Shenzhen Nsiway Tech NS4818

NS4818 is a filterless Class-G audio power amplifier with automatic gain control (AGC) and an integrated high-efficiency charge pump boost power supply. The device continuously monitors output power and adjusts the internal gain accordingly to prevent prolonged speaker overload. The integrated charge pump generates a 5.9V supply voltage for the amplifier output stage. With an 8Ω load under lithium battery supply conditions, it delivers a continuous output power of 1W (THD+N = 1%). The NS4818 achieves a peak efficiency of up to 81%, significantly extending battery life during music playback. The multi-level constant output power AGC technology helps designers select the appropriate power level to match different speakers. The NS4818 is available in a WLCSP package (1.63mm × 1.63mm). It is a high-efficiency Class-G audio amplifier with an integrated charge pump converter. The filterless modulation architecture reduces the number of external components and PCB area, thereby lowering overall system cost. When no input signal is present, both positive and negative outputs simultaneously produce a 50% duty cycle square wave in phase, which cancel each other out, resulting in no voltage across the speaker load and therefore no current through the load in idle state. When an input signal is present, the duty cycle changes: for a rising output voltage, the VOP duty cycle increases while the VON duty cycle decreases, and vice versa for a falling output voltage. The two unequal output square waves generate a differential output signal. The NS4818 is a fully differential amplifier with differential inputs and outputs; the differential output voltage equals the differential input voltage multiplied by the gain. The NS4818 can also be used with single-ended input, but in high-noise environments such as wireless intercoms, differential input ensures superior system noise rejection. The NS4818 incorporates a 1.5× charge pump converter, which boosts the supply voltage VDD to a higher voltage PVDD for powering the output stage. An overvoltage protection circuit is activated when PVDD exceeds 5.9V, protecting PVDD from exceeding the maximum allowable operating voltage. The NS4818 uses a single-wire pulse control scheme for operating mode selection; users can select the desired mode by applying pulse signals to the SHDN pin. The AGC function enables automatic gain adjustment of the amplifier through an internal PGA. The device continuously monitors the output and adjusts the gain in the amplifier signal path. This function detects audio volume information and prevents speaker overload. The gain varies with the audio signal in steps of 0.5dB voltage (1dB power), and remains stable when the signal amplitude is steady. Under sustained high-power operating conditions, the AGC function effectively extends speaker lifetime.

• Built-in AGC with 4-level constant output power control: 1.2W, 1W, 0.8W, 0.6W (8Ω)
• Built-in charge pump power system
• High efficiency: 81%
• Maximum output power P₀ = 2.3W (Rₗ = 8Ω, VDD = 4.2V, THD+N = 10%)
• Low THD+N = 0.013% (f = 1kHz, Rₗ = 8Ω, P₀ = 0.5W, VDD = 3.8V)
• Built-in thermal protection and overvoltage protection
• Built-in POP and CLICK noise suppression
• High RF interference immunity
• Single-wire pulse control
• WLCSP package (1.63mm * 1.63mm)

• Mobile phones and tablets
• Portable media players