EMC FLEX BLOG A site dedicated to Automotive EMC Testing for Electronic Modules

ISO 7637-2 Pulse 1

Conducted Immunity to Transients on battery lines.

Pulse 1 (Us = -150V, Ri = 10Ω, td = 2 ms, tr = 1µs, t1 = ≥ 0.5s (repetition rate), t2 = 200 ms, t3 < 100µs) can upset functionality of electronic modules. Most automotive OEM specs are accepting Class B response (DUT self-recoverable deviations), others are asking Class A response (no deviations) during Pulse 1.

In this particular case the pass/fail criteria was Charging Voltage remains 5V ±0.5V for 12V Battery dropouts ≤ 500µs. The EMC test plan asked the use of DMM to monitor the USB charging function for a Class A expected response:

• This was a simulation of a mobile phone charging event.
• DMM can only detect 5V Charging Voltage dips/drops ≥ 250 µs. A FLUKE can be set to count MAX and MIN voltage peaks, otherwise to monitor 5V fast voltage fluctuations is not practically possible.
• The EMC test plan allowed the use of oscilloscope only for information.

Download this movie to see how the charging function was monitored simultaneously on both oscilloscope and DMM:

5V_Charging_during_P1.mp4 (127.57 mb)  

A similar monitoring equipment limitation was imposed the EMC Test Plan for dropouts test. Download this movie to see how the charging function was monitored simultaneously on both oscilloscope and DMM:

5V_Charging_during_500_microSec_dropout.mp4 (30.91 mb) 

 Christian Rosu, Nov 8, 2021

In EMC "dropout" means Battery drops to 0V. FMC1278R3 (CI 260) is an example of various combinations of such battery voltage dropouts. The problem is that no automotive battery can really drop its output to 0V for say 5 seconds as well as for 50 ms without to blowout a fuse.

 Therefore the only way to simulate correctly a “battery drop to 0V” is to disconnect DUT's B+ line from battery. The test equipment offers such capability to momentarily disconnect the battery during “voltage dropout” simulating a “0V” like condition, practically no current through supply lines to DUT.

This involves the use of PFM200N + VDS200Q + AutoWave to generate the CI 260 type of pulses. PFM200N acts like a very fast switcher disconnecting its output from DUT. So far only FCA (CS.00054) figure it out to ask “open condition” during “0V” battery voltage dropouts. 

In EMC we use the wording “voltage dip” to describe a momentary battery voltage drop (e.g. 4.5V) below minimum supply voltage (e.g. 9V). Obviously in this scenario the Battery B+ line is not disconnected from DUT during the “voltage dip to 4.5V” of 100ms.

Christian Rosu Feb 17, 2021

Test Procedure:

• what the activity is (DUT type)
• who is to perform the activity (EMC Testing Laboratory)
• when the activity is to take place

This is more of an EMC Test Plan Template document that:

• defines the DUT classification and category
• lists required EMC Test Methods defined by the automotive OEM specs or International Standards (ISO, CISPR, SAE, etc.).

Test Method:

• how  the actual EMC testing is to be carried out (test equipment configuration)
• defines measurable data format for reporting and acceptable stress level limits 

This more of a Work Instruction outlined by automotive OEM EMC specs and international standards.

Christian Rosu, Dec 11, 2020.

The automotive OEM specs do not specify how to configure the DUT during CISPR 25 chamber ambient measurements. DUT must be unpowered, all other DUT support equipment must be powered and as much as possible functional to correctly evaluate RF emissions noise floor before start testing. This leaves at least three scenarios for how to configure the DUT.

1.  Test harness connectors are removed from
2.  DUT is unpowered.
3.  The 1.7 m test harness is unterminated on DUT side, no potential ground loops with Load Simulator.
4.  The 5uH LISN remains present.
5.  The Load Simulator and all support equipment remains powered.

CISPR-25 Generic Test Setup for compliance to CS.00054:2018