Equivalent & Substitute Parts for 1338AC-18SRGI

Part Overview

The 1338AC-18SRGI is a Real Time Clock (RTC) IC manufactured by Renesas Electronics Corporation, designed for clock/calendar applications with I2C serial interface. This 16-SOIC surface mount device provides 56 bytes of memory with 12/24-hour time format and leap year capability. The part is currently listed as obsolete, making equivalent and substitute parts necessary for ongoing system support and new designs requiring similar functionality.

Key Parameters

Parameter	Value
Manufacturer Part Number	1338AC-18SRGI
Manufacturer	Renesas Electronics Corporation
Category	Clock/Timing
Type	Clock/Calendar
Package / Case	16-SOIC (0.295", 7.50mm Width)
Memory Size	56B
Interface	I2C, 2-Wire Serial
Voltage - Supply	1.8V ~ 5.5V
Voltage - Supply, Battery	1.3V ~ 3.7V
Current - Timekeeping (Max)	2µA @ 3.3V
Operating Temperature	-40°C ~ 85°C
Mounting Type	Surface Mount
Features	Leap Year, NVSRAM, Square Wave Output
Time Format	HH:MM:SS (12/24 hr)
Date Format	YY-MM-DD-dd
Product Status	Obsolete
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution for the 1338AC-18SRGI is determined by the following critical parameters:

Primary Substitution Criteria:

Interface: I2C, 2-Wire Serial (mandatory match)
Memory Size: 56B (functional equivalence)
Time Format: HH:MM:SS (12/24 hr) support
Date Format: YY-MM-DD-dd support
Features: Leap Year, NVSRAM, Square Wave Output
Operating Temperature: -40°C ~ 85°C range
RoHS Compliance: ROHS3 Compliant

Package Considerations: The original part uses 16-SOIC (0.295", 7.50mm Width) surface mount packaging. Substitutes may use alternative packages (8-SOIC, 8-TSSOP, 8-MSOP, 8-DIP, 20-SOIC) provided the application PCB layout can accommodate the different form factor and pin configuration.

Voltage Compatibility: The 1338AC-18SRGI operates from 1.8V ~ 5.5V supply with battery backup from 1.3V ~ 3.7V. Substitute parts must support overlapping or equivalent voltage ranges to ensure compatibility with existing power supply designs.

Product Status: Direct substitutes with Active product status are preferred for long-term availability and supply chain stability.

Parameter Comparison

Parameter	1338AC-18SRGI (Main)	DS1338C-18#	DS1307+	DS1307Z+T&R	DS1308U-18+	DS1338U-3+T&R	DS1339AU+T	DS3232MZ+	DS3232SN#	M41ST87WMX6TR	M41T83RMY6F
Manufacturer	Renesas	Analog Devices/Maxim	Analog Devices/Maxim	Analog Devices/Maxim	Analog Devices/Maxim	Analog Devices/Maxim	Analog Devices/Maxim	Analog Devices/Maxim	Analog Devices/Maxim	STMicroelectronics	STMicroelectronics
Product Status	Obsolete	Active	Active	Active	Active	Active	Active	Active	Active	Active	Active
Package / Case	16-SOIC (7.50mm)	16-SOIC (7.50mm)	8-DIP (7.62mm)	8-SOIC (3.90mm)	8-TSSOP/MSOP (3.00mm)	8-TSSOP/MSOP (3.00mm)	8-TSSOP/MSOP (3.00mm)	8-SOIC (3.90mm)	20-SOIC (7.50mm)	28-SOIC (7.50mm)	18-SOX (7.50mm)
Mounting Type	Surface Mount	Surface Mount	Through Hole	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Interface	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial
Memory Size	56B	56B	56B	56B	56B	56B	Not Specified	236B	236B	128B	7B
Time Format	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS:hh (24 hr)	HH:MM:SS:hh (24 hr)
Date Format	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd
Voltage - Supply	1.8V ~ 5.5V	1.71V ~ 5.5V	4.5V ~ 5.5V	4.5V ~ 5.5V	1.71V ~ 5.5V	2.7V ~ 5.5V	1.71V ~ 5.5V	2.3V ~ 4.5V	2.3V ~ 5.5V	2.7V ~ 3.6V	2.7V ~ 5.5V
Voltage - Supply, Battery	1.3V ~ 3.7V	1.3V ~ 3.7V	2V ~ 4.6V	2V ~ 4.6V	1.3V ~ 5.5V	1.3V ~ 3.7V	1.3V ~ 3.7V	2.3V ~ 4.5V	2.3V ~ 5.5V	2.5V ~ 3.6V	2V ~ 5.5V
Current - Timekeeping (Max)	2µA @ 3.3V	100µA @ 1.89V	200µA @ 5V	200µA @ 5V	100µA @ 1.89V ~ 5.5V	200µA @ 3.3V	200µA @ 1.71V ~ 5.5V	175µA @ 2.3V ~ 4.5V	120µA ~ 160µA @ 3.3V ~ 5.5V	0.5mA @ 2.7V ~ 3.6V	10µA @ 5.5V
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	0°C ~ 70°C	0°C ~ 70°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C
Features	Leap Year, NVSRAM, Square Wave Output	Leap Year, NVSRAM, Square Wave Output	Leap Year, NVSRAM, Square Wave Output	Leap Year, NVSRAM, Square Wave Output	Leap Year, NVSRAM, Square Wave Output	Leap Year, NVSRAM, Square Wave Output	Alarm, Leap Year, Square Wave Output, Trickle-Charger	Alarm, Leap Year, Square Wave Output, SRAM	Alarm, Leap Year, Square Wave Output, SRAM, TCXO/Crystal	Alarm, Leap Year, NVSRAM, Square Wave Output, Supervisor, Watchdog Timer	Alarm, Leap Year, Square Wave Output, SRAM, Watchdog Timer
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
MSL Rating	3 (168 Hours)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	3 (168 Hours)	1 (Unlimited)

Engineering Selection Recommendations

Tier 1 - Direct Package Equivalent (16-SOIC Surface Mount):

DS1338C-18# is the closest functional equivalent to the 1338AC-18SRGI. Both devices use 16-SOIC packaging with identical memory size (56B), interface (I2C), and feature set (Leap Year, NVSRAM, Square Wave Output). DS1338C-18# is manufactured by Analog Devices Inc./Maxim Integrated with Active product status, ensuring long-term availability. The supply voltage range (1.71V ~ 5.5V) overlaps the original specification, and operating temperature range (-40°C ~ 85°C) is identical. MSL rating improves from 3 to 1, reducing moisture sensitivity concerns during storage and handling.

Tier 2 - Alternative Surface Mount Packages (Reduced Footprint):

For applications where PCB layout permits smaller packages, DS1307Z+T&R (8-SOIC), DS1308U-18+ (8-TSSOP/MSOP), and DS1338U-3+T&R (8-TSSOP/MSOP) provide equivalent functionality with reduced board space. These parts maintain I2C interface, 56B memory, and -40°C ~ 85°C operating range. DS1308U-18+ and DS1338U-3+T&R support the full 1.71V ~ 2.7V lower voltage range, beneficial for battery-powered applications. All three are Active status with MSL rating of 1.

Tier 3 - Enhanced Functionality Alternatives:

DS3232MZ+ and DS3232SN# offer expanded memory (236B versus 56B) with integrated alarm functionality and SRAM. These parts maintain I2C interface and -40°C ~ 85°C operating range but operate within narrower voltage windows (2.3V ~ 4.5V or 2.3V ~ 5.5V). Selection depends on whether additional memory and alarm features justify voltage range constraints.

M41ST87WMX6TR (STMicroelectronics, 28-SOIC) provides 128B memory with supervisor and watchdog timer functions. Voltage range (2.7V ~ 3.6V) is more restrictive than the original part. M41T83RMY6F offers integrated crystal with minimal memory (7B) and lowest timekeeping current (10µA @ 5.5V), suitable for ultra-low-power applications.

Tier 4 - Legacy Through-Hole Option:

DS1307+ (8-DIP) provides backward compatibility for through-hole designs but operates within narrower voltage range (4.5V ~ 5.5V) and reduced temperature range (0°C ~ 70°C). This option is suitable only when PCB layout mandates through-hole mounting.

Compliance and Certification:

All substitute parts are ROHS3 Compliant and REACH Unaffected, matching the original part's regulatory status. MSL ratings for Analog Devices/Maxim and STMicroelectronics parts are generally 1 (Unlimited), providing superior moisture handling compared to the original MSL 3 rating.

Frequently Asked Questions (FAQ)

Q: Can DS1338C-18# directly replace 1338AC-18SRGI without PCB modifications?

A: Yes. DS1338C-18# uses identical 16-SOIC (0.295", 7.50mm Width) packaging with the same pin configuration. Both devices support I2C interface, 56B memory, and identical time/date formats. No PCB layout changes are required for direct substitution.

Q: What is the primary difference between DS1338C-18# and DS1307Z+T&R?

A: Package size and voltage range. DS1338C-18# uses 16-SOIC (7.50mm width) while DS1307Z+T&R uses 8-SOIC (3.90mm width), reducing board footprint by approximately 50%. DS1307Z+T&R operates at 4.5V ~ 5.5V (narrower range) and 0°C ~ 70°C (narrower temperature range) compared to DS1338C-18#'s 1.71V ~ 5.5V and -40°C ~ 85°C. Select DS1307Z+T&R only if your application operates within these narrower specifications and requires smaller package size.

Q: Why do DS3232MZ+ and DS3232SN# have higher memory (236B) but narrower voltage range?

A: DS3232 series integrates additional features (alarm, SRAM, temperature-compensated oscillator) that require more silicon area and operate optimally within 2.3V ~ 4.5V range. The original 1338AC-18SRGI supports 1.8V ~ 5.5V for simpler functionality. Select DS3232 only if your application requires expanded memory and alarm features and operates within the specified voltage window.

Q: Is MSL rating important for my application?

A: MSL (Moisture Sensitivity Level) rating indicates how long a component can be stored in dry conditions before moisture absorption becomes problematic. The original 1338AC-18SRGI has MSL 3 (168 hours maximum), requiring careful handling. Most substitute parts (DS1338C-18#, DS1307Z+T&R, DS1308U-18+, DS1338U-3+T&R, DS1339AU+T, DS3232MZ+, DS3232SN#, M41T83RMY6F) have MSL 1 (Unlimited), eliminating moisture-related storage constraints. M41ST87WMX6TR retains MSL 3, matching the original specification.

Q: Can I use M41ST87WMX6TR as a direct replacement?

A: M41ST87WMX6TR is functionally compatible but requires PCB redesign. It uses 28-SOIC (7.50mm width) packaging versus the original 16-SOIC, increasing board footprint. Voltage range (2.7V ~ 3.6V) is more restrictive than 1338AC-18SRGI (1.8V ~ 5.5V). Select M41ST87WMX6TR only if your application operates within 2.7V ~ 3.6V and you require supervisor and watchdog timer functions not present in the original part.

Q: Which substitute offers the lowest power consumption?

A: M41T83RMY6F provides the lowest timekeeping current at 10µA @ 5.5V, compared to 1338AC-18SRGI's 2µA @ 3.3V. However, M41T83RMY6F's 7B memory is significantly reduced from the original 56B. For low-power applications requiring 56B memory, DS1338C-18# (100µA @ 1.89V) or DS1308U-18+ (100µA @ 1.89V ~ 5.5V) are preferred.

Q: What is the difference between DS1338U-3+T&R and DS1308U-18+?

A: Both use 8-TSSOP/MSOP (3.00mm width) packaging and support I2C interface with 56B memory. DS1308U-18+ operates from 1.71V ~ 5.5V with -40°C ~ 85°C range. DS1338U-3+T&R operates from 2.7V ~ 5.5V with -40°C ~ 85°C range. DS1308U-18+ supports lower minimum voltage (1.71V versus 2.7V), making it suitable for battery-powered applications requiring extended voltage range.

Q: Can I use DS1307+ (through-hole DIP) in a surface mount design?

A: DS1307+ requires through-hole mounting and is not suitable for surface mount PCBs. Use only if your application mandates through-hole components. Operating temperature range (0°C ~ 70°C) is narrower than the original part (-40°C ~ 85°C), limiting use in industrial or automotive environments.

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