PGA2311_06 Datasheet, PDF (10/17 Pages) Burr-Brown (TI) – Stereo Audio VOLUME CONTROL

PGA2311
SBOS218A – DECEMBER 2001 – REVISED JUNE 2002
DAISY-CHAINING MULTIPLE PGA2311 DEVICES
In order to reduce the number of control signals re-
quired to support multiple PGA2311 devices on a
printed circuit board, the serial control port supports
daisy-chaining of multiple PGA2311 devices. Figure 4
shows the connection requirements for daisy-chain
operation. This arrangement allows a 3-wire serial in-
terface to control many PGA2311 devices.
As shown in Figure 4, the SDO pin from device #1 is con-
nected to the SDI input of device #2, and is repeated for
additional devices. This in turn forms a large shift regis-
ter, in which gain data may be written for all PGA2311s
connected to the serial bus. The length of the shift regis-
ter is 16 • N bits, where N is equal to the number of
PGA2311 devices included in the chain. The CS input
must remain LOW for 16 • N SCLK periods, where N is
the number of devices connected in the chain, in order
to allow enough SCLK cycles to load all devices.
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ZERO CROSSING DETECTION
The PGA2311 includes a zero crossing detection func-
tion that can provide for noise-free level transitions.
The concept is to change gain settings on a zero cross-
ing of the input signal, thus minimizing audible glitches.
This function is enabled or disabled using the ZCEN in-
put (pin 1). When ZCEN is LOW, zero crossing detec-
tion is disabled. When ZCEN is HIGH, zero crossing
detection will be enabled.
The zero crossing detection takes effect with a change
in gain setting for a corresponding channel. The new
gain setting will not be implemented until either positive
slope zero crossing is detected or a time-out period of
16ms has elapsed. In the case of a time-out, the new
gain setting takes effect with no attempt to minimize
audible artifacts.
Figure 4. Daisy-Chaining Multiple PGA2311 Devices.
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