TDA7256

Overview

The TDA7256 is a Class AB fully protected bridge power amplifier designed for car radio applications. It features a Multiwatt11 package with 11 pins and supports an operating supply voltage range of 8V to 18V. The device delivers up to 30W output power into a 2Ω load, 26W into 3.2Ω, and 22W into 4Ω at 1kHz with 10% distortion. Key electrical characteristics include a quiescent drain current of 80-150mA, input resistance of 50kΩ, common mode rejection of 60dB, and supply voltage rejection of 45-60dB. Thermal protection activates at a junction temperature of 145°C.

Feature Summary

• Differential inputs provide system immunity to common-mode noise during long wire connections.
• TTL-compatible mute circuit operates at the preamplifier level to ensure fully popless operation without changing DC voltage values.
• Programmable turn-on delay circuit keeps the output low during capacitor charge transients to prevent audible pops.
• Comprehensive short-circuit protections cover output-to-ground, output-to-Vs, and output-to-output conditions.

Applications

• Car radio amplifiers
• Booster systems
• Active loudspeaker applications

Procurement Notes

Verify component authenticity through authorized STMicroelectronics distributors or certified partners. Confirm the specific ordering suffix matches the required packaging configuration. Ensure thermal management solutions align with the specified junction-to-case thermal resistance limits. Review datasheet revisions for any updates to absolute maximum ratings or electrical characteristics before finalizing procurement orders.

Selection Notes

Select this component for high-current automotive audio designs requiring drive capability down to 2Ω loads. The differential input architecture is suitable for environments with significant electromagnetic interference. Evaluate the programmable turn-on delay requirements against the external capacitor values needed for the desired startup transient behavior. Ensure the Multiwatt11 package fits within the available chassis space and thermal dissipation constraints.

Part Context

The TDA7256 belongs to STMicroelectronics' dedicated automotive audio amplifier portfolio. It utilizes advanced BCD technology to integrate high-voltage power stages with low-voltage control logic on a single chip. This integration allows for compact designs with minimal external components while maintaining robust performance in harsh automotive electrical environments.

Replacement Considerations

Check for updated product line replacements such as the TDA7265 series. Verify pin compatibility and thermal performance metrics when substituting. Ensure that alternative devices maintain the same bridge configuration and short-circuit protection levels.

FAQ

How is the turn-on delay time determined?

The delay time is determined by the external capacitors C9, C10, and C11 connected to the standby pin, following the formula: To = 800 * C10 + 600 * (C9 + C11) * (C10 / (C9 + C11 + 1)).

What protects the amplifier from load dump voltage surges?

The device includes specific protection circuits designed to handle load dump voltage surges, preventing damage to the internal power stage during transient automotive electrical events.

Does the mute function cause audible popping?

No, the mute circuit acts at the preamplifier level and disables inputs without changing DC voltages. Combined with a soft reduction RC network, it ensures fully popless operation.