KA3843BD Equivalent & Substitute Parts

Part Overview

The KA3843BD is an offline switch IC manufactured by onsemi, designed for power management applications in converter topologies operating up to 500kHz. This 14-SOIC surface mount device features frequency control and operates across a 12V to 25V supply voltage range with a 97% duty cycle. The product is currently obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity.

Key Parameters

Parameter	KA3843BD Value
Manufacturer	onsemi
Category	Power Management (PMIC)
Package / Case	14-SOIC (0.154", 3.90mm Width)
Voltage - Supply (Vcc/Vdd)	12V ~ 25V
Frequency - Switching	Up to 500kHz
Duty Cycle	97%
Control Features	Frequency Control
Operating Temperature	0°C ~ 70°C (TA)
Mounting Type	Surface Mount
Product Status	Obsolete
Moisture Sensitivity Level (MSL)	1 (Unlimited)
REACH Status	REACH Unaffected

Substitute Part Grouping Explanation

Substitution for the KA3843BD is determined by strict alignment of the following electrical and mechanical parameters:

Critical Matching Parameters:

Package / Case: 14-SOIC (0.154", 3.90mm Width)
Frequency - Switching: Up to 500kHz
Control Features: Frequency Control
Mounting Type: Surface Mount
Voltage - Supply (Vcc/Vdd): Minimum 7.6V to 30V range (encompasses the KA3843BD's 12V ~ 25V requirement)
Duty Cycle (Max): 96% or higher (KA3843BD operates at 97%)

All substitute parts listed below meet these core electrical and mechanical requirements, ensuring functional compatibility in offline switch applications. Substitutes are grouped by manufacturer and product status to facilitate selection based on availability and lifecycle considerations.

Parameter Comparison

Part Number	Manufacturer	Package	Voltage Supply (Vcc/Vdd)	Frequency - Switching	Duty Cycle (Max)	Operating Temperature	Product Status	Inventory
KA3843BD	onsemi	14-SOIC	12V ~ 25V	Up to 500kHz	97%	0°C ~ 70°C (TA)	Obsolete	2800 Pcs
NCV3843BVDR2G	onsemi	14-SOIC	7.6V ~ 30V	500kHz	96%	-40°C ~ 125°C (TJ)	Active	15722 Pcs
UC3843BDR2G	onsemi	14-SOIC	7.6V ~ 30V	Up to 500kHz	96%	0°C ~ 70°C (TA)	Active	3500 Pcs
UC3843BVDR2G	onsemi	14-SOIC	7.6V ~ 30V	Up to 500kHz	96%	-40°C ~ 105°C (TA)	Active	2469 Pcs
TL3843BD	Texas Instruments	14-SOIC	7.6V ~ 30V	Up to 500kHz	96%	0°C ~ 70°C (TA)	Last Time Buy	1439 Pcs
TL3843BDR	Texas Instruments	14-SOIC	7.6V ~ 30V	Up to 500kHz	96%	0°C ~ 70°C (TA)	Active	18200 Pcs
TL3843D	Texas Instruments	14-SOIC	7.6V ~ 30V	Up to 500kHz	97%	0°C ~ 70°C (TA)	Last Time Buy	1600 Pcs
TL3843DR	Texas Instruments	14-SOIC	7.6V ~ 30V	Up to 500kHz	97%	0°C ~ 70°C (TA)	Active	19350 Pcs

Engineering Selection Recommendations

Primary Recommendation - Active Status: TL3843DR (Texas Instruments) and TL3843BDR (Texas Instruments) are the preferred substitutes. Both are active products with high inventory availability (19350 Pcs and 18200 Pcs respectively), ensuring long-term supply continuity. TL3843DR matches the KA3843BD's 97% duty cycle specification exactly and operates within the identical 0°C ~ 70°C temperature range.

Secondary Recommendation - onsemi Active Options: UC3843BDR2G and UC3843BVDR2G (onsemi) provide active product alternatives with established supply chains. UC3843BDR2G maintains the 0°C ~ 70°C operating temperature range matching the original part. UC3843BVDR2G extends the temperature range to -40°C ~ 105°C, suitable for applications requiring broader thermal performance.

Alternative - Automotive Grade: NCV3843BVDR2G (onsemi) is an automotive-qualified part (AEC-Q100) with the widest operating temperature range (-40°C ~ 125°C). This option is appropriate for designs requiring automotive-grade reliability and extended thermal specifications.

Avoid - Obsolete Status: TL3843BD and TL3843D carry Last Time Buy status, indicating limited remaining availability. These should be selected only when existing inventory commitments or design lock-in requirements necessitate their use.

Frequently Asked Questions (FAQ)

Q: Can I directly replace KA3843BD with any of these substitute parts? A: Yes, all listed substitutes are electrically and mechanically compatible. They share the same 14-SOIC package, operate at up to 500kHz switching frequency, support frequency control, and meet the voltage supply and duty cycle requirements of the KA3843BD.

Q: What is the difference between TL3843DR and TL3843BDR? A: Both are Texas Instruments TL3843 variants in 14-SOIC packaging with identical electrical specifications. TL3843DR is supplied on tape and reel (TR) with 19350 Pcs inventory. TL3843BDR is supplied on cut tape and digi-reel with 18200 Pcs inventory. Selection depends on packaging and handling requirements.

Q: Why does NCV3843BVDR2G have a different operating temperature range? A: NCV3843BVDR2G is qualified to automotive standards (AEC-Q100) and is rated for -40°C ~ 125°C operation. This extended range is a result of automotive-grade qualification and does not affect substitution compatibility for standard industrial applications operating within 0°C ~ 70°C.

Q: Is the 96% duty cycle of most substitutes compatible with the KA3843BD's 97% specification? A: Yes. The 1% difference is within normal design margins for offline switch applications. TL3843D and TL3843DR both specify 97% duty cycle, matching the original part exactly if this specification is critical.

Q: What packaging options are available? A: All substitutes use the same 14-SOIC (0.154", 3.90mm Width) surface mount package as the KA3843BD. Packaging variations (Cut Tape, Tape & Reel, Tube) affect handling and delivery format but not electrical or mechanical compatibility.

Q: Which substitute has the best long-term availability? A: TL3843DR (Texas Instruments, Active status, 19350 Pcs) and TL3843BDR (Texas Instruments, Active status, 18200 Pcs) offer the strongest supply continuity. Both are active products with substantial inventory levels.

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