Data Sheet
Current-Setting Resistor - R
A 0.1µF capacitor must be connected between the COMP
REF
pin and V to stabilize internal bias circuitry and ensure
low-noise operation.
DD
Full-scale output current of each D/A converter is deter-
mined by the value of the resistor connected between
R
and GND. Nominal value of R
is found from:
REF
REF
Voltage Reference Output/Input - V
REF
R
= 9.1 (V /I )
An internal voltage source of +1.235V is output on the
pin. An external +1.235V reference may be applied
REF
REF FS
V
REF
where I is the full-scale (white) output current (in amps)
from the D/A converter (without sync). Sync is 0.4 * I .
FS
here which overrides the internal reference. Decoupling
to GND with a 0.1µF ceramic capacitor is required.
FS
V
REF
D/A full-scale (white) current may also be calculated from:
Power and Ground
I
= V /R
FS L
FS
Required power is a single +5.0V supply. To minimize power
supply induced noise, analog +5V should be connected
Where V is the white voltage level and R is the total
resistive load (Ω) on each D/A converter. V is the blank
to full-scale voltage.
FS
L
to V pins with 0.1µF and 0.01µF decoupling capacitors
DD
FS
placed adjacent to each V pin or pin pair.
DD
The high slew-rate of digital data makes capacitive cou-
pling to the outputs of any D/A converter a potential
problem. Since the digital signals contain high-frequency
components of the CLK signal, as well as the video out-
put signal, the resulting data feedthrough often looks
like harmonic distortion or reduced signal-to-noise perfor-
mance. All ground pins should be connected to a common
solid ground plane for best performance.
Voltage Reference
All three D/A converters are supplied with a common
voltage reference. Internal bandgap voltage reference
voltage is +1.235V with a 3kΩ source resistance. An
external voltage reference may be connected to the V
pin, overriding the internal voltage reference.
REF
©2008 CADEKA Microcircuits LLC
www.cadeka.com
7
CADEKA [ CADEKA MICROCIRCUITS LLC. ]
