ISL54210 Datasheet, PDF (13/21 Pages) Intersil Corporation – MP3/USB 2.0 High Speed Switch with Negative Signal Handling/Click and Pop Suppression

ISL54210
speaker loads during power-up and power-down. See
Figure 30 in the “Typical Performance Curves” on
page 18.
AC-COUPLED CLICK AND POP OPERATION
Single supply audio drivers have their signal biased at a
DC offset voltage (usually at 1/2 the DC supply voltage of
the driver). As this DC bias voltage comes up or goes
down during power-up or power-down of the driver, a
transient can be coupled into the speaker load through
the DC blocking capacitor (see the“Typical Application
Block Diagram” on page 11).
When a driver is OFF and then turned ON, the rapidly
changing DC bias voltage at the output of the driver will
cause an equal voltage at the input side of the switch due
to the fact that the voltage across the blocking capacitor
cannot change instantly. If the switch is in the Audio
mode or there is no low impedance path to discharge the
blocking capacitor voltage at the input of the switch,
before turning on the audio switch, a transient discharge
will occur in the speaker, generating a click/pop noise.
Proper elimination of a click/pop transient at the
speaker loads while powering up or down of the audio
drivers requires that the ISL54210 have its click/pop
circuitry activated by putting the part in the Mute
mode. This allows the transients generated by the
audio drivers to be discharged through the click and
pop shunt circuitry.
Once the driver DC bias has reached V_DD/2 and the
transient on the switch side of the DC blocking capacitor
has been discharged to ground through the click/pop
shunt circuitry, the audio switches can be turned ON and
connected through to the speaker loads without
generating any undesirable click/pop noise in the
speakers.
With a typical DC blocking capacitor of 220µF and the
click/pop shunt circuitry designed to have a resistance
of 20Ω to 70Ω, allowing a 100ms wait time to discharge
the transient before placing the switch in the Audio
mode will prevent the transient from getting through
to the speaker load. See Figures 28 and 29 in the
“Typical Performance Curves” page 17.
Typical Performance Curves T_A = +25°C, Unless Otherwise Specified
2.70
I_COM = 40mA
4.0
I_COM = 40mA
V_DD = 3.0V
2.65
3.6
V_DD = 2.5V
V_DD = 3.6V
V_DD = 3.3V
3.2
2.60
V_DD = 4.3V
2.8
V_DD = 2.7V
2.55
V_DD = 3.6V
2.4
2.50
-1.5
-1.0
-0.5
0
0.5
1.0
1.5
2.0
-1.5
-1.0
-0.5
0
0.5
1.0
1.5
V_COM (V)
V_COM (V)
FIGURE 10. AUDIO ON-RESISTANCE vs SUPPLY
VOLTAGE vs SWITCH VOLTAGE
FIGURE 11. AUDIO ON-RESISTANCE vs SUPPLY
VOLTAGE vs SWITCH VOLTAGE
13
FN6661.2
March 18, 2010