1. Overview

️· Function: The LTC1686 is a driver (transmitter) and the LTC1687 is a receiver (line receiver). They're designed to work together for data transmission over a single-wire line.
️· Key Features:
- Differential Signaling: Uses both A and B inputs for the receiver, providing noise immunity.
- Enable/Disable Functionality: Drivers can be enabled/disabled (DE). Receivers can be put into a high-impedance state (RE).
- Fault Detection: The LTC1687 has a fault condition, where an output current is forced if a fault is detected.

2. Pin Functions:

Let's condense the crucial pinouts:

️· LTC1686 (Driver):
- VDD: Positive supply (5V) – requires a 0.1µF bypass capacitor.
- D: Driver input – controls Y & Z outputs.
- GND: Ground
- Y: Non-inverting Driver Output.
- Z: Inverting Driver Output.
️· LTC1687 (Receiver):
- NC: No Connection (pins 1, 13).
- R: Receiver output.
- RE: Receiver Enable (low enables the receiver).
- D: Driver Input (for LTC1686 to control).
- GND: Ground
- Y: Noninverting Receiver Input.
- Z: Inverting Receiver Input.
- A: Non-inverting Receiver Input.
- B: Inverting Receiver Input.
- VDD: Positive supply (5V) – requires a 0.1µF bypass capacitor.

3. Truth Tables:

️· Transmitter Truth Table (LTC1686):
- When DE (Driver Enable) is high:
■ If D is high, Z is low and Y is high.
■ If D is low, Z is high and Y is low.
- When DE is low, the driver outputs are in a high-impedance state.
️· Receiver Truth Table (LTC1687):
- If A is greater than B by 300mV, R is high.
- If A is less than B by 300mV, R is low.
- If RE is high, the receiver output (R) is in a high-impedance state.
- If inputs A and B are shorted and voltages are between -7V and 12V, R will be high.

4. Test Circuits and Waveforms

️· Driver DC Test Load (Figures 1 & 2): Shows how to test the driver's DC characteristics.
️· Driver/Receiver Timing Test Circuit (Figure 3): Demonstrates how to test the timing of the driver and receiver.
️· Driver Enable/Disable Timing (Figure 6): Shows waveforms for the enable and disable times for the driver.
️· Receiver Enable/Disable Timing (Figure 8): Shows the waveforms for the receiver enable/disable.
️· Propagation Delays (Figure 3 & 7): Provides waveforms to understand propagation delays.

Key Takeaways:

️· Differential Pair: The data transmission is a differential signal - it uses both A/B on the receiver and Y/Z on the driver. This provides better noise immunity.
️· Enable Control: The ability to enable/disable the driver/receiver is important for power saving and system control.
️· Standard Operating Conditions: The IC operates at 5V.
️· Fault Indication: The receiver offers a fault-detection mechanism for indicating error conditions.