature.
Power dissipated in the device correlates directly with speaker efficiency, hence there are separate
de-rating curves for class D and class AB operation.
Under no circumstances should the recommended maximum powers be exceeded.
CLASS D DE-RATING CURVES
The de-rating curves shown in Figure 2 are based on a full scale sinusoidal input.
P
[W]
SPKVDD = 5.5V
SPKVDD = 5V
SPKVDD = 4.2V
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
SPKVDD = 3.6V
SPKVDD = 3.3V
SPKVDD = 3V
SPKVDD = 2.7V
T
[ºC]
55
60
65
70
75
80
85
Figure 2 Class D Speaker Power De-Rating Curve
PP, May 2008, Rev 3.1
9
w
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
