CS3310_05 Datasheet, PDF (8/17 Pages) Cirrus Logic – Stereo Digital Volume Control

CS3310
Changing the Analog Output Level
Care has been taken to ensure that there are no audible artifacts in the analog output signal dur-
ing volume control changes. The gain/attenuation changes of the CS3310 occur at zero cross-
ings to eliminate glitches during level transitions. The zero crossing for the left channel is the
voltage potential at the AGNDL pin; the voltage potential at the AGNDR pin defines the right
channel zero crossing.
A volume control change occurs after chip select latches the data in the volume control data reg-
ister and two zero crossings are detected. If two zero crossings are not detected within 18 ms of
the change in CS, the new volume setting is implemented. The zero crossing enable pin, ZCEN,
enables or disables the zero crossing detection function as well as the 18 ms time-out circuit.
Input Code
(Left or Right Channel) Gain or Attenuation (dB)
11111111
11111110
•
•
11000000
•
00000010
00000001
00000000
+31.5
+31.0
•
•
0
•
-95.0
-95.5
Software Mute
Table 1. Input Code Definition
Analog Inputs and Outputs
The maximum input level is limited by the common-mode voltage capabilities of the internal op-
amp. Signals approaching the analog supply voltages may be applied to the AIN pins if the inter-
nal attenuator limits the output signal to within 1.25 volts of the analog supply rails.
The outputs are capable of driving 600 Ω loads to within 1.25 volts of the analog supply rails and
are short circuit protected to 20 mA.
As with any adjustable gain stage the affects of a DC offset at the input must be considered. Ca-
pacitively coupling the analog inputs may be required to prevent “clicks and pops” which occur
with gain changes if an appreciable offset is present.
Source Impedance Requirements
The CS3310 requires a low source impedance to achieve maximum performance. The ESD pro-
tection diodes on the analog input pins are reversed biased during normal operation. A charac-
teristic of a reversed biased diode is a non-linear voltage dependent capacitance which can be
8
DS82F1