Datasheet

Function Tables
Devices with Receiver/Driver Enable
(MAX3483/MAX3485/MAX3486/MAX3491)
Devices without Receiver/Driver Enable
(MAX3488/MAX3490)
Applications Information
The MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/
MAX3491 are low-power transceivers for RS-485 and
RS-422 communications. The MAX3483 and MAX3488
can transmit and receive at data rates up to 250kbps, the
MAX3486 at up to 2.5Mbps, and the MAX3485/MAX3490/
MAX3491 at up to 10Mbps. The MAX3488/MAX3490/
MAX3491 are full-duplex transceivers, while the MAX3483/
MAX3485/MAX3486 are half-duplex. Driver Enable (DE)
and Receiver Enable (RE) pins are included on the
MAX3483/MAX3485/MAX3486/MAX3491. When disabled,
the driver and receiver outputs are high impedance.
Reduced EMI and Reections
(MAX3483/MAX3486/MAX3488)
The MAX3483/MAX3488 are slew-rate limited, minimizing
EMI and reducing reflections caused by improperly
terminated cables. Figure 13 shows both the driver output
waveform of a MAX3485/MAX3490/MAX3491 transmitting
a 125kHz signal and the Fourier analysis of that wave-
form. High-frequency harmonics with large amplitudes are
evident. Figure 14 shows the same information, but for
the slew-rate-limited MAX3483/MAX3488 transmitting the
same signal. The high-frequency harmonics have much
lower amplitudes, and the potential for EMI is significantly
reduced.
Low-Power Shutdown Mode
(MAX3483/MAX3485/MAX3486/MAX3491)
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.
Figure 13. Driver Output Waveform and FFT Plot of MAX3485/
MAX3490/MAX3491 Transmitting a 125kHz Signal
Figure 14. Driver Output Waveform and FFT Plot of MAX3483/
MAX3488 Transmitting a 125kHz Signal
* B and A outputs are Z and Y, respectively, for full-duplex part
(MAX3491).
X = Don’t care; High-Z = High impedance
* DE is a “don’t care” (x) for the full-duplex part (MAX3491).
X = Don’t care; High-Z = High impedance
Table 1. Transmitting
Table 2. Receiving
Table 3. Transmitting Table 4. Receiving
INPUTS OUTPUTS
MODE
RE DE DI B* A*
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 OUTPUTS
MODE
RE DE A, B B*
0 0* ≥ +0.2V 1 Normal
0 0* ≤ -0.2V 0 Normal
0 0* Inputs Open 1 Normal
1 0 X High-Z Shutdown
INPUT OUTPUTS
DI Z Y
1 0 1
0 1 0
INPUTS OUTPUT
A, B RO
≥ +0.2V 1
≤ -0.2V 0
Inputs Open 1
5MHz500kHz/div0Hz
10dB/div
5MHz500kHz/div0Hz
10dB/div
MAX3483/MAX3485/
MAX3486/MAX3488/
MAX3490/MAX3491
3.3V-Powered, 10Mbps and Slew-Rate-Limited
True RS-485/RS-422 Transceivers
www.maximintegrated.com
Maxim Integrated │ 12