RENESAS RTKA788152DE0000BU 5V Half-Duplex RS-485 Transceivers Evaluation Board Instruction Manual
- June 4, 2024
- RENESAS
Table of Contents
RENESAS RTKA788152DE0000BU 5V Half-Duplex RS-485 Transceivers Evaluation
Board Instruction Manual
RTKA788152DE0000BU, the RS-485 evaluation board, allows you to evaluate the half-duplex transceivers of the RAA78815x family of RS-485 transceivers.
Specifications
- 4.5V to 5.5V Supply Voltage
- 115kbps Half-Duplex Transceiver RAA788152
Features
- Single 115kbps Half-Duplex Transceiver
- RAA788152 (115kbps version currently installed) can be unsoldered and replaced by RAA788155 (1Mbps version) or RAA788158 (20Mbps version)
- Place holders for fail-safe biasing resistors
- Configuration jumpers to operate the transceiver as transmitter or receiver, or as a transmitter with loopback
Figure 1. Block Diagram
1. Functional Description
Figure 2. Typical Operating Circuits of Half-Duplex and Full-Duplex Transceivers
1.1 Operational Characteristics
1.1.1 Driver Operation
A logic high at the driver enable pin (DE) activates the driver and causes the
differential driver outputs (Y and Z) to follow the logic states at the data
input (DI). A logic high at DI causes Y to turn high and Z to turn low. In
this case, the differential output voltage, defined as VOD = VY – VZ, is
positive. A logic low at DI reverses the output states reverse, turning Y low
and Z high, therefore, making VOD negative. A logic low at DE disables the
driver, making Y and Z high-impedance. In this condition, the logic state at
DI is irrelevant. To ensure the driver remains disabled after device power-up,
Renesas recommends connecting DE through a 1kΩ to 10kΩ pull-down resistor to
ground.
Table 1. Driver Truth Table
1.1.2 Receiver Operation
A logic low at the receiver enable pin (RE) activates the receiver and causes
its output (RO) to follow the bus voltage at the differential receiver inputs
(A and B); the bus voltage is defined as VAB = VA – VB. For VAB ≥ -0.05V, RO
turns high, and for VAB ≤ -0.2V, RO turns low. For input voltages between
-50mV and -200mV, the state of RO is undetermined, and therefore can be high
or low. A logic high at RE disables the receiver, making RO highimpedance. In
this condition, the polarity and magnitude of the input voltage is irrelevant.
To ensure the receiver
output remains high when the receiver is disabled, Renesas recommends
connecting RO, using a 1kΩ to 10kΩ pull-up resistor to VCC. To enable the
receiver to immediately monitor the bus traffic after device power- up,
connect RE through a 1kΩ to 10kΩ pull-down resistor to ground.
Table 2. Receiver Truth Table
1.2 Bus and Receiver Output Voltages
1.2.1 Set Up
Before connecting measurement equipment, set up the evaluation board and make
sure to remove the JP1 socket, which is a jumper connection between two output
channels A/Y and B/Z. Removal of JP1 socket allows for measurement of output
voltage across driver outputs. Follow the schematic diagram to enable driver
by placing sockets to connect DE_J positions 1 and 2. Enable the receiver by
placing the socket to connect RE#_J positions 7 and 8. Placing a socket
between positions 1 and 2 connects the Driver Enable function to VCC and
activates the
driver. Otherwise, placing a socket between positions 7 and 8 connects the
Receiver Enable function to ground, and because this function is inverted, the
receiver is activated. To ensure there is voltage across the bus, attach the
load resistor of 60Ω over the A/Y and B/Z channels. Without this resistive
load, the bus is an open circuit. Therefore, no voltage reading would be
across the bus.
Attach VCC to the power supply and set the voltage to 5VDC. Attach the Oscilloscope channel 1 and channel 2 probes to the A/Y and B/Z channels accordingly for bus voltage reading. For channel 3, attach to RO for receiver output voltage reading. Connect the pulse generator to driver input (DI) and set it up for square wave function.
Figure 3. Setup for Bus and Receiver Output Voltage Measurement with Oscilloscope, Power Supply, and Function Generator
1.2.2 Measurement Graphs
Figure 4. Driver Input Voltage vs Time
Figure 5. A/Y Channel Output Voltage vs Time
Figure 6. B/Z Channel Output Voltage vs Time
Figure 7. Bus Output Voltages vs Time
Figure 8. Receiver Output Voltage vs Time
Figure 9. Driver Input Voltage vs Receiver Output Voltage
Figure 10. Bus Output Voltage vs Receiver Output Voltage
2. Board Design
Figure 11. RTKA788152DE0000BU Evaluation Board (Top)
2.1 Schematic Diagrams
Figure 12. RTKA788152DE0000BU Schematic
2.2 Bill of Materials
2.3 Board Layout
Figure 15. Top Silkscreen
3. Ordering Information
4. Revision History
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References
- Renesas Electronics Corporation
- Distributor Network | Renesas Semiconductors | Renesas
- Renesas Electronics Corporation
- Distributor Network | Renesas Semiconductors | Renesas
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