Powering car electronics with no switching noise and 99.9% efficiency: Page 7 of 7

August 20, 2020 //By David Megaw, ADI
Powering car electronics with no switching noise and 99.9% efficiency
Powering automotive electronics systems can be challenging due to requirements of high reliability while contending with a relatively unstable battery voltage. This article describes a solution that keeps voltage stable – at lowest power dissipation and without the need for fuses.

Figure 6, Figure 7, and Figure 8 show the response of the LT8210 circuit to the load dump, reverse voltage, and starting profile tests, respectively. Figure 9 and Figure 10 demonstrate the efficiency improvement and low current operation possible while in the Pass-Thru window (it’s amazing how efficient doing nothing can be). Figure 11 shows the dynamic transition between Pass-Thru mode and CCM operation. An LTspice simulation of this circuit along with sped up versions of the toughest ISO 16750-2 test pulses is available at analog.com/media/en/simulation-models/LTspice-demo-circuits/LT8210_AutomotivePassThru.asc.


Figure 6. Pass-Thru response to unsuppressed load dump


Figure 7. LT8210 response to reverse battery condition


Figure 8. Pass-Thru response to engine cold crank

 


Figure 9. Efficiency for CCM and Pass-Thru operation


Figure 10. No load input current in Pass-Thru mode (VIN = 12 V)

 


Figure 11. Dynamic transition between Pass-Thru and CCM operation

Conclusion

When designing a power supply for an automotive electronic system, the LT8210 4-switch buck-boost dc-to-dc controller offers a superior solution with its 2.8 V to 100 V input operating range, built-in reverse battery protection, and its new Pass-Thru operating mode. Pass-Thru mode improves upon buck-boost operation, achieving no switching noise, no switching losses, and ultralow quiescent current while regulating the output to a user-programmed window rather than a fixed voltage. The output voltage minimum and maximum values are bounded during large amplitude transients such as load dump and cold crank without MOSFET SOA concerns, or the current or timing limitations that come from linear solutions.

The novel LT8210 control scheme results in clean and fast transitions between the different switching regions (boost, buck-boost, buck, and nonswitching) allowing it to regulate through large signal, high frequency ac voltage on the input. The LT8210 can be toggled between Pass-Thru operation and conventional, fixed output voltage, buck-boost operating modes (CCM, DCM, or Burst Mode) while running, and the fixed output can be set to any voltage within the Pass-Thru window (for example, VOUT = 12 V for an 8 V-to-16 V window). This flexibility allows the user to alternate between Pass-Thru and normal buck-boost operation to trade the low noise, low IQ, high efficiency operation of Pass-Thru mode for the tighter regulation and improved transient response in CCM, DCM, or Burst Mode.

References

1 Dan Eddleman. “Low Quiescent Current Surge Stopper: Robust Automotive Supply Protection for ISO 7637-2 and ISO 16750-2 Compliance.” LT Journal of Analog Innovation, January 2017.

2 Christian Kueck. “Distilled Automotive Electronics Design.” Analog Devices, Inc., April 2013.

3 Bin Wu and Zhongming Yi. “Comprehensive Power Supply System Designs for Harsh Automotive Environments Consume Minimal Space, Preserve Battery Charge, Feature Low EMI.” Analog Dialogue, Vol. 53, August 2019.

4 Dan Eddleman. “LTspice: Models of ISO 7367-2 and ISO 16750-2 Transients.” Analog Devices, Inc., 2019.

ISO 7637-2:2011. International Organization of Standardization, March 2011.

ISO 16750-2:2012. International Organization of Standardization, November 2012.

About the Author

David Megaw is a senior design engineer with ADI. He can be reached at david.megaw@analog.com.

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