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AN4143
Application note
Demonstration board user guidelines for the low voltage high
bandwidth STG3220 dual SPDT switch
By Libor Ruzicka
Introduction
This application note concerns the STG3220 demonstration board, designed to show the
performance of the low-voltage high bandwidth STG3220 dual SPDT switch.
This document contains:
■
a brief description of the STG3220 device
■
a description of the demonstration board and all of its components
■
the layout of the demonstration board
About the STG3220 device
The STG3220 device is a high-speed CMOS low-voltage dual analog SPDT (single pole
dual throw) switch or 2:1 multiplexer/de-multiplexer switch fabricated in silicon gate C2MOS
technology. It is designed to operate from 1.65 to 4.3 V, making it ideal for portable
applications.
Key features of the STG3220 include
■
Ultra low power dissipation: ICC = 1 μA (max.) at TA = 85 °C
■
Low on-resistance:
– RON = 4.8 Ω (TA = 25 °C) at VCC = 4.3 V
– RON = 5.9 Ω (TA = 25 °C) at VCC = 3.0 V
■
Wide operating voltage range: VCC (oper.) = 1.65 V to 4.3 V
■
4.3 V tolerant and 1.8 V compatible threshold on digital control input
at VCC = 2.3 to 3.0 V
■
Typical bandwidth (-3 dB) at 800 MHz on all channels
■
USB (2.0) high speed (480 Mbps) signal switching compliance
■
Integrated fail safe function
■
Interrupt function to indicate to the processor that the device is in dedicated port charging
mode
■
Latch-up performance exceeds 500 mA per JESD78, Clas3s II
■
ESD performance exceeds JESD22:
– Dn pins: 4000 V human body model (A114-A)
– All other pins: 2000 V human body model (A114-A)
For further information on the STG3220 device, refer to the datasheet.
August 2012
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www.st.com
Description
1
AN4143
Description
The STG3220 demonstration board is designed for the low-voltage high bandwidth
STG3220 dual SPDT switch. The STG3220 device, in a tiny QFN package, is mounted on
a 4-layer PCB with impedance matched signal tracks. An easily accessible USB connector
on the board allows the board to be used as the USB switch and can be connected to
another USB port (PC host, USB hub, etc.). On the other side of the board there are two
USB receptacles and thanks to the STG3220 device, one of the USB receptacles is active
and connected to the USB port. The active (ON path) is chosen by the manual switch and it
is indicated by the luminous LED diode.
Table 1.
Main components and connectors
Designator
SW1
Description
USB path selector switch:
USB2 position: P0 - P2 USB path selected, D1 green LED diode is luminous
USB1 position: P0 - P1 USB path selected, D2 green LED diode is luminous
USB2
PO
P1, P2
D3
USB1
USB connector. Can be connected to USB port (PC, USB hub, etc.)
USB receptacle. USB port for USB device
The yellow LED diode is luminous if the host is in dedicated port charging mode. The
STG3220 device has a built-in dedicated port charging detection circuit to detect the
condition when the USB D+/D- lines are both in high state.
The demonstration board is powered through a USB connector P0, so that it is fully
functional if the P0 is properly connected to the USB port. For the STG3220 device, the USB
VBUS line voltage is decreased to 3.3 V and stabilized by the adjustable and fixed low drop
positive voltage regulator LD1117S33 (component U2).
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Description
Schematic diagram
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Description
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Table 2.
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Component list
Designator
Quantity
Description
P0
1
USB connector
P1, P2
2
USB receptacle
SW1
1
Dual SPDT switch
U1
1
STG3220
U2
1
LD1117S33
C1
1
100 nF/50 V, ceramic capacitor, 0603
C2
1
1 μF/50 V, ceramic capacitor, 0603
D1, D2
2
Green LED, 0805
D3
1
Yellow LED, 0805
R1, R2
2
330 Ω, resistor, 0603
R3
1
220 Ω, resistor, 0603
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Layout
Layout
Figure 2 to Figure 6 show the layers and the top view of the demonstration board.
Figure 2.
PCB top layer
Figure 3.
PCB mid1 layer (close to the top)
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Layout
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Figure 4.
PCB mid2 layer (close to the bottom)
Figure 5.
PCB bottom layer
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Layout
Figure 6.
Top view and dimensions
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Revision history
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Revision history
Table 3.
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Document revision history
Date
Revision
28-Aug-2012
1
Changes
Initial release.
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