TEA0679 NXP Semiconductors, TEA0679 Datasheet - Page 17

• Manufacturer Part Number: TEA0679
• Description: I2c-bus Controlled dual Dolby* B-type Noise Reduction Circuit for Playback Applications
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Soft head switching
In general the head switching procedure is recommended
to be performed in four steps:
1. Activate the mute function
2. Switch to the alternative head
3. Adjust the offset for the new head
4. Deactivate the mute function.
In applications without a mute function a soft head switch
via the I
connected to pin 18. A proposal for this switching
mechanism is shown in Fig.11. To guarantee the internal
timing for the head switching operation an externally
connected device to pin 18 should not modify the output
current significantly.
An additional resistor is necessary if the head switching is
performed externally via the optional switching input
capability at pin 18. A proposal for this kind of switching is
shown in Fig.12.
In general soft head switching is only suitable if equal
offset values for head 1 and head 2 exist. A soft offset
value switching is not possible with the TEA0679T.
1998 Nov 12
handbook, full pagewidth
I
reduction circuit for playback applications
V
2
C
C-bus controlled dual Dolby* B-type noise
; integration capacitor voltage: t
upper threshold
lower threshold
2
C-bus can be realized using a capacitor
OUTPUT
INPUT
V HIGH
V LOW
V C
t sw(P-M)
sw(P-M)
; switching time pause-to-music: t
Fig.10 Blank skip timing diagram.
t sw(M-P)
17
sw(M-P)
handbook, halfpage
handbook, halfpage
; switching time music-to-pause.
Fig.11 Soft head switching via the I
t sw(P-M)
Fig.12 External soft head switching.
IN1
8 k
IN2
10 F
10 F
pin 18
HS (optional)
pin 18
HS (optional)
MHB126
t sw(M-P)
Product specification
MHB127
TEA0679T
2
MHB125
C-bus.
t
t
t