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

ISO 7637-2 Pulse #1 & Droputs monitoring tricks

5. November 2021 20:04 by Christian in EMC/EMI, EMC TEST PLAN, OEM Specs, Test Methods
EMC Test Plan tricks

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