AN4138
Application note
HSP061-2 / HSP062-2 high speed line protection on HDMI 1.4 link
Introduction
This application note presents the HSP061-2 and HSP062-2 series and their capability to
protect HDMI 1.3 and HDMI 1.4 TMDS lines.
The HDMI interface is used for transmitting digital television audiovisual signals from DVD
players, set-top- boxes and other sources to television sets and other video displays.
The HSP series have been developed to be compliant with:
■
HDMI version 1.4 standard knowing the key point is the capability to transfer data with a
maximum rate of 3.4 Gbps per channel without distortion. This leads the HSP061-2 and
HSP062-2 to have a large bandwidth, to pass fast voltage slopes and to contain the 100
line impedance, HSP061-2 and HSP062-2 are used on the TMDS line.
IEC 61000-4-2 level 4 (8 kV contact discharge)
■
HSP061-2 and HSP062-2 series are composed of several packages and topologies (see
Chapter 1)
to better fit customer requirements in terms of PCB design.
HSP061-2 has the ground pin in the middle of the package and is proposed in:
■
■
■
SOT-666: HSP061-2P6
µQFN-6L: HSP061-2M6
µQFN-4L: HSP061-2N4
SOT-666: HSP062-2P6
µQFN-6L: HSP062-2M6
HSP062-2 has the ground pin on the side of the package and is proposed in:
■
■
All these devices are flow-through.
January 2013
Doc ID 023404 Rev 1
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HSP061-2 and HSP062-2 topology
AN4138
1
HSP061-2 and HSP062-2 topology
HSP061-2 series protects two high speed lines (see
Figure 1).
This is a flow-through
package to get an easy layout and to ensure the 100
differential impedance on HDMI
(Figure
2).
As PCB tracks are not cut, this offers the possibility to test a board with or without
protection depending on circuit portion to test.
The device is rated V
BR
min = 6 V @ 1 mA with a low typical leakage current of
0.1 nA @ 25 °C.
Figure 1.
HSP061-2 topology
HSP061-2M6
HSP061-2N4
Figure 2.
HSP061-2 footprint
HSP061-2P6
Via to
GND
Via to
GND
HSP061-2N4
HSP061-2P6
Via to
GND
HSP061-2M6
For further information refer to the product datasheet for HSP061-2.
HSP062-2 series uses the same technology as the HSP061-2.The only difference is
location the ground pin as shown in
Figure 3
and
Figure 4.
Figure 3.
HSP062-2 topology
HSP061-2P6
HSP061-2M6
Figure 4.
HSP062-2 footprint
HSP061-2M6
HSP061-2P6
Via to
GND
For further information refer to the product datasheet for HSP062-2.
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Characteristics related to HDMI 1.4
2
Characteristics related to HDMI 1.4
Protection bandwidth must be large enough to be transparent when a high bit rate is
transferred on the line. The equation below give the relationship between lines, pixels, color
depth and bit rate per channel:
⎛
Color_depth
⎞
10
Lane data rate = (H_total_pixels) × (V_total_lines) ×
⎜
⎜
× (Frame_rate) × 8
⎝
⎠
3
Table 1.
Sample characteristics
Frame
rate (Hz)
Color
depth
(bits)
24
30
HDMI
data rate
(Gbps)
4.46
5.57
6.68
8.91
Lane
data rate
(Gbps)
1.49
1.86
2.23
2.97
Horizontal Vertical
CEA video
Video format total pixel total lines
code
per line
per frame
16
1920 x 1080p
2200
1125
60
36
48
HDMI standard give a minimum rise time of 75 ps between 20% and 80%. Considering a
constant slope, this is equal to 100 ps between 10% and 90%.
In order to be transparent, the ESD protection must have a bandwidth in accordance with a
rise time of 100 ps.
Usually, the relations between bandwidth and rise time is defined by the following formula:
BW = 1 / (PI × tr)
tr = 100 ps gives a BW = 3.2 GHz.
Figure 5
shows the cut-off frequency of the HSP061-2N4 is 6 GHz which is high enough to
correctly manage HDMI signals.
Figure 5.
S21 attenuation measurement
0
-1
-2
-3
-4
-5
-6
-7
-8
-9
-10
300k
1M
3M
IO1
10M
30M
S21 (dB)
F (Hz)
100M 300M 1G
IO2
3G
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Characteristics related to HDMI 1.4
Figure 6.
Differential impedance
AN4138
Figure 6
shows the differential impedance measured with the “Time Domain Reflectometry”
method. This method consists of sending a pulse with a short rise time (200 ps between
10% and 90% for HDMI) and to measure the reflected pulse. This gives the impedance of
the line along the signal path.
The HDMI standard requires 100
±15% differential impedance (between 85
and
115
).
As shown
Figure 6,
TDR measurement on HSP062-2 gives an impedance between
91 and 100
.
These values are in accordance with the HDMI standard.
The eye diagrams defined in the HDMI standard are related to bit rate of the signal and to
location (source or sink). There are more constraints on the source side, this is why we have
chosen this one in the datasheet. The duration of the eye corresponds to a bit time. This
diagram visualizes signal duration, synchronization, overshoot and capability of the signal to
move from one state to another one. The key point for protection is to be sure there is no
slow down effect.
Figure 7
shows the eye diagram for a 3.4 Gbps signal. This measurement
is done directly on the HSP061-2 to avoid PCB measurement effects. Measurement shows
a large safety margin between the eye pattern and the signal.
Figure 7.
Eye diagram- HDMI mask at 3.4Gbps per channel (HSP061-2M6)
250 mV/div
250 mV/div
49 ps/div
49 ps/div
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Characteristics related to HDMI 1.4
The goal of a protection device is to protect against parasitic disturbances. HDMI 1.4
standard specifies a 8 kV contact discharge requirement according to IEC 61000-4-2. The
test must be performed 5 times with 1 second between each shot.
Figure 8
shows the ESD measurement when applied to HSP061-2M6. After a first short
spike at around 55 V, the clamping voltage is limited at around 30 V at 30 ns instead of 8 kV.
There is no ageing phenomenon and the protection remains efficient whatever the number
of surges. It is important to keep in mind most of the integrated circuits are ESD rated
between 500 V and 2 kV (Human body model) thanks to internal protection.It is important to
note IEC 61000-4-2 is much more severe than HBM, and for this reason it is mandatory to
add an external protection.
Figure 8.
IEC 61000-4-2 response
10V/Div
100ns/Div
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