MAX481E/MAX483E/MAX485E/
MAX487E–MAX491E/MAX1487E
±±15kV ESD-Potected,VElewDRateDLimited,
LowD-oweP,VRED481/RED422VTPansceivePs
10dB/div
10dB/div
0Hz
5MHz
0Hz
5MHz
500kHz/div
500kHz/div
Figure 16. ꢂriver Output Waveform and FFT Plot of
MAX485E/MAX490E/MAX491E/MAX1487E Transmitting a
150ꢀHz Signal
Figure 17. ꢂriver Output Waveform and FFT Plot of
MAX483E/MAX487E–MAX489E Transmitting a 150ꢀHz Signal
The major difference between tests done using the
Human Body Model and IEC1000-4-2 is higher peaꢀ
current in IEC1000-4-2, because series resistance is
lower in the IEC1000-4-2 model. Hence, the ESꢂ with-
stand voltage measured to IEC1000-4-2 is generally
lower than that measured using the Human Body
Model. Figure 7 shows the current waveform for the 8ꢀk
IEC1000-4-2 ESꢂ contact-discharge test.
MAX483 /MAX487 /MAX488 /MAX489 :
ReducedV MIVandVReflections
The MAX483E and MAX487E–MAX489E are slew-rate
limited, minimizing EMI and reducing reflections
caused by improperly terminated cables. Figure 16
shows the driver output waveform and its Fourier analy-
sis of a 150ꢀHz signal transmitted by a MAX481E,
MAX485E, MAX490E, MAX491E, or MAX1487E. High-
frequency harmonics with large amplitudes are evident.
Figure 17 shows the same information displayed for a
MAX483E, MAX487E, MAX488E, or MAX489E transmit-
ting under the same conditions. Figure 17’s high-fre-
quency harmonics have much lower amplitudes, and
the potential for EMI is significantly reduced.
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.
Machine Moꢂel
The Machine Model for ESꢂ tests all pins using a
200pF storage capacitor and zero discharge resis-
tance. Its objective is to emulate the stress caused by
contact that occurs with handling and assembly during
manufacturing. Of course, all pins require this protec-
tion during manufacturing—not just inputs and outputs.
Therefore, after PC board assembly, the Machine Model
is less relevant to I/O ports.
LowD-owePVEhutdownVMode
(MAX48± /MAX483 /MAX487 )
A low-power shutdown mode is initiated by bringing
both RE high and ꢂE low. The devices will not shut
down unless both the driver and receiver are disabled.
In shutdown, the devices typically draw only 0.5µA of
supply current.
MAX487 /MAX±487 :
±28VTPansceivePsVonVtheVBus
RE and ꢂE may be driven simultaneously; the parts are
guaranteed not to enter shutdown if RE is high and ꢂE
is low for less than 50ns. If the inputs are in this state
for at least 600ns, the parts are guaranteed to enter
shutdown.
The 48ꢀΩ, 1/4-unit-load receiver input impedance of the
MAX487E and MAX1487E allows up to 128 transceivers
on a bus, compared to the 1-unit load ꢁ12ꢀΩ input
impedanceD of standard RS-485 drivers ꢁ32 transceivers
maximumD. Any combination of MAX487E/MAX1487E
and other RS-485 transceivers with a total of 32 unit
loads or less can be put on the bus. The MAX481E,
MAX483E, MAX485E, and MAX488E–MAX491E have
standard 12ꢀΩ receiver input impedance.
For the MAX481E, MAX483E, and MAX487E, the t
ZH
and t enable times assume the part was not in the
ZL
low-power shutdown state ꢁthe MAX485E, MAX488E–
MAX491E, and MAX1487E can not be shut downD. The
t
and t
enable times assume the
ZLꢁSHꢂND
ZHꢁSHꢂND
parts were shut down ꢁsee Electrical CharacteristicsD.
12
Maxim Integrated
ROCHESTER [ Rochester Electronics ]
