Sot Line; Simplified Schematic; Sink Mode - Controlling External Devices - Keithley 6220 Reference Manual

9-6 Limit Test and Digital I/O

SOT line

The SOT (start-of-test) line provides an alternate method of triggering the unit.
You can set up the unit to trigger on a positive-going, negative-going, or a both
positive and negative-going pulse. See triggering in

Simplified schematic

The simplified schematic for the digital outputs is shown in
this illustration shows the schematic for one digital output. All four digital output
circuits are identical.
Figure 9-3
Digital I/O port simplified schematic
Sink mode — controlling external devices
Each output can be operated from an external supply (voltage range from +5V to
+33V applied through the external device being driven). The high current sink
capacity of the output driver allows direct control of relays, solenoids, and lamps
(no additional circuitry needed).
As shown in
built-in pull up resistor to +5V. The output transistor is capable of sinking 500mA
from voltages up to +33V. Each output channel contains a flyback diode for pro-
tection when switching inductive loads (such as a low power solenoid or relay
coils). To use these flyback diodes, connect the external supply voltage to pin 5 of
the digital I/O port. Make sure the external supply voltage is between +5V and
+33V and the current required by the device does not exceed 500mA.
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Figure 9-3, each of the four digital, open-collector outputs includes a
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Model 6220/6221 Reference Manual
Section 8
Figure
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for complete details.
9-3. Note that