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STMicroelectronics SM4T39AY — Circuit Protection

STMicroelectronics SM4T39AY Zener, 400W, AEC-Q101, DO-214AC

MPNSM4T39AY
Active

STMicroelectronics SM4T39AY, Automotive Zener, 400W Peak Pulse, 33V Reverse Standoff, 36.7V Breakdown, 69.7V Clamping, DO-214AC SMA, AEC-Q101, -55°C to 150°C.

$0.8900Ref. price · indicative, final on quote
STMicroelectronics SM4T39AY datasheet (PDF)
Sourced new & surplus through independent channelsAuthenticity-screened · ESD-safe packingListing updated Aug 2026

Specifications

SM4T39AY specifications
ParameterValue
TypeZener
Series*
MountingSurface Mount
Voltage - breakdown36.7V
Voltage - clamping (Max) @ ipp69.7V
Voltage - reverse standoff33V
Current - peak pulse (10/1000μs)33A (8/20µs)
Power - peak pulse400W
Power line protectionNo
Operating temperature-55°C ~ 150°C (TJ)
GradeAutomotive
PackageTape & Reel (TR) Cut Tape (CT)
QualificationAEC-Q101
CaseDO-214AC, SMA
Unidirectional channels1

Product details

Automotive-grade Zener for 33V rail clamping

It protects a 33V nominal rail with a breakdown voltage range starting at 36.7V and clamping at 69.7V maximum under surge.

The 69.7V clamping max at 33A (8/20µs pulse) sets the voltage the downstream circuitry must survive during a transient event. The 400W peak pulse power rating gives the energy absorption headroom for automotive load-dump and inductive kickback scenarios. The single unidirectional channel is polarity-specific — confirm the cathode orientation on the board.

Frequently asked questions

Is SM4T39AY AEC-Q101 qualified?

Yes, the SM4T39AY is AEC-Q101 qualified, making it suitable for automotive-grade applications including under-hood and chassis-domain electronics.

What is the difference between SM4T39AY and SM4T39?

The SM4T39AY is the automotive-grade variant with AEC-Q101 qualification, while the base SM4T39 lacks that certification. Electrical characteristics — 33V standoff, 400W peak pulse — are identical.