VOS617A-4T - 3750Vrms Phototransistor Optocoupler, SSOP-4 | Vishay
MPN: VOS617A-4T ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.85 | $0.85 |
| 10 | $0.74 | $7.40 |
| 100 | $0.58 | $58.00 |
| 500 | $0.46 | $230.00 |
| 1,000 | $0.38 | $380.00 |
| 3,000 | $0.31 | $930.00 |
VOS617A-4T Overview
A phototransistor optocoupler is a type of optoisolator that transfers electrical signals between two circuits using a light beam inside an electrically insulating package. The internal LED emits infrared light when forward-biased, and the phototransistor on the receiving side conducts proportionally to the received light intensity. This category belongs to the broader optocoupler / opto-isolator family, which itself sits within isolator ICs and discrete optoelectronic components used for safety isolation, ground-loop elimination, and high-voltage signal interfacing in industrial, medical, and switching power supply designs.
Key features include a low forward voltage of approximately 1.1 V at 10 mA, a collector-emitter voltage of 80 V, and a low coupling capacitance that preserves signal integrity in high-speed digital interfaces. The device supports an operating temperature range of -55 °C to +110 °C, enabling deployment in harsh industrial environments. With a low typical input current requirement and SSOP-4 footprint of approximately 4.4 mm x 3.85 mm, the VOS617A-4T enables compact PCB layouts where board real estate is at a premium.
The architecture combines a GaAs IR emitter with a silicon planar phototransistor detector in a half-pitch mini-flat package. Compared with DIP-4 optocouplers, the SSOP-4 form factor reduces board footprint by roughly 70%, while maintaining 3750 Vrms isolation - well above the requirements of most IEC 62368-1 reinforced insulation applications. The planar phototransistor process also gives lower dark current than conventional mesa phototransistors, improving noise immunity in low-signal designs.
Typical applications include digital logic interfacing between low-voltage microcontrollers and high-voltage industrial buses, isolated gate drive feedback in switch-mode power supplies, PLC input/output isolation modules, and AC line detection circuits. The wide CTR range and high isolation voltage also make it suitable for medical equipment requiring patient-applied circuit protection.
When designing with this device, place a bypass capacitor in parallel with the input LED to filter high-frequency noise, and verify that the CTR derating curve over temperature is acceptable for the minimum expected gain at the lowest operating temperature of your application. Also confirm that the load resistor value does not exceed the maximum collector current rating under worst-case CTR.
This page synthesizes Vishay datasheet parameters, distributor stock and pricing data, drop-in compatible alternatives, and practical design notes that extend beyond the manufacturer's datasheet presentation.
Drop-in alternatives for VOS617A-4T — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with VOS617A-4T (same form factor and footprint) — differing in Isolation Voltage, Mounting Type, Number of Channels, Output Type, Package.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
VOS617A-3T
✅ Drop-In📋 Reference alternative (not in catalog)
VOS617A-7T
✅ Drop-In📋 Reference alternative (not in catalog)
VOS617A-9T
✅ Drop-In📋 Reference alternative (not in catalog)
VOS617A-2T
✅ Drop-In📋 Reference alternative (not in catalog)
LTV-817S-TA1-C
✅ Drop-In✓ In Stock
$0.03 / Unit
View Datasheet →EL817S
✅ Drop-In📋 Reference alternative (not in catalog)
VOS617A-4T Maximum Ratings & Electrical Characteristics
| Isolation Voltage | 3750 Vrms |
| Output Type | Phototransistor (single channel) |
| Number of Channels | 1 |
| Current Transfer Ratio (CTR) | 160% to 320% (at IF = 5 mA, VCE = 5 V) |
| Forward Voltage (VF) typ. | 1.1 V (at IF = 10 mA) |
| Collector-Emitter Voltage (VCEO) max. | 80 V |
| Emitter-Collector Voltage (VECO) | 7 V |
| Collector Current (IC) max. | 50 mA |
| Operating Temperature Range | -55 °C to +110 °C |
| Package | SSOP-4 (50 mil lead pitch, mini-flat) |
| Lead Pitch | 1.27 mm (50 mil) |
| Input Type | DC (GaAs IR LED) |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant |
VOS617A-4T Pin Configuration
| Pin 1 | Anode — LED anode (input side, forward-biased to emit IR) |
| Pin 2 | Cathode — LED cathode (input side, connect to ground) |
| Pin 3 | Emitter — Phototransistor emitter (output side) |
| Pin 4 | Collector — Phototransistor collector (output side) |
Typical Applications
VOS617A-4T is suitable for 6 applications: Switch-Mode Power Supply Feedback Isolation, Industrial PLC Digital Input Isolation, AC Line Zero-Cross Detection, Medical Equipment Patient Isolation, Communication Interface Isolation (RS-232 / RS-485), Home Appliance Control Board Isolation.
Switch-Mode Power Supply Feedback Isolation
The VOS617A-4T is widely deployed as the primary-to-secondary feedback element in isolated AC-DC and DC-DC converters from 5W to 50W output. Its 160-320% CTR bin drives TL431 reference networks directly without an additional transistor stage, simplifying the optocoupler-to-TL431 feedback loop. The 80 V VCEO rating comfortably handles the swing seen across the opto-coupler collector in quasi-resonant and flyback topologies, while the 3750 Vrms isolation meets IEC 62368-1 reinforced insulation for consumer adapters and industrial auxiliary supplies.
Recommended
Industrial PLC Digital Input Isolation
In PLC digital input modules, the VOS617A-4T provides the required 3750 Vrms isolation between the 24V field wiring and the 3.3V/5V logic backplane. Its SSOP-4 footprint enables high channel density on the input card PCB, and the 160-320% CTR allows the input to work from the limited current available from 24V field sensors through current-limiting resistors. The -55 °C to +110 °C operating range covers the harsh industrial environment typical of factory automation cabinets.
Recommended
AC Line Zero-Cross Detection
The VOS617A-4T isolates low-voltage microcontrollers from 115V/230V AC mains when used in zero-cross detection circuits. The phototransistor output, biased through a high-value resistor from a DC rail, pulls low each time the AC input LED forward-biases. The 80 V VCEO easily tolerates the off-state voltage in 230V designs, while the 3750 Vrms isolation provides the safety barrier required by IEC 61010-1 for measurement and control equipment. CTR bin -4 (160-320%) ensures reliable switching even at low LED current.
Recommended
Medical Equipment Patient Isolation
Medical devices with patient-applied circuits require reinforced isolation between the patient connection and the mains-powered circuitry. The VOS617A-4T's 3750 Vrms isolation combined with its small SSOP-4 footprint supports compact patient monitor and diagnostic equipment designs. The phototransistor output provides a linear response suitable for low-frequency signal transmission such as ECG lead-off detection, while the GaAs LED and silicon phototransistor ensure long-term reliability in continuous-monitoring applications.
Recommended
Communication Interface Isolation (RS-232 / RS-485)
The VOS617A-4T isolates slow-speed control lines in communication interfaces such as RS-232 handshake signals or RS-485 direction-control lines in half-duplex transceivers. While its bandwidth is too low for the data lines themselves (which require digital isolators), it is ideal for isolating the flow-control and direction-control sideband signals. The 3750 Vrms isolation protects downstream MCUs from ground-potential differences between networked nodes.
Recommended
Home Appliance Control Board Isolation
In white goods such as washing machines, dishwashers, and induction cooktops, the VOS617A-4T isolates the low-voltage control MCU from the 230V AC power stage. Its compact SSOP-4 package supports the miniaturized PCB layouts common in modern appliance designs, and its -55 °C to +110 °C operating range covers the elevated temperatures found near motor drivers and IGBT modules. The 160-320% CTR bin provides reliable switching across the appliance's full input voltage tolerance.
Recommended
Recommended Products Summary
Engineering reference data for VOS617A-4T — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | VOS617A-3T | VOS617A-7T | LTV-817S | EL817S |
|---|---|---|---|---|---|
| Package | SSOP-4 (50 mil pitch, mini-flat) | SSOP-4 (50 mil pitch, mini-flat) - same | SSOP-4 (50 mil pitch, mini-flat) - same | SSOP-4 (4-pin mini-flat) - same | SSOP-4 (4-pin mini-flat) - same |
| Brand | Vishay Intertechnology | Vishay Intertechnology | Vishay Intertechnology | Lite-On | Everlight |
| Isolation Voltage | 3750 Vrms | 3750 Vrms | 3750 Vrms | 5000 Vrms | 5000 Vrms |
| CTR Range (at IF=5mA) | 160% to 320% | 100% to 200% | 80% to 160% | 50% to 600% | 50% to 600% |
| VCEO Maximum | 80 V | 80 V | 80 V | 35 V | 80 V |
| Collector Current Max | 50 mA | 50 mA | 50 mA | 50 mA | 50 mA |
| Operating Temperature | -55 °C to +110 °C | -55 °C to +110 °C | -55 °C to +110 °C | -30 °C to +110 °C | -55 °C to +110 °C |
| Forward Voltage (typ. at 10mA) | 1.1 V | 1.1 V | 1.1 V | 1.2 V | 1.2 V |
| Approx. Unit Price (qty 1000) | $0.38 USD | $0.38 USD | $0.38 USD | $0.18 USD | $0.20 USD |
Key Differentiators
- Higher CTR than lower-bin alternatives (vs VOS617A-7T)
- Compact SSOP-4 footprint versus DIP-4 alternatives (vs EL817 (DIP-4))
- 80V VCEO versus lower-rated cross-brand alternatives (vs LTV-817S)
- Wide operating temperature range (vs LTV-817S)
Design Notes
Drive the input LED with a current-limiting resistor sized for IF = 5 mA nominal. For a 5V logic-level drive, R = (5V - 1.1V) / 5mA = 780 ohm (use 680 ohm standard value). For 3.3V logic, R = (3.3V - 1.1V) / 5mA = 440 ohm. Include a 1kohm pull-up or pull-down on the phototransistor output to define the off-state. Worst-case power dissipation in the LED is 5mA * 1.1V = 5.5mW; collector power is 50mA * 80V = 4W theoretical max but typically limited to <50mW in switching applications.
The SSOP-4 mini-flat package has a theta_JA of approximately 250 °C/W (estimated: based on 4-pin SSOP land pattern with standard JEDEC test board). At 50 mA collector current with 30V VCE, internal power is 1.5W, which would push the junction temperature 375 °C above ambient - clearly above rating. Therefore, design for VCE * IC < 50 mW in continuous operation to keep self-heating under 12 °C above ambient. Higher dissipation requires active cooling or moving to a DIP-4 package.
Per IPC-7351 guidelines for SSOP-4 land pattern, use a 0.4 mm lead width pad with 1.27 mm pitch and 0.6 mm pad length. Maintain a 2 mm creepage clearance between the input (pins 1-2) and output (pins 3-4) sides of the device on the PCB surface to preserve the rated isolation voltage - reducing this below 1 mm can compromise the 3750 Vrms rating. Place a 100 nF Y-cap or X-cap-rated bypass capacitor on the input side if the LED is driven from a noisy switching node.
Do not assume CTR is constant over temperature. Per Vishay datasheet 83497, CTR drops approximately 20% when going from +25 °C to -25 °C, and continues to drop at lower temperatures. Design the optocoupler interface with the minimum CTR (lower bound of bin) at the minimum operating temperature, not at +25 °C. Also verify that the maximum CTR at high temperature does not saturate downstream circuitry (e.g., a TL431 reference has minimum cathode current requirements).
Compliance Information
RoHS and REACH compliant per Vishay product page. Not AEC-Q100 qualified (not applicable for optocouplers used in non-automotive applications). Halogen-free per Vishay optoelectronics product family policy.
