SPT7814(1991) Ver la hoja de datos (PDF) - Signal Processing Technologies
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SPT7814 Datasheet PDF : 13 Pages
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POWER SUPPLIES
EB7810/14 requires four power supply sources: +15 V, -15 V,
+5 V and -5.2 V. P3 is the power connector (see figure 2). The
recommended operating voltage range is shown in table I.
Table I - Recommended Power Supply Operating
Range
PS
Min
Typ
Max Typ Current
+15
+14.25 V +15.00 V +15.75 V
168 mA
-15
-14.25 V -15.00 V -15.75 V 190 mA
+5
+4.75 V +5.00 V +5.25 V 150 mA
-5.2
- 4.50 V
-5.20 V - 5.50 V
570 mA
Figure 2 - P3, Pin Assignment for Power Supply
Connector
1
4
7
FEMALE
TERMINAL
2
5
8
3
6
9
P3 (TOP VIEW)
PIN #
1
2
3
4
5
6
7
8
9
PIN'S ASSIGNMENT
-5..2V RETURN # 1
-15V RETURN
-15V
-5.2V RETURN # 2
+15V RETURN
+15V
-5.2V
+5V RETURN
+5V
P3 (PIN ASSIGNMENT)
The total power dissipation is typically 9 Watts, including the
SPT7810 or SPT7814 (3.8 W drawn from ±15 V supplies
though the U4 and U5 regulators).
POWER SUPPLY HOOK-UPS
Figure 3 - P3 Connector/Hook-UP
POWER
SUPPLIES
5V
-5.2 V
15 V
15 V
+
+
+
+
-
-
-
-
9
8 14 7
6
5
2
3
P3 - POWER CONNECTOR
GROUNDING
AGND and DGND are not internally connected together on
the SPT7810 or SPT7814. Both Vee and Vcc should be
treated as analog supply sources. As in most very high speed
ADCs grounding is critical, therefore, the ground plane tech-
nique is most desired for the SPT7810/14. To accomplish
this, AGND and DGND ground planes must be split and tied
together only at the device (SPT7810/14) through an RF
bead inductor. EB7810/14 treats the ±15 V supplies as
analog power supplies, the +5 V and the -5.2 V as digital
supplies.
REFERENCE CIRCUIT
SPT7810/14 requires the use of two voltage references, VFT
and VFB. VFT (+2.5 V typ) is the force for the top of the
voltage reference ladder, VFB (-2.5 V typ) is the force for the
bottom of the voltage reference ladder. Both voltages are
applied across an internal reference ladder resistance of 800
Ω. In addition, there are three reference ladder taps, VSB,
VRM and VST. VST is the sense for the top of the reference
ladder (+2 V), VRM is the middle point of the ladder (0.0 V
typ), and VSB is the sense for the bottom of the reference
ladder (-2 V). The voltage seen at VST and VSB are the
expected full scale input voltages of the device when VFT and
VFB are driven to the recommended voltages (+2.5 V and -
2.5 V typical, respectively). These points should be used to
monitor the actual full scale input voltages and should not be
driven as is commonly done with the standard flash ADC
converter. When not being used a decoupling capacitor of
0.01 µFd to AGND from each tap is recommended to mini-
mize high frequency noise injection.
The EB7810/14 provides a reference driver circuit to VFT and
VFB. U2 (REF-03) is the +2.5 V precision reference to drive
the VFT. Its absolute tolerance is ±0.6% maximum. The
potentiometer R1 supports the adjustable range of typically
±6%. TP1 is the monitoring test point for the VFT. U3 (OP-
07) is an inverting unity amplifier to drive the VFB. R6 and R7
are 5% resistors. The potentiometer R2 will support the
adjustable range of ±450 mV or ±18%. TP2 is the monitoring
test point for the VFB. Because VFT and VFB are the analog
pins, both U2 and U3 are generated from the analog ±15 V
supplies.
The top reference calibration is done by adjusting R1 for
+2.000 Volts at VST (pin 20). The bottom reference calibra-
tion is achieved by tuning R2 for - 2.000 Volts at VSB (pin 24).
Repeat the first calibration step and tuning R1 if necessary
(reference table II below). All reference monitoring test points
must be referenced to the AGND test point (provided).
The top and bottom references can be driven by using Kelvin
force and sense techniques as recommended in the SPT7810/
SPT
AN7810/14
2
12/11/91
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