Cirrus Logic CS42L52 - Manual (Page 33)

DS680F2 33
CS42L52
3/1/13
4.5.2 VP Battery Compensation
The CS42L52 provides the option to maintain a desired power output level, independent of the VP supply.
When enabled, this feature works by monitoring the voltage on the VP supply and reducing the attenua-
tion on the speaker outputs when VP voltage levels fall.
Note: The internal ADC that monitors the VP supply operates from the VA supply. Calculations are
based on typical VA levels of 1.8 V and 2.5 V using the VPREF bits.
4.5.2.1 Maintaining a Desired Output Level
Using SPKxVOL, the speaker output level must first be attenuated by the decibel equivalent of the expect-
ed VP supply range (MAX relative to MIN). The CS42L52 then gradually reduces the attenuation as the
VP supply drops from its maximum level, maintaining a nearly constant power output.
Compensation Example 1 (VP Battery supply ranges from 4.5 V to 3.0 V)
1. Set speaker attenuation (SPKxVOL) to -3.5 dB. The VP supply changes ~3.5 dB.
2. Set the reference VP supply (VPREF) to 4.5 V.
3. Enable battery compensation (BATTCMP).
The CS42L52 automatically adjusts the output level as the battery discharges.
Compensation Example 2 (VP Battery supply ranges from 5.0 V to 1.6 V)
1. Set speaker attenuation (SPKxVOL) to -10 dB. The VP supply changes ~9.9 dB.
2. Set the reference VP supply (VPREF) to 5.0 V.
3. Enable battery compensation (BATTCMP).
The CS42L52 automatically adjusts the output level as the battery discharges. Refer to Figure 15 on page
33 . In this example, the VP supply changes over a wide range, illustrating the accuracy of the CS42L52’s
battery compensation.
4.6 Serial Port Clocking
The CODEC serial audio interface port operates either as a slave or master, determined by the M/S bit. It
accepts externally generated clocks in Slave Mode and will generate synchronous clocks derived from an
Referenced Control Register Location
VPREF ................................
SPKxVOL ............................ “VP Reference” on page 72
“Speaker Volume Control” on page 64
-24
-22
-20
-18
-16
-14
-12
-10
-8
-6
1.6 1.9 2.2 2.5 2.8 3.1 3.4 3.7 4 4.3 4.6 4.9
Uncompensated
PWM Output
Level
Battery Compensated
PWM Output Level
VP Supply (V)
P
W
M
O
u
tp
ut
L
e
v
el
(d
B)
Figure 15. Battery Compensation