Philips TDA4670 Datasheet

INTEGRATED CIRCUITS

DATA SH EET

TDA4670

Picture Signal Improvement (PSI) circuit

Product speciﬁcation Supersedes data of May 1991 File under Integrated Circuits, IC02

1996 Dec 11

Philips Semiconductors Product speciﬁcation

Picture Signal Improvement (PSI) circuit TDA4670

FEATURES

• Luminance signal delay from 20 to 1100 ns (minimum step 45 ns)

• Luminance signal peaking with selectable symmetrical overshoots

• 2.6 or 5 MHz peaking centre frequency and selectable degree of peaking (−3, 0, +3 and +6 dB)

• Selectable noise reduction by coring

• Handles negative and positive colour-difference signals

• Selectable Colour Transient Improvement (CTI) to

decrease the colour-difference signal transient times to those of the high frequency luminance signals

• Selectable 5 or 12 V sandcastle input voltage

• All controls selected via the I

C-bus

• Timing pulse generation for clamping and delay time control synchronized by sandcastle pulse

• Automatic luminance signal delay correction using a control loop

• Luminance and colour-difference input signal clamping with coupling capacitor

• 4.5 to 8.8 V supply voltage range

• Minimum of external components required.

GENERAL DESCRIPTION

The TDA4670 delays the luminance signal and improves colour-difference signal transients. Additionally, the luminance signal can be improved by peaking and noise reduction (coring).

QUICK REFERENCE DATA

SYMBOL PARAMETER MIN. TYP. MAX. UNIT

P(tot)

d(Y)

i(VBS)

i(CD)(p-p)

supply voltage (pins 1 and 5) 4.5 5 8.8 V total supply current 31 41 52 mA Y signal delay time 20 − 1130 ns composite Y input signal (peak-to-peak value, pin 16) − 450 640 mV colour-difference input signal (peak-to-peak value)

±(R − Y) on pin 3 − 1.05 1.48 V ±(R − Y) on pin 7 − 1.33 1.88 V

amb

gain of Y channel −−1−dB gain of colour-difference channel − 0 − dB operating ambient temperature 0 − 70 °C

ORDERING INFORMATION

TYPE

NUMBER

NAME DESCRIPTION VERSION

PACKAGE

TDA4670 DIP18 plastic dual in-line package; 18 leads (300 mil) SOT102-1

1996 Dec 11 2

Philips Semiconductors Product speciﬁcation

Picture Signal Improvement (PSI) circuit TDA4670

BLOCK DIAGRAM

100 nF

= 5 to 8 V

SCL

ref

GENERATION

degree of

peaking

peaking

frequency

coring

on/off

ref

CORING

−0.5

5 MHz

90

2.6 MHz

100

CORING

−0.5

5 MHz

C-BUS

2.6 MHz

PEAKING

C-BUS

BLACK

LEVEL

100

CLAMP

TDA4670

analog switch

capacitors

comparator

−(B − Y) 6

MSA557

analog switch

= 5 to 8 V

−(R − Y) 4

storage

C-BUS

9 10

SDA

100 nF

sandcastle

pulse

CTI

on/off

C-BUS RECEIVER

ref

5 V/12 V

sandcastle

Y delay

ref

CONTROL

DELAY TIME

C-BUS

BK, H + V

DETECTOR

SANDCASTLE PULSE

100

ref

CLAMP

BLACK LEVEL

control signal

90

45

90

180

LEVEL

BLACK

180

450

CLAMP

FILTER

HIGH-PASS

8 18 5

handbook, full pagewidth

Fig.1 Block diagram.

RECTIFIER

FULL-WAVE

ref

CLAMP

BLACK LEVEL

ref

RECTIFIER

FULL-WAVE

DIFFERENTIATOR

BLACK LEVEL

CLAMP

ref

100 nF

1996 Dec 11 3

100 nF13100 nF

−(R − Y)

10 nF

−(B − Y)

Philips Semiconductors Product speciﬁcation

Picture Signal Improvement (PSI) circuit TDA4670

PINNING

SYMBOL PIN DESCRIPTION

i(R − Y)

o(R − Y)

o(B − Y)

i(B − Y)

GND2 8 ground 2 (0 V) SDA 9 I SCL 10 I C

COR

CLP1

CLP2

ref

SAND 17 sandcastle pulse input GND1 18 ground 1 (0 V)

1 positive supply voltage 1 2 capacitor of delay time control 3 ±(R − Y) colour-difference input signal 4 ±(R − Y) colour-difference output

signal 5 positive supply voltage 2 6 ±(B − Y) colour-difference output

signal 7 ±(B − Y) colour-difference input signal

C-bus serial data input/output

C-bus serial clock input 11 coring capacitor 12 delayed luminance output signal 13 black level clamping capacitor 1 14 black level clamping capacitor 2 15 capacitor of reference voltage 16 luminance input signal

handbook, halfpage

i(R − Y)

o(R − Y)

o(B − Y)

i(B − Y)

GND2

SDA

3 4 5 6 7 8 9

TDA4670

Fig.2 Pin configuration.

MEH188

GND1

SAND

ref

CLP2

CLP1

COR

SCL

1996 Dec 11 4

Philips Semiconductors Product speciﬁcation

Picture Signal Improvement (PSI) circuit TDA4670

FUNCTIONAL DESCRIPTION

The TDA4670 contains luminance signal processing and colour-difference signal processing. The luminance signal section comprises a variable integrated luminance delay line with luminance signal peaking and noise reduction by coring.

The colour-difference section consists of a transient improvement circuit to decrease the rise and fall times of the colour-difference signal transients. All functions and parameters are controlled via the I2C-bus.

Y-signal path

The video and blanking signal is AC-coupled to the input at pin 16. Its black porch is clamped to a DC reference voltage to ensure the correct operating range of the luminance delay stage.

The luminance delay line consists of all-pass filter sections with delay times of 45, 90, 100, 180 and 450 ns (see Fig.1). The luminance signal delay is controlled via

the I

C-bus in steps of 45 ns in the range of 20 to 1100 ns, this ensures that the maximum delay difference between the luminance and colour-difference signals is ±22.5 ns.

An automatic luminance delay time adjustment in an internal control loop (with the horizontal frequency as a reference) is used to correct changes in the delay time, due to component tolerances. The control loop is automatically enabled between the burst key pulses of lines 16 (330) and 17 (331) during the vertical blanking interval. The control voltage is stored in the capacitor C

connected to pin 2. The peaking section uses a transversal filter circuit with

selectable centre frequencies of 2.6 and 5 MHz.

The output buffer stage ensures a low-ohmic VBS output signal on pin 12 (<160 Ω). The gain of the luminance signal path from pin 16 to pin 12 is unity.

An oscillation signal of the delay time control loop is present on output pin 12 instead of the VBS signal during the vertical blanking interval in lines 16 (330) to 18 (332). Therefore, this output signal should not be applied for synchronization.

Colour-difference signal paths

The colour-difference input signals (on pins 3 and 7) are clamped to a reference voltage.

Each colour-difference signal is fed to a transient detector and to an analog signal switch with an attached voltage storage stage.

The transient detectors consist of differentiators and full-wave rectifiers. The output voltages of both transient detectors are added and then compared in a comparator. This comparator controls both following analog signal switches simultaneously.

The analog signal switches are in an open position at a certain value of transient time; the held value (held by storage capacitors) is then applied to the outputs. The switches close to rapidly accept the actual signal levels at the end of these transients. The improved transient time is approximately 100 ns long and independent of the input signal transient time.

Colour-difference paths are independent of the input signal polarity and have a gain of unity.

The CTI functions are switched on and off via the I

C-bus.

It provides selectable degrees of peaking of −3, 0, +3 and +6 dB and a noise reduction by coring, which attenuates the high-frequency noise introduced by peaking.

1996 Dec 11 5

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