■ Overview
YDA137 (D-2) is a high efficient digital audio power amplifier IC that operates on a single 5V power supply. With YDA137 in BTL connection, an audio power amplifier with a maximum output of 5W (RL=2Ω )×2ch can be configured with one chip.
YDA137 converts an input analog data into a digital pulse by the digital modulation circuit in the IC and outputs a high current digital pulse from the output buffer circuit. This digital pulse signal is converted into an audio signal by an external low-pass filter and is output to the speaker. Low-distortion rate characteristics and high S/N ratio are realized as a digital amplifier among same class, by adopting Yamaha’s unique modulation system.
In addition, class AB headphone amplifier with output of 20mW (RL=16Ω )×2ch is embedded and switching between digital amplifier output and headphone amplifier output can be done by the control of terminal termination. YDA137 has the over-current protection function for speaker terminals, the high-temperature protection function for IC, and the pop noise rejection function.

■ Features
• High Output Power
   5.0 W ＠ VDD=5.0V, RL=2Ω , THD+N<10%
   3.7 W ＠ VDD=5.0V, RL=3Ω , THD+N<10%
   3.0 W ＠ VDD=5.0V, RL=4Ω , THD+N<10%
• High Efficient Operation
   75 % ＠ VDD=5.0V, RL=2Ω , Po=5W
   80 % ＠ VDD=5.0V, RL=3Ω , Po=3W
• Low Distortion Rate (THD+N)
   0.03 % ＠ 1kHz, RL=2Ω , Po=2.5W
   0.02 % ＠ 1kHz, RL=3Ω , Po=1.5W
• High S/N Ratio
   105dB ＠VDD=5.0V, input sensitivity 1.0Vrms, RL=2Ω , Po=5W
   98dB ＠VDD=5.0V, input sensitivity 150mVrms, RL=2Ω , Po=5W
• IC Low Consumption Current
   25 mA ＠ VDD=5.0V, no signal (no filter)
   10 mA ＠ VDD=5.0V, at mute
   1 µA ＠ VDD=5.0V, at sleep
• CS(Channel Separation)
   80dB ＠ 1kHz
• Class AB headphone amp. is embedded.
   20mW ＠ VDD=5.0V, RL=16Ω , THD+N<1.0%
• Arbitral gain setting with external resistor is possible.
• Sleep function by /SLEEP terminal
• Output mute function by /MUTE terminal
• Output Over-Current Protection Function (Ground short-circuit/Load short-circuit)
• Over-Temperature Protection Function
• Auto Resume Function from Over-Current, High-Temperature Protection.
• Monaural Function by /MONO terminal
• Pop Noise Rejection Function at power-up or power-cutoff.
• Analog input / BTL(Bridge-Tied Load) output
• 28pin plastic TSSOP
   pin lead plating with Pd-free (YDA137-AZ)