MAX485EESA Detailed explanation of pin function specifications and circuit principle instructions

The MAX485EESA is a product from Maxim Integrated (now part of Analog Devices). It is a low-power, differential bus transceiver designed for data communications in systems using the RS-485 standard.

The MAX485EESA is an 8-pin DIP (Dual In-line Package), and its detailed pinout and circuit principle are described below:

Pinout and Function of Each Pin (8 Pins):

Pin No. Pin Name Function 1 RO Receiver Output (Logic Output) 2 RE Receiver Enable (Active Low) 3 DE Driver Enable (Active High) 4 DI Driver Input (Logic Input) 5 A Non-inverting Bus (RS-485 A) 6 GND Ground (Reference Ground for the device) 7 B Inverting Bus (RS-485 B) 8 VCC Supply Voltage (typically 5V)

Detailed Description of Pin Functions:

RO (Receiver Output): This pin outputs the logic signal from the differential receiver. It drives the logic level based on the differential voltage between the A and B pins. The RO pin will output a logic high or low (0 or 1) based on the voltage difference on the RS-485 bus. RE (Receiver Enable): This pin controls the state of the receiver. When RE is low, the receiver is enabled, and data on the RS-485 bus is output on the RO pin. When RE is high, the receiver is disabled, and RO will not output any data. DE (Driver Enable): The DE pin controls the driver (transmitter) of the device. When DE is high, the driver is enabled, and the device can transmit data to the RS-485 bus. When DE is low, the driver is disabled, and the device will not transmit data. DI (Driver Input): The DI pin is the input to the driver (transmitter). Data received at this pin is sent onto the RS-485 bus when the DE pin is enabled (high). This is where the data for transmission is received. A (Non-inverting Bus): This pin is connected to the non-inverting side of the differential pair on the RS-485 bus. It is typically referred to as the A line. The voltage between A and B defines the data that is transmitted or received. GND (Ground): This is the ground connection of the MAX485EESA. It is the reference for the device’s power supply and signal levels. B (Inverting Bus): This pin is connected to the inverting side of the differential pair. This is referred to as the B line in RS-485 terminology. The differential voltage between the A and B pins determines the logic level. VCC (Supply Voltage): This is the power supply pin. The MAX485EESA typically operates with a VCC of 5V but can also work at a range of supply voltages from 3V to 5.5V.

Frequently Asked Questions (FAQs)

What is the operating voltage range for the MAX485EESA? The MAX485EESA operates with a voltage range of 3.0V to 5.5V. What type of data bus does the MAX485EESA use? It uses the RS-485 differential data bus for communication. What is the purpose of the RE pin? The RE pin enables or disables the receiver on the MAX485EESA. When RE is low, the receiver is active, and when RE is high, the receiver is disabled. Can the MAX485EESA be used for both transmitting and receiving data? Yes, it can both transmit and receive data on the RS-485 bus depending on the state of the DE and RE pins. What happens when the DE pin is set high? When the DE pin is high, the driver is enabled, allowing the MAX485EESA to transmit data onto the RS-485 bus. What happens when the RE pin is set high? When the RE pin is high, the receiver is disabled, and the RO pin will not output any data. What is the maximum data rate supported by the MAX485EESA? The MAX485EESA supports data rates up to 2.5Mbps. How does the MAX485EESA handle the RS-485 bus’s differential voltage? The MAX485EESA receives or transmits data based on the voltage difference between the A and B pins, where a voltage difference of more than 200mV determines the logic level. Is the MAX485EESA suitable for long-distance communication? Yes, RS-485 communication is designed for long-distance transmission, and the MAX485EESA can be used in networks up to 1200 meters with proper termination and biasing.

What is the difference between the A and B pins on the MAX485EESA?

The A pin is the non-inverting bus, while the B pin is the inverting bus. The data is interpreted based on the voltage difference between A and B.

Can the MAX485EESA operate on a 3.3V power supply?

Yes, the MAX485EESA can operate on a 3.3V supply, but the data rate may decrease at lower voltages.

Can multiple MAX485EESA devices be connected on the same bus?

Yes, multiple MAX485EESA devices can be connected to the same RS-485 bus, allowing for multi-point communication.

What is the function of the GND pin?

The GND pin is the ground reference for the device, ensuring proper voltage levels for both the transmitter and receiver.

How does the MAX485EESA handle noise on the RS-485 bus?

RS-485 is designed for differential signaling, which helps reduce the effects of common-mode noise. The MAX485EESA ensures reliable communication even in noisy environments.

Can the MAX485EESA be used in full-duplex communication?

No, the MAX485EESA is designed for half-duplex communication, meaning it cannot transmit and receive at the same time on the same bus.

How should the termination resistors be configured in an RS-485 network using MAX485EESA?

Termination resistors (typically 120 ohms) should be placed at both ends of the RS-485 bus to minimize signal reflections.

What is the typical power consumption of the MAX485EESA?

The typical power consumption is low, typically around 0.5mA when idle and around 120mA when actively driving the bus.

What is the maximum output drive capability of the MAX485EESA?

The MAX485EESA can drive the RS-485 bus with a differential output voltage of ±1.5V.

What kind of protection does the MAX485EESA have against voltage spikes?

The MAX485EESA has built-in protection against voltage spikes and can withstand short circuits and over-voltage conditions on the bus pins.

What is the default state of the receiver and transmitter when the MAX485EESA is powered on?

Upon power-up, the receiver is enabled, and the transmitter is disabled, assuming no external control of the RE and DE pins.

If you need further clarification or additional information, feel free to ask!