Chapter 8 Tutorial

Multifunction Module

Digital Output

The HP 34907A module has two non-isolated 8-bit input/output ports which you can use for outputting digital patterns. You can combine the two ports to output a 16-bit word. A simplified diagram of a single output bit is shown below.

 

+5 V

External Circuit

 

 

 

 

+V

 

 

10 kΩ

Output

 

I/O Line

 

 

 

 

(1 of 16)

 

 

0.2Ω

∙Each output bit is capable of directly driving up to 10 TTL loads (less than 1 mA). The buffer for each port is used to drive a high output from the internal +5V supply through the diode. The drive is rated at +2.4V minimum at 1 mA.

∙Each output bit is also an active sink, capable of sinking up to

400 mA from an external power supply. The FET is used to sink currents and has a nominal “on” resistance of 0.2Ω.

∙For non-TTL logic you must provide an external pull-up.

A description of the pull-up calculation is given on the following page.

∙If used with an external power supply and pull-up, the external supply must be greater than +5 Vdc and less than +42 Vdc.

Reference Module

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