How should Isat be evaluated for ECU DC-DC converters?
For ECU DC-DC converters, Isat should be evaluated under actual operating conditions, including elevated ambient temperature and self-heating caused by load current. Datasheet values measured at room temperature may not represent real system behavior.
A practical approach is to assess DC bias characteristics at the highest expected operating temperature and confirm sufficient inductance margin during peak load and transient events.
Practical design considerations:
Datasheet saturation current values are frequently specified at 20–25°C. In real ECU environments, ambient temperatures may reach 105°C or higher, significantly reducing the effective saturation margin. Engineers should evaluate DC bias curves at elevated temperatures and include sufficient margin for transient current peaks.
Common pitfalls:
A common mistake is selecting inductors based solely on room-temperature Isat values. This may result in unexpected inductance collapse under load in vehicle operation, leading to increased ripple current, EMI issues, or converter instability.