PI5A100
Precision, Wide-Bandwidth, Quad SPDT Analog Switch
Applications
Audio Muting Function
Figure 8 shows the PI5A100 in an audio card muting application.
The original problem was one of excessive popping/clicking noise
appearing when connecting disconnecting external loads, and at
power on/off. The PI5A100 performs a muting function by grounding
the outputs at power on/off and during the transition time. The
32Ω headset impedance demands a very low and very flat switch-
on resistance to reduce THD and signal loss.
Paralleling two sections of the PI5A100 produces a Ron of 2.5Ω
with an unsurpassed ±0.5Ω flatness.
To handle AC signals it was necessary to power the device with
±3V provided by two Zener diodes: Z1 and Z2. The select and
Enable control signals are shifted by using twpo 2.5V Zener diodes
Z3,Z4 and pull down resistors connected to -3V.
Stereo Audio
Input
From DAC
J1
Select
Enable
Z3
2.5V
Z4
2.5V
Stereo Audio
Output
10kΩ
J2
32!
GND -3V
-5V
Vcc
+5V
Z1
Z2
Z1/Z2 - Dual SMT 3.0V Zener
22k!
-3V
Figure 10: The PI5A100 momentarily mutes the stereo outputs by connecting them to ground during transition times.
10
PS7012H
08/30/04