Detailed Description
±15kV ESD Protection
As with all Maxim devices, ESD-protection structures
are incorporated on all pins to protect against electro-
static discharges (ESD) encountered during handling and
assembly. The MAX3095/MAX3096 receiver inputs have
extra protection against static electricity found in normal
operation. Maxim’s engineers developed state-of-the-art
structures to protect these pins against ±15kV ESD, with-
out damage. After an ESD event, the MAX3095/MAX3096
continue working without latchup.
ESD protection can be tested in several ways. The receiver
inputs are characterized for protection to the following:
1) ±15kV using the Human Body Model
2) ±8kV using the Contact-Discharge Method specified in
IEC 1000-4-2 (formerly IEC 801-2)
3) ±15kV using the Air-Gap Method specified in IEC
1000-4-2 (formerly IEC 801-2)
ESD Test Conditions
ESD performance depends on a number of conditions.
Contact Maxim for a reliability report that documents test
setup, methodology, and results.
Human Body Model
Figure 4a shows the Human Body Model, and Figure
4b shows the current waveform it generates when
discharged into a low impedance. This model consists of
a 100pF capacitor charged to the ESD voltage of interest,
which is then discharged into the device through a 1.5kΩ
resistor.
IEC 1000-4-2
Since January 1996, all equipment manufactured and/
or sold in the European community has been required to
meet the stringent IEC 1000-4-2 specification. The IEC
1000-4-2 standard covers ESD testing and performance
of finished equipment; it does not specifically refer to integrated
circuits. The MAX3095/MAX3096 help you design equipment
that meets Level 4 (the highest level) of IEC 1000-4-2,
without additional ESD-protection components.
The main difference between tests done using the Human
Body Model and IEC 1000-4-2 is higher peak current
in IEC 1000-4-2. Because series resistance is lower in
the IEC 1000-4-2 ESD test model (Figure 5a), the ESD-
withstand voltage measured to this standard is generally
lower than that measured using the Human Body Model.
Figure 5b shows the current waveform for the ±8kV IEC
1000-4-2 Level 4 ESD Contact-Discharge test. The Air-
Gap test involves approaching the device with a charge
probe. The Contact-Discharge method connects the
probe to the device before the probe is energized.
Machine Model
The Machine Model for ESD testing uses a 200pF storage
capacitor and zero-discharge resistance. It mimics the
stress caused by handling during manufacturing and
assembly. Of course, all pins (not just RS-485 inputs)
require this protection during manufacturing. Therefore,
the Machine Model is less relevant to the I/O ports than
are the Human Body Model and IEC 1000-4-2.
Low-Power Shutdown Mode
Table 1 shows the functionality of the enable inputs. The
MAX3095/MAX3096 enter shutdown when G is low and
G is high. In shutdown, all outputs go high impedance and
the devices typically draw less than 1nA. The devices exit
shutdown by taking G high or G low. The typical shutdown
exit time is 600ns.
Table 1. Function Table
X = don’t care, High-Z = high impedance
GG
(A - B)
OUTPUT
Y
DEVICE
MODE
1
X
≥ 200mV
1
On
1
X
≤ -200mV
0
On
1
X
Open
1
On
X
0
≥ 200mV
1
On
X
0
≤ -200mV
0
On
X
0
Open
1
On
0 1
X
High-Z Shutdown
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MAX3095/MAX3096 ±15kV ESD-Protected, 10Mbps, 3V/5V,
Quad RS-422/RS-485 Receivers