Equivalent & Substitute Parts for X1226S8 Real Time Clock IC

Part Overview

The X1226S8 is a Real Time Clock (RTC) IC manufactured by Renesas Electronics Corporation, designed for clock/calendar applications with I2C 2-Wire Serial interface in an 8-SOIC package. The device provides time and date tracking with alarm and leap year functionality, operating across a 2.7V to 5.5V supply range with battery backup support from 1.8V to 5.5V.

The X1226S8 is classified as obsolete. Identifying functionally equivalent substitute parts is essential for design continuity, system redesigns, and procurement when original inventory becomes unavailable.

Key Parameters

Parameter	X1226S8 Specification
Manufacturer	Renesas Electronics Corporation
Product Status	Obsolete
Package / Case	8-SOIC (0.154", 3.90mm Width)
Type	Clock/Calendar
Interface	I2C, 2-Wire Serial
Time Format	HH:MM:SS (12/24 hr)
Date Format	YY-MM-DD-dd
Features	Alarm, Leap Year
Voltage - Supply	2.7V ~ 5.5V
Voltage - Supply, Battery	1.8V ~ 5.5V
Current - Timekeeping (Max)	10µA ~ 20µA @ 2.7V ~ 5V
Operating Temperature	0°C ~ 70°C
Mounting Type	Surface Mount
RoHS Status	RoHS non-compliant

Substitute Part Grouping Explanation

Substitute parts for the X1226S8 are identified based on the following critical parameters that determine functional compatibility:

Primary Substitution Criteria:

Interface type: I2C, 2-Wire Serial
Package compatibility: 8-SOIC form factor preferred for direct PCB replacement
Time/Date format support: HH:MM:SS and YY-MM-DD-dd capability
Supply voltage overlap: Minimum 2.7V operation or lower
Battery backup support: Presence of backup voltage capability
Core features: Alarm and Leap Year support

Substitution Groups:

Group 1: Direct 8-SOIC Package Replacements (Preferred) Parts maintaining the same 8-SOIC (0.154", 3.90mm Width) package enable direct PCB substitution without layout modifications. These include DS1338Z-33+T&R, M41T56M6F, and MCP79400-I/SN.

Group 2: Alternative Package Formats (8-TSSOP/8-MSOP) Parts using 8-TSSOP or 8-MSOP packages (0.118", 3.00mm Width) provide functional equivalence but require PCB layout redesign. These include DS1339AU+, DS1340U-18+, and DS1342U+.

Group 3: Enhanced Feature Variants (Larger Packages) Parts with expanded memory, additional features, or larger packages (16-SOIC, 20-SOIC, 28-SOIC, 16-QFN) provide functional superset capability but require significant PCB redesign. These include DS3231SN#, DS3232SN#T&R, M41ST85WMX6TR, and M41T83ZQA6F.

Parameter Comparison

Part Number	Manufacturer	Package	Status	Interface	Supply Voltage	Battery Voltage	Time Format	Date Format	Features	RoHS
X1226S8	Renesas	8-SOIC	Obsolete	I2C	2.7V ~ 5.5V	1.8V ~ 5.5V	HH:MM:SS (12/24)	YY-MM-DD-dd	Alarm, Leap Year	Non-compliant
DS1338Z-33+T&R	Analog Devices/Maxim	8-SOIC	Active	I2C	3V ~ 5.5V	1.3V ~ 3.7V	HH:MM:SS (12/24)	YY-MM-DD-dd	Leap Year, NVSRAM, Square Wave	ROHS3
DS1339AU+	Analog Devices/Maxim	8-TSSOP/MSOP	Active	I2C	1.71V ~ 5.5V	1.3V ~ 3.7V	HH:MM:SS (12/24)	YY-MM-DD-dd	Alarm, Leap Year, Square Wave, Trickle-Charger	ROHS3
DS1340U-18+	Analog Devices/Maxim	8-TSSOP/MSOP	Active	I2C	1.71V ~ 5.5V	1.3V ~ 3.7V	HH:MM:SS (24)	YY-MM-DD-dd	Leap Year, Trickle-Charger	ROHS3
DS1342U+	Analog Devices/Maxim	8-TSSOP/MSOP	Active	I2C	1.8V ~ 5.5V	Not specified	HH:MM:SS (12/24)	YY-MM-DD-dd	Alarm, Leap Year, Square Wave	ROHS3
DS3231SN#	Analog Devices/Maxim	16-SOIC	Active	I2C	2.3V ~ 5.5V	2.3V ~ 5.5V	HH:MM:SS (12/24)	YY-MM-DD-dd	Alarm, Leap Year, Square Wave, TCXO/Crystal	ROHS3
DS3232SN#T&R	Analog Devices/Maxim	20-SOIC	Active	I2C	2.3V ~ 5.5V	2.3V ~ 5.5V	HH:MM:SS (12/24)	YY-MM-DD-dd	Alarm, Leap Year, Square Wave, SRAM, TCXO/Crystal	ROHS3
M41ST85WMX6TR	STMicroelectronics	28-SOIC	Active	I2C	2.7V ~ 3.6V	2.5V ~ 4.6V	HH:MM:SS:hh (24)	YY-MM-DD-dd	Alarm, Leap Year, NVSRAM, Square Wave, Supervisor, Watchdog	ROHS3
M41T56M6F	STMicroelectronics	8-SOIC	Active	I2C	4.5V ~ 5.5V	2.5V ~ 4.6V	HH:MM:SS (24)	YY-MM-DD-dd	Leap Year, NVSRAM	ROHS3
M41T83ZQA6F	STMicroelectronics	16-VQFN	Active	I2C	2.38V ~ 5.5V	2V ~ 5.5V	HH:MM:SS:hh (24)	YY-MM-DD-dd	Alarm, Leap Year, Square Wave, SRAM, Watchdog	ROHS3
MCP79400-I/SN	Microchip Technology	8-SOIC	Active	I2C	1.8V ~ 5.5V	1.3V ~ 5.5V	HH:MM:SS (12/24)	YY-MM-DD-dd	Alarm, Leap Year, Square Wave, SRAM, Unique ID	ROHS3

Engineering Selection Recommendations

For Direct PCB Replacement (No Layout Changes):

Select from Group 1 parts maintaining 8-SOIC packaging: DS1338Z-33+T&R, M41T56M6F, or MCP79400-I/SN. All three are active products with ROHS3 compliance. DS1338Z-33+T&R and MCP79400-I/SN provide the broadest supply voltage range (1.8V minimum or lower) and support both 12/24-hour time formats matching the X1226S8. M41T56M6F operates at 4.5V minimum, limiting low-voltage applications.

For Low-Power Applications:

MCP79400-I/SN offers 1.2µA typical timekeeping current at 3.3V, significantly lower than the X1226S8 specification. DS1342U+ provides 0.6µA to 0.7µA at 3V to 5V, the lowest power consumption among all candidates, though it requires PCB redesign due to 8-TSSOP/MSOP packaging.

For Extended Temperature Range:

All substitute parts operate across -40°C to 85°C, exceeding the X1226S8 range of 0°C to 70°C. This provides design margin for industrial applications.

For Compliance-Critical Applications:

All substitute parts carry ROHS3 compliance, whereas the X1226S8 is RoHS non-compliant. Select any active substitute when regulatory compliance is required.

For Enhanced Features:

DS3232SN#T&R and M41ST85WMX6TR provide integrated SRAM and additional supervisory functions. These require PCB redesign but offer expanded functionality for complex timing applications.

Frequently Asked Questions (FAQ)

Q: Can DS1338Z-33+T&R directly replace X1226S8 without PCB modification?

A: Yes. Both use 8-SOIC (0.154", 3.90mm Width) packaging, enabling direct footprint compatibility. DS1338Z-33+T&R supports I2C interface, HH:MM:SS (12/24 hr) and YY-MM-DD-dd formats, and includes Leap Year functionality. Supply voltage range is 3V to 5.5V, which overlaps the X1226S8 range above 3V. Verify your application does not require operation below 3V.

Q: Why do some substitutes use different packages like 8-TSSOP/MSOP?

A: DS1339AU+, DS1340U-18+, and DS1342U+ use 8-TSSOP/MSOP (0.118", 3.00mm Width) packaging, which is physically smaller than 8-SOIC. These parts require PCB layout redesign but may offer advantages in space-constrained designs or lower power consumption.

Q: What is the key difference between M41T56M6F and MCP79400-I/SN?

A: M41T56M6F operates at 4.5V to 5.5V supply voltage, limiting use in 3.3V or lower systems. MCP79400-I/SN operates at 1.8V to 5.5V, providing broader voltage compatibility. MCP79400-I/SN also includes SRAM and Unique ID features. Both maintain 8-SOIC packaging.

Q: Are all substitute parts RoHS compliant?

A: Yes. All listed substitute parts carry ROHS3 compliance. The original X1226S8 is RoHS non-compliant. Select any substitute when regulatory compliance is mandatory.

Q: Can I use DS3232SN#T&R as a drop-in replacement?

A: No. DS3232SN#T&R uses 20-SOIC packaging versus the 8-SOIC of X1226S8, requiring significant PCB redesign. However, it provides functional superset capability with integrated SRAM (236B), TCXO/Crystal support, and active product status with full compliance certifications.

Q: Which substitute offers the lowest power consumption?

A: DS1342U+ provides 0.6µA to 0.7µA timekeeping current at 3V to 5V, the lowest among all candidates. This requires 8-TSSOP/MSOP packaging and PCB redesign. For 8-SOIC direct replacement, MCP79400-I/SN at 1.2µA typical is the lowest-power option.

Q: What is NVSRAM and why does it matter?

A: NVSRAM (Non-Volatile Static RAM) is battery-backed memory that retains data during power loss. DS1338Z-33+T&R and M41T56M6F include NVSRAM, enabling storage of application data beyond time/date. The X1226S8 does not specify NVSRAM, so this is an optional enhancement in substitutes.

Q: Can I use a 16-SOIC or larger package substitute?

A: Yes, but it requires PCB redesign. DS3231SN# (16-SOIC), DS3232SN#T&R (20-SOIC), M41ST85WMX6TR (28-SOIC), and M41T83ZQA6F (16-VQFN) all provide functional equivalence with enhanced features. These are suitable for new designs or major board revisions where layout flexibility exists.

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