1www.semtech.com
PROTECTION PRODUCTS
STF202-22 & STF202-30
USB Upstream Por t Filter & T VS
For EMI Filtering and ESD Protection
Description Features
Schematic & PIN Configuration
Revision 4/19/01
The STF202 is a combination EMI filter and line termi-
nation device with integrated TVS diodes for use on
upstream USB ports. It is constructed using a propri-
etary technology that allows passive components and
TVS diodes to be integrated in the same package.
Each device will provide termination, filtering, and ESD
protection for one upstream USB port. The STF202 is
an easily implemented solution for meeting the require-
ments of revision 1.1 of the Universal Serial Bus
specification.
USB line termination is achieved with series 22Ω or
30Ω resistors on both the D+ and D- USB lines. These
resistors preserve signal integrity by matching the cable
impedance to that of the differential driver. The 1.5kΩ
pull-up resistor completes the termination circuit on
each line. This resistor is required by the USB specifi-
cation to identify the equipment as either a full-speed
(connected to D+ line) or low-speed (connected to D-
line) device. The 47pF capacitors are used to bypass
high frequency energy to ground and for edge rate
control of the USB signals. Finally, the STF202 con-
tains TVS diodes for ESD protection of both (D+ & D-)
data lines and the voltage bus (VBUS). The T VS diodes
provide effective suppression of ESD voltages in
excess of 15kV (air discharge) and 8kV (contact
discharge) per IEC 61000-4-2, level 4.
The small size and integrated feature of the STF202
minimizes required board space and increases system
reliability. The STF202 is suitable for use in USB hubs,
computers, peripherals, and portable devices.
Applications
Mechanical Characteristics
!USB Hubs
!Portable electronics
!Cellular Handsets
!Modems
!Peripherals
!Servers, Desktop, Notebook, and Handheld
Computers
!Bidirectional EMI/RFI filtering and line termination
with integrated ESD protection
!ESD protection for USB power (VBUS) and data lines
(D+ & D-) to IEC 61000-4-2 Level 4
!Filtering and termination for two USB data lines
!Different series resistors for impedance matching
!Low TVS operating voltage (5.25V)
!Low leakage current
!Low capacitance
!Solid-state technology
!EIAJ SOT23-6L package
!Molding compound flammability rating: UL 94V-0
!Marking : Marking Code
!Packaging : Tape and Reel per EIA 481
S0T23-6L (Top View)
Circuit Diagram
.
22001 Semtech Corp. www.semtech.com
PROTECTION PRODUCTS
PROTECTION PRODUCTS
STF202-22 & STF202-30
Absolute Maximum Rating
Electrical Characteristics
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32001 Semtech Corp. www.semtech.com
PROTECTION PRODUCTS
PROTECTION PRODUCTS
STF202-22 & STF202-30
Typical Characteristics
ESD Clamping (8kV Contact) ESD Clamping (15kV Air)
Typical Insertion Loss
0.030MHz 2.0GHz
0 dB
-10 dB
-20 dB
Analog Crosstalk (D+ to D-)
0.030 MHz 1 GHz
0 dB
-20 dB
-60 dB
42001 Semtech Corp. www.semtech.com
PROTECTION PRODUCTS
PROTECTION PRODUCTS
STF202-22 & STF202-30
Figure 1 - STF202 Circuit Diagram
Device Connection
The STF202 is designed to provide termination, EMI
filtering and ESD protection for two USB I/O lines. The
equivalent circuit diagram is shown in Figure 1. The
device is connected as follows:
1.1.
1.1.
1. Full-Speed Devices: For full-speed devices the pull-
up resistor is connected to the D+ line. Pin 1 is
connected to the voltage supply line (VBUS). The
input of the D+ line is routed into pin 3 and out of
pin 4. The input of the D- line is connected at pin 2
and the output at pin 5. Pin 6 is connected to
ground.
2.2.
2.2.
2. Low-Speed Devices: For low speed devices the
pull-up resistor is connected to the D- line. Pins 1
is connected to the voltage supply line (VBUS). The
input of the D- line is connected at pin 3 with the
output taken at pin 4. The input of the D+ line is
connected to pin 2 and the output is at pin 5. Pin
6 is connected to ground.
USB Port Design Considerations
The Universal Serial Bus (USB) specification requires
termination and filtering components for proper opera-
tion. In addition, an open USB socket is vulnerable to
hazardous ESD discharges in excess of 15kV. These
discharges can may occur on the data lines or the
voltage bus. The STF202 is an easily implemented
solution designed to meet the termination & EMI filter
requirements of the USB specification revision 1.1. It
also provides ESD protection to IEC 61000-4-2, level
4.
A simplified USB port is shown in Figure 3. USB line
termination is achieved with series resistors on both
the D+ and D- lines. These resistors preserve signal
integrity by matching the cable impedance to that of
the differential driver. 15kΩ pull-down resistors are
used to identify a downstream port while an upstream
port is identified with a 1.5KΩ pull up resistor on either
the D+ (full speed devices) or the D- (low speed de-
vices) data line. Capacitors are used to bypass high
frequency energy to ground and for edge rate control
of the USB signals. TVS diodes are added for ESD
protection of both (D+ & D-) data lines and the voltage
bus (VBUS). A power distribution switch and voltage
regulator provide the power management functions of
the port.
Figure 2 - STF202 Connection Diagram
(Full Speed Devices)
Semtech provides a complete solution to simplify USB
port design (Figure 4). The STF201 & STF202 inte-
grate all of the components necessary for line termina-
tion, bidirectional EMI filtering, and ESD protection on
downstream (STF201) or upstream (STF202) ports.
The SC5826 is a dual port power switch that provides
individual or ganged port switching, fault reporting, and
inrush current limiting as required by the USB specifica-
tion. The SC5205 ULDO provides a stable voltage to
the USB controller.
Board Placement & Layout Guidelines.
Designing a USB hub to meet EMI & ESD immunity
requirements requires a combination of optimum
component placement, trace routing, and good circuit
design practices. Some general guidelines are given
below:
"Avoid running D+ & D- signal line traces near high
speed clock lines or similar signal lines.
"Avoid running critical signal lines near board edges.
"Locate the USB controller chip near the USB
connectors.
"Place the STF202 near the USB connector to
restrict transient coupling.
"Minimize the path length between the USB connec-
tor and the STF202
1
2
34
5
6
.
Applications Information
52001 Semtech Corp. www.semtech.com
PROTECTION PRODUCTS
PROTECTION PRODUCTS
STF202-22 & STF202-30
Figure 3 - USB Port Components
Figure 4 - Typical USB Hub Design
Applications Information
62001 Semtech Corp. www.semtech.com
PROTECTION PRODUCTS
PROTECTION PRODUCTS
STF202-22 & STF202-30
Outline Drawing - SOT23-6L
Land Pattern - SOT23-6L
72001 Semtech Corp. www.semtech.com
PROTECTION PRODUCTS
PROTECTION PRODUCTS
STF202-22 & STF202-30
Contact Information
Semtech Corporation
Protection Products Division
652 Mitchell Rd., Newbury Park, CA 9 1320
Phone: (805)498-2111 F AX (805)498-3804
Marking Codes
Ordering Information
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CT.22-202FTS22Ω000,3hcnI7
CT.03-202FTS03Ω000,3hcnI7
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22-202FTS222
03-202FTS032