The electrical fast transient (EFT) immunity test indicates the capability of the device to maintain data integrity during repetitive electrical fast transients and bursts, which often occur from arcing contacts in switches and relays.
|Level||Voltage Peak (kV)||Repetition Frequency(kHz)|
|1||0.25||5 or 100|
|2||0.5||5 or 100|
|3||1||5 or 100|
|4||2||5 or 100|
Per the IEC 61000-4-4 standard, the DUT (Device under test) is tested with 2000 V discharges on the analog input cable. Positive and negative polarity discharges are applied. The duration time of each test is 1 min. The transient and burst waveform is in accordance with IEC 61000-4-4, 5 ns rising time with 50 ns pulse width. 5 kHz repetition frequency was used for the test. The configuration consists of a 0.8 m high wooden table, covered with a sheet of copper that is at least 0.25 mm thick, and connected to the protective grounding system. The DUT is placed on a 0.1 m thick isolating support. A minimum distance of 0.5 m is provided between the DUT and the walls of the laboratory.
Due to the configurability of the AD74115H some use cases were covered other use cases by default reducing the amount of testing required. Some use cases used a different measurement path to cover another use case. The list below shows the coverage:
There was a digital multi meter (DMM) connected to the output load to ensure there was no loss of output during testing and also to ensure the integrity of the internal ADC measurement. To protect the DMM a low pass filter was placed between the load and DMM. The measurements were streamed back to the laptop throughout the testing.
Figure 1 ADP1034 and AD74115H EFT Current Use Case Setup
Figure 2 ADP1034 and AD74115H 4 wire RTD EFT Setup
Figure 3 ADP1034 and AD74115H Current Output Test Setup
Figure 4 ADP1034 and AD74115H Digital Input Logic Test Setup
The software was written in python to facilitate interaction with DMM and DUT simultaneously. At the beginning of each test the pre test configuration was performed. Before the discharges were applied the pre measurement flow of 1000 samples were taken. After discharges the post measurement of 1000 samples were taken. Each sample (ADC and DMM) was taken approximately every 25 ms. Pre test configuration
Pre and Post Measurement Flow
Table 2 gives a summary of the EFT test results. The AD74115H was tested to level 4 according to IEC 61000-4-4 and achieved class B. There were no alert status bits activated throughout the testing. For the digital output use cases a deviation is not recorded as the accuracy is dependent on the load. The test verified that the digital output did not turn off unexpectedly.
|Test Level||Use Case||Measurement Method||Pre Test Average||Post Test Average||Deviation (%FSR)||Performance|
|2 kV||Current Output||DMM||12.47058 mA||12.47095 mA||- 0.00112||Class B|
|Current Output RSENSE||ADC||12.48626 mA||12.48615 mA||- 0.000438||Class B|
|4 Wire RTD||ADC||108.60329 Ω||108.58727 Ω||- 0.00305||Class B|
|Digital Input Logic||Internal Counter||6||6||0||Class B|
|Digital Output Internal||DMM||57.49649 mA||57.50053 mA||N/A||Class B|
|Digital Output External||DMM||80.8106 mA||80.65714 mA||N/A||Class B|
|- 2 kV||Current Output||DMM||12.49751 mA||12.49579 mA||- 0.00688||Class B|
|Current Output RSENSE||ADC||12.48614 mA||12.48626 mA||0.00046||Class B|
|4 Wire RTD||ADC||108.59528 Ω||108.59528 Ω||0.00000||Class B|
|Digital Input Logic||Internal Counter||7||7||0||Class B|
|Digital Output Internal||DMM||57.49162 mA||57.50294 mA||N/A||Class B|
|Digital Output External||DMM||80.66309 mA||80.66651 mA||N/A||Class B|