Optical disc ICs Headphone amplifier with internal LPF and EVR for CD-ROM BH3540AFS The BH3540AFS is an H / P amplifier with internal secondary LPF and EVR circuits. When multibit output from a D / A converter is input, the secondary LPF outputs an audio signal. Output level for headphones can be changed with the EVR circuit. This IC also has independent internal mute circuits for the left and right channels. Applications CD-ROM drives and other products (with line and headphone output pins) that process digital audio signals Features 1) Internal LPF, line amplifier and EVR. 2) Internal mute function. 3) Internal thermal shutdown circuit. Block diagram 146 4) No attached oscillation prevention components are needed, even at a load of 8Ω. 5) Mute function reduces the popping noises that can occur when the power is turned on and off. Optical disc ICs FAbsolute maximum ratings (Ta = 25_C) BH3540AFS FRecommended operating conditions FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 5.0V, line RL1 = 50kΩ, H / P RL2 = 32Ω, VIN = 1.8dBV, f = 1kHz, EVR = Max.) 147 Optical disc ICs Measurment circuit 148 BH3540AFS Optical disc ICs BH3540AFS Application example 149 Optical disc ICs Operation notes (1) Preventing popping noises The BH3540AFS has a mute function that reduces the popping noises that can occur when the power is turned on or off. To further reduce these popping noises, attach a capacitor and resistor to the mute pin (pins 3 and 14). Electrical characteristic curves External dimensions (Units: mm) 150 BH3540AFS (2) Recommended time chart