STF201-22.TCT Semtech, STF201-22.TCT Datasheet - Page 4

• Manufacturer Part Number: STF201-22.TCT
• Description: EMI FILTER/TVS DIODE, 5.25V, SOT-23
• Manufacturer: Semtech

Specifications of STF201-22.TCT

• Diode Type: Bidirectional TVS
• Operating Voltage: 5.25V
• Diode Case Style: SOT-23
• No. Of Pins: 6
• Junction Capacitance: 47pF
• Breakdown Voltage Min: 6V
• Capacitance, Cd: 47pF
• Breakdown Voltage Vbr: 6V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Device Connection
The STF201 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:
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 occur on the data lines or the voltage
bus. The STF201 is an easily implemented solution
designed to meet the termination & EMI filter require-
ments 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. 15k
used to identify a downstream port while an upstream
port is identified with a 1.5K
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 (V
regulator provide the power management functions of
the port.
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-
PROTECTION PRODUCTS
PROTECTION PRODUCTS
Applications Information
2004 Semtech Corp.
USB data lines are routed through the STF201 for
easy implementation and optimum pc board layout.
Pin 1 is connected to the voltage supply line. The
input of the D+ line is routed into pin 2 and out of
pin 5. The input of the D- line is connected at pin 3
and the output at pin 4. Pin 6 is connected to
ground. The ground connection should be made
directly to the ground plane for best results. The
path length is kept as short as possible to reduce
the effects of parasitic inductance in the board
traces.
BUS
). A power distribution switch and voltage
pull-down resistors are
pull up resistor on either
4
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.
Board layout and placement of the STF201 play a
critical role in EMI & ESD suppression. Designing a
USB hub to meet EMI & ESD immunity requirements
requires a combination of optimum component place-
ment, 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 physically near the
USB connectors.
Place the STF201 near the USB connector to
restrict transient coupling.
Minimize the path length between the USB connec-
tor and the STF201 as well as between the USB
controller and the STF201.
Figure 1 - STF201 Functional Circuit Diagram
Figure 2 - STF201 Connection Diagram
STF201-22 & STF201-30
1
2
3
6
5
4
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