intersil EL4581 DATA SHEET

®

EL4581

Data Sheet August 16, 2002

Sync Separator , 50% Slice, S-H, Filter

The EL4581 extracts timing informa­tion from standard negative going

video sync found in NTSC, PAL, and
SECAM broadcast systems. It can also be used in non stan­dard formats and with computer graphics systems at higher
scan rates, by adjusting a single external resistor. When the
input does not have correct serration pulses in the vertical
interval, a default vertical output is produced.

Outputs are composite sync, vertical sync, burst/back porch
output, and odd/even output. The later operates only in inter­laced scan formats.

The EL4581 provides a reliable method of determining cor­rect sync slide level by setting it to the mid-point between
sync tip and blanking level at the back porch. This 50% level
is determined by two internal self timing sample and hold cir­cuits that track sync tip and back porch levels. This also
provides a degree of hum and noise rejection to the input sig­nal, and compensates for varying input levels of 0.5

2.0V

P-P

.

A built in linear phase, third order, low pass filter attenuates
the chroma signal in color systems to prevent incorrectly set
color burst from disturbing the 50% sync slide.

This device may be used to replace the industry standard
LM1881, offering improved performance and reduced power
consumption.

P-P

to

FN7172

Features

• NTSC, PAL and SECAM sync separation

• Single supply, +5V

• Precision 50% slicing, internal caps

• Built-in color burst filter

• Decodes non-standard verticals

• Pin compatible with LM1881

•Low power

• Typically 1.5mA supply current

• Resistor programmable scan rate

• Few external components

• Available in 8-pin PDIP and SO packages

Applications

• Video special effects

• Video test equipment

• Video distribution

• Displays

•Imaging

• Video data capture

• Video triggers

The EL4581 video sync separator is manufactured using
Elantec’s high performance analog CMOS process.

Pinout

EL4581

(8-Pin SO, DIP)

TOP VIEW

COMPOSITE

SYNC OUT

COMPOSITE

VIDEO IN

VERTICAL

SYNC OUT

All other trademarks mentioned are the property of their respective owners. Manufactured under U.S. Patent 5,528,303. Manufactured under License, U .S . Patents 5,486,869; 5,754,250.

GND

1

2

3

4

1

8

VDD 5V

7

ODD/EVEN OUTPUT

RSET

6

BURST/BACK

5

PORCH OUTPUT

CAUTION: These devices are sensitiv e to electrostatic discharge; follow proper IC Handling Procedures.

Copyright © Intersil Americas Inc. 2003. All Rights Reserved. Elantec is a registered trademark of Elantec Semiconductor, Inc.

1-888-INTERSIL or 321-724-7143

Ordering Information

PART

NUMBER

EL4581CN -40°C to +85°C 8-Pin PDIP MDP0031
EL4581CS -40°C to +85°C 8-Pin SO MDP0027

TEMP.

RANGE PACKAGE PKG. NO.

Demo Board

A dedicated demo board is not available. However, this
device can be placed on the EL4584/5 Demo Board.

| Intersil (and design) is a registered trademark of Intersil Americas Inc.

EL4581

Absolute Maximum Ratings (T

Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7V

V

CC

Storage Temperature. . . . . . . . . . . . . . . . . . . . . . . .-65°C to +150°C

Pin Voltages. . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.5V to V

CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the
device at these or any other conditions above those indicated in the operational sections of this specification is not implied.

IMPORTANT NOTE: All parameters having Min/Max specifications are guaranteed. Typical values are for information purposes only. Unless otherwise noted, all tests
are at the specified temperature and are pulsed tests , therefore: T

DC Electrical Specifications Unless otherwise state V

= 25 °C)

A

+0.5V

CC

= TC = T

J

Operating Temperature Range . . . . . . . . . . . . . . . . .-40°C to +85°C

Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150°C

Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Curves

A

= 5V, TA = 25°C, R

DD

SET

= 680kΩ.

PARAMETER DESCRIPTION TEMP MIN TYP MAX UNIT

I

DD

VDD = 5V (Note 1) 25°C 0.75 1.7 3 mA
Clamp Voltage Pin 2, Unloaded 25°C 1.3 1.5 1.9 V
Discharge Current Pin 2 = 2V 25°C 6 10 20 µA
Clamp Charge Current Pin 2, V
Ref Voltage Pin 6, V

= 1V 25°C 2 3 mA

IN

= 5V (Note 2) 25°C 1.5 1.8 2.1 V

DD

VOL Output Low Voltage IOL = 1.6mA 25°C 800 mV
V

Output High Voltage IOH = -40µA 25°C 4 V

OH

I

= -1.6mA 25°C 2.4 V

OH

NOTES:

1. No video signal, outputs unloaded.

2. Tested for V

5V ±5% which guarantees timing of output pulses over this range.

DD

Dynamic Specifications V

= 5V, IVpk-pk video, TA = 25°C, CL = 15pF, IOH = -1.6mA, IOL = 1.6mA. Signal voltages are peak to peak.

DD

PARAMETER DESCRIPTION TEMP MIN TYP MAX UNIT

Vertical Sync Width, t
Burst/Back Porch Width, t

VS

B

Vertical Sync Default Delay t
Filter Attenuation F
Composite Sync Prop Delay V

(Note 1) 25°C 190 230 300 µs

(Note 1) 25°C 2.5 3.5 4.5 µs

VSD

= 3.4MHz (Note 2) 25°C 24 dB

IN

- Composite Sync (Note 1) 25°C 260 400 ns

IN

25°C405570µs

Input Dynamic Range p-p NTSC Signal (Note 3) 25°C 0.5 2 V
Slice Level Input Voltage = 1V

P-P

25°C 40% 50% 60%

(Note 4) Full 40% 50% 60%

NOTES:

1. C/S, Vertical and Burst outputs are all active low - V

2. Attenuation is a function of R

3. Typical min. is 0.3V

4. Refers to threshold level of sync. tip to back porch amplitude.

P-P

.

SET

(PIN6).

= 2.4V, VOL = 0.8V.

OH

2

EL4581

Pin Descriptions

PIN NUMBER PIN NAME FUNCTION

1 Composite Sync Out Composite sync pulse output. Sync pulses start on a falling edge and end on a rising edge.
2 Composite Video in AC coupled composite video input. Sync tip must be at the lowest potential (Positive picture phase).
3 Vertical Sync Out Vertical sync pulse output. The falling edge of Vert Sync is the start of the vertical period.
4 GND Supply ground.
5 Burst/Back Porch Output Burst/Back porch output. Low during burst portion of composite video.
6R

7 Odd/Even Output Odd/Even field output. Low during odd fields, high during even fields. Transitions occur at start of

8V

NOTE 1. R

SET

(Note 1) An external resistor to ground sets all internal timing. 681k, 1% resistor will provide correct timing

SET

5V Positive supply. (5V)

DD

must be a 1% resistor.

for NTSC signals.

Vert Sync pulse.

3

Typical Performance Curves

R

vs Horizontal

SET

Frequency

EL4581

Back Porch Clamp
On Time vs R

SET

Vertical Pulse Width
vs R

SET

Vertical Default Delay
Time vs R

SET

Package Power Dissipation vs Ambient Temperature

JEDEC JESD51-3 Low Effective Thermal Conductivity Test Board

1.8

1.6

1.4

1.25W

1.2
1

781mW

0.8

0.6

0.4

Power Dissipation (W)

θ

0.2
0

0 25 50 75 100 125 150

PDIP8

θ

=100°C/W

JA

SO8

=160°C/W

JA

Ambient Temperature (°C)

85

Vertical Pulse Width
vs Temperature

Input Signal = 300mV
EL4581 Filter Characteristic
Constant Delay 240ns

P-P

Package Power Dissipation vs Ambient Temperature

JEDEC JESD51-7 High Effective Thermal Conductivity Test Board

2

1.8

1.6

1.4

1.2
1

0.8

0.6

Power Dissipation (W)

0.4

0.2
0

0 25 50 75 100 125 150

1.471W

1.136

PDIP8

θ

=85°C/W

JA

SO8

θ

=110°C/W

JA

Ambient Temperature (°C)

Supply Current
vs Temperature

85

4

Timing Diagrams

EL4581

NOTES:

b. The composite sync output reproduces all the video input sync pulses, with a propagation delay.
c. Vertical sync leading edge is coincident with the first vertical serration pulse leading edge, with a propagation delay.
d. Odd-even output is low for even field, and high for odd field.
e. Back porch goes low for a fixed pulse width on the trailing edge of video input sync pulses. Note that for serration pulses during vertical, the back porch starts

on the rising edge of the serration pulse (with propagation delay).

FIGURE 1.

5

Timing Diagrams (Continued)

EL4581

FIGURE 2.

6

Timing Diagrams (Continued)

EL4581

FIGURE 3.

FIGURE 4. STANDARD (NTSC INPUT) H. SYNC DETAIL

7

EL4581

Description of Operation

A simplified block schematic is shown in Figure 2. The follow­ing description is intended to provide the user with sufficient
information to be able to understand the effects that the
external components and signal conditions have on the out­puts of the integrated circuit.

The video signal is AC coupled to pin 2 via the capacitor C
nominally 0.1µF. The clamp circuit A1 will prevent the input
signal on pin 2 going any more negative than 1.5V, the value
of reference voltage V

. Thus the sync tip, the most nega-

R1

tive part of the video waveform, will be clamped at 1.5V. The
current source I

, nominally 10µA, charges the coupling

1

capacitor during the remaining portion of the H line, approxi­mately 58µs for a 15.75kHz timebase. From I • t = C • V, the
video time-constant can be calculated. It is important to note
that the charge taken from the capacitor during video must
be replaced during the sync tip time, which is much shorter,
(ratio of x 12.5). The corresponding current to restore the
charge during sync will therefore be an order of magnitude
higher, and any resistance in series with C

will cause sync

I

tip crushing. For this reason, the internal series resistance
has been minimized and external high resistance values in
series with the input coupling capacitor should be avoided.
The user can exercise some control over the value of the
input time constant by introducing an external pull-up resis­tance from pin 2 to the 5V supply. The maximum voltage
across the resistance will be V

less 1.5V, for black level.

DD

For a net discharge current greater than zero, the resistance
should be greater than 450k. This will have the effect of
increasing the time constant and reducing the degree of pic­ture tilt. The current source I
current I

and thus increases with scan rate adjustment, as

TR

directly tracks reference

1

explained later.
The signal is processed through an active 3 pole filter (F1)

designed for minimum ripple with constant phase delay. The
filter attenuates the color burst by 24dB and eliminates fast
transient spikes without sync crushing. An external filter is
not necessary. The filter also amplifies the video signal by
6dB to improve the detection accuracy. Note that the filter
cut-off frequency is a function of R
proportional to I

OT

.

Internal reference voltages (block V

through IOT and is

SET

) with high immunity

REF

to supply voltage variation are derived o n the chip. Refer­ence V

with op-amp A2 forces pin 6 to a reference voltage

R4

of 1.7V nominal. Consequently, it can be seen that the exter­nal resistance R
current I

. The internal resistance R3 is only about 6kΩ,

TR

much less than R
chip are referenced to I

will determine the value of the reference

SET

. All the internal timing functions on the

SET

and have excellent supply voltage

TR

rejection.

1

fixed level above the clamp voltage V

. The output of C2

R1

initiates the timing one-shots for gating the sample and hold
circuits. The sample of the sync tip is delayed by 0.8µs to
enable the actual sample of 2µs to be taken on the optimum
section of the sync. pulse tip. The acquisition time of the cir­cuit is about three horizontal lines. The double poly CMOS
technology enables long time constants to be achieved with

,

small high quality on-chip capacitors. The back porch voltage
is similarly derived from the trailing edge of sync, which also
serves to cut off the tip sample if the gate time exceeds the
tip period. Note that the sample and hold gating times will
track RSET through I

OT

.

The 50% level of the sync tip is derived, through the resistor
divider R1 and R2, from the sample and held voltages V
and V

, and applied to the plus input of comparator C1.

BP

TIP

This comparator has built in hysteresis to avoid false trigger­ing. The output of C2 is a digital 5V signal which feeds the
C/S output buffer B1 and the other internal circuit blocks, the
vertical, back porch and odd/even functions.

The vertical circuit senses the C/S edges and initiates an
integrator which is reset by the shorter horizontal sync pulses
but times out the longer vertical sync. pulse widths. The
internal timing circuits are referenced to I

and VR3, the

OT

time-out period being inversely proportional to the timing cur­rent. The vertical output pulse is started on the first serration
pulse in the vertical interval and is then self-timed out. In the
absence of a serration pulse, an internal timer will default the
start of vertical.

The back porch is triggered from the sync tip trailing edge
and initiates a one-shot pulse. The period of this pulse is
again a function of I
set by R

SET

.

and will therefore track the scan rate

OT

The odd/even circuit (O/E) comprises of flip flops which track
the relationship of the horizontal pulses to the leading edge
of the vertical output, and will switch on every field at the start
of vertical. Pin 7 is high during the odd field.

Loss of video signal can be detected by monitoring the C/S
output. The 50% level of the previous video signal will remain
held on the S/H capacitors after the input video signal has
gone and the input on pin 2 has defaulted to the clamp volt­age. Consequently the C/S output will remain low longer than
the normal vertical pulse period. An external timing circuit
could be used to detect this condition.

Comparator C2 on the input to the sample and hold block
(S/H) compares the leading and trailing edges of the sync.
pulse with a threshold voltage V

which is referenced at a

R2

8

Block Diagram

EL4581

*Note:

RSET must be
a 1% resistor.

FIGURE 5. STANDARD (NTSC INPUT) H. SYNC DETAIL

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reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result
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