ISL54227_10 Datasheet, PDF (10/18 Pages) Intersil Corporation – High-Speed USB 2.0 (480Mbps) DPST Switch with Overvoltage Protection (OVP) and Dedicated Charger Port Detection

ISL54227
With a negative -5V fault voltage at both com pins, the
graph in Figure 7 shows the IDD current draw for
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_DD current will
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 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
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_DD current
of the IC produces an insignificant voltage drop across
the series resistor resulting in no impact to switch
operation or performance.
V_SUPPLY
C
PROTECTION
RESISTOR
100Ω TO 1kΩ
I_DD
-5V
FAULT
VOLTAGE
COM+
V_DD
COM- ^OVP
OE _LOGIC
LP
GND
D+
D-
ALM
INT
LOW
TO
INDICATE
OVP
FIGURE 6. V_DD SERIES RESISTOR TO LIMIT I_DD
CURRENT DURING NEGATIVE OVP AND FOR
ENHANCED ESD AND LATCH-UP IMMUNITY
25
20
5.25V
15
V_COM+ = V_COM- = -5V
10
3.6V
5 2.7V
0
100 200 300 400 500 600 700 800 900 1k
RESISTOR (Ω)
FIGURE 7. NEGATIVE OVP I_DD CURRRENT vs
RESISTOR VALUE vs V_SUPPLY
CHARGER PORT DETECTION
V_SUPPLY
V_BUS
C
BATTERY
CHARGER
200Ω
D+ COM+ ^VDD
CHG DET
D-
COM-
GND
LOGIC
OE LP GND
POWER
MANAGEMENT
BATTERY CHARGER
CIRCUITRY
“LOW” TO
INDICATE
CHARGER
CONNECTED
D+
USB
D-
TRANCEIVER
ALM
INT
µP
OE = “0”
OR
TRI-STATE
FIGURE 8. CHARGER PORT DETECTION
The ISL54227 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 into the USB
connector, it shorts the COM+ and COM- pins together.
The shorting of the pins is sensed by the ISL54227 IC
and it pulls the COM+ and COM- lines high and as long as
the OE = “0” or is tri-stated by the µP, it 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 use the USB connector V_BUS line to
charge the battery.
ISL54227 Operation
The following will discuss using the ISL54227 shown in
the “Application Block Diagram” on page 8.
POWER
The power supply connected at the VDD pin provides the
DC bias voltage required by the ISL54227 part for proper
operation. The ISL54227 can be operated with a V_DD
voltage in the range of 2.7V to 5.25V.
For lowest power consumption you should use the lowest
V_DD supply.
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.
In a typical application, V_DD will be in the range of
2.8V to 4.3V and will be connected to the battery or
LDO of the portable media device.
LOGIC CONTROL
The state of the ISL54227 device is determined by the
voltage at the OE pin, LP pin, and the signal voltage at
the COM pins. Refer to “Truth Table” on page 2.
10
FN7593.0
July 2, 2010