ISL54208 Datasheet, PDF (11/15 Pages) Intersil Corporation – Low Voltage, Dual SPDT, USB/CVBS/ Audio Switches, with Negative Signal Capability

ISL54208
EXTERNAL SERIES RESISTOR AT IN LOGIC CONTROL
PIN
The ISL54208 contains a clamp circuit between IN and VDD.
Whenever the IN voltage is greater than the V_DD voltage by
more than 2.55V, current will flow through this clamp circuitry
into the V_DD power supply bus.
During normal USB operation, V_DD is in the range of 2.7V to
3.6V and IN (V_BUS voltage from computer or USB hub) is in
the range of 4.4V to 5.25V, the clamp circuit is not active and
no current will flow through the clamp into the V_DD supply.
In a USB application, the situation can exist where the V_BUS
voltage from the computer could be applied at the IN pin
before the V_DD voltage is up to its normal operating voltage
range and current will flow through the clamp into the V_DD
power supply bus. This current could be quite high when
V_DD is OFF or at 0V and could potentially damage other
components connected in the circuit. In the application
circuit, a 22kΩ resistor has been put in series with the IN pin
to limit the current to a safe level during this situation.
It is recommended that a current limiting resistor in the range
of 10kΩ to 50kΩ be connected in series with the IN pin. It will
have minimal impact on the logic level at the IN pin during
normal USB operation and protect the circuit during the time
V_BUS is present before V_DD is up to its normal operating
voltage.
Note: No external resistor is required in applications where
IN pin voltage will not exceed V_DD by more than 2.55V.
Typical Performance Curves T_A = +25°C, Unless Otherwise Specified
0.11
0.4
R_LOAD = 32Ω
0.1 ^{VLOAD = 0.707VRMS}
R_LOAD = 32Ω
V_DD = 3V
0.3
0.09
V_DD = 2.6V
3V_P-P
0.08
0.2
0.07
V_DD = 2.7V
0.06
0.05
V_DD = 3.6V
0.1
V_DD = 3V
2.5V_P-P
2V_P-P
0.04
20
200
2K
20K
FREQUENCY (Hz)
FIGURE 10. THD+N vs SUPPLY VOLTAGE vs FREQUENCY
1V_P-P
0
20
200
2K
20K
FREQUENCY (Hz)
FIGURE 11. THD+N vs SIGNAL LEVELS vs FREQUENCY
0.5
R_LOAD = 32Ω
FREQ = 1kHz
0.4 ^{VDD = 3V}
0.3
0.2
0.1
0
0
0.5
1
1.5
2
2.5
3
3.5
OUTPUT VOLTAGE (V_P-P)
FIGURE 12. THD+N vs OUTPUT VOLTAGE
11
0.5
R_LOAD = 32Ω
FREQ = 1kHz
V_DD = 3V
0.4
0.3
0.2
0.1
0
0
10
20
30
40
50
OUTPUT POWER (mW)
FIGURE 13. THD+N vs OUTPUT POWER
FN6410.0
December 18, 2006