ISL54226 INTERSIL [Intersil Corporation], ISL54226 Datasheet - Page 10

• Manufacturer Part Number: ISL54226
• Description: High-Speed USB 2.0 (480Mbps) DPST Switch with Overvoltage Protection (OVP) and Dedicated Charger Port Detection
• Manufacturer: INTERSIL [Intersil Corporation]

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
from 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
2.7V, 3.6V, and 5.25V. 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 25µA to 45µA.
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 V
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 V
overstress situation and has been found to prevent
latch-up or destructive damage for many overvoltage
transient events.
Under normal operation the low microamp I
the IC produces an insignificant voltage drop across the
series resistor resulting in no impact to switch operation
or performance.
FIGURE 6. V
-5V
FAULT
VOLTAGE
DD
CURRENT DURING NEGATIVE OVP AND FOR
ENHANCED ESD AND LATCH-UP IMMUNITY
DD
resistor limits the current during this
PROTECTION
100Ω TO 1kΩ
DD
COM+
COM-
RESISTOR
SERIES RESISTOR TO LIMIT I
Series Resistor to Limit I
LOGIC
OVP
V
SUPPLY
V
10
DD
GND
DD
I
OE/ALM
C
DD
current draw for
INT
D+
D-
DD
DD
100kΩ
DD
current will
current draw
DD
power
LOW
TO
INDICATE
OVP
current of
DD
DD
ISL54226
CHARGER PORT DETECTION
The ISL54226 has special charger port detection circuitry
that monitors the voltage at the com pins to detect when
a battery charger has been connected into the USB port
(see Figure 8).
When the battery charger is connected to the USB
connector it shorts the COM+ and COM- pins together.
The shorting of the pins is sensed by the ISL54226 IC
and it pulls the COM+ and COM- lines high and as long as
the OE/ALM pin is driven low (OE/ALM = “0”) by the
will drive its INT logic output “Low” to tell the power
management circuitry that a battery charger is
connected at the port and not a USB host transceiver.
The power management circuitry will then set the
appropriate current level and use the USB connector
VBUS line to charge the battery.
FIGURE 7. NEGATIVE OVP I
BATTERY
CHARGER
200Ω
25
20
15
10
5
0
100
FIGURE 8. CHARGER PORT DETECTION
2.7V
200
3.6V
VALUE vs V
5.25V
V
GND
BUS
D+ COM+
D-
300
COM-
400
LOGIC
CHG DET
V
SUPPLY
SUPPLY
VDD
RESISTOR (Ω)
500
GND
DD
C
OE/ALM
600
CURRENT vs RESISTOR
INT
D+
D-
V
700
COM+
BATTERY CHARGER
DRIVEN LOW BY µP
(OE/ALM = “0”)
MANAGEMENT
CIRCUITRY
= V
800
POWER
TRANCEIVER
CONNECTED
COM-
µP
“LOW” TO
INDICATE
CHARGER
USB
900
July 29, 2010
= -5V
FN7614.0
µ
1k
P, it