KA3844B Equivalent & Substitute Parts

Part Overview

The KA3844B is an offline switch IC manufactured by onsemi, designed for power management applications in converter topologies operating up to 500kHz. This 8-DIP through-hole component provides frequency control for offline power supply designs with a supply voltage range of 12V to 25V and 48% duty cycle capability. The part is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production support.

Key Parameters

Parameter	KA3844B Value
Manufacturer	onsemi
Category	Power Management (PMIC)
Package / Case	8-DIP (0.300", 7.62mm)
Mounting Type	Through Hole
Voltage - Supply (Vcc/Vdd)	12V ~ 25V
Frequency - Switching	Up to 500kHz
Duty Cycle	48%
Voltage - Start Up	16 V
Control Features	Frequency Control
Operating Temperature	0°C ~ 70°C (TA)
RoHS Status	ROHS3 Compliant
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution for the KA3844B is determined by strict alignment of the following electrical and mechanical parameters:

Package compatibility: 8-DIP (0.300", 7.62mm) through-hole mounting
Supply voltage range: Minimum 12V operation capability
Switching frequency: Up to 500kHz operation
Duty cycle: 48% maximum
Control features: Frequency control capability
Operating temperature: 0°C to 70°C minimum range
RoHS compliance: ROHS3 Compliant preferred for new designs

Substitute parts are grouped into two categories: direct equivalents (matching all parameters within tolerance) and compatible alternatives (meeting core electrical and mechanical requirements with minor specification variations).

Parameter Comparison

Parameter	KA3844B	UC3844BNG	UC3844BVNG	SG3844M	TL3844BP	TL3844P	UC2845BN	UC3844AN	UC3844BN	UC3844N
Manufacturer	onsemi	onsemi	onsemi	Microchip Technology	Texas Instruments	Texas Instruments	STMicroelectronics	STMicroelectronics	STMicroelectronics	onsemi
Package / Case	8-DIP (0.300", 7.62mm)	8-DIP (0.300", 7.62mm)	8-DIP (0.300", 7.62mm)	8-DIP (0.300", 7.62mm)	8-DIP (0.300", 7.62mm)	8-DIP (0.300", 7.62mm)	8-DIP (0.300", 7.62mm)	8-DIP (0.300", 7.62mm)	8-DIP (0.300", 7.62mm)	8-DIP (0.300", 7.62mm)
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole
Voltage - Supply (Vcc/Vdd)	12V ~ 25V	10V ~ 36V	10V ~ 36V	10V ~ 30V	10V ~ 30V	10V ~ 30V	7.6V ~ 30V	10V ~ 30V	10V ~ 30V	10V ~ 30V
Frequency - Switching	Up to 500kHz	Up to 500kHz	Up to 500kHz	100Hz ~ 500kHz	Up to 500kHz	Up to 500kHz	Up to 500kHz	Up to 500kHz	Up to 500kHz	Up to 500kHz
Duty Cycle	48%	48%	48%	48%	48%	48%	48%	48%	48%	48%
Control Features	Frequency Control	Frequency Control	Frequency Control	Frequency Control	Frequency Control	Frequency Control	Frequency Control	Frequency Control	Frequency Control	Frequency Control
Operating Temperature	0°C ~ 70°C (TA)	0°C ~ 70°C (TA)	-40°C ~ 105°C (TA)	0°C ~ 70°C (TA)	0°C ~ 70°C (TA)	0°C ~ 70°C (TA)	-40°C ~ 150°C (TJ)	0°C ~ 70°C (TA)	0°C ~ 70°C (TJ)	0°C ~ 70°C (TA)
Product Status	Obsolete	Active	Obsolete	Discontinued at DiGi Electronics	Active	Active	Active	Obsolete	Active	Obsolete
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	RoHS non-compliant	ROHS3 Compliant	RoHS non-compliant

Engineering Selection Recommendations

For new designs requiring KA3844B replacement, UC3844BNG is the primary direct equivalent. This part maintains identical electrical specifications, package configuration, and ROHS3 compliance while offering active product status with high inventory availability (364,322 units).

TL3844BP and TL3844P from Texas Instruments provide active alternatives with extended supply voltage range (10V ~ 30V) and identical switching characteristics. Both parts maintain ROHS3 compliance and are suitable for designs operating within the 0°C to 70°C temperature range.

UC2845BN from STMicroelectronics offers extended operating temperature range (-40°C ~ 150°C) and lower minimum supply voltage (7.6V), making it suitable for applications requiring enhanced thermal performance. This part maintains ROHS3 compliance and active product status.

Parts with obsolete or discontinued status (UC3844BVNG, UC3844AN, UC3844N, SG3844M) should be avoided for new production designs. UC3844BN remains available as an active alternative from STMicroelectronics with ROHS3 compliance.

Frequently Asked Questions (FAQ)

Q: Can UC3844BNG directly replace KA3844B in existing designs? A: Yes. UC3844BNG matches the KA3844B in package (8-DIP), mounting type (through-hole), switching frequency (up to 500kHz), duty cycle (48%), and control features (frequency control). The supply voltage range of UC3844BNG (10V ~ 36V) encompasses the KA3844B specification (12V ~ 25V). No circuit modifications are required.

Q: What is the difference between UC3844BNG and UC3844BN? A: Both parts share identical electrical specifications and package configuration. UC3844BNG is supplied in tube packaging by onsemi, while UC3844BN is supplied in tube packaging by STMicroelectronics. Both maintain ROHS3 compliance and active product status. Selection depends on supplier availability and procurement preferences.

Q: Why is UC2845BN listed as a substitute if it has a lower minimum supply voltage? A: UC2845BN meets all core substitution criteria: 8-DIP package, through-hole mounting, up to 500kHz switching frequency, 48% duty cycle, and frequency control. The lower minimum supply voltage (7.6V vs. 12V) represents an expanded operating range that maintains backward compatibility with KA3844B designs. The extended operating temperature range (-40°C ~ 150°C) provides additional design flexibility for thermal-demanding applications.

Q: Are there package alternatives to 8-DIP for KA3844B? A: No. All listed substitutes maintain the 8-DIP (0.300", 7.62mm) through-hole package configuration. Package compatibility is a mandatory substitution criterion for this component category.

Q: Should I use obsolete parts like UC3844BVNG or UC3844AN? A: Obsolete parts should not be selected for new production designs. UC3844BVNG and UC3844AN are listed for reference in legacy system maintenance only. Active alternatives such as UC3844BNG, TL3844BP, TL3844P, UC2845BN, and UC3844BN are recommended for all new applications.

Q: What is the significance of RoHS compliance in selecting a substitute? A: ROHS3 compliance is required for products sold in regulated markets. KA3844B is ROHS3 compliant. Substitutes UC3844AN and UC3844N are RoHS non-compliant and unsuitable for applications requiring regulatory compliance. All other listed substitutes maintain ROHS3 compliance.

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