
Theory of Operation
Detailed Circuit Description
4
4-19
Break-Detect Circuitry
4-31.
The 6303Y divides the 4.9152-MHz crystal frequency by four to create the 1.2288-MHz
ECLK. This signal serves as the clock for the 74HC4020 counter (U506), which is
configured as a divide-by-16384. The RECEIVE line is usually high, except for the brief
interval when characters are being transmitted. As long as the low state is less than 13.34
ms, RECEIVE holds the CLR of the 74HC4020 TRUE. However, if communication
between the 5725A Amplifier and the 5700A Calibrator fails, the 5700A attempts to
reset the 5725A by sending a break (holding RECEIVE low for greater than 26.7 ms).
This action causes the 74HC4020 counter output (BREAK) to go high. Signal BREAK is
NOR’ed with CABLEOFF from the High Voltage Sense assembly (A6); either signal
causes a NON-MASKABLE INTERRUPT to the 6303Y. The 5700A also uses BREAK
to reset the 5725A.
Power Up and Reset Circuitry
4-32.
Reset and glitch-detection circuitry primarily consists of U508, a TL7705A. This chip
detects if the power supply falls below 4.5V, if a reset input from a momentary contact
switch occurs, or if there is an output from the watchdog timer. Any combination of
these conditions resets the board via RESET* for 130 ms.
Watchdog Timer
4-33.
Watchdog circuitry contains a 4538 Dual Monostable Multivibrator. The first
multivibrator (U509A) is configured as a 300 ms retriggerable one-shot that can fire a
second 3 ms one-shot (U509B). Control line STROBE 2 of the 6303 (bit 1, port 6)
retriggers the first one-shot every 50 ms and refreshes the high voltage relay driver. If
STROBE 2 is stuck high or low during operation, the first one-shot is no longer
retriggered, and its output transitions low. The second one-shot, configured to trigger on
a falling edge, now sends a pulse via RESIN* to the TL7705A reset IC U508. This
action forces the reset circuit to pull a hard reset on the 6303Y for 130 ms.
The first trigger to the 4538 occurs when the 7705A RESET* line makes a transition
from low to high. During normal operation, STROBE 2 prevents another reset by
retriggering the first one-shot well before the 300 ms timeout. The watchdog fires only if
the CPU is executing erroneous code which does not activate STROBE 2.
Current Amplifier Assembly (A2)
4-34.
The Current Amplifier assembly enables the 5725A to extend the current output range of
the 5700A Calibrator to
±
11A dc or 11A ac. The 5700A drives the Current Amplifier
assembly input through the 5725A interface cable. There are no user input terminals.
Output current is available at binding posts on the 5725A front or rear panel. Selection of
front or rear 5725A binding posts is done by unplugging one cable and plugging in
another cable on the Current Amplifier assembly inside the 5725A chassis. Additionally,
relays on the Current Amplifier assembly can route the 5700A current source to the
5725A output terminals, if so selected at the 5700A front panel (or by remote command).
The Current Amplifier assembly has five distinct sections: the error amplifier, output,
control, monitor, and power supply. Each section is first briefly described, then
described in detail in the following paragraphs. Refer to Figure 4-3, a block diagram of
the Current Amplifier assembly, to see the interrelationship of the following function
blocks.
Summary of Contents for 5725A
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Page 78: ...5725A Instruction Manual 4 20 aq20f eps Figure 4 3 Current Amplifier Assembly Block Diagram...
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Page 132: ...5725A Instruction Manual 8 6 aq24f tif Figure 8 1 Final Assembly...
Page 133: ...List of Replaceable Parts 8 8 7 aq25f tif Figure 8 1 Final Assembly cont...
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Page 135: ...List of Replaceable Parts 8 8 9 aq27f tif Figure 8 1 Final Assembly cont...
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Page 139: ...List of Replaceable Parts 8 8 13 aq31f tif Figure 8 1 Final Assembly cont...
Page 141: ...List of Replaceable Parts 8 8 15 5725A 1611 aq36f eps Figure 8 2 A1 Interconnect PCA...
Page 145: ...List of Replaceable Parts 8 8 19 5725A 1650 aq37f eps Figure 8 3 A2 Current Amplifier PCA...
Page 149: ...List of Replaceable Parts 8 8 23 5725A 1661 aq38f eps Figure 8 4 A3 High Voltage Amplifier PCA...
Page 153: ...List of Replaceable Parts 8 8 27 5725A 1631 aq39f eps Figure 8 5 A4 Power Supply PCA...
Page 155: ...List of Replaceable Parts 8 8 29 5725A 1650 aq40f eps Figure 8 6 A5 Digital PCA...
Page 159: ...List of Replaceable Parts 8 8 33 5725A 1601 aq41f eps Figure 8 7 A6 High Voltage Sense PCA...
Page 161: ...List of Replaceable Parts 8 8 35 aq32f tif Figure 8 8 A12 Transformer Enclosure Assembly...
Page 162: ...5725A Instruction Manual 8 36 aq33f tif Figure 8 8 A12 Transformer Enclosure Assembly cont...
Page 163: ...List of Replaceable Parts 8 8 37 aq34f tif Figure 8 8 A12 Transformer Enclosure Assembly cont...
Page 164: ...5725A Instruction Manual 8 38 aq35f tif Figure 8 8 A12 Transformer Enclosure Assembly cont...
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Page 169: ...Schematic Diagrams 9 3 9 Figure 9 1 A1 Interconnect PCA 5725A 1611 aq48f eps...
Page 170: ...5725A Instruction Manual 9 4 Figure 9 1 A1 Interconnect PCA cont...
Page 171: ...Schematic Diagrams 9 5 9 Figure 9 1 A1 Interconnect PCA cont...
Page 172: ...5725A Instruction Manual 9 6 Figure 9 2 A2 Current Amplifier PCA 5725A 1650 aq52f eps...
Page 173: ...Schematic Diagrams 9 7 9 Figure 9 2 A2 Current Amplifier PCA cont...
Page 174: ...5725A Instruction Manual 9 8 Figure 9 2 A2 Current Amplifier PCA cont...
Page 175: ...Schematic Diagrams 9 9 9 Figure 9 2 A2 Current Amplifier PCA cont...
Page 176: ...5725A Instruction Manual 9 10 Figure 9 3 A3 High Voltage Amplifier PCA 5725A 1661 aq56f eps...
Page 177: ...Schematic Diagrams 9 11 9 Figure 9 3 A3 High Voltage Amplifier PCA cont...
Page 178: ...5725A Instruction Manual 9 12 Figure 9 3 A3 High Voltage Amplifier PCA cont...
Page 179: ...Schematic Diagrams 9 13 9 Figure 9 4 A4 Power Supply PCA 5725A 1631 aq59f eps...
Page 180: ...5725A Instruction Manual 9 14 Figure 9 4 A4 Power Supply PCA cont...
Page 181: ...Schematic Diagrams 9 15 9 Figure 9 4 A4 Power Supply PCA cont...
Page 183: ...Schematic Diagrams 9 17 9 Figure 9 5 A5 Digital PCA cont...
Page 185: ...Schematic Diagrams 9 19 9 Figure 9 6 A6 High Voltage Sense PCA cont...
Page 186: ...5725A Instruction Manual 9 20 Figure 9 6 A6 High Voltage Sense PCA cont...
Page 187: ...Schematic Diagrams 9 21 9 Figure 9 6 A6 High Voltage Sense PCA cont...
Page 188: ...5725A Instruction Manual 9 22 Figure 9 6 A6 High Voltage Sense PCA cont...
Page 189: ...Schematic Diagrams 9 9 23 aq45f eps Figure 9 7 A12 Transformer Enclosure Assembly...
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