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1999 Apr 14 11
Philips Semiconductors Product specification
Audio processor with head amplifier for VHS hi-fi TDA9605H
Table 2 Selection of recording modes
6.4.3 R
ECORD MODE
The record mode is selected by setting bit AFM = 1 and
setting bits DOC, SHH and DETH from logic 001 to 111
and switching the RM control signal to LOW-level.
During the record mode actual recording is activated and
the recording current is output on pin RECOUT
(see Fig.6). Pins PBIN2 and PBIN1 form a connection to
the 5 V head amplifier supply voltage (V
CCH
). Pin HMSW
is internally connected to pin RECOUT and the external
capacitor has no function in this mode.
The desired carrier mix ratio is set via I
2
C-bus control
bits DOC, SHH and DETH. A wide selection of recording
currents is available to fit different head and head
transformer specifications and are set via bits HAC2,
HAC1, HAC0 and range bit HRL. The setting of the carrier
mix ratio does not change the selected recording current.
RM
SIGNAL
LEVEL ON
PIN RMHID
RECORD MODE
LOW lower than 2.35 V record or record-mute
mode as defined by
I
2
C-bus control
HIGH higher than 2.65 V record-mute mode
The DC bias current on pin RECOUT is changed
proportional to the selected recording current for
optimizing the performance and minimizing the power
consumption for each recording current selected.
A Boucherot damping circuit is connected between
pin HMSW and ground to prevent head current resonance
peaking. A capacitor of 10 nF and a resistor of 470 Ω are
specified in Fig.14, but the component values are not
critical.
6.4.4 H
EAD AMPLIFIER POWER SUPPLY AND GROUND
The head amplifier is supplied via a separate 5 V supply
(pin V
CCH
) and ground (pin GNDH).
A capacitor of 100 nF should be placed close to the device
between pins V
CCH
and GNDH for proper decoupling of
the power supply.
The head amplifier ground (pin GNDH) should be
connected to the main ground (pin GND).
Fig.6 Simplified circuit diagrams of the head amplifier modes.
handbook, full pagewidth
MGR841
35 kΩ
GNDH
GNDH
AH2
PBIN2
PBIN1
HMSW
RECOUT
AH1
35 kΩ
GNDH
TDA9605H
38
37
36
35
PBIN2
PBIN1
HMSW
RECOUT
38
37
36
35
5 Ω
GNDH
AH2
AH1
V
CCH
V
CCH
TDA9605H
a. Playback mode and record-mute mode. b. Record mode.