Datasheet

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SBOS218A − DECEMBER 2001 − REVISED JUNE 2002
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GENERAL DESCRIPTION
The PGA2311 is a stereo audio volume control. It may
be used in a wide array of professional and consumer
audio equipment. The PGA2311 is fabricated in a sub−
micron CMOS process.
The heart of the PGA2311 is a resistor network, an ana-
log switch array, and a high−performance op amp
stage. The switches are used to select taps in the resis-
tor network that, in turn, determine the gain of the am-
plifier stage. Switch selections are programmed using
a serial control port. The serial port allows connection
to a wide variety of host controllers. Figure 1 shows a
functional block diagram of the PGA2311.
POWER−UP STATE
On power up, “power−up reset” is activated for about
100ms during which the circuit is in hardware MUTE
state and all internal flip-flops are reset. At the end of this
period, the offset calibration is initiated without any exter-
nal signals. Once this has been completed, the gain byte
value for both the left and right channels are set to 00
HEX
,
or the software MUTE
condition. The gain will remain at
this setting until the host controller programs new set-
tings for for each channel via the serial control port.
If during normal operation the power supply voltage
drops below ±3.2V, the circuit enters a hardware MUTE
state. A power-up sequence will be initiated if the power
supply voltage returns to greater than ±3.2V.
ANALOG INPUTS AND OUTPUTS
The PGA2311 includes two independent channels, re-
ferred to as the left and right channels. Each channel has
a corresponding input and output pin. The input and out-
put pins are unbalanced, or referenced to analog ground
(either AGNDR or AGNDL). The inputs are named V
IN
R
(pin 9) and V
IN
L (pin 16), while the outputs are named
V
OUT
R (pin 11) and V
OUT
L (pin 14).
The input and output pins may swing within 1.25V of the
analog power supplies, V
A
+ (pin 12) and V
A
− (pin 13).
Given V
A
+ = +5V and V
A
− = −5V, the maximum input or
output voltage range is 7.5Vp-p.
For optimal performance, it is best to drive the PGA2311
with a low source impedance. A source impedance of
600 or less is recommended. Source impedances up
to 2k will cause minimal degradation of THD+N. Please
refer to the “THD+N vs Source Impedance” plot in the
Typical Characteristics section of the datasheet.
Figure 1. PGA2311 Block Diagram.