ISL54228IRTZ-T7A Intersil, ISL54228IRTZ-T7A Datasheet - Page 10

• Manufacturer Part Number: ISL54228IRTZ-T7A
• Description: IC USB SWITCH DPST OVP 8TDFN
• Manufacturer: Intersil

Specifications of ISL54228IRTZ-T7A

• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

distortion and meet all the USB requirements for USB
2.0 full-speed signaling. See Figure 15 in the “Typical
Performance Curves” on page 14 for USB Full-speed
Eye Pattern taken with switch in the signal path.
The switches are active (turned ON) whenever the OE
voltage is logic “1” (High) and the LP voltage is logic
“X” (Don’t Care) and OFF when the OE voltage is logic
“0” (Low) and the LP voltage is logic “X” (Don’t Care).
When the OE voltage is logic “0” (Low) and the LP
voltage is logic “1” (High) the part goes into low power
mode.
OVERVOLTAGE PROTECTION (OVP)
The maximum normal operating signal range for the Dx
switches is from 0V to 3.6V. For normal operation, the
signal voltage should not be allowed to exceed these
voltage levels or go below ground by more than -0.3V.
However, in the event that a positive voltage >3.8V
(typ) to 5.25V, such as the USB 5V V
shorted to one or both of the COM+ and COM- pins or
a negative voltage < -0.45V (typ) to -5V gets shorted
to one or both of the COM pins, the ISL54228 has OVP
circuitry to detect the overvoltage condition and open
the SPST switches to prevent damage to the USB
down-stream transceiver connected at the signal pins
(D-, D+).
The OVP and power-off protection circuitry allows the
COM pins (COM-, COM+) to be driven up to 5.25V
while the V
5.25V. In this condition, the part draws < 100µA of
I
In addition, the SPST switches are OFF and the fault
voltage is isolated from the other side of the switch.
External V
Current During Negative OVP Condition
A 100Ω to 1kΩ resistor in series with the VDD pin (see
Figure 6) is required to limit the I
the system power supply rail during a negative OVP
fault event.
With a negative -5V fault voltage at both COM pins, the
graph in Figure 7 shows the I
different external resistor values for supply voltages of
5.25V, 3.6V, and 2.7V. Note: With a 500Ω resistor, the
current draw is limited to around 5mA. When the
negative fault voltage is removed, the I
return to it’s normal operation current of 25
The series resistor also provides improved ESD and
latch-up immunity. During an overvoltage transient
event (such as occurs during system level IEC 61000
ESD testing), substrate currents can be generated in
the IC that can trigger parasitic SCR structures to
turn ON, creating a low impedance path from the
VDD power supply to ground. This will result in a
significant amount of current flow in the IC, which
can potentially create a latch-up state or
permanently damage the IC. The external VDD
resistor limits the current during this over-stress
COMx
and I
DD
DD
DD
supply voltage is in the range of 0V to
current and causes no stress to the IC.
Series Resistor to Limit I
10
DD
current draw for
DD
current draw from
BUS
DD
voltage, gets
current will
µ
DD
A to 45
ISL54228
ISL54228
µ
A
.
situation and has been found to prevent latch-up or
destructive damage for many overvoltage transient
events.
Under normal operation, the low microamp I
current of the IC produces an insignificant voltage
drop across the series resistor resulting in no impact
to switch operation or performance.
ISL54228 Operation
The following will discuss using the ISL54228 shown
in the “Application Block Diagram” on page 9.
POWER
The power supply connected at the VDD pin provides
the DC bias voltage required by the ISL54228 part for
proper operation. The ISL54228 can be operated with
a V
For lowest power consumption you should use the
lowest V
A 0.01µF or 0.1µF decoupling capacitor should be
connected from the VDD pin to ground to filter out
any power supply noise from entering the part. The
capacitor should be located as close to the VDD pin
as possible.
-5V
FAULT
VOLTAGE
FIGURE 6. VDD SERIES RESISTOR TO LIMIT IDD
FIGURE 7. NEGATIVE OVP I
DD
25
20
15
10
5
0
100
voltage in the range of 2.7V to 5.25V.
DD
2.7V
200
3.6V
supply.
CURRENT DURING NEGATIVE OVP AND
FOR ENHANCED ESD AND LATCH-UP
IMMUNITY
RESISTOR VALUE vs V
5.25V
100Ω to 1kΩ
PROTECTION
RESISTOR
300
COM+
COM-
OE
LP
LOGIC
400
V
OVP
SUPPLY
RESISTOR (Ω)
VDD
500
GND
DD
I
C
DD
600
CURRENT vs
V
ALM
INT
COM+
D+
SUPPLY
D-
700
= V
800
COM-
OVP
July 29, 2010
TO
INDICATE
LOW
DD
900 1k
= -5V
FN7628.0