Datasheet

MAX3160E/MAX3161E/MAX3162E
±15kV ESD-Protected, +3.0V to +5.5V, 10nA,
RS-232/RS-485/RS-422 Multiprotocol Transceivers
______________________________________________________________________________________ 17
Machine Model
The Machine Model for ESD testing uses a 200pF stor-
age 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.
Applications Information
Capacitor Selection
The capacitor type used for C1–C4 is not critical for
proper operation; polarized or nonpolarized capacitors
can be used. Ceramic chip capacitors with an X7R
dielectric provide the best combination of performance,
cost, and size. The charge pump requires 0.1µF
capacitors for 3.3V operation. For other supply volt-
ages, see Table 13 for required capacitor values. Do
not use values smaller than those listed in Table 13.
Increasing the capacitor values reduces ripple on the
transmitter outputs and slightly reduces power con-
sumption. C2, C3, and C4 can be changed without
changing C1’s value. However, do not increase C1
without also increasing the values of C2, C3, C4,
and C
BYPASS
to maintain the proper ratios to the
other capacitors.
When using the minimum required capacitor values,
make sure the capacitance value does not degrade
excessively with temperature or voltage. This is typical
of Y5V and Z5U dielectric ceramic capacitors. If in
doubt, use capacitors with a larger nominal value. The
capacitor’s equivalent series resistance (ESR), which
usually rises at low temperatures, influences the
amount of ripple on V+ and V-.
Power-Supply Decoupling
In applications that are sensitive to power-supply noise,
decouple V
CC
to ground with a capacitor of the same
value as reservoir capacitors C2, C3, and C4. Connect
the bypass capacitor as close to the IC as possible.
40µs/div
SHDN
5V/div
T1OUT
2V/div
GND
T2OUT
2V/div
Figure 12. RS-232 Transmitter Outputs when Exiting Shutdown
CHARGE-CURRENT
LIMIT RESISTOR
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
C
s
100pF
R
C
1MΩ
R
D
1.5kΩ
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
Figure 13a. Human Body ESD Test Model
I
P
100%
90%
36.8%
t
RL
TIME
t
DL
CURRENT WAVEFORM
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
I
r
10%
0
0
AMPERES
Figure 13b. Human Body Model Current Waveform