Figure 5 – CONVert, CONVert Switching Levels
V
IDF
0.0 V
V
ICM MIN
Figure 6A – Standard Load
OUT –
75
Ω
COAX
Video Monitor
R
S
75
Ω
R
L
75
Ω
SPT5140
–1.3 V
CONV
V
ICM MAX
CONV
R
S
75
Ω
R
L
75
Ω
OUT +
75
Ω
COAX
Inverse
Video
CONVERT CLOCK
For best performance, the clock should be ECL driven,
differentially, by utilizing CONV and
CONV
(figure 5). By
driving the clock this way, clock noise and power supply/
output intermodulation will be minimized. The rising edge
of the clock synchronizes the data and control inputs to
the SPT5140. Since the actual switching threshold of
CONV is determined by
CONV
, the clock can be driven
single-ended by connecting a bias voltage to
CONV
. The
switching threshold of CONV is set by this bias voltage.
ANALOG OUTPUTS
The SPT5140 has two analog outputs that are high im-
pedance, complementary current sinks. The outputs vary
in proportion to the input data, controls and reference cur-
rent values so that the full-scale output can be changed
by setting I
Set
as mentioned earlier.
In video applications, the outputs can drive a doubly ter-
minated 50 or 75 ohm load to standard video levels. In
the standard configuration of figure 6, the output voltage
is the product of the output current and load impedance
and is between 0 and –1.07 V. The Out– output (figure 4)
will provide a video output waveform with the Sync pulse
bottom at the –1.07 V level. The Out+ is inverted with
Sync up.
Figure 6B – Test Load
OUT +
OUT –
C
L
<5 pF
R
L
37.5
Ω
Video Out
0 to –1 Volt
Figure 7 – Burn-In Circuit
–5.9 V
(Max 200 mA)
6.5
Ω
6.5
Ω
24-Pin DIP
All Resistors Are 5% 1/4 W cc
Clock = –0.9 to –1.7 V, 100 kHz
V
EE
Out–
1 kΩ
–1.2 V
(Max 1.5 mA)
Ref In
(Max 50 mA)
(Max 50 mA)
Out+
100
Ω
100
Ω
1 kΩ
1 kΩ
–1.3 V
(Max 60
µA)
CONV
CONV
1 kΩ
Clock
(Max 60
µA)
V
CC
I
Set
(Max 1.5 mA)
SPT5140
8
3/28/00
CADEKA [ CADEKA MICROCIRCUITS LLC. ]
