Keysight 34972A - Using an External Pull-Up

Tutorial 7
Keysight 34970A/34972A User’s Guide 331
Using an External Pull-Up
In general, an external pull-up is required only when you want to set the output
“high” value greater than TTL levels. For example, to use a +12V external power
supply, the value of the external pull-up resistor is calculated as follows:
VDC
I
max
= I
out low
x safety factor = 1 mA x 0.5 + 0.5 ma
= 24 kΩ
The value of the logic “high” level with the external 24 kΩ pull-up resistor is
calculated as follows:
V
high
= V
cc
x = 12 x = 8.47 VDC
V
cc
12=
R
V
cc
I
max
--------
12
0.0005
·
-------------==
R
external
R
external
R
external
+
---------------------------------------
24 kΩ
24 kΩ 10 kΩ+
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