LM556CM Equivalent & Substitute Parts

Part Overview

The LM556CM is a dual timer/oscillator integrated circuit manufactured by onsemi, housed in a 14-SOIC surface mount package. This device is classified as a 555-type timer IC, designed for clock and timing applications. The LM556CM is currently listed as obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity. Substitute parts must maintain functional compatibility through matching package type, pin configuration, and electrical operating parameters.

Key Parameters

Parameter	LM556CM Value
Manufacturer	onsemi
Package / Case	14-SOIC (0.154", 3.90mm Width)
Mounting Type	Surface Mount
Type	555 Type, Timer/Oscillator (Dual)
Voltage - Supply	4.5V ~ 16V
Current - Supply	30 mA
Operating Temperature	0°C ~ 70°C
Moisture Sensitivity Level (MSL)	1 (Unlimited)
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution of the LM556CM is determined by strict adherence to the following electrical and mechanical parameters:

Primary Compatibility Criteria:

Package type: 14-SOIC form factor with 0.154" (3.90mm) width
Mounting type: Surface mount configuration
Device type: Dual 555-type timer/oscillator IC
Voltage supply range: Minimum 4.5V operation capability
Pin configuration: 14-pin SOIC standard

Substitution Categories:

Upgrade Parts maintain full backward compatibility with identical electrical specifications and enhanced product status:

NA556D and NA556DR (Texas Instruments) — Active product status, extended temperature range (-40°C to 105°C), reduced supply current (20 mA)

Similar Parts provide functional equivalence with variations in frequency rating, supply current, or temperature range:

NE556D and NE556DR (STMicroelectronics / Texas Instruments) — Frequency-rated variants (500kHz / 100kHz), reduced supply current (20 mA)
TLC556 series (Texas Instruments) — LinCMOS™ technology variants with extended frequency capability (2.1MHz), reduced supply current (720 µA), wider voltage range (2V ~ 15V or 3V ~ 15V), active product status

All substitute parts maintain the 14-SOIC package specification and surface mount configuration required for direct PCB replacement.

Parameter Comparison

Part Number	Manufacturer	Package	Voltage Supply	Current Supply	Operating Temp	Frequency	Product Status	RoHS Status
LM556CM	onsemi	14-SOIC	4.5V ~ 16V	30 mA	0°C ~ 70°C	—	Obsolete	—
NA556D	Texas Instruments	14-SOIC	4.5V ~ 16V	20 mA	-40°C ~ 105°C	—	Obsolete	ROHS3 Compliant
NA556DR	Texas Instruments	14-SOIC	4.5V ~ 16V	20 mA	-40°C ~ 105°C	—	Active	ROHS3 Compliant
NE556D	STMicroelectronics	14-SOIC	4.5V ~ 16V	20 mA	0°C ~ 70°C	500kHz	Obsolete	ROHS3 Compliant
NE556DR	Texas Instruments	14-SOIC	4.5V ~ 16V	20 mA	0°C ~ 70°C	100kHz	Active	ROHS3 Compliant
TLC556CD	Texas Instruments	14-SOIC	2V ~ 15V	720 µA	0°C ~ 70°C	2.1MHz	Active	ROHS3 Compliant
TLC556CDR	Texas Instruments	14-SOIC	2V ~ 15V	720 µA	0°C ~ 70°C	2.1MHz	Active	ROHS3 Compliant
TLC556ID	Texas Instruments	14-SOIC	3V ~ 15V	720 µA	-40°C ~ 85°C	2.1MHz	Active	ROHS3 Compliant
TLC556IDR	Texas Instruments	14-SOIC	3V ~ 15V	720 µA	-40°C ~ 85°C	2.1MHz	Active	ROHS3 Compliant
TLC556MD	Texas Instruments	14-SOIC	5V ~ 15V	720 µA	-55°C ~ 125°C	2.1MHz	Last Time Buy	ROHS3 Compliant
TLC556MDG4	Texas Instruments	14-SOIC	5V ~ 15V	720 µA	-55°C ~ 125°C	2.1MHz	Last Time Buy	ROHS3 Compliant

Engineering Selection Recommendations

For Direct Replacement (Obsolete to Active): NA556DR is the primary upgrade path. It maintains identical electrical specifications to the LM556CM (4.5V ~ 16V supply, 14-SOIC package) while offering active product status and ROHS3 compliance. The reduced supply current (20 mA vs. 30 mA) provides improved power efficiency without functional compromise.

For Extended Temperature Range Applications: NE556DR provides active product status with identical supply voltage range and package configuration. The 100kHz frequency rating and 0°C ~ 70°C operating temperature match the LM556CM thermal envelope, with ROHS3 compliance.

For Low-Power or High-Frequency Applications: TLC556 series variants (CD, CDR, ID, IDR, MD, MDG4) offer LinCMOS™ technology with significantly reduced supply current (720 µA) and extended frequency capability (2.1MHz). These parts are suitable for applications requiring lower power consumption or higher operating frequencies. All variants maintain 14-SOIC packaging and active product status (except MD and MDG4, which are Last Time Buy).

Compliance Considerations: All substitute parts listed carry ROHS3 compliance certification. The LM556CM does not specify RoHS status; substitution with ROHS3-compliant parts ensures regulatory alignment for new designs and production runs.

Frequently Asked Questions (FAQ)

Q: Can NA556DR directly replace LM556CM in existing designs? A: Yes. NA556DR maintains identical supply voltage range (4.5V ~ 16V), 14-SOIC package configuration, and dual 555-type timer functionality. The reduced supply current (20 mA vs. 30 mA) is a beneficial characteristic. No circuit modifications are required.

Q: What is the difference between NE556D and NE556DR? A: Both parts are functionally identical 555-type dual timers in 14-SOIC packages with 100kHz frequency rating. NE556D is obsolete; NE556DR is active product status. For new designs, NE556DR is the recommended selection.

Q: Why do TLC556 variants have lower supply current? A: TLC556 series uses LinCMOS™ technology, which inherently reduces power consumption to 720 µA compared to 30 mA for the LM556CM. This is a technology advantage, not a limitation. Functional compatibility is maintained across all 555-type timer applications.

Q: Are TLC556 parts pin-compatible with LM556CM? A: Yes. All TLC556 variants (CD, CDR, ID, IDR, MD, MDG4) use the same 14-SOIC package and pin configuration as the LM556CM. Direct PCB substitution is possible.

Q: What is the difference between TLC556CD and TLC556ID? A: Both are 2.1MHz dual timers in 14-SOIC packages with identical supply current (720 µA). TLC556CD operates at 0°C ~ 70°C with 2V ~ 15V supply range. TLC556ID operates at -40°C ~ 85°C with 3V ~ 15V supply range. Select based on required temperature and voltage specifications.

Q: Can I use TLC556MD for applications requiring -55°C operation? A: Yes. TLC556MD and TLC556MDG4 are rated for -55°C ~ 125°C operating temperature, making them suitable for extended temperature range applications. Both maintain 14-SOIC packaging and 2.1MHz frequency capability. Note: Both parts are Last Time Buy status.

Q: What packaging options are available for substitute parts? A: All substitute parts are available in 14-SOIC surface mount package. Packaging variants (Tube, Cut Tape & Digi-Reel®) differ by supplier but do not affect electrical or mechanical compatibility. Select based on procurement and assembly requirements.

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