an1722

Application Note 1722
Author: Allan Robinson
ISL54228IRTZEVAL1Z Evaluation Board User Manual
Description
Key Features
The ISL54228IRTZEVAL1Z evaluation board is designed to
provide a quick and easy method for evaluating the ISL54228
USB Switch IC.
• Standard USB connectors
The ISL54228 device is a unique IC. To use this evaluation
board properly, requires a thorough knowledge of the
operation of the IC. See the ISL54228 datasheet for an
understanding of the functions and features of the device.
Studying the device’s truth-table along with its pinout diagram
on page 2 of the datasheet is the best way to get a quick
understanding of how the part works.
A picture of the evaluation board is shown in Figure 1. The
ISL54228 TDFN IC is soldered onto the evaluation board. It is
located in the center of the board and is designated as U1.
The evaluation board contains USB connectors, banana jacks,
and toggle switches to allow the user to easily interface with
the IC to evaluate its functions, features, and performance. For
example, with the board properly powered and configured as
shown in Figure 2 you can control the logic pins with the toggle
switches, S1 (OE) and S2 (LP), to connect and disconnect the
USB device from the USB host (computer).
In a typical application, the ISL54228 dual SPST part is used
for switching or isolating a USB source in portable powered
products.
This application note will guide the user through the process of
configuring and using the evaluation board to evaluate the
ISL54228 device.
Evaluation Board Photo
• Banana jacks for power, ground and logic input
• Toggle switches for easy control of the logic pins
• Convenient test points and connections for test equipment
Board Architecture/Layout
Basic Layout of Evaluation Board
The basic layout of the evaluation board is as follows: Refer to
Figure 1 or the “ISL54228IRTZEVAL1Z Board Schematic” on
page 4.
• Power and Ground connections are at banana jacks J1
(VDD) and J2 (GND) located at the top of the board.
• Logic input connections are at banana jacks J3 (OE) and J4
(LP) located at the top of the board or by using the toggle
switches S1 and S2. Jumpers JP1 and JP2 must be installed
to use the toggle switches. To control the logic through the
banana jacks (J3 and J4) the JP1 and JP2 jumpers must not
be populated.
• USB connection to an upstream host controller (Computer)
is made at the USB connector J6 (USB TO HOST), located at
the left side of the board.
• USB connection to the downstream USB device is made at
USB connector J5 (USB TO DEVICE), located on right side of
the board.
• The ISL54228 IC (U1) is located in the center of the board.
The evaluation board has a Pin 1 indicator dot to show how
the IC should be oriented on the evaluation board. The IC
Pin 1 indicator dot should be aligned with the evaluation
board Pin 1 indicator dot.
IC Power Supply
A DC power supply connected at banana jacks J1 (VDD) and J2
(GND) provides power to the ISL54228 IC. The IC requires a
2.7VDC to 5.25VDC power supply for proper operation. The
power supply should be capable of delivering 500µA of
current.
Logic Control
The state of the ISL54228 device is determined by the voltage
at the LP pin and the OE pin. Access to the LP pin is through
the banana jack J4 (LP) or the toggle switch S2. Access to the
OE pin is through the banana jack J3 (OE) or the toggle switch
S1. To use the toggle switches to control the logic, jumpers
must be installed at JP1 and JP2. Remove jumpers to control
the logic through the banana jacks.
FIGURE 1. ISL54228IRTZEVAL1Z EVALUATION BOARD
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If OE is driven “HIGH” (pulled up to VDD) and LP = “LOW”
(to ground) with the signal voltage in the range of 0V to 3.6V,
the SPST switches will be ON. The USB host controller
(computer) connected at J6 (USB TO HOST) will be connected
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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Application Note 1722
through to the USB device connected at J5 (USB TO DEVICE) and
data will be transmitted between the computer and the device.
If OE is driven “LOW” (to ground) and LP = “LOW” (to ground) with
the signal voltage in the range of 0V to 3.6V, the SPST switches
will be OFF. The USB host controller (computer) connected at J6
(USB TO HOST) will be disconnected from the USB device
connected at J5 (USB TO DEVICE) and no data will be transferred.
If OE = “LOW” and LP = “HIGH” the switches will be OFF and the
part will be put in the low power state. In the low power state the
part draws only 5µA (typ) of IDD current.
If the signal at the host (computer side) of the switch is >3.8V
(typ) or ≤0.45V (typ) the ISL54228 IC will turn the switches OFF.
USB Connections
A “B” type USB receptacle labeled “USB TO HOST” (J6) is located
at the right side of the board. This receptacle should be
connected, using a standard USB cable, to the upstream USB
host controller, which is usually a PC computer or hub.
An “A” type USB receptacle labeled “USB TO DEVICE” (J5) is
located on the right side of the board. A USB device can be
plugged directly into this receptacle or through a standard USB
cable.
The USB switches are bidirectional, which allows the host
(computer) and downstream USB device to both send and receive
data.
High-Speed Switches
The two SPST switches are bidirectional switches that can pass
signals up to 3.6V with a VDD supply voltage in the range of 2.7V
to 5.25V.
When powered with a 2.7V supply, these switches have a
nominal rON of 3.5Ω over the signal range of 0V to 400mV with a
rON flatness of 0.26Ω. The rON matching between the SPST
switches over this signal range is only 0.2Ω ensuring minimal
impact by the switches to USB high speed signal transitions. As
the signal level increases, the rON switch resistance increases. At
signal level of 3.3V the switch resistance is nominally 6.8Ω.
However, in the event that a positive voltage > 3.8V (typ) to
5.25V, (such as the USB 5V VBUS voltage) gets shorted to one or
both of the (COM+ and COM-) pins or a negative voltage ≤0.5V
(typ) to -5V gets shorted to one or both of the COM pins, the
ISL54228 has overvoltage protection (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+ and D-).
The OVP and power-off protection circuitry allows the COM pins
(COM-, COM+) to be driven up to 5.25V while the VDD supply
voltage is in the range of 0V to 5.25V. In this condition, the part
draws <100µA of ICOMx and IDD current and causes no stress to
the IC. In addition, the SPST switches are OFF and the fault
voltage is isolated from the other side of the switch.
Board Component Definitions
Evaluation board components and their functions are shown in
Table 1.
TABLE 1. BOARD COMPONENT DESCRIPTIONS
DESIGNATOR
DESCRIPTION
U1
ISL54228IRTZ IC
J6
“B” type USB Receptacle
J5
“A” type USB Receptacle
J1
VDD Positive Connection
J2
VDD Negative Connection
J3
OE Logic Control
J4
LP Logic Control
S1
OE Toggle Switch
S2
LP Toggle Switch
JP1
Toggle Switch S1 (OE) Jumper
JP2
Toggle Switch S2 (LP) Jumper
JP3, JP4
D-/D+ Differential Probe Connection
The SPST switches were specifically designed to pass USB 2.0
high-speed (480Mbps) differential signals typically in the range
of 0V to 400mV. They have low capacitance and high bandwidth
to pass the USB high-speed signals with minimum edge and
phase distortion to meet USB 2.0 high-speed signal quality
specifications.
The SPST switches can also pass USB full-speed signals
(12Mbps) with minimal distortion and meet all the USB
requirements for USB 2.0 full-speed signaling.
The maximum normal operating signal range for the SPST
switches is from 0V to 3.6V. For normal operation, the signal
voltage should not be allowed to exceed this voltage range or go
below ground by more than -0.3V.
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Application Note 1722
DC POWER
SUPPLY
+3.3V
+
-
LP
VDD
J4
OE
GND
J3
J1
J2
JP1
JP2
1
1
S1
S2
0
0
COMPUTER
J6
J5
U1
USB HIGH-SPEED DEVICE
USB PORT
USB
TO
HOST
JP4
JP3
USB
TO
DEVICE
ISL54228IRTZEVAL1Z
FIGURE 2. BASIC EVALUATION TEST SETUP BLOCK DIAGRAM
Using the ISL54228IRTZEVAL1Z
Evaluation Board (see Figure 2)
5. Drive the OE control pin LOW to open the SPST switches of
the ISL54228 IC by putting toggle switch S1 (OE) in the
down position.
Lab Equipment
6. Connect USB cable from host (PC computer) to the USB “B”
type receptacle, J6 (USB TO HOST).
The equipment, external supplies and signal sources needed
to operate the board are listed as follow:
1. +2.7V to +5.25V DC Power Supply
2. One High-Speed USB device (i.e. USB memory stick, MP3
Player, etc.)
3. Computer with 2.0 High-Speed USB Port
4. Standard USB Cable
Initial Board Setup Procedure
1. Install jumpers at JP1 and JP2. Allows logic control from S1
and S2 toggle switches.
2. Attach the main evaluation board to a DC power supply at
J1 (VDD) and J2 (GND). Positive terminal at J1 and negative
terminal at J2. The supply should be capable of delivering
2.7V to 5.25V and 500µA of current. Set the supply voltage
to 3.3V.
3. Connect the high-speed USB device at USB connector J5.
This connector is located on the right side of the evaluation
board.
4. Drive the LP control pin LOW by putting toggle switch S2
(LP) in the down position.
3
High-Speed Operation
1. Apply a logic LOW to the LP pin by putting toggle switch S2
(LP) in the down position.
2. Apply a logic HIGH to the OE pin by putting toggle switch S1
(OE) in the up position.
3. You should now be able to send and receive data between
the computer and the USB device connected at J5.
4. To disconnect the USB device from the computer take the
OE pin LOW by putting toggle switch S1 (OE) in the down
position.
Low Power Operation
1. Apply a logic LOW to the OE pin by putting toggle switch S1
(OE) in the down position.
2. Apply a logic HIGH to the LP pin by putting toggle switch S2
(LP) in the up position.
3. The part will now be in the low power state. The IDD current
will drop from 23µA (typ) to 5µA (typ).
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Application Note 1722
Test Points
TABLE 2. (Continued)
The board has various test points to allow the user to connect
probes to make measurements. The test points are described
in Table 2.
DESIGNATOR
JP3
D-/D+ Differential Probe Connection - COM Side of
Switch
TABLE 2.
JP4
D-/D+ Differential Probe Connection - USB Device
Side of Switch
DESIGNATOR
DESCRIPTION
TP1
VDD test point
TP2
Ground Test Point
TP3
OE Test Point
TP4
LP Test Point
TP5
VBUS Test Point
DESCRIPTION
You can observe the D- and D+ USB signal at the device side of
the switch on an oscilloscope or other test equipment by
connecting a differential probe at JP4.
You can observe the D- and D+ USB signal at the COM side of
the switch on an oscilloscope or other test equipment by
connecting a differential probe at JP3.
ISL54228IRTZEVAL1Z Board Schematic
Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is
cautioned to verify that the Application Note or Technical Brief is current before proceeding.
For information regarding Intersil Corporation and its products, see www.intersil.com
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