ESD-CDE Circuit Protection for DisplayPort

Application Brief
4&.5&$)1305&$5*0/130%6$54
ESD/CDE Protection
For DisplayPort
Semtech’s RClamp®0524P Protects DisplayPort Interfaces from
ESD/CDE and Latchup without Loss of Signal Integrity
DisplayPort is an emerging high speed digital
video interface standard. It provides interconnect
between a Source (such as PC) and Sink (such as
monitor). As such, the DisplayPort plug is frequently
exposed to electrostatic discharge (ESD) directly
from the user or a cable discharge (CDE) event.
The DisplayPort Compliance Test Specification
(CTS) requires immunity to ESD set forth in IEC
61000-4-2. These stringent requirements can
not be met by on-chip ESD protection; therefore,
external off chip ESD protection circuitry is
necessary. DisplayPort supports two link rates of
2.7Gbps and 1.62Gbps. At such high data rates,
proper selection of a protection device is not trivial.
The chosen device needs to provide adequate
protection, as well as meet signal integrity and
impedance requirements.
Semtech’s RClamp0524P is designed specifically
to provide ESD protection in excess of IEC 61000-4-2
Level 4 ( ±15kV air, ±8kV contact). It exhibits superior
low clamping voltage characteristic. In event an
ESD strike, it limits the over-voltage stress across
the protected DisplayPort IC to a level well below
the destructive threshold, which increases the
system reliability.
Semtech’s RClamp0524P is a unique
offering for high speed interface protection.
It is designed specifically to provide ESD
protection in excess of IEC 61000-4-2 Level 4
( ±15kV air, ±8kV contact). With its industry
leading low capacitance of 0.3pF between
I/Os, the RClamp0524P can be used in circuits
operating in excess of 3GHz without PCB
trace compensation.
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RClamp®0524P for DisplayPort
The RClamp0524P has a typical capacitance value of
0.3pF between I/O pins. This minimizes its impact on
the high speed signal lines and enables it to be used
in circuits operating in excess of 3GHz without board
compensation. It has a flow through design which
allows the traces to run straight through the device,
thus reducing discontinuities as well as easing the
PCB layout design. To further facilitate the high speed
design, RClamp0524P is housed in a small leadless
package with a size of 2.5x1.0x0.58mm and a 0.5mm
pitch. Traces within a differential pair of the DisplayPort
connector can be routed tightly coupled at 0.5mm pitch
for good common mode rejection. Separate differential
pairs can be routed loosely coupled at 1.0mm pitch
between the pairs to reduce crosstalk. Figure 1
shows the application diagram of RClamp0524P for
DisplayPort.
Test Results and Recommendations
The low capacitance, clamping voltage, and operating
voltage of Semtech’s RClamp0524P, coupled with its
innovative package design, make it a superior protection
device for DisplayPort applications.
Semtech has produced 4-layer DisplayPort evaluation
boards, which can be used to evaluate RClamp0524P’s
ESD characteristics as well as TDR and Eye Pattern
performance. Figure 2 shows the TDR result on 4-layer
DisplayPort evaluation board. It has met, and is well
within, the DisplayPort CTS requirements (100 Ohm
±15% per differential pair). Figure 3 and Figure 4 show
the Eye Mask Testing results of a DisplayPort protected by
RClamp0524P at 1.62Gbps and 2.7Gbps, respectively.
In both cases, there is sufficient margin between the
eye diagram and the eye mask.
DISPLAY PORT
CONNECTOR
Ohm

Figure 1: Flow-through layout of Semtech RClamp0524P for DisplayPort Applications
W W W .SE MTE C H .C O M
RClamp®0524P for DisplayPort
A
B
A
B
X-axis
0.875
1.085
(nsec)
Y-axis
101
88
(Ohm)
Figure 2: RClamp0524P DisplayPort TDR Result
Figure 4: RClamp0524P DisplayPort Eye Mask Testing
Result (2.7Gbps)
Conclusion
DisplayPort system designers are faced with the challenging
task of providing reliable ESD protection while maintaining
signal integrity per DisplayPort CTS. Proper selection of
off-chip protection devices is crucial. The chosen device
must exhibit very low capacitance while keeping low
clamping voltage to maintain quality and reliability of the
protected IC. This will ensure that the DisplayPort IC will
not experience catastrophic or latent failure during a
transient threat.
Semtech’s RClamp0524P offers ultra low capacitance
and superior ESD and signal integrity performance.
It will ensure the compliance of a DisplayPort application
to DisplayPort CTS without the need for any further
board compensation.
Figure 3: RClamp0524P DisplayPort Eye Mask Testing
Result (1.62Gbps)
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Application Brief
Electrical Characteristics (T=25°)
Parameter
Symbol
Conditions
Minimum
Typical
Maximum
Units
Reverse Stand-Off Voltage
VRWM
Any I/O pin to ground
5
V
Reverse Breakdown Voltage
VBR
It=1mA
Any I/O pin to ground
Reverse Leakage Current
IR
VRWM=5V, T=25°C
Any I/O pin to ground
1
µA
Clamping Voltage
Vc
Ipp=1A, tp=8/20µs
Any I/O pin to ground
15
V
Junction Capacitance
Cj
VR=OV, f=1MHZ
Between I/O pins
0.4
pF
Junction Capacitance
Cj
VR=OV, f=1MHz
Any I/O pin to ground
0.8
pF
6
V
0.30
Outline Drawing – SLP2510P8
DIMENSIONS
INCHES
DIM
MIN NOM MAX
A
.020 .023 .026
A1 0.00 .001 .002
A2
(.005)
b
.006 .008 .010
b1 .014 .016 .018
D .094 .098 .102
E
.035 .039 .043
e
.020 BSC
L
.012 .015 .017
N
8
aaa
.003
bbb
.004
MILLIMETERS
MIN NOM MAX
.050 0.58 0.65
0.00 0.03 0.05
(0.13)
0.15 0.20 0.25
0.35 0.40 0.45
2.40 2.50 2.60
0.90 1.00 1.10
0.50 BSC
0.30 0.38 0.425
8
0.08
0.10
Notes:
1. Controlling dimensions are in millimeters
(Angles in degrees).
Land Pattern – SLP2510P8
DIM
C
G
P
P1
X
X1
Y
Y1
Z
DIMENSIONS
INCHES
MILLIMETERS
(0.875)
(.034)
0.20
.008
0.50
0.20
1.00
.039
0.20
.008
0.40
.016
0.675
.027
(1.55)
(.061)
1.55
.061
Notes:
1. Controlling dimensions are in millimeters
(Angles in degrees).
2. This land pattern is for reference
purposes only.
3. Consult your manufacturing group to
ensure your company’s manufacturing
guidelines are met.
Visit our website to locate the most current product specifications, datasheets and contact information for your local Semtech Field Applications Engineer.
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TVS-DP-APB-0208
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