Two Technologies TechTerm TT1R2, Technical Reference Manual

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Document 15776(1.0.0.0) vii
Determining the Maximum Input Voltage Allowed
The maximum input voltage allowed is based on a unit’s current draw.
To determine the maximum input voltage allowed based on current:
3.
Calculate the maximum current draw using the table on the previous page.
4.
On the following chart, locate the Calculated Total Current on the Calculated Operating
Current axis of the chart, and then move to the top of Operating Voltage range.
5.
Look at the corresponding Maximum Input Voltage Allowed where the intersection occurs to
find the maximum useable voltage for your terminal configuration.
Restricted Input Voltage vs. Current Draw
7.5
8.5
9.5
10.5
11.5
12.5
13.5
14.5
15.5
16.5
17.5
18.5
19.5
20.5
21.5
22.5
23.5
24.5
25.5
26.5
27.5
400 370 340 310 280 250 220 190 160 130 100 70 40
Calculated Operating Current (mA)
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Using Example 1 and the chart above, the 80 mA drawn by the TT1NEL45R2 intersects with
17.5 volts. If the maximum supply voltage to the terminal is greater than 17.5 VDC, it requires
a -H power supply configuration.
Using Example 2 and the chart above, the 335 mA drawn by the TT1VFD45R2 intersects with
8.0 volts. If the maximum supply voltage to the terminal is greater than 8.0 VDC, it requires a -
H power supply configuration.
To clarify, if your system is supplying 12.0 VDC, the power is acceptable for the TT1NEL45R2
(Example 1), but not for the TT1VFD45R2 (Example 2). Applying 12.0 VDC to the
TT1VFD45R2 (Example 2) will
damage it.
Operating
Voltage
Example 1
80 mA, 17.5 VDC
Example 2
335 mA, 8.0 VDC