Daewoo DTR-14D3VG, Service Manual

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16
(4) Pin Description
No Name Description
1 SOUND IF INPUT The sound equivalent input impedance is 8k5 ohm // 5pF which has to be
taken into account for proper termination of the ceramic filters.
The DC impedance is very high.
The minimum input signal for catching is l mV rms.
2 EXT AUDIO INPUT An external sound signal (500mVrms) for example from SCART can be applied to this
pin via a coupling capacitor. The input has been made suitable to allow maximum
2Vrms. The input impedance is 25kohm.
3 VCO REF FILTER The IF VCO tuned circuit is applied to these pin.
4 Its resonance frequency must be two times the IF-frequency and in between a
range of 64-120MHz.
This range is suitable for the IF standards as 33.4, 38.9, 45.75 and 58.75MHz.
The VCO frequency can be adjusted by I
2 C bus so a fixed coil can be used.
5 PLL LOOP FILTER Standard loopfilter is : R=390
Ω
and c=100nF in series to ground. The loopfilter band-
width is 60kHz and is optimal for both fast catching and sufficient video suppression for
optimal sound performance.
The loopfilter time constant can be changed by I
2 C bus function FFI (Fast filter IF-PlLL).
When FFI=1, the PLL can better handle non-standard transmitter signals with large
phase modulation. The standard PLL loopfilter value can be left unchanged.
FFI=0 Normally selected or standard transmitter signals
FFI=1 Specially to handle non-standard transmitter signals with large phase
modulation. The function can be used for both positive and negative
modulated signals
6 IF VIDEO OUTPUT Although the video output impedance is low it is recommended to avoid high frequency
current in the output due to for instance sound trap filters.
This can be achieved by means of an emitter follower at the video output with a 1K
Ω
resistor in series with the base.
7 BUS INPUT : SCL Serial clock line
8 BUS INPUT : SDA Serial data line
9 BANDGAP The bandgap circuit provides a very stable and temperature independent
DECOUPLING reference voltage.
This reference voltage (6.7V) ensures optimal performance of the TDA8842
and is used in almost all functional circuit blocks.
10 CHROMA INPUT The supplied C S-VHS input burst amplitude should be nominally 300mV
PP
(assumed
is a colour bar signal with 75% saturation and with chroma/burst
ratio of 2.2/1 ). The C S-VHS input is internally clamped to 4V via 50K
Ω
.
The external AC coupling capacitor with 50K
Ω
forms a high pass filter. A recommended
coupling capacitor is 1 nF; the high pass filter cut off
frequency is then approximately 3KHz.
11 CVBS/Y INPUT The CVBS/Y signal of 1Vpp ( inclusive sync amplitude) is AC coupled to pin11.
12 SUPPLY The TDA884X has two supply pins 12 and 37. Both pins must be supplied simultane
37 ously. Notice that the IC has not been designed to use one of both pins as start pin.The
nominal supply voltage is 8V with min/max values of 7.2-8.8V. The current consumption
is about 60mA for each pin 12 and 37.
In stand-by condition the 8V IC-supply can be switched off as to safe energy. After
switching on the 8V again the normal start-up procedure must be followed.
A voltage detection circuit is connected to both pins.