MAX3280E/MAX3281E/
MAX3283E/MAX3284E
1ꢀ5kVEꢁSD-PotectedVꢀ2Mbps,V3kVtoVꢀ.ꢀk,VꢁOT23
RꢁD48ꢀ/RꢁD422VTPueVFailDꢁafeVReceivePs
users design equipment that meets Level 3 of IEC 1000-
Table 1. MꢇX3281E/MꢇX3283E Enable
Table
4-2, without additional ESD-protection components.
The main difference between tests done using the
PꢇRT
MAX3281E
MAX3283E
ENꢇꢂLE = ꢁꢃꢈꢁ
Active
ENꢇꢂLE = LOW
High Z
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 4a),
the ESD-withstand voltage measured to this standard is
generally lower than that measured using the Human
Body Model. 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 charger probe. The Contact Discharge method
connects the probe to the device before the probe is
energized.
High Z
Active
LowDkoltageVLogicVLevelsV
(MAX3284EVonly)
An increasing number of applications now operate at
low-voltage logic levels. To enable compatibility with
these low-voltage logic level applications, such as digi-
tal FPGAs, the MAX3284E V pin is a user-defined sup-
L
ply voltage that designates the voltage threshold for a
logic high.
MachineVModel
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. All pins (not just the 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.
At lower V voltages, the data rate will also be lower. A
L
logic-high level of 1.65V will receive data at 20Mbps.
Table 2 gives data rates at various voltages at V .
L
Table 2. MꢇX3284E Data Rate Table
k
ꢄꢄ
= 3k TO ꢀ.ꢀk
k
MꢇXꢃMUM DꢇTꢇ RꢇTE
TPueVFailDꢁafeV
The MAX3280E/MAX3281E/MAX3283E/MAX3284E
guarantee a logic-high receiver output when the receiv-
er inputs are shorted or open, or when they are con-
nected to a terminated transmission line with all drivers
disabled. This guaranteed logic high is achieved by
setting the receiver threshold between -50mV and
-200mV. If the differential receiver input voltage
L
1.65V
2.2V
20Mbps
33Mbps
52Mbps
≥3.3V
ApplicationsVInfoPmation
(V - V ) is greater than or equal to -50mV, RO is logic
A
B
-PopagationVSelayVMatching
high. If (V - V ) is less than or equal to -200mV, RO is
A
B
The MAX3280E/MAX3281E/MAX3283E/MAX3284E
logic low.
(V
= V ) exhibit propagation delays that are closely
L
CC
In the case of a terminated bus with all transmitters dis-
abled, the receiver’s differential input voltage is pulled
to ground by the termination. This results in a logic high
with a 50mV minimum noise margin. Unlike previous
fail-safe devices, the -50mV to -200mV threshold com-
plies with the 200mV EIA/TIA-485 standard.
matched from one device to another, even between
devices from different production lots. This feature
allows multiple data lines to receive data and clock sig-
nals with minimal skew with respect to each other.
Figure 5 shows the typical propagation delays. Small
receiver skew times, the difference between the low-to-
high and high-to-low propagation delay, help maintain a
symmetrical ratio (50% duty cycle). The receiver skew
ReceivePVEnableV
(MAX3281EVandVMAX3283EVonly)
time | t
- t
| is under 2ns for either a 3.3V supply
PLH PHL
The MAX3281E and MAX3283E feature a receiver out-
put enable (EN, MAX3281E or EN, MAX3283E) input
that controls the receiver. The MAX3281E receiver
enable (EN) pin is active high, meaning the receiver
outputs are active when EN is high. The MAX3283E
receiver enable (EN) pin is active low. Receiver outputs
are high impedance when the MAX3281E’s EN pin is
low and when the MAX3283E’s EN pin is high.
or a 5V supply.
MultidPopVCloc5VSistPibution
Low package-to-package skew (8ns max) makes the
MAX3280E/MAX3281E/MAX3283E/MAX3284E
(V
CC
= V ) ideal for multidrop clock distribution. When
L
distributing a clock signal to multiple circuits over long
transmission lines, receivers in separate locations, and
possibly at two different temperatures, would ideally
6
Maxim Integrated
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