User Manual
2400 Series SourceMeter
®
User’s Manual Digital I/O Port, Output Enable, & Output Configuration 13-3
Digital output lines
The port provides four output lines. Each open-collector output can be set high
(+5V) or low (0V). Each output line can source up to 2mA or sink up to 500mA.
When using a category register handler for limit testing, output line #4 is typically
used for the end-of-test (EOT) or BUSY pulse. This pulse from the SourceMeter sig-
nals the handler to perform the binning operation, or indicates a busy condition.
(See Section 12, “Configuring limit tests.”)
SOT line
The input line (SOT) is used by the handler to start limit testing. With the ↓STEST
arm event selected (Section 11, “Configuring triggering”), the handler must pulse
SOT low in order to provide event detection which starts the testing process. With
the
↑ STEST arm event selected, the handler must pulse SOT high in order to pro-
vide event detection, which starts the testing process. With
↑↓STEST selected,
either a high or low SOT pulse starts the testing process.
Output enable line
The output enable line (/OE) is intended for use with an output enable circuit on a
device handler or test fixture. See“Output enable,” page 13-5), for more details.
+5V output
The Digital I/O Port provides a +5V output that can be used to drive external logic
circuitry. Maximum current output for this line is 300mA. This line is protected by a
self-resetting fuse (one hour recovery time).
Digital output configuration
There are two basic methods to connect external components to the digital output
lines, sink operation and source operation.
Sink operation
Figure 13-2 shows the basic output configuration for sink operation. Note that the
external relay coil is connected between the digital output line (pins 1 to 4) and
+5V (pin 7). With this configuration, the digital output line must be set LO to ener-
gize the relay, and the maximum sink current is 500mA.