LM4780 L4780TA amplifier 2x60W 1x120W class AB 0.03% to 0.5% THD ZIP27

The LM4780 is an advanced high-power audio amplifier that can support a wide range of audio applications thanks to its versatility and robust protection. The chip delivers a continuous average power (RMS) of 60 watts per channel into an 8Ω load, making it ideal for applications requiring precise and clean sound. In bridge mode, when both channels are combined, its output power doubles to 120 W, allowing it to drive speakers with higher power requirements.

Thanks to its innovative SPiKe™ protection, the circuit is able to monitor temperature and voltage variations, automatically adjusting its operation to protect against overload, overvoltage, overload and short-circuit, as well as sudden temperature changes. Its power supply range is ±20V to ±42V, providing a wide range of application possibilities and allowing it to operate under a variety of power supply conditions. The chip also features very low harmonic distortion and noise (THD+N), which at 30W per channel and an 8Ω load is only 0.03% over the full 20 Hz - 20 kHz bandwidth.

In addition, the LM4780 features a high power supply noise rejection ratio (PSRR) of at least 85 dB, which improves noise immunity. The circuit is capable of operating with an input signal with a high rise factor (19 V/µs), allowing it to respond quickly to changes in the input signal, translating into precise and dynamic sound.

Electrical specifications :

Output power (RMS):

• 60 watts per channel into an 8Ω load, ±35 V supply voltage, and 0.5% THD+N (1 kHz)
• 120 watts in bridge mode into 8Ω load

Total harmonic distortion + noise (THD+N):

• 0.03% at 2 x 30 W and 8Ω load (20 Hz - 20 kHz)
• 0.05% into 2 x 30 W and 6Ω load
• 0.07% into 2 x 30 W into a 4Ω load

• Slew Rate (rise rate): 19 V/µs (typical)
• Signal-to-noise ratio (SNR): ≥97 dB at 1 W output power
• Power supply rejection ratio (PSRR): 85 dB minimum
• Open loop voltage gain (AVOL): 115 dB into a 2 kΩ load
• Resting current: 110 mA (typical), 170 mA (maximum)

Voltage range and limitations

Supply voltage:

• Maximum supply voltage without signal: 94 V (sum of positive and negative voltages) - supply voltage symmetrical + 0 -.
  
• Supply voltage with signal: ±20 V to ±42 V (sum of 84 V)
• Input differential voltage: 60 V maximum
• Maximum loss power: 125 W
• Operating temperature range: -20°C to +85°C

Protection functions

SPiKe™ (Self Peak Instantaneous Temperature): Protects against overload, overvoltage, overtemperature, underload, short circuit and sudden temperature spikes.
Under- and over-voltage protection: Allows the system to function properly at start-up and shut-down without output voltage spikes.
Thermal protection: The system shuts down when the temperature exceeds 150°C and automatically resumes operation when it drops below 145°C, acting as a Schmitt trigger in cycles to limit overheating.

Operating characteristics

• Mute Attenuation: 110 dB (typical)
• Channel separation: 70 dB at 1 kHz, 72 dB at 10 kHz
• Crosstalk (crosstalk between channels): low, dependent on PCB layout
• Input impedance: Typical values for resistance and input capacitors allow low-pass and high-pass responses to be tailored to the design.

Applications and configurations

• Stereo Mode: Standard configuration where the amplifier delivers 60 watts per channel.
• Bridge Mode: Increases the output voltage and produces higher power (120 W at 8Ω).
• Parallel mode (Parallel Mode): Allows increased output current, which is particularly useful at lower impedances (4Ω).

Installation and cooling recommendations

• Thermal resistance of the enclosure to ambient (θJA): 30°C/W
• Thermal resistance of connector to housing (θJC): 0.8°C/W
• Maximum connector temperature: 150°C
• Recommended heatsink: The circuit requires adequate cooling; it is recommended to use thermal conductive paste or a mica insulator and to attach the circuit to a heatsink.

Characteristics for different loads

Output power:

• 4Ω: up to 55 W at ±25 V supply
• 6Ω: up to 55 W at ±30 V
• 8Ω: up to 60 W at ±35 V