Operation
6
SNOU153A – October 2017 – Revised February 2019
Copyright © 2017–2019, Texas Instruments Incorporated
LM74700 Evaluation Module
3.2
ORing Application
When using the LM74700-Q1 as an ORing device, if the input supplies operate at slightly different
voltages, the voltage at the common load point will follow the higher voltage. The LM74700-Q1 prevents
reverse current flow from the common load point to the lower voltage supply rail. This test uses two
LM74700EVMs with 15 V at the input of the first EVM and 12 V at the input of the second EVM and the
output of both the EVMs are shorted. As
shows, the 15-V source at EVM1 is turned off for a
period of time and the output (CH2) drops to 12-V source from EVM2. When the 15-V source is turned on
again, the output rises to 15 V from EVM1. CH1 shows the input to EVM1, CH2 shows the output and
CH3 shows input of EVM2.
Figure 6. ORing Application – Higher Supply Switchover
Next, the 12-V source at EVM2 is turned off for a period of time and turned on again, the output (CH2)
does not change.
captures this test.
Figure 7. ORing Application 12-V – Lower Supply Test
