_____________________Function Tables
Devices with Receiver/Driver Enable
(MAX3483E/MAX3485E/MAX3486E/MAX3491E)
Table 1. Transmitting
* B and A outputs are Z and Y, respectively, for full-duplex part
(MAX3491E).
X = Don’t care; High-Z = High impedance
Table 2. Receiving
* DE is a “don’t care” (x) for the full-duplex part (MAX3491E).
X = Don’t care; High-Z = High impedance
Devices without Receiver/Driver Enable
(MAX3488E/MAX3490E)
Table 3. Transmitting Table 4. Receiving
___________Applications Information
The MAX3483E/MAX3485E/MAX3486E/MAX3488E/
MAX3490E/MAX3491E are low-power transceivers for
RS-485 and RS-422 communications. The MAX3483E
and MAX3488E can transmit and receive at data rates
up to 250kbps, the MAX3486E at up to 2.5Mbps, and the
MAX3485E/MAX3490E/MAX3491E at up to 12Mbps. The
MAX3488E/MAX3490E/MAX3491E are full-duplex trans-
ceivers, while the MAX3483E/MAX3485E/MAX3486E are
half-duplex. Driver Enable (DE) and Receiver Enable
(RE) pins are included on the MAX3483E/MAX3485E/
MAX3486E/MAX3491E. When disabled, the driver and
receiver outputs are high impedance.
Reduced EMI and Reflections
(MAX3483E/MAX3486E/MAX3488E)
The MAX3483E/MAX3488E are slew-rate limited, mini-
mizing EMI and reducing reflections caused by improp-
erly terminated cables. Figure 13 shows the driver
output waveform of a MAX3485E/MAX3490E/MAX3491E
transmitting a 125kHz signal, as well as the Fourier
analysis of that waveform. High-frequency harmonics
with large amplitudes are evident. Figure 14 shows the
same information, but for the slew-rate-limited
MAX3483E/MAX3488E transmitting the same signal. The
high-frequency harmonics have much lower amplitudes,
and the potential for EMI is significantly reduced.
Low-Power Shutdown Mode
(MAX3483E/MAX3485E/MAX3486E/MAX3491E)
A low-power shutdown mode is initiated by bringing both
RE high and DE low. The devices will not shut down
unless both the driver and receiver are disabled (high
impedance). In shutdown, the devices typically draw
only 2nA of supply current.
For these devices, the t
PSH
and t
PSL
enable times
assume the part was in the low-power shutdown mode;
the t
PZH
and t
PZL
enable times assume the receiver or
driver was disabled, but the part was not shut down.
MAX3483E/MAX3485E/MAX3486E/MAX3488E/MAX3490E/MAX3491E
3.3V-Powered, ±15kV ESD-Protected, 12Mbps and
Slew-Rate-Limited True RS-485/RS-422 Transceivers
______________________________________________________________________________________ 11
INPUTS OUTPUTS
RE
DE DI B* A*
MODE
X 1 1 0 1 Normal
X 1 0 1 0 Normal
0 0 X High-Z High-Z Normal
1 0 X High-Z High-Z Shutdown
INPUTS
RE
DE A, B RO
MODE
0 0* ≥+0.2V 1 Normal
0 0* ≤-0.2V 0 Normal
0 0* Inputs Open 1 Normal
1 0 X High-Z Shutdown
OUTPUTS
INPUTS OUTPUT
A, B RO
≥+0.2V 1
≤-0.2V 0
Inputs Open 1
INPUT OUTPUTS
DI Z Y
1 0 1
0 1 0
