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SPT1018 View Datasheet(PDF) - Signal Processing Technologies

Part Name
Description
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SPT1018
SPT
Signal Processing Technologies SPT
SPT1018 Datasheet PDF : 11 Pages
1 2 3 4 5 6 7 8 9 10
Figure 2 - Typical Interface Circuit
Video
Control
Inputs
FT
FH
Blank
BRT
Sync
Video
Data
Inputs
D0 (LSB)
D1
D2
D3
D4
D5
D6
D7 (MSB)
R1
500
Clock
R2
750
CONV
CONV
ISet
LM113/313
1 k
2 k
V+ ( ISet * )
V-
.01 µF
– 5.2 V
FB
4
4
4 To 15
Decode
Ref+
Ref
Buffer
Ref-
VCC
.01 µF
10 µF
VEE
-5.2 V
Out-
R3
50/75
Out+
Video Monitor
50/75 COAX
R4
50/75
NOTES:
1. V- = -1.2 V (typical) for LM113.
2. V+ = -1.2 V
3.
ISet
=
V+
αT(R 1+R
2)
4. RL = R3 / / R4
5.
VOut-
= K 255-Digital
Input
255
Code
x I Set
RL
+ [KI
x
I
Set
x RL (Bright)]
6. VSync = (K x ISet x RL) + (K2 x ISet x RL)
K = 15.8069
COMP
K1 = 1.7617
K2 = 10.0392
7. FB = Ferrite bead, Fair-rite P/N 217430011 or equivalent.
8. All reference resistors 1/8 W 1% metal film
power supply decoupling 50 V ceramic disc.
9. x = ECL Termination
10.
= VCC = AGND
11. See figure 8 for detail on Ref Buffer.
10. = DGND (digital input drivers).
TYPICAL INTERFACE CIRCUIT
GENERAL
A typical interface circuit using the SPT1018 in a color raster
application is shown in figure 2. The SPT1018 requires few
external components and is extremely easy to use. The very
high operating speeds of the SPT1018 require good circuit
layout, decoupling of supplies, and proper design of trans-
mission lines. The following considerations should be noted
to achieve best performance.
INPUT CONSIDERATIONS
Video input data and controls may be directly connected to
the SPT1018. Note that all ECL inputs are terminated as
closely to the device as possible to reduce ringing, crosstalk
and reflections. A convenient and commonly used microstrip
impedance is about 130 ohms, which is easily terminated
using a 330 ohm resistor to VEE and a 220 ohm resistor to
Ground. This arrangement gives a Thevenin equivalent ter-
mination of 130 ohms to -2 volts without the need for a
-2 volt supply. Standard SIP (Single Inline Package) 220/330
resistor networks are available for this purpose. It is recom-
mended that stripline or microstrip techniques be used for all
ECL interface. Printed circuit wiring of known impedance
over a solid ground plane is recommended.
OUTPUT CONSIDERATIONS
The analog outputs are designed to directly drive a dual 50 or
75 ohm load transmission system as shown. The source
impedances of the SPT1018 outputs are high impedance
current sinks. The load impedance (RL) must be 25
or 37.5 ohms to attain standard RS-343-A video levels. Any
deviation from this impedance will affect the resulting video
output levels proportionally. As with the data interface, it is
important that the analog transmission lines have matched
impedance throughout, including connectors and transitions
between printed wiring and coaxial cable. The combination of
matched source termination resistor RS and load terminator
RL minimizes reflections of both forward and reverse travel-
ing waves in the analog transmission system. The return path
for analog output current is VCC which is connected to the
source termination resistor RS.
SPT
5
SPT1018
5/14/97
 

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