Measurement Computing USB-2020 - Manual (Page 20)

USB-2020 User's Guide Specifications
Digital input/output
Table 5. Digital I/O specifications
Parameter Specification
Digital type CMOS
Number of I/O 8
Configuration Each bit can be independently configured as input (power on default) or
output
Input bits can be read at any time whether the digital output is active or tri-
stated.
Input voltage range 0 V to 15 V
Input characteristics 47 kΩ pull-up/pull-down resistor, 28 kΩ series resistor
Abs. Maximum input voltage +20 V max
Pull-up/pull-down configuration The port has 47 kΩ resistors that can be configured as pull-up or pull-down
with an internal jumper. The factory configuration is pull-up (J10 shorting
block default position is pins 1 and 2)
Pull down capability is available by placing the J10 shorting block across
pins 2 and 3.
Digital I/O transfer rate (software paced) 33 S/s to 4,000 S/s typ; system-dependent
Input high voltage 2.0 V min
Input low voltage 0.8 V max
Output characteristics 47 kΩ pull-up, open drain (DMOS transistor, source connected to ground)
Output voltage range 0 V to 5 V (using 47 KΩ internal pull up resistors)
0 V to 15 V max through optional, user-supplied external pull-up resistors
(Note 1)
Drain to source breakdown voltage 42.5 V min (Note 2)
Off state leakage current 1.0 µA
Sink current capability

150 mA max (continuous) per output pin

150 mA max (continuous), total for all eight channels
DMOS transistor on-resistance (drain to
source)
4 Ω
Note 1:
Adding external pull-up resistors connects the output bit in parallel with the internal 47 kΩ pull-up
resistor. The resulting load voltage depends on the value of the external resistor value and the pull-up
voltage used. In general, external 10 KΩ pull-up resistors are sufficient for most applications.
Note 2:
Does not include the additional leakage current contribution that can occur when using an external
pull-up resistor.
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