TS4871M/TR

The TS4871 is a 3W mono Class AB audio power amplifier. It operates over a voltage range of 1.9–5.5V in BTL bridge configuration. Powered by a 5V supply, it delivers an average output power of 3.0W into a 4Ω load with THD less than 10%. Typical shutdown current is less than 0.5μA. The device provides full-power, high-fidelity audio output with minimal external components, and requires no external coupling or bootstrap capacitors at the output. Available in SOP-8, MSOP-8, and DFN-8 packages to help minimize board area, it is well suited for mobile phones and a wide range of portable devices employing low-voltage, low-power solutions. Power dissipation is one of the key amplifier parameters. The maximum self-dissipation of a differential output amplifier is PDMAX = 4 × (VDD)² / (2 × π² × RL). Note that self-dissipation is a function of output power. During circuit design, ensure that the internal junction temperature does not exceed TJMAX (150℃), and design according to the chip's thermal resistance θJA. Thermal performance can be improved by adding heatsink copper pours. If this is still insufficient, the issue must be resolved by increasing the load resistance, reducing the supply voltage, or lowering the ambient temperature. In amplifier applications, power supply bypass design is critical for noise performance and power supply rejection. Bypass capacitors should be placed as close as possible to the supply pins of the chip. The typical configuration is a 10μF electrolytic capacitor in parallel with a 0.1μF ceramic capacitor. Another key capacitor in the application, CB (connected to the BYP pin), affects PSRR and switching/click-pop noise performance; a ceramic capacitor of 0.1μF–1μF is typically selected. To conserve power, the Shutdown pin can be used to control the operating state of the amplifier: a logic low puts the chip in normal operating mode; a logic high places the chip in shutdown mode, disabling the amplifier with no signal output to effectively reduce power consumption. If the pin is left floating, the chip enters an indeterminate state that not only fails to reduce power consumption but may also adversely affect the chip. Therefore, this pin must never be left floating during prolonged operation. Correct selection of external components is important for ensuring chip performance. The TS4871 is unity-gain stable with a wide range of applications. Unity-gain amplification is typically used to reduce THD+N and maximize SNR, but this requires maximizing the input voltage — codecs are typically capable of providing 1Vrms output voltage. In addition, closed-loop bandwidth must be ensured. The input coupling capacitor Ci forms a first-order high-pass filter that determines the low-frequency response. An excessively large input capacitor increases cost and board area, which is disadvantageous for cost- and space-sensitive applications. In practice, speakers in many applications cannot reproduce low-frequency audio below 100Hz–150Hz, so using a large capacitor does not improve system performance. Beyond system performance, switching/click-pop noise suppression is also affected by capacitor selection. A large coupling capacitor increases feedback network delay, which may cause pop noise; therefore, a smaller coupling capacitor helps reduce such noise. In addition, the value of CB must be considered — selecting CB = 1μF and Ci = 0.1μF–0.39μF can satisfy system performance requirements. Maximum power dissipation depends on three factors: TJMAX, TA, and θJA, calculated as PDMAX = (TJMAX - TA) / θJA. For the TS4871, TJMAX = 150℃. TA is the ambient temperature, and θJA depends on the package type.

Applications

• Mobile phones
• Amplifiers
• Bluetooth speakers
• Radios
• GPS

Key features

• Operating voltage: 1.9 - 5.5V
• Innovative "click and pop" suppression technology eliminates noise during power-up and power-down
• Output power up to 2.9W at 10% THD+N, VDD=5V, 4Ω load
• Output power up to 1.8W at 10% THD+N, VDD=5V, 8Ω load
• Shutdown current < 0.5μA
• Over-temperature protection
• Available in SOP-8, MSOP-8, and DFN-8 packages