3.0V, ±15kV ESD-Protected RS-232
Transceiver for PDAs and Cell Phones
V
L
Logic Supply Input
Unlike other RS-232 interface devices where the receiver
outputs swing between 0 and V
CC
, the MAX3386E fea-
tures a separate logic supply input (V
L
) that sets V
OH
for the receiver outputs and sets thresholds for the
receiver inputs. This feature allows a great deal of flexi-
bility in interfacing to many different types of systems
with different logic levels. Connect this input to the host
logic supply (1.8V
≤
V
L
≤
V
CC
). Also see the
Typical
PDA/Cell-Phone Application
section.
R
C
1M
CHARGE-CURRENT
LIMIT RESISTOR
HIGH-
VOLTAGE
DC
SOURCE
R
D
1500Ω
DISCHARGE
RESISTANCE
DEVICE
UNDER
TEST
MAX3386E
Cs
100pF
STORAGE
CAPACITOR
±15kV ESD Protection
As with all Maxim devices, ESD-protection structures are
incorporated on all pins to protect against electrostatic
discharges (ESDs) encountered during handling and
assembly. The MAX3386E’s driver outputs and receiver
inputs have extra protection against static electricity.
Maxim has developed state-of-the-art structures to pro-
tect these pins against an ESD of ±15kV without damage.
The ESD structures withstand high ESD in all states: nor-
mal operation, shutdown, and powered down. After an
ESD event, Maxim’s “E” version devices keep working
without latchup, whereas competing RS-232 products
can latch and must be powered down to remove latchup.
ESD protection can be tested in various ways. The trans-
mitter outputs and receiver inputs of this product family
are characterized for protection to the following limits:
1) ±15kV using the Human Body Model
2) ±8kV using the Contact Discharge method specified
in IEC 1000-4-2
3) ±15kV using IEC 1000-4-2’s Air-Gap Discharge
method
Figure 3a. Human Body ESD Test Model
I
P
100%
90%
AMPERES
36.8%
10%
0
0
t
RL
TIME
Ir
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
t
DL
CURRENT WAVEFORM
ESD Test Conditions
ESD performance depends on a variety of conditions.
Contact Maxim for a reliability report that documents
test setup, methodology, and results.
Figure 3b. Human Body Current Waveform
Human Body Model
Figure 3a shows the Human Body Model, and Figure 3b
shows the current waveform it generates when dis-
charged into a low impedance. This model consists of
a 100pF capacitor charged to the ESD voltage of interest,
which is then discharged into the test device through a
1.5kΩ resistor.
IEC 1000-4-2
The IEC 1000-4-2 standard covers ESD testing and
performance of finished equipment; it does not specifi-
cally refer to ICs. The MAX3386E helps you design
equipment that meets Level 4 (the highest level) of IEC
1000-4-2, without the need for additional ESD-protection
components.
The major 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 model. Hence, the ESD with-
stand voltage measured to IEC 1000-4-2 is generally
lower than that measured using the Human Body
Model. Figure 4a shows the IEC 1000-4-2 model, and
Figure 4b 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
charged probe. The contact-discharge method connects
the probe to the device before the probe is energized.
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7
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