Philips TDA8708T Datasheet

DATA SH EET

Product specification
Supersedes data of June 1994
File under Integrated Circuits, IC02

1996 Nov 26

INTEGRATED CIRCUITS

TDA8708B

Video analog input interface

1996 Nov 26 2

Philips Semiconductors Product specification

Video analog input interface TDA8708B

FEATURES

• 8-bit resolution

• Sampling rate up to 32 MHz

• Binary or two’s complement 3-state TTL outputs

• TTL-compatible digital inputs and outputs

• Internal reference voltage regulator

• Power dissipation of 365 mW (typical)

• Input selector circuit (one out of three video inputs)

• Clamp and Automatic Gain Control (AGC) functions for

CVBS and Y signals

• No sample-and-hold circuit required

• The TDA8708B has no white peak control in mode 2

whereas the TDA8708A has control in modes 1 and 2

• In-range output (not TTL levels).

APPLICATIONS

• Video signal decoding

• Scrambled TV (encoding and decoding)

• Digital picture processing

• Frame grabbing.

GENERAL DESCRIPTION

The TDA8708B is an analog input interface for video signal
processing. It includes a video amplifier with clamp and
gain control, an 8-bit Analog-to-Digital Converter (ADC)
with a sampling rate of 32 MHz and an input selector.

QUICK REFERENCE DATA

ORDERING INFORMATION

SYMBOL PARAMETER MIN. TYP. MAX. UNIT

V

CCA

analog supply voltage 4.5 5.0 5.5 V

V

CCD

digital supply voltage 4.5 5.0 5.5 V

V

CCO

TTL output supply voltage 4.2 5.0 5.5 V

I

CCA

analog supply current − 37 45 mA

I

CCD

digital supply current − 24 30 mA

I

CCO

TTL output supply current − 12 16 mA
ILE DC integral linearity error −−±1 LSB
DLE DC differential linearity error −−±0.5 LSB
f

clk(max)

maximum clock frequency 30 32 − MHz
B maximum −3 dB bandwidth (AGC amplifier) 12 18 − MHz
P

tot

total power dissipation − 365 500 mW

TYPE NUMBER

PACKAGE

NAME DESCRIPTION VERSION

TDA8708BT SO28 plastic small outline package; 28 leads; body width 7.5 mm SOT136-1

1996 Nov 26 3

Philips Semiconductors Product specification

Video analog input interface TDA8708B

BLOCK DIAGRAM

Fig.1 Block diagram.

handbook, full pagewidth

MSA672

TTL

OUTPUTS

9
1

2
3

4
10
11
12
13

output format/

chip enable

(3-state input)

D7
D6
D5
D4
D3
D2
D1
D0

8 - bit

ADC

AMP.

VIDEO

AMPLIFIER

INPUT

SELECTOR

16
17
18

19 2014 15

video input

selection bit 0

video input
selection bit 1

analog

voltage

output

ADC
input

clock
input

decoupling
input

521 7

video input 0
video input 1
video input 2

clamp capacitor

connection

AGC capacitor

connection

24

25

AGC &

CLAMP

LOGIC

&

MODE

SELECTION

PEAK LEVEL

DIGITAL COMPARATOR

27 26

sync level

sync pulse

black level
sync pulse

6

digital

ground

8 22

analog
ground

23

TDA8708B

28

BLACK LEVEL

DIGITAL COMPARATOR

SYNC LEVEL

DIGITAL COMPARATOR

in-range

output

TTL outputs V (+ 5 V)

digital V

CCD

(+ 5 V)

analog V

CCA

(+ 5 V)

CCO

1996 Nov 26 4

Philips Semiconductors Product specification

Video analog input interface TDA8708B

PINNING

SYMBOL PIN DESCRIPTION

D7 1 data output; bit 7 (MSB)
D6 2 data output; bit 6
D5 3 data output; bit 5
D4 4 data output; bit 4
CLK 5 clock input
V

CCD

6 digital supply voltage (+5 V)

V

CCO

7 TTL outputs supply voltage (+5 V)
DGND 8 digital ground
OF 9 output format/chip enable

(3-state input)
D3 10 data output; bit 3
D2 11 data output; bit 2
D1 12 data output; bit 1
D0 13 data output; bit 0 (LSB)
I0 14 video input selection bit 0
I1 15 video input selection bit 1
VIN0 16 video input 0
VIN1 17 video input 1
VIN2 18 video input 2
ANOUT 19 analog voltage output
ADCIN 20 analog-to-digital converter input
DEC 21 decoupling input
V

CCA

22 analog supply voltage (+5 V)
AGND 23 analog ground
CLAMP 24 clamp capacitor connection
AGC 25 AGC capacitor connection
GATE B 26 black level synchronization pulse
GATE A 27 sync level synchronization pulse
IR 28 in-range output

Fig.2 Pin configuration.

1
2
3
4
5
6
7
8

9
10
11
12
13

28
27
26
25
24
23
22
21
20
19
18
17
16
1514

TDA8708B

D7

D6
D5
D4

CLK

V

CCD

V

CCO

DGND

OF
D3
D2
D1
D0

I0

ADCIN
ANOUT
VIN2

VIN1
VIN0

I1

GATE B

AGC

CLAMP

AGND

V

CCA

DEC

IR
GATE A

MSA671

1996 Nov 26 5

Philips Semiconductors Product specification

Video analog input interface TDA8708B

FUNCTIONAL DESCRIPTION

The TDA8708B provides a simple interface for decoding
video signals.

The TDA8708B operates in configuration mode 1
(see Fig.4) when the video signals are weak (i.e. when the
gain of the AGC amplifier has not yet reached its optimum
value). This enables a fast recovery of the synchronization
pulses in the decoder circuit. When the pulses at the
GATE A and GATE B inputs become distinct (GATE A and
GATE B pulses are synchronization pulses occurring
during the sync period and rear porch respectively) the
TDA8708B automatically switches to configuration mode 2
(see Fig.5).

When the TDA8708B is in configuration mode 1, the gain
of the AGC amplifier will be roughly adjusted (sync level to
a digital output level of 0 and the peak level to a digital
output level of 255).

In configuration mode 2 the digital output of the ADC is
compared to internal digital reference levels.

The voltage across the capacitor connected to the AGC
pin controls the gain of the video amplifier. This is the gain
control loop.

The sync level comparator is active during a positive-going
pulse at the GATE A input. This means that the sync pulse
of the composite video signal is used as an amplitude
reference. The bottom of the sync pulse is adjusted to
obtain a digital output of logic 0 at the converter output.
As the black level is at digital level 64, the sync pulse will
have a digital amplitude of 64 LSBs.

The use of nominal signals will prevent the output from
exceeding a digital code of 213.

The clamp level control is accomplished by using the same
techniques as used for the gain control. The black-level
digital comparator is active during a positive-going pulse at
the GATE B input. The clamp capacitor will be charged or
discharged to adjust the digital output to code 64.

LIMITING VALUES

In accordance with the Absolute Maximum Rating System (IEC 134).

THERMAL CHARACTERISTICS

SYMBOL PARAMETER MIN. MAX. UNIT

V

CCA

analog supply voltage −0.3 +7.0 V

V

CCD

digital supply voltage −0.3 +7.0 V

V

CCO

TTL output supply voltage −0.3 +7.0 V

∆V

CC

supply voltage differences:

V

CCA

− V

CCD

−1.0 +1.0 V

V

CCO

− V

CCD

−1.0 +1.0 V

V

CCA

− V

CCO

−1.0 +1.0 V

V

I

input voltage −0.3 V

CCA

V

I

O

output current 0 +10 mA

T

stg

storage temperature −55 +150 °C

T

amb

operating ambient temperature 0 +70 °C

T

j

junction temperature 0 +125 °C

SYMBOL PARAMETER VALUE UNIT

R

th j-a

thermal resistance from junction to ambient in free air 70 K/W

1996 Nov 26 6

Philips Semiconductors Product specification

Video analog input interface TDA8708B

CHARACTERISTICS

V

CCA=V22

to V23= 4.5 to 5.5 V; V

CCD=V6

to V8= 4.5 to 5.5 V; V

CCO=V7

to V8= 4.2 to 5.5 V; AGND and DGND

shorted together; V

CCA

to V

CCD

= −0.5 to +0.5 V; V

CCO

to V

CCD

= −0.5 to +0.5 V; V

CCA

to V

CCO

= −0.5 to +0.5 V;

T

amb

= 0 to +70 °C; typical readings taken at V

CCA=VCCD=VCCO

= 5 V and T

amb

=25°C; unless otherwise specified.

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT

Supplies

V

CCA

analog supply voltage 4.5 5.0 5.5 V

V

CCD

digital supply voltage 4.5 5.0 5.5 V

V

CCO

TTL output supply voltage 4.2 5.0 5.5 V

I

CCA

analog supply current − 37 45 mA

I

CCD

digital supply current − 24 30 mA

I

CCO

TTL output supply current TTL load (see Fig.8) − 12 16 mA

Video amplifier inputs

VIN0

TO VIN2 INPUTS

V

I(p-p)

input voltage (peak-to-peak value) AGC load with external

capacitor; note 1

0.6 − 1.5 V

Z

i

 input impedance fi= 6 MHz 10 20 − kΩ

C

i

input capacitance fi= 6 MHz − 1 − pF
I0 AND I1 TTL INPUTS (see Table 1)
V

IL

LOW level input voltage 0 − 0.8 V
V

IH

HIGH level input voltage 2.0 − V

CCD

V

I

IL

LOW level input current VI= 0.4 V −400 −−µA
I

IH

HIGH level input current VI= 2.7 V −− 20 µA
GATE A AND GATE B TTL INPUTS (see Figs 4 and 5)
V

IL

LOW level input voltage 0 − 0.8 V
V

IH

HIGH level input voltage 2.0 − V

CCD

V

I

IL

LOW level input current VI= 0.4 V −400 −−µA
I

IH

HIGH level input current VI= 2.7 V −− 20 µA
t

W

pulse width see Fig.5 2 −−µs
AGC INPUT (PIN 25)
V

25(min)

AGC voltage for minimum gain − 2.8 − V
V

25(max)

AGC voltage for maximum gain − 4.0 − V

AGC output current see Table 2
CLAMP

INPUT (PIN 24)

V

24

clamp voltage for code 128 output − 3.5 − V
I

24

clamp output current see Table 3

1996 Nov 26 7

Philips Semiconductors Product specification

Video analog input interface TDA8708B

Video amplifier outputs

ANOUT OUTPUT (PIN 19)
V

19(p-p)

AC output voltage

(peak-to-peak value)

V

VIN

= 1.33 V (p-p);

V25= 3.6 V

− 1.33 − V

I

19

internal current source RL= ∞ 2.0 2.5 − mA
I

O(p-p)

output current driven by the load V

ANOUT

= 1.33 V (p-p);

note 2

−− 1.0 mA

V

19

DC output voltage for black level note 3 − V

CCA

− 2.24 − V

Z

19

output impedance − 20 −Ω

Video amplifier dynamic characteristics

α

ct

crosstalk between VIN inputs V

CCA

= 4.75 to 5.25 V −−50 −45 dB

G

diff

differential gain V

VIN

= 1.33 V (p-p);

V25= 3.6 V

− 2 − %

ϕ

diff

differential phase V

VIN

= 1.33 V (p-p);

V25= 3.6 V

− 0.8 − deg

B −3 dB bandwidth 12 −−MHz
S/N signal-to-noise ratio note 4 60 −−dB
SVRR1 supply voltage ripple rejection note 5 − 45 − dB
∆G gain range see Fig.10 −4.5 − +6.0 dB
G

stab

gain stability as a function of supply

voltage and temperature

see Fig.10 −− 5%

Analog-to-digital converter inputs

CLK

INPUT (PIN 5)

V

IL

LOW level input voltage 0 − 0.8 V
V

IH

HIGH level input voltage 2.0 − V

CCD

V

I

IL

LOW level input current V

clk

= 0.4 V −400 −−µA

I

IH

HIGH level input current V

clk

= 2.7 V −− 100 µA

|Z

i

| input impedance f

clk

= 10 MHz − 4 − kΩ

C

I

input capacitance f

clk

= 10 MHz − 4.5 − pF
OF INPUT (3-STATE; see Table 4)
V

IL

LOW level input voltage 0 − 0.2 V

V

IH

HIGH level input voltage 2.6 − V

CCD

V

V

9

input voltage in high impedance state − 1.15 − V

I

IL

LOW level input current −370 −300 −µA

I

IH

HIGH level input current − 300 450 µA

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT

1996 Nov 26 8

Philips Semiconductors Product specification

Video analog input interface TDA8708B

ADCIN INPUT (PIN 20; see Table 5)
V

20

input voltage digital output = 00 − V

CCA

− 2.42 − V

V

20

input voltage digital output = 255 − V

CCA

− 1.41 − V

V

20(p-p)

input voltage amplitude
(peak-to-peak value)

− 1.0 − V

I

20

input current − 1.0 10 µA

Z

i

 input impedance fi= 6 MHz − 50 − MΩ

C

i

input capacitance fi= 6 MHz − 1 − pF

Analog-to-digital converter outputs

IR

OUTPUT (PIN 28)

V

OL

LOW level output voltage −− 1.7 V

V

OH

HIGH level output voltage 1.9 −−V

I

O

output current −500 −−µA
DIGITAL OUTPUTS D0 TO D7
V

OL

LOW level output voltage IOL= 2 mA 0 − 0.6 V
V

OH

HIGH level output voltage IOL= −0.4 mA 2.4 − V

CCD

V

I

OZ

output current in 3-state mode 0.4 V < VO<V

CCD

−20 − +20 µA

Switching characteristics

f

clk(max)

maximum clock input frequency see Fig.6; note 6 30 32 − MHz

Analog signal processing (f

clk

= 32 MHz); see Fig.8

G

diff

differential gain V20= 1.0 V (p-p);

see Fig.7; note 7

− 2 − %

ϕ

diff

differential phase see Fig.7; note 7 − 2 − deg
f

1

fundamental harmonics (full-scale) fi= 4.43 MHz; note 7 −− 0dB
f

all

harmonics (full-scale);

all components

fi= 4.43 MHz; note 7 −−55 − dB

SVRR2 supply voltage ripple rejection note 8 − 1 5 %/V
Transfer function (see Fig.8)
ILE DC integral linearity error −− ±1 LSB

DLE DC differential linearity error −− ±0.5 LSB
ILE AC integral linearity error note 9 −− ±2 LSB

Timing (f

clk

= 32 MHz) see Figs 6, 7 and 8

D

IGITAL OUTPUTS (C

L

= 15 pF; IOL= 2 mA; RL=2kΩ)

t

ds

sampling delay time − 2 − ns
t

h

output hold time 6 8 − ns
t

d

output delay time − 16 20 ns
t

dEZ

3-state delay time; output enable − 19 25 ns
t

dDZ

3-state delay time; output disable − 14 20 ns

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT