FMS3110_04 Datasheet, PDF (5/11 Pages) Fairchild Semiconductor – Triple Video D/A Converters 3 x 10 bit, 150 Ms/s

DATA SHEET
FMS3110/3115
Pin Descriptions (continued)
Pin Name Pin Number
Voltage Reference
VREF
35
RREF
36
Value
+1.235 V
560 Ω
Description
Voltage Reference Output/Input. An internal voltage source of
+1.235 Volts is output on this pin. An external +1.235 Volt reference
may be applied here which overrides the internal reference.
Decoupling VREF to GND with a 0.1µF ceramic capacitor is required.
Current-Setting Resistor. Full-scale output current of each D/A
converter is determined by the value of the resistor connected
between RREF and GND. Nominal value of RREF is found from:
RREF = 9.1 (VREF/IFS)
where IFS is the full-scale (white) output current (in amps) from the
D/A converter (without sync). Sync is 0.4 * IFS.
D/A full-scale (white) current may also be calculated from:
IFS = VFS/RL
COMP
34
Power and Ground
VDD
12, 30, 31
GND
27, 28
0.1 µF
Where VFS is the white voltage level and RL is the total resistive load
(in ohms) on each D/A converter. VFS is the blank to full-scale
voltage.
Compensation Capacitor. A 0.1 µF ceramic capacitor must be
connected between COMP and VDD to stabilize internal bias circuitry.
+5 V
0.0V
Power Supply.
Ground.
Equivalent Circuits
V_DD
V_DD
p
Digital
Input
n
GND
Figure 2. Equivalent Digital Input Circuit
n
p
V_DD
GND
OUT
Figure 3. Equivalent Analog Output Circuit
Rev. 1.07 12/8/04
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