Daewoo DTR-14D3VG Service Manual page 18

(4) Pin Description
No Name
1 SOUND IF INPUT
2 EXT AUDIO INPUT
3 VCO REF FILTER
4
5 PLL LOOP FILTER
6 IF VIDEO OUTPUT
7 BUS INPUT : SCL
8 BUS INPUT : SDA
9 BANDGAP
DECOUPLING
10 CHROMA INPUT
11 CVBS/Y INPUT
12 SUPPLY
37
Description
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.
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.
The IF VCO tuned circuit is applied to these pin.
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
Standard loopfilter is : R=390Ω 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
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
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 1KΩ
resistor in series with the base.
Serial clock line
Serial data line
The bandgap circuit provides a very stable and temperature independent
reference voltage.
This reference voltage (6.7V) ensures optimal performance of the TDA8842
and is used in almost all functional circuit blocks.
The supplied C S-VHS input burst amplitude should be nominally 300mV
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 50KΩ.
The external AC coupling capacitor with 50KΩ forms a high pass filter. A recommended
coupling capacitor is 1 nF; the high pass filter cut off
frequency is then approximately 3KHz.
The CVBS/Y signal of 1Vpp ( inclusive sync amplitude) is AC coupled to pin11.
The TDA884X has two supply pins 12 and 37. Both pins must be supplied simultane
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.
16
2 C bus so a fixed coil can be used.
2 C bus function FFI (Fast filter IF-PlLL).
(assumed
PP