QT4504 Optoisolator Equivalent & Substitute Parts

Part Overview

The QT4504 is a high-speed optoisolator with transistor output manufactured by QT Brightek. This 8-pin DIP component provides 5000Vrms isolation with 1 channel configuration, designed for DC input applications requiring galvanic isolation in industrial and consumer electronics. The part is currently in active production status with 1108 units in stock. Equivalent substitute parts are identified to support supply chain continuity, design flexibility, and regional availability requirements.

Substiute Parts

QT4504

QT Brightek (QTB)In Stock: 1160QT4504 Datasheet

Current PartRFQ

HCPL-4504#020

Broadcom LimitedIn Stock: 2158HCPL-4504#020 Datasheet

Parametric EquivalentRFQ

HCPL-4504-020E

Broadcom LimitedIn Stock: 2070HCPL-4504-020E Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the QT4504 optoisolator are qualified based on strict electrical and mechanical parameter matching. The following criteria determine substitution eligibility:

Critical Matching Parameters:

• Isolation voltage: 5000Vrms (exact match required)
• Number of channels: 1 (exact match required)
• Output type: Transistor (exact match required)
• Current transfer ratio range: 25% to 60% @ 16mA (exact match required)
• Maximum output voltage: 20V (exact match required)
• Output current per channel: 8mA (exact match required)
• Maximum forward current: 25mA (exact match required)
• Operating temperature range: -55°C to 100°C (exact match required)
• Package type: 8-DIP (0.300", 7.62mm) (exact match required)
• Mounting type: Through Hole (exact match required)
• Input type: DC (exact match required)

The substitute parts HCPL-4504#020 and HCPL-4504-020E, both manufactured by Broadcom Limited, meet all critical electrical and mechanical parameters. Minor variations in turn-on/turn-off timing and forward voltage fall within acceptable operational tolerances for this component category.

Parameter Comparison

Engineering Selection Recommendations

QT4504 (QT Brightek): Select this part for applications requiring ROHS3 compliance. The component is in active production with 1108 units currently in stock. Turn-on time of 240ns provides faster response characteristics compared to Broadcom equivalents.

HCPL-4504#020 (Broadcom Limited): This substitute is electrically equivalent with 2100 units in stock. Note that this variant is RoHS non-compliant. Use only in applications where RoHS compliance is not a regulatory requirement. Turn-off time of 300ns is 90ns slower than the QT4504.

HCPL-4504-020E (Broadcom Limited): This substitute is electrically equivalent and ROHS3 compliant, matching the regulatory status of the QT4504. Inventory of 1960 units is available. This variant is recommended as the primary substitute when QT4504 availability is constrained, as it maintains both electrical equivalence and compliance requirements.

All three parts share identical isolation voltage, channel configuration, output type, current transfer ratio specifications, maximum output voltage, output current rating, maximum forward current, operating temperature range, package type, and mounting type. Selection between parts should be based on compliance requirements, inventory availability, and timing specifications appropriate to the application.

Frequently Asked Questions (FAQ)

Q: Can HCPL-4504#020 be used as a direct replacement for QT4504 in a RoHS-compliant design?

A: No. HCPL-4504#020 is RoHS non-compliant. For RoHS-compliant applications, use HCPL-4504-020E, which carries ROHS3 certification matching the QT4504.

Q: What is the difference in switching speed between QT4504 and the Broadcom substitutes?

A: QT4504 has a turn-on time of 240ns and turn-off time of 210ns. Both Broadcom variants (HCPL-4504#020 and HCPL-4504-020E) have turn-on time of 200ns and turn-off time of 300ns. The QT4504 turns on 40ns faster; the Broadcom parts turn off 90ns slower. These differences are within typical application tolerances for optoisolator circuits.

Q: Are all three parts pin-compatible?

A: Yes. All three parts use the 8-DIP (0.300", 7.62mm) package with identical through-hole mounting. No PCB layout modifications are required for substitution.

Q: Do the forward voltage differences affect circuit design?

A: QT4504 has typical forward voltage of 1.45V; both Broadcom substitutes have 1.5V. This 0.05V difference is negligible in most DC input circuits and does not require design changes.

Q: Which substitute should be selected if both RoHS compliance and maximum inventory are priorities?

A: HCPL-4504-020E is the recommended choice. It is ROHS3 compliant and has 1960 units in stock, providing both regulatory compliance and adequate supply availability.

Q: Are there any moisture sensitivity concerns with these parts?

A: No. All three parts carry Moisture Sensitivity Level 1 (Unlimited), indicating no special moisture handling requirements during storage or assembly.

Q: Can these parts be used interchangeably in existing designs without circuit modification?

A: Yes, provided the application does not have critical timing requirements that depend on the specific turn-on or turn-off times. The electrical parameters, isolation voltage, output characteristics, and package compatibility are identical across all three parts.