ON CM1235-08DE Small footprint picoguard xsâ® esd clamp array for high speed data line protection Datasheet

Small Footprint PicoGuard XS® ESD Clamp
Array For High Speed Data Line Protection
CM1235
Features
•
•
•
•
•
•
•
•
ESD protection for 4 pairs of differential
channels
ESD protection to:
•
IEC61000-4-2 Level 4 (ESD) at ±8kV contact discharge
•
IEC61000-4-4 (EFT) 40A (5/50ns)
•
IEC61000-4-5 (Lighting) 3.5A (8/20µs)
Pass-through impedance matched clamp
architecture
Flow-through routing for high-speed signal integrity
Minimal line capacitance change with
temperature and voltage
100Ω matched impedance for each paired
differential channel
Each I/O pin can withstand over 1000 ESD
strikes*
RoHS compliant (lead-free), small footprint
4.0mm x 1.7mm TDFN-16 package
Applications
•
•
Product Description
The PicoGuard XS protection family is specifically
designed for next generation deep sub-micron high
speed data line protection.
The CM1235 is ideal for protecting systems with
high data and clock rates or for circuits requiring low
capacitive loading and tightly controlled signal
skews (with channel-to-channel matching at 2% max
deviation).
The device is particularly well-suited for protecting
systems using high-speed ports such as DisplayPort
or HDMI, along with corresponding ports in
removable storage, digital camcorders, DVD-RW
drives and other applications where extremely low
loading capacitance with ESD protection are
required.
The CM1235 also features easily routed "passthrough" pinouts in a RoHS compliant (lead-free),
4.0mm x 1.7mm, 16-lead TDFN, small footprint
package.
DVI, DisplayPort, and HDMI ports in notebooks,
set top boxes, digital TVs, LCD displays
General purpose high-speed data line ESD
protection
©2010 SCILLC. All rights reserved.
April 2010 – Rev. 3
Publication Order Number:
CM1235/D
CM1235
Block Diagram
*Standard test condition is IEC61000-4-2 level 4 test circuit with each pin subjected to ±8kV contact discharge for 1000 pulses. Discharges are timed at 1 second intervals and all 1000 strikes are completed in one continuous
test run. The part is then subjected to standard production test to verify that all of the tested parameters are within spec after the 1000 strikes.
PicoGuard XS ESD Protection Architecture
Conceptually, an ESD protection device performs the following actions upon an ESD strike discharge into a
protected ASIC (see Figure 1):
1. When an ESD potential is applied to the system under test (contact or air-discharge), Kirchoff’s Current Law
(KCL) dictates that the Electrical Overstress (EOS) currents will immediately divide throughout the circuit,
based on the dynamic impedance of each path.
2. Ideally, the classic shunt ESD clamp will switch within 1ns to a low-impedance path and return the majority of
the EOS current to the chassis shield/reference ground. In actuality, if the ESD component's response time
(tCLAMP) is slower than the ASIC it is protecting, or if the Dynamic Clamping Resistance (RDYN) is not significantly lower than the ASIC's I/O cell circuitry, then the ASIC will have to absorb a large amount of the EOS
energy, and be more likely to fail.
3. Subsequent to the ESD/EOS event, both devices must immediately return to their original specifications, and
be ready for an additional strike. Any deterioration in parasitics or clamping capability should be considered a
failure, since it can then affect signal integrity or subsequent protection capability. (This is known as "multistrike" capability.)
Rev. 3 | Page 2 of 14 | www.onsemi.com
CM1235
In the CM1235 PicoGuard XS architecture, the signal line leading the connector to the ASIC routes through the
CM1235 chip which provides 100Ω matched differential channel characteristic impedance that helps optimize
100Ω load impedance applications such as the HDMI high speed data lines.
Note:When each of the channels are used individually for single-ended signal lines protection, the individual
channel provides 50Ω characteristic impedance matching.
The load impedance matching feature of the CM1235 helps to simplify system designer’s PCB layout
considerations in impedance matching and also eliminates associated passive components.
The route through the PicoGuard XS architecture enables the CM1235 to provide matched impedance for the
signal path between the connector and the ASIC. Besides this function, this circuit arrangement also changes the
way the parasitic inductance interacts with the ESD protection circuit and helps reduce the IRESIDUAL current to the
ASIC.
Figure 1. Standard ESD Protection Device Block Diagram
Rev. 3 | Page 3 of 14 | www.onsemi.com
CM1235
The PicoGuard XS Architecture Advantages
Figure 2 illustrates a standard ESD protection device. The inductor element represents the parasitic inductance
arising from the bond wire and the PCB trace leading to the ESD protection diodes.
Figure 2. Standard ESD Protection Model
Figure 3 illustrates a standard ESD protection device. The inductor element represents the parasitic inductance
arising from the bond wire and the PCB trace leading to the ESD protection diodes.
Figure 3. CM1234 PicoGuard XS ESD Protection Model
Rev. 3 | Page 4 of 14 | www.onsemi.com
CM1235
CM1235 Inductor Elements
In the CM1235 PicoGuard XS architecture, the inductor elements and ESD protection diodes interact differently
compared to the standard ESD model.
In the standard ESD protection device model, the inductive element presents high impedance against high slew
rate strike voltage, i.e. during an ESD strike. The impedance increases the resistance of the conduction path
leading to the ESD protection element. This limits the speed that the ESD pulse can discharge through the ESD
protection element.
In the PicoGuard XS architecture, the inductive elements are in series to the conduction path leading to the
protected device. The elements actually help to limit the current and voltage striking the protected device.
First the reactance of the inductive element, L1, on the connector side when an ESD strike occurs, acts in the
opposite direction of the ESD striking current. This helps limit the peak striking voltage. Then the reactance of the
inductive element, L2, on the ASIC side forces this limited ESD strike current to be shunted through the ESD
protection diodes. At the same time, the voltage drop across both series element acts to lower the clamping
voltage at the protected device terminal.
Through this arrangement, the inductive elements also tune the impedance of the ESD protection element by
cancelling the capacitive load presented by the ESD diodes to the signal line. This improves the signal integrity
and makes the overall ESD protection device more transparent to the high bandwidth data signals passing
through the channel.
The innovative PicoGuard XS architecture turns the disadvantages of the parasitic inductive elements into useful
components that help to limit the ESD current strike to the protected device and also improves the signal integrity
of the system by balancing the capacitive loading effects of the ESD diodes. At the same time, this architecture
provides an impedance matched signal path for 50Ω loading applications.
Board designs can take advantage of precision internal component matching for improved signal integrity, which
is not otherwise possible with discrete components at the system level. This helps to simplify the PCB layout
considerations by the system designer and eliminates the associated passive components for load matching that
is normally required with standard ESD protection circuits.
Each ESD channel consists of a pair of diodes in series that steer the positive or negative ESD current pulse to
either the Zener diode or to ground. This embedded Zener diode also serves to eliminate the need for a separate
bypass capacitor to absorb positive ESD strikes to ground. The CM1235 protects against ESD pulses up to ±8kV
contact per the IEC 61000-4-2 standard.
Rev. 3 | Page 5 of 14 | www.onsemi.com
CM1235
PIN DESCRIPTIONS
Pin
Name
Description
1
2
In_1+
In_1-
Bidrectional Clamp to ASIC (inside system)
Bidrectional Clamp to ASIC (inside system)
3
4
In_2+
In_2-
Bidrectional Clamp to ASIC (inside system)
Bidrectional Clamp to ASIC (inside system)
5
6
In_3+
In_3-
Bidrectional Clamp to ASIC (inside system)
Bidrectional Clamp to ASIC (inside system)
7
8
In_4+
In_4-
Bidrectional Clamp to ASIC (inside system)
Bidrectional Clamp to ASIC (inside system)
9
10
Out_4Out_4+
Bidrectional Clamp to Connector (outside system)
Bidrectional Clamp to Connector (outside system)
11
12
Out_3Out_3+
Bidrectional Clamp to Connector (outside system)
Bidrectional Clamp to Connector (outside system)
13
14
Out_2Out_2+
Bidrectional Clamp to Connector (outside system)
Bidrectional Clamp to Connector (outside system)
15
16
Out_1Out_1+
Bidrectional Clamp to Connector (outside system)
Bidrectional Clamp to Connector (outside system)
PAD
GND
Ground return to shield
Rev. 3 | Page 6 of 14 | www.onsemi.com
CM1235
Ordering Information
PART NUMBERING INFORMATION
PIN
PACKAGE
ORDERING PART NUMBER
(LEAD-FREE FINISH)
PART MARKING
16
TDFN-16
CM1235-08DE
CM1235
Note 1: Parts are shipped in Tape & Reel form unless otherwise specified.
Specifications
ABSOLUTE MAXIMUM RATINGS*
PARAMETER
Operating Temperature Range
RATING
-40 to +85
UNITS
°C
Storage Temperature Range
Breakdown Voltage
(Positive)
-65 to +150
6
°C
V
*Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Rev. 3 | Page 7 of 14 | www.onsemi.com
CM1235
ELECTRICAL OPERATING CHARACTERISTICS
SYMBOL PARAMETER
CONDITIONS
VIN
I/O Voltage Relative to GND
IIN
Continuous Current through signal pins (IN
to OUT) 1000 Hr
IF
Channel Leakage Current
TA = 25°C; VIN = 5V
ESD Protection - Peak Discharge Voltage at
any channel input, in system:
Contact discharge per IEC 61000-4-2
Standard
TA = 25°C
VESD
TYP
MAX
UNITS
5.5
V
100
Residual ESD Peak Current on RDUP (Resistance of Device Under Protection)
IEC 61000-4-2 8kV;
RDUP = 5Ω TA = 25°C;
See Figure 6.
VCL
Channel Clamp Voltage
(Channel clamp voltage per IEC 61000-4-5
Standard)
Positive Transients
Negative Transients
IPP = 1A, TA = 25°C,
tP = 8/20µS
Dynamic Resistance
Positive Transients
Negative Transients
IPP = 1A, TA = 25ºC
tP = 8/20µS
ZTDR
Differential Impedance
TDR excursion from 100Ω
characteristic impedance transmission line;
TR = 200ps; Note 2
Zo
Differential Channels pair characteristic
impedance
TR = 200ps;
Note 2
Channel-to-Channel Impedance Match (Differential)
TR = 200ps; TA = 25ºC;
Note 2
∆Zo
MIN
-0.5
IRES
RDYN
(SEE NOTE 1)
±0.1
mA
±1.0
µA
kV
±8
3.0
A
+9.2
-1.6
V
V
0.6
0.5
Ω
Ω
87
103
Ω
100
Ω
2
%
Note 1: All parameters specified at TA = –40°C to +85°C unless otherwise noted.
Note 2: Impedance values for deviation from continuous 100Ω uncompensated differential microstrip, with typical layout as
measured. See Figure 7.
Rev. 3 | Page 8 of 14 | www.onsemi.com
CM1235
Performance Information
Graphical Comparison and Test Setup
Figure 4 shows that the CM1235 (PicoGuard XS ESD protector) lowers the peak voltage and clamping voltage by
45% across a wide range of loading conditions in comparison to a standard ESD protection device. Figure 5 also
indicates that the DUP/ASIC protected by the CM1235 dissipates less energy than a standard ESD protection
device. This data was derived using the test setups shown in Figure 6.
Figure 4. Normalized VPeak (8KV IEC-61000 4-2 ESD Contact Strike) vs. Loading (RDUP)*
Figure 5. Normalized Residual Current into DUP vs RDUP*
* RDUP is the emulated Dynamic Resistance (load) of the Device Under Protection (DUP).
Rev. 3 | Page 9 of 14 | www.onsemi.com
CM1235
Figure 6. Test Setups: Standard Device (Left) and CM1235 (Right)
Figure 7. Typical Channel TDR Measured Across Out_x and In_x Per Each Differential Channels Pair
(Typical 200ps Incident Rise Time)
Rev. 3 | Page 10 of 14 | www.onsemi.com
CM1235
CM1235 Application and Guidelines
As a general rule, the CM1235 ESD protection array should be located as close as possible to the point of entry
of expected electrostatic discharges with minimum PCB trace lengths to the ground planes and between the signal input and the ESD device to minimize stray series inductance.
Figure 8. Application of Positive ESD Pulse Between Input Channel and Ground
Figure 9. Typical PCB Layout
Additional Information
See also California Micro Devices Application Note AP209, “Design Considerations for ESD Protection,” in the
Applications section at www.calmicro.com.
Rev. 3 | Page 11 of 14 | www.onsemi.com
CM1235
Mechanical Details
TDFN-16 Mechanical Specifications, 0.5mm
The 16-lead, 1.7x4.0mm, 0.5mm pitch TDFN package dimensions are presented below.
PACKAGE DIMENSIONS
Package
TDFN
JEDEC
No.
MO-229C
Leads
16
*
Millimeters
Dim.
Inches
Min
Nom
Max
Min
Nom
Max
A
0.70
0.75
0.80
0.028
0.030
0.031
A1
0.00
0.02
0.05
0.000
0.001
0.002
A3
0.175
0.200
0.225
0.007
0.008
0.009
b
0.20
0.25
0.30
0.008
0.010
0.012
D
3.90
4.00
4.10
0.153
0.157
0.161
D2
3.15
3.20
3.25
0.124
0.126
0.128
E
1.60
1.70
1.80
0.063
0.067
0.071
E2
0.45
0.50
0.55
0.018
0.020
0.022
e
0.50 BSC
0.020 BSC
K
0.30 REF
0.012 REF
L
# per
tape and
reel
0.25
0.30
0.35
0.010
0.012
0.014
3000 pieces
Dimensions for 16-Lead, 0.5mm pitch
TDFN package
Controlling dimension: millimeters
*
This package is compliant with JEDEC standard MO-229C with
the exception of the D, D2, E, E2, K and L dimensions as called
out in the table above.
Rev. 3 | Page 12 of 14 | www.onsemi.com
CM1235
Tape and Reel Specifications
PART NUMBER
PACKAGE SIZE
(mm)
POCKET SIZE (mm)
B0 X A0 X K0
TAPE WIDTH
W
REEL
DIAMETER
QTY PER
REEL
P0
P1
CM1235
4.00 X 1.70 X 0.75
4.30 X 1.90 X 1.20
12mm
178mm (7")
3000
4mm
4mm
Rev. 3 | Page 13 of 14 | www.onsemi.com
CM1235
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Rev. 3 | Page 14 of 14 | www.onsemi.com
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