AN9799: Intersil RS-232 Transmitter/Receivers Provide High Speed and 15K.V ESD Protection

Intersil RS-232 Transmitter/Receivers Provide
High Speed and 15KV ESD Protection
®
Application Note
November 21, 2005
AN9799.2
Author: Gene Faherty
Introduction
EOS/ESD
The Intersil family of high-speed, 15kV ESD-protected
devices (HIN202E - HIN241E) offers the user unparalleled
performance in RS-232 communication. The devices feature
high speed (230kbits/s) ISDN-compatible operation together
with exceptional ±15kV ESD protection and offer a wide
variety of RS-232 transmitter/receiver combinations to suit
various applications.
ESD (Electrostatic Discharge) which is a subset of EOS
(Electrical Overstress), has become increasingly important
and of major concern to the electronics industry as a whole
and of particular importance to organizations such as
EOS/ESD Association which has attempted to standardize
this phenomena. Many manufacturers, realizing the
significance of EOS/ESD, specify ESD protection limits
when purchasing components. Virtually all electronic
components can be damaged due to EOS/ESD and the
costs associated with this damage has been estimated to be
in the billions of dollars, industry-wide. Compounding these
costs are the additional costs associated with the customer
perception of the product’s diminished quality and reliability.
The HIN202E - HIN241E interface circuits meet all EIA RS232E and V.28 specifications and are ideally suited to those
applications where ±12V supplies are not available. The
devices require a single 5V supply and incorporate on-chip
charge pumps and converter circuitry which derive the ±10V
levels. In addition, the HIN203E, HIN205E, HIN233E and
HIN235E require no external capacitors and are particularly
suited for those applications where board space is critical.
The HIN205E, HIN206E, HIN211E, HIN213E, HIN235E,
HIN236E and HIN241E feature a low power shutdown mode
and TTL three-state outputs. The typical current draw in the
low power shutdown mode is 1µA. The HIN213E also
provides two active receivers in shutdown mode allowing for
easy “wakeup” capability.
The family of HIN202E - HIN241E devices are designed to
be used in modems, printers, terminals, desktops, laptops,
notebooks, bar code scanners, portable instrumentation and
any system requiring RS-232 communication. Portable,
battery-powered, or handheld devices are inherently
susceptible to electrical stress such as ESD. Their I/O ports
conduct ESD noise which may likely zap a system unusable.
ESD-protected RS-232 serial ports in this equipment
eliminate the need for additional external protection in most
applications.
Evolution
With the “never ending” trend of shrinking technologies,
submicron CMOS processes, higher pin count devices,
higher operating frequencies and lower supply voltages, the
importance of robust ESD protection becomes even more
critical. With the smaller geometry devices comes reduced
gate oxide thickness, shallow junctions, and higher resistive
connections. These factors make these new devices
inherently more susceptible to ESD damage, compromising
the products reliability and performance.
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To define EOS, or Electrical Overstress, it is typically
generated by power supplies or test equipment and
generally lasts from milliseconds to seconds and often
results in a catastrophic failure. From an IC level, indications
of an EOS event are blown metal lines, molten damage, and
often, thermal damage. ESD or Electrostatic Discharge on
the other hand is a subset of EOS. ESD events are typically
characterized by much less power dissipation (limited
energy), events last for much shorter periods, in the range of
nanoseconds to milliseconds, and may result in catastrophic
failures but frequently result in performance degradation or
latent failures. Also, the cumulative effect of repeated
exposure can lead to complete failure. Typical indications of
ESD damage are gate oxide breakdown, junction spiking, or
input leakage failures. ESD events typically occur with
device handling by automated handlers or assembly. The
fundamental mechanism of ESD is called “tribocharging”.
Tribocharging occurs when different materials come in
contact with one another and then separate, such as the
sole of a person’s shoe as they walk across a carpet, or
when an IC rubs against a rail on an automatic handler. The
magnitude of the charge generated is dependent upon many
factors such as type of materials, speed at which they rub
together, and the relative humidity of the environment.
The extent to which a device can tolerate ESD is measured
in kV. The actual definitions of an ESD failures varies
among different vendors, some requiring complete
functional failure of the device. Intersil defines an ESD
failure in the strictest sense. After ESD “zapping” of the
device it is subject to full production testing and any part
failing to meet any of the DC parametric, AC propagation,
or functional testing to the data sheet specifications, is
rejected. Maintaining this strict level of testing assures the
user the most reliable devices possible.
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Copyright Intersil Americas Inc. 1999, 2005. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
Application Note 9799
ESD Testing
There are several test methods currently in use for ESD
testing. These methods are:
metal stop at the bottom. Standards that apply to the CDM are
the ESD Association Standard EOS/ESD-DS5.3-1993 and
JEDEC’s Test method C101.
• Human Body Model (HBM)
• Machine Model (MM)
2pF
• Charge Device Model (CDM)
VDC
• International Electromechanical Commission
(IEC61000-4-2 previously IEC801-X series)
The Human Body Model (HBM) essentially charges a 100pF
capacitor in increasing voltages in steps of 100V (100V,
200V, 300V, etc.) and then discharges the capacitor through
a 1500Ω resistor into the device pin. (Figure 1). This model
simulates that of a human finger contacting a device pin.
Specifications that apply to HBM testing are MIL-STD-883,
ESD Association Standard EOS/ESD-S5.1-1993 and
JEDEC’s Test method A114A.
1500Ω
VDC
+
-
100pF
DUT
FIGURE 1.
The next, Machine Model (MM), is similar to the HBM. The
MM charges a 200pF capacitor in increasing voltages in
steps of 100V and then discharges the capacitor directly into
the device pin. This model simulates a worst case HBM or
that of a charged metallic object contacting a device pin.
(Figure 2) Specifications that apply to the MM are ESD
Association Standard EOS/ESD-DS5.2-1992 and JEDEC’s
Test method A115A and EIAJ’s IC-121-1988 test Method 20.
VDC
+
-
200pF
DUT
FIGURE 2.
The Charged Device Model (CDM) directly charges the device
pin to increasing voltage levels through a 300MΩ or 1GΩ
resistor then discharges the pin, to ground, through 1Ω resistor.
(Figure 3) This model simulates a device pin acquiring a static
charge and then touching ground. This scenario has been
observed on lead trimming assemblies where the IC devices
run along a rail, developing a static charge, and then contacts a
2
+
-
DUT
1Ω
METAL PLATE
FIGURE 3.
Next is the International Electromechanical Commission
Human Body Model (IEC61000-4-2). The IEC61000 is
actually a system level specification but some customers
have been applying this standard to individual IC’s. The
IEC61000-4-2 again simulates that of a human finger. Two
modes are specified within the test. The Contact Mode and
the Air Discharge Mode. As its name implies, the contact
mode simulates actual contact made to device pin, whereas
in the air discharge mode, after charging, the device pin is
approached with a probe until arc occurs. With the air
discharge mode, the results are influenced by humidity,
temperature, barometric pressure and closure rate of probe.
The IEC standard is being applied to all systems and
equipment entering the market of the European Union (EU).
OEMs are playing it safe by using ESD-protected
components inside their systems although the standard is
not directed to individual integrated circuits (IC’s). Whole
systems are awarded the “CE” mark once they conform to
the EU directive on electromagnetic compatibility.
Benefits of HIN202E - HIN241E
The HIN202E - HIN241E series of devices offer the following
levels of ESD protection:
• Human Body Model . . . . . . . . . . . . . TOUT, RIN
±15kV
• IEC61000-4-2 Contact Discharge . . TOUT, RIN
±8kV
• IEC61000-4-2 Air Gap . . . . . . . . . . . TOUT, RIN
±15kV
• Human Body Model . . . . . . . . . . . . . TIN, ROUT
±2kV
Simply touching or plugging in a cable can result in an ESD
strike. Since the device I/O pins are most susceptible to an
ESD strike (the pins that route off the board) TOUT and RIN
are all protected to ±15kV HBM.
In addition to the robust ESD and inherent latch-up
protection provided by the HIN202E - HIN241E devices, is
the high data rate capability. The guaranteed data rate of
230kbits/s far exceeds the RS-232 requirement of
19.2kbits/s. These features together with the variety of
transmitter/receiver combinations, low power shutdown,
three-state mode, active receivers in shutdown, single 5V
supply, 0.1µF or no capacitor versions and a variety of
package options provide the user a total solution for their
RS-232 needs.
Application Note 9799
SUMMARY OF ESD PROTECTION LEVELS OF VARIOUS RS-232 INTERFACE FAMILIES
HBM
IEC61000-4-2
CONTACT DISCHARGE
IEC61000-4-2
AIR GAP
Intersil HIN202E-HIN241E
±15kv
±8kV
±15kV
Sipex SP200-SP213
±10kV
-
-
Maxim MAX202E-MAX213E
±15kv
±8kV
±15kV
Linear Technology LT1130A/LT1140A Series
±10kV
-
-
Maxim MAX202E-MAX213E
±15kv
±8kV
±15kV
All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems.
Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without
notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and
reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result
from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see www.intersil.com
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