YDA137 View Datasheet(PDF) - Yamaha Corporation

Part Name

Description

View to exact match

YDA137

STEREO 5W DIGITAL AUDIO POWER AMPLIFIER

Yamaha Corporation 

YDA137

●Headphone Amplifier Function

Analog

Input

CI

Rsw=

400Ω

INL/R

RI

ENB

19.6kΩ

30kΩ

30kΩ

VREFL/R

VREFL/R

HPOL/R

Headphone Amplifier Circuit

When setting H to HP terminal, it enters headphone amplifier output mode. At this time, the digital amplifier enters the

Mute Mode.

Headphone amplifier section is comprised of the first stage operational amplifier and a class AB single-end output

amplifier.

In the first stage operational amplifier section, gain can be set by connecting an input resistor RI externally.

The latter stage is a high current output amplifier applicable to 16Ω load. VREF terminal voltage (vias) is applied to the

headphone amplifier output, so that connect the output to headphone through AC coupling capacitor, as shown in the

application circuit example.

Gain Setting

Gain of the first inverting amplifier can be calculated according to the following formula. In addition, class AB amplifier

gain is 0dB.

AVHP = 20×log10(19.6k / (RI + 400))

4.7kΩis selected as an input resistor RI, and total gain is set to 11.7dB.

In this setting, 150mVrms input can yield the maximum output of 20mW.

Relation between an external resistor value and output level in typical input sensitivity is shown in the table below.

Input Sensitivity

External input resistor RI

External feedback resistor RFB

for digital amplifier

Digital amplifier output (RL=3Ω)

Headphone amplifier output (RL=16Ω)

150mVrms

4.7kΩ

39kΩ

3.14Vrms (3.28W or so)

0.566Vrms (20.0mW)

1.0Vrms

33kΩ

39kΩ

2.98Vrms (2.96W or so)

0.586Vrms (21.4mW)

2.0Vrms

68kΩ

43kΩ

3.19Vrms (3.38W or so)

0.573Vrms (20.5mW)

A low cutoff frequency is found by the following formula with an AC coupling capacitor (CHO) and a load resistor (RHO)

of the headphone amplifier.

fCHP = 1 ／ (2×π×CHO×RHO) ：RHO＝load resistor

Headphone Amplifier Switching Function

By making up a headphone circuit as shown in the application circuit example, two modes can be switched automatically

according to the existence of headphone.

11

Share Link: