Optocoupler Datasheet: A1458

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. Current Transfer Ratio (CTR) CTR is the gain of an optocoupler: (I_C / I_F) * 100%. The A1458 offers multiple rank options:

Inside the package, pin 1 connects to the LED’s anode, pin 2 to its cathode. The phototransistor sits with its collector on pin 4 and emitter on pin 3. There is no base pin exposed; base current is generated solely by illumination. a1458 optocoupler datasheet

Many A1458 variants carry UL 1577, VDE 0884 (reinforced insulation), and CSA approvals. Always check the specific datasheet for regulatory marks if your design requires safety certification. Part 7: Typical Application Circuits (From Datasheet Examples) The A1458 optocoupler datasheet often includes reference circuits. Here are two common ones. Circuit 1: Digital Logic Isolation (High → Low) Scenario: Isolating a 24V PLC output to a 3.3V microcontroller input. Dark current doubles approximately every 10°C

Switching speed is heavily dependent on the load resistor (R_L). A smaller R_L reduces the time constant (R_L * C_CE) but also reduces output voltage swing. For higher speeds (>100 kHz), consider a phototransistor optocoupler with a base access pin or a digital optocoupler. Part 6: Isolation Characteristics The isolation barrier is the primary reason to use the A1458. The datasheet provides the following isolation parameters: The A1458 offers multiple rank options: Inside the

| Rank | CTR Min (%) | CTR Max (%) | Conditions | |------|-------------|-------------|-------------| | A | 50 | 150 | I_F = 5 mA, V_CE = 5V, Ta=25°C | | B | 80 | 240 | I_F = 5 mA, V_CE = 5V, Ta=25°C | | C | 130 | 400 | I_F = 5 mA, V_CE = 5V, Ta=25°C | | D | 200 | 600 | I_F = 5 mA, V_CE = 5V, Ta=25°C |

| Pin Number | Name | Description | |------------|-------------|------------------------------------| | 1 | Anode (A) | Positive terminal of the IR LED | | 2 | Cathode (C) | Negative terminal of the IR LED | | 3 | Emitter (E) | Output phototransistor emitter | | 4 | Collector (C)| Output phototransistor collector |

| Model | CTR (%) | V_CEO (V) | t_on/t_off (μs) | Isolation (Vrms) | Best For | |-------|---------|-----------|-----------------|------------------|-----------| | | 50-600 | 80 | 5/4 | 5,000 | General purpose, wide CTR | | PC817 | 50-600 | 35 | 4/3 | 5,000 | SMPS feedback (lower V_CEO) | | 4N35 | 100 (min) | 30 | 10/10 | 5,000 | Hobbyist, older designs | | 6N137 | - (logic) | 7 | 0.075 | 5,000 | High-speed data (10 Mbps) |