isl54210 Intersil Corporation, isl54210 Datasheet - Page 11

• Manufacturer Part Number: isl54210
• Description: Mp3/usb 2.0 High Speed Switch With Negative Signal Handling/click And Pop Suppression
• Manufacturer: Intersil Corporation

headphones. See “AC-Coupled click and pop operation” on
page 11.
Before power-up and power-down of the ISL54210 part, the
V
tri-stated. This will put the switch in the mute state, which
turns all switches OFF and activates the click and pop
circuitry. This will minimize transients at the speaker loads
during power-up and power-down. See Figure 30 in the
“Typical Performance Curves” on page 16.
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 9).
When a driver is OFF and suddenly 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
Typical Performance Curves
BUS
FIGURE 10. AUDIO ON-RESISTANCE vs SUPPLY VOLTAGE vs
2.70
2.65
2.60
2.55
2.50
-1.5
and CTRL control pins should be driven to ground or
I
COM
SWITCH VOLTAGE
= 40mA
-1.0
-0.5
V
V
V
V
DD
V
V
DD
DD
DD
DD
DD
= 3.0V
= 4.3V
= 4.3V
11
= 3.6V
= 5.0V
= 5.0V
V
COM
0
(V)
0.5
T
A
V
V
DD
DD
= +25°C, Unless Otherwise Specified
= 3.3V
= 3.3V
1.0
1.5
ISL54210
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
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 16.
FIGURE 11. AUDIO ON-RESISTANCE vs SUPPLY VOLTAGE vs
4.0
3.6
3.2
2.8
2.4
2.0
-1.5
I
COM
= 40mA
SWITCH VOLTAGE
-1.0
-0.5
V
V
V
DD
DD
DD
V
COM
= 2.5V
= 5.0V
= 2.7V
0
(V)
DD
0.5
/2 and the
V
DD
1.0
= 3.6V
October 3, 2008
FN6661.1
1.5