SMAJ8.5C Transient Voltage Suppressor Equivalent & Substitute Parts

Part Overview

The SMAJ8.5C is a bidirectional Zener transient voltage suppressor (TVS) diode manufactured by Littelfuse, designed for general-purpose overvoltage protection in surface-mount applications. The device features an 8.5V reverse standoff voltage with a 15.12V maximum clamping voltage at peak pulse current of 27.8A. The SMAJ8.5C is classified as obsolete, necessitating identification of active equivalent and substitute parts that maintain electrical and mechanical compatibility for new designs and production continuity.

Key Parameters

Parameter	Value	Unit
Reverse Standoff Voltage (Typ)	8.5	V
Breakdown Voltage (Min)	8.93	V
Clamping Voltage (Max) @ Ipp	15.12	V
Peak Pulse Current (10/1000µs)	27.8	A
Peak Pulse Power	400	W
Package / Case	DO-214AC, SMA	—
Mounting Type	Surface Mount	—
Operating Temperature Range	-65°C to 150°C	TJ
Type	Zener	—
Bidirectional Channels	1	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution of the SMAJ8.5C is determined by strict alignment of the following electrical and mechanical parameters:

Primary Substitution Criteria:

Reverse standoff voltage: 8.5V (±tolerance)
Bidirectional channels: 1
Package / Case: DO-214AC (SMA)
Mounting type: Surface Mount
Type: Zener diode

Secondary Compatibility Parameters:

Breakdown voltage minimum: 9.4V to 9.5V range
Clamping voltage maximum @ Ipp: 14.4V to 19.5V range
Peak pulse current: 27.6A to 205A (dependent on application requirements)
Peak pulse power: 400W to 600W
Operating temperature range: minimum -55°C to -65°C; maximum 150°C to 175°C

Substitute parts are grouped into two categories based on clamping voltage performance:

Group A (Lower Clamping Voltage: 14.4V): SMAJ8.5CA (MDD), SMAJ8.5CA-13 (Diodes Incorporated), SMAJ8.5CA-13-F (Diodes Incorporated), SMAJ8.5CA-TP (Micro Commercial Co), SMAJ8.5CAE3/TR13 (Microchip Technology), P4SMA10CA-E3/5A (Vishay), P4SMA10CA-E3/61 (Vishay)

Group B (Higher Clamping Voltage: 18.7V–19.5V): SMA6J8.5CA-TR (STMicroelectronics), SMAJ8.5CA-TR (STMicroelectronics)

All substitute parts maintain the 8.5V reverse standoff voltage, single bidirectional channel configuration, and DO-214AC (SMA) package specification required for direct mechanical and electrical compatibility.

Parameter Comparison

Part Number	Manufacturer	Reverse Standoff (V)	Breakdown Min (V)	Clamping Max @ Ipp (V)	Peak Pulse Current (A)	Peak Pulse Power (W)	Operating Temp (°C)	Product Status	RoHS Status
SMAJ8.5C	Littelfuse	8.5	8.93	15.12	27.8	400	-65 to 150	Obsolete	ROHS3
SMAJ8.5CA	MDD	8.5	9.44	14.4	27.8	400	-50 to 150	Active	ROHS3
P4SMA10CA-E3/5A	Vishay	8.55	9.5	14.5	27.6	400	-65 to 150	Active	ROHS3
P4SMA10CA-E3/61	Vishay	8.55	9.5	14.5	27.6	400	-65 to 150	Active	ROHS3
SMA6J8.5CA-TR	STMicroelectronics	8.5	9.4	18.7	205 (8/20µs)	600	-55 to 175	Active	ROHS3
SMAJ8.5CA-13	Diodes Incorporated	8.5	9.44	14.4	27.7	400	-55 to 150	Discontinued	Non-compliant
SMAJ8.5CA-13-F	Diodes Incorporated	8.5	9.44	14.4	27.7	400	-55 to 150	Active	ROHS3
SMAJ8.5CA-TP	Micro Commercial Co	8.5	9.44	14.4	27.7	400	-55 to 175	Active	ROHS3
SMAJ8.5CA-TR	STMicroelectronics	8.5	9.4	19.5	124 (8/20µs)	400	-55 to 150	Active	ROHS3
SMAJ8.5CAE3/TR13	Microchip Technology	8.5	9.44	14.4	34.7	500	-65 to 150	Active	ROHS3

Engineering Selection Recommendations

Primary Recommendation for Direct Replacement:

SMAJ8.5CA-13-F (Diodes Incorporated) provides the closest electrical and mechanical match to the SMAJ8.5C. This part maintains identical reverse standoff voltage (8.5V), clamping voltage (14.4V), peak pulse current (27.7A), and peak pulse power (400W) specifications. The device is ROHS3 compliant, carries active product status, and is available in high inventory quantities (130,200 pcs). Operating temperature range (-55°C to 150°C) covers the original specification minimum of -65°C with a 10°C reduction, acceptable for most general-purpose applications.

Alternative Selections Based on Application Requirements:

For applications requiring extended low-temperature operation to -65°C, select P4SMA10CA-E3/5A or P4SMA10CA-E3/61 (Vishay). Both maintain 8.55V reverse standoff voltage, 14.5V clamping voltage, and 27.6A peak pulse current. These parts are ROHS3 compliant and active, with full -65°C to 150°C operating temperature coverage.

For applications requiring higher peak pulse current capability (34.7A) and increased power dissipation (500W), select SMAJ8.5CAE3/TR13 (Microchip Technology). This part maintains the full -65°C to 150°C operating temperature range and ROHS3 compliance.

For applications requiring higher clamping voltage performance (18.7V–19.5V) and enhanced transient suppression, select SMA6J8.5CA-TR or SMAJ8.5CA-TR (STMicroelectronics). These parts provide increased peak pulse power (600W for SMA6J8.5CA-TR) and higher peak pulse current ratings, suitable for more demanding overvoltage protection scenarios.

Avoid:

SMAJ8.5CA-13 (Diodes Incorporated) is discontinued at DiGi Electronics and carries RoHS non-compliant status. This part is not recommended for new designs.

Frequently Asked Questions (FAQ)

Q: Can SMAJ8.5CA-13-F directly replace SMAJ8.5C in existing designs?

A: Yes. SMAJ8.5CA-13-F maintains identical reverse standoff voltage (8.5V), clamping voltage (14.4V), peak pulse current (27.7A), and package specification (DO-214AC, SMA). The operating temperature range is -55°C to 150°C versus the original -65°C to 150°C; this 10°C reduction at the low end is acceptable for general-purpose applications operating above -55°C.

Q: What is the difference between Group A and Group B substitute parts?

A: Group A parts (SMAJ8.5CA, SMAJ8.5CA-13-F, SMAJ8.5CA-TP, SMAJ8.5CAE3/TR13, P4SMA10CA-E3/5A, P4SMA10CA-E3/61) feature clamping voltages of 14.4V to 14.5V, matching the original SMAJ8.5C specification of 15.12V within acceptable tolerance. Group B parts (SMA6J8.5CA-TR, SMAJ8.5CA-TR) feature higher clamping voltages of 18.7V to 19.5V, providing enhanced transient suppression at the cost of higher voltage clamping. Selection depends on circuit voltage margin requirements.

Q: Are all substitute parts ROHS3 compliant?

A: All recommended substitute parts are ROHS3 compliant except SMAJ8.5CA-13 (Diodes Incorporated), which is RoHS non-compliant and discontinued. SMAJ8.5CA-13-F is the ROHS3-compliant active variant of the same base part number.

Q: What packaging options are available for substitute parts?

A: All substitute parts use DO-214AC (SMA) surface-mount package, identical to the original SMAJ8.5C. Packaging variants include Tape & Reel (TR), Cut Tape (CT) & Digi-Reel®, and bulk options. Tape & Reel packaging is standard for production quantities.

Q: Which substitute part offers the widest operating temperature range?

A: SMA6J8.5CA-TR (STMicroelectronics) and SMAJ8.5CA-TP (Micro Commercial Co) both support -55°C to 175°C operating range, extending the upper temperature limit by 25°C compared to the original SMAJ8.5C specification of -65°C to 150°C.

Q: Can I use SMAJ8.5CAE3/TR13 as a drop-in replacement?

A: Yes. SMAJ8.5CAE3/TR13 (Microchip Technology) is a direct mechanical and electrical replacement with identical reverse standoff voltage (8.5V) and clamping voltage (14.4V). It offers enhanced peak pulse current (34.7A versus 27.8A) and increased power dissipation (500W versus 400W), making it suitable for higher-stress applications while maintaining full -65°C to 150°C temperature coverage and ROHS3 compliance.

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