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 Reflections

(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.

assume the part was in the low-power shutdown mode;

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

5MHz

500kHz/div

0Hz

10dB/div

5MHz

500kHz/div

0Hz

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