Skip to content

A1458 Optocoupler Datasheet ((hot)) -

The Complete Guide to the A1458 Optocoupler: Datasheet Breakdown, Applications, and Technical Analysis

3. Switching Characteristics (Typical at VCE = 5V, IC = 2mA)

| Parameter | Symbol | Typical Value | Unit | | :--- | :--- | :--- | :--- | | Rise Time | tr | 4 | µs | | Fall Time | tf | 3 | µs | | Turn-on Time | ton | 5 | µs | | Turn-off Time | toff | 4 | µs |

These values make the A1458 suitable for signals up to 100 kHz. For higher frequencies (e.g., >200 kHz), consider a high-speed optocoupler like the 6N137. a1458 optocoupler datasheet

Detailed A1458 Optocoupler Datasheet Analysis

To use any component effectively, you must understand its absolute maximum ratings and electrical characteristics. Below is a distilation of the official a1458 optocoupler datasheet. The Complete Guide to the A1458 Optocoupler: Datasheet

Common Applications

  1. Microcontroller I/O Isolation: Protecting a 5V MCU from 24V industrial inputs.
  2. AC/DC Power Supplies: Feedback loop isolation in flyback converters.
  3. Solid State Relays (SSR): Driving triacs or MOSFETs in AC switching.
  4. Signal Isolation: Isolating RS-232, RS-485, or CAN bus lines.
  5. Noise Suppression: Eliminating ground loops in audio or measurement systems.

Part 8: Layout and Design Guidelines

Based on recommendations in the A1458 optocoupler datasheet and industry best practices: Microcontroller I/O Isolation: Protecting a 5V MCU from

  1. Keep Input and Output Separate: Do not route high-voltage or noisy traces under the optocoupler. Maintain a physical and electrical gap.
  2. Creepage on PCB: On the PCB, ensure at least 4 mm clearance between input-side copper and output-side copper (more for >250V applications).
  3. Slotted PCB: For high isolation (>5kV), consider a slot in the PCB under the optocoupler.
  4. Bypass Capacitors: Place a 0.1 μF ceramic capacitor near the output VCC and ground (if using external pull-up) to reduce switching noise.
  5. Current Limit: Never drive the LED directly from a voltage source without a series resistor. A small change in voltage leads to a large change in current – potentially destructive.

Output (Phototransistor) Characteristics

| Parameter | Symbol | Conditions | Min | Typ | Max | Unit | |-----------|--------|-------------|-----|-----|-----|------| | Collector-Electron Breakdown | BV_CEO | I_C = 100 μA, I_F = 0 | 80 | - | - | V | | Emitter-Collector Breakdown | BV_ECO | I_E = 100 μA | 6 | - | - | V | | Dark Current (Leakage) | I_CEO | V_CE = 20V, I_F = 0, Ta=25°C | - | 10 | 100 | nA | | Dark Current at 100°C | I_CEO | V_CE = 20V, I_F = 0, Ta=100°C | - | 1 | 10 | μA |

Important: Dark current doubles approximately every 10°C. At high temperatures, it can become significant, so ensure your pull-up resistor and logic threshold account for this.