BU7831KN_10 Datasheet, PDF (8/17 Pages) Rohm – Voice/Audio Mixer & Selector IC

BU7831KN
Technical Note
・Analog output part
The following is about Analog output part (EXTO, SPL, SPR, HPL, HPR).
Each output amplifier is linked path select (MIXER1～5).
Because stereo output is presumed, HPL and HPR are turned ON/OFF at the same time, and with pop sound decrease
function.
MIXER1
At the time of path choice
SPL output amplifier ON
MIXER2
At the time of path choice
SPR output amplifier ON
MIXER3
At the time of path choice
EXTO output amplifier ON
MIXER4 or MIXER5 At the time of path choice
HPL, HPR output amplifier ON
Be careful that noise from the outside and so on doesn't turn because it becomes Hi-z though the output that isn’t used is
open and there is no problem. When it is anxious, pull-down in about 100kΩ.
Output Port
EXTO
SPL
SPR
HPL
HPR
Output impedance (DC)
At ON
1.4Ω
2.2Ω
1.5Ω
0.6Ω
Output impedance (DC)
At OFF
Hi-z
Hi-z
GND short
・Attenuator
Each attenuator has 16 steps (4bit), which contains mute. ATT6L and ATT6R that is attenuator of the headphone output
has soft mute that decreases pop sound in switching. (ATT1 - 5 don't have this function.)
The amount of software depends on a capacitor to connect to the CSTEP terminal. Decide the value of a capacitor to
connect to the CSTEP terminal after you take pop volume and delay time into consideration because a fixed number
becomes the bottom mostly at the time of that switching.
ATT setting
ATT
ATT
Mute
HP output
T hs mute
Thsmute
Thsmute=200×103×CSTEP [S]
Fig.24
・Analog path part
About the internal pass circuit, the circuit that it has a path setting by the register turns it on. For example, when
MIXSEL*_0 is chosen with either ATT, ST1R input is chosen, and a group of input amplifiers of ST1R turns it on. And a
connected output amplifier is turned on when either input is chosen with MIXSEL* in the same way to the output circuit.
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8/16
2010.09 - Rev.A