Equivalent & Substitute Parts for 1338AC-31SRGI

Part Overview

The 1338AC-31SRGI is a Real Time Clock (RTC) IC Clock/Calendar manufactured by Renesas Electronics Corporation in a 16-SOIC package. This device provides 56 bytes of memory with I2C/2-Wire Serial interface, supporting both 12/24-hour time formats and calendar functions with leap year capability. The part is classified as obsolete, making equivalent and substitute components necessary for new designs and ongoing production support.

Key Parameters

Parameter	Value
Manufacturer Part Number	1338AC-31SRGI
Manufacturer	Renesas Electronics Corporation
Product Category	Clock/Timing - RTC Clock/Calendar
Product Status	Obsolete
Package Type	16-SOIC (0.295", 7.50mm Width)
Memory Size	56B
Interface	I2C, 2-Wire Serial
Time Format	HH:MM:SS (12/24 hr)
Date Format	YY-MM-DD-dd
Supply Voltage	3.3V ~ 5.5V
Battery Voltage	1.3V ~ 3.7V
Timekeeping Current (Max)	5µA @ 3.63V ~ 5.5V
Operating Temperature	-40°C ~ 85°C
Features	Leap Year, NVSRAM, Square Wave Output
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level	3 (168 Hours)

Substitute Part Grouping Explanation

Substitution for the 1338AC-31SRGI is determined by the following critical parameters:

Primary Substitution Criteria:

Interface type: I2C, 2-Wire Serial
Time format support: HH:MM:SS (12/24 hr)
Date format support: YY-MM-DD-dd
Operating temperature range: -40°C ~ 85°C
RoHS3 compliance
Memory capacity: minimum 56B for direct replacement

Substitution Categories:

Category 1: Direct Package Equivalents (16-SOIC) Parts maintaining the same 16-SOIC package footprint with identical or superior electrical specifications. DS1338C-33# qualifies as a direct substitute with active product status and equivalent feature set.

Category 2: Functional Equivalents with Alternative Packages Parts providing identical RTC functionality with I2C interface but in different package types (8-SOIC, 8-TSSOP, 6-WDFN, 16-QFN). These require PCB layout modification but maintain electrical compatibility within specified voltage and temperature ranges.

Category 3: Enhanced Functionality Alternatives Parts offering additional features (alarm, trickle-charger, watchdog timer, expanded memory) while maintaining core RTC and I2C interface requirements. These provide design flexibility for applications requiring extended capabilities.

Category 4: Compact Module Solutions Integrated RTC modules (10-SMD) providing complete clock/calendar functionality in a smaller footprint with superior power efficiency.

Parameter Comparison

Parameter	1338AC-31SRGI	DS1338C-33#	AB-RTCMC-32.768KHZ-B5GA-S3-T	AB1805-T3	BU9873F-GTE2	DS1308U-18+	DS1337S+T&R	DS1338U-18+	DS1339U-2+	DS1340Z-3+T&R	DS1375T+
Manufacturer	Renesas	Analog Devices/Maxim	Abracon LLC	Abracon LLC	Rohm Semiconductor	Analog Devices/Maxim	Analog Devices/Maxim	Analog Devices/Maxim	Analog Devices/Maxim	Analog Devices/Maxim	Analog Devices/Maxim
Product Status	Obsolete	Active	Active	Active	Not For New Designs	Active	Active	Active	Active	Active	Active
Package Type	16-SOIC (7.50mm)	16-SOIC (7.50mm)	10-SMD Module	16-VFQFN (3x3)	8-SOIC (4.40mm)	8-TSSOP/MSOP (3.00mm)	8-SOIC (3.90mm)	8-TSSOP/MSOP (3.00mm)	8-TSSOP/MSOP (3.00mm)	8-SOIC (3.90mm)	6-WDFN (3x3)
Memory Size	56B	56B	—	256B	—	56B	—	56B	—	—	16B
Interface	I2C, 2-Wire	I2C, 2-Wire	I2C, 2-Wire	I2C, 2-Wire	I2C, 2-Wire	I2C, 2-Wire	I2C, 2-Wire	I2C, 2-Wire	I2C, 2-Wire	I2C, 2-Wire	I2C, 2-Wire
Time Format	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (24 hr)	HH:MM:SS:hh	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 (24 hr)	HH:MM:SS (12/24 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
Supply Voltage	3.3V ~ 5.5V	3V ~ 5.5V	1.2V ~ 5.5V	1.7V ~ 3.6V	1.8V ~ 5.5V	1.71V ~ 5.5V	1.8V ~ 5.5V	1.71V ~ 5.5V	1.8V ~ 5.5V	2.7V ~ 5.5V	1.7V ~ 5.5V
Battery Voltage	1.3V ~ 3.7V	1.3V ~ 3.7V	—	1.5V ~ 3.6V	—	1.3V ~ 5.5V	—	1.3V ~ 3.7V	1.3V ~ 3.7V	1.3V ~ 3.7V	—
Timekeeping Current (Max)	5µA @ 3.63V~5.5V	125µA~200µA @ 3.63V~5.5V	0.45µA~0.55µA @ 2V~5V	0.17µA~0.22µA @ 1.8V~3V	1µA~1.35µA @ 3V~5.5V	100µA @ 200µA @ 1.89V~5.5V	0.6µA @ 1.3V~1.8V	100µA @ 1.89V	100µA @ 2.2V	125µA @ 3.3V	0.5µA @ 1.7V~5.5V
Operating Temperature	-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	-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	Alarm, Leap Year, Square Wave Output	Alarm, Leap Year, SRAM, Trickle-Charger, Watchdog Timer	Alarm, Leap Year	Leap Year, NVSRAM, Square Wave Output	Alarm, Leap Year, Square Wave Output	Leap Year, NVSRAM, Square Wave Output	Alarm, Leap Year, Square Wave Output, Trickle-Charger	Leap Year, Trickle-Charger	Alarm, Leap Year, Square Wave Output
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)	1 (Unlimited)	1 (Unlimited)

Engineering Selection Recommendations

Primary Recommendation: DS1338C-33#

DS1338C-33# from Analog Devices Inc./Maxim Integrated is the optimal direct substitute for 1338AC-31SRGI. This part maintains identical package geometry (16-SOIC, 7.50mm width), memory capacity (56B), interface protocol (I2C, 2-Wire Serial), and feature set (Leap Year, NVSRAM, Square Wave Output). The device is in active production status with superior moisture sensitivity rating (MSL 1 vs. MSL 3), ensuring better long-term reliability. Supply voltage range (3V ~ 5.5V) encompasses the original specification (3.3V ~ 5.5V). All regulatory compliance requirements (ROHS3, REACH Unaffected, EAR99) are met.

Secondary Recommendation: DS1308U-18+ or DS1338U-18+

Both devices provide identical electrical functionality and feature set with active product status. These parts use 8-TSSOP/MSOP packages (3.00mm width), requiring PCB layout modification. Memory capacity and interface specifications match the original. Supply voltage range (1.71V ~ 5.5V) exceeds original requirements. These options are suitable when board space constraints permit package change.

Alternative for Enhanced Functionality: AB1805-T3

AB1805-T3 from Abracon LLC offers expanded capabilities (256B memory, watchdog timer, trickle-charger) in a 16-VFQFN package. This part is appropriate for new designs requiring additional features beyond basic RTC functionality. Supply voltage range (1.7V ~ 3.6V) is narrower than the original, requiring design verification for 5V applications.

Alternative for Power-Constrained Applications: AB-RTCMC-32.768KHZ-B5GA-S3-T

This integrated RTC module from Abracon LLC provides superior power efficiency (0.45µA ~ 0.55µA timekeeping current) in a compact 10-SMD module package. Suitable for battery-powered applications where power consumption is critical. Module format eliminates discrete crystal requirements.

Not Recommended for New Designs: BU9873F-GTE2

BU9873F-GTE2 from Rohm Semiconductor carries "Not For New Designs" status, limiting its applicability to legacy system maintenance only.

Frequently Asked Questions (FAQ)

Q: Can DS1338C-33# directly replace 1338AC-31SRGI without PCB modification?

A: Yes. DS1338C-33# maintains identical 16-SOIC (0.295", 7.50mm Width) package footprint, pin count, and electrical interface. No PCB layout changes are required. Firmware compatibility depends on application-specific I2C command implementation, which should be verified against device datasheets.

Q: What is the primary difference between 1338AC-31SRGI and DS1338C-33# that affects reliability?

A: The moisture sensitivity level (MSL) differs significantly. 1338AC-31SRGI has MSL 3 (168-hour floor life), while DS1338C-33# has MSL 1 (unlimited floor life). This means DS1338C-33# can be stored longer without baking before reflow soldering, reducing manufacturing risk and cost.

Q: Are the 8-TSSOP alternatives (DS1308U-18+, DS1338U-18+) electrically compatible with the original 16-SOIC part?

A: Yes, electrically compatible. Both devices provide identical I2C interface, memory capacity (56B), time/date formats, and feature set. The primary difference is package type, which requires PCB redesign. Supply voltage and operating temperature ranges are equivalent or superior.

Q: Why does AB-RTCMC-32.768KHZ-B5GA-S3-T consume significantly less current than other options?

A: This is an integrated module combining the RTC IC with the 32.768 kHz crystal in a single package. The module-level integration and optimized circuit design reduce parasitic power consumption. The trade-off is reduced flexibility compared to discrete IC solutions.

Q: Can I use DS1340Z-3+T&R as a substitute if my application only requires 24-hour time format?

A: DS1340Z-3+T&R supports only 24-hour time format (not 12/24 selectable like the original). If your firmware is hardcoded for 12/24-hour capability, this part may not be suitable. Verify application requirements before selection.

Q: What is the significance of the "NVSRAM" feature in the original part?

A: NVSRAM (Non-Volatile Static RAM) provides battery-backed memory that retains data during power loss. This feature is present in 1338AC-31SRGI, DS1338C-33#, DS1308U-18+, and DS1338U-18+. Parts without this feature (DS1337S+T&R, DS1340Z-3+T&R, DS1375T+) lack this capability and are suitable only for applications not requiring non-volatile user data storage.

Q: Is AB1805-T3 suitable for 5V-only applications?

A: No. AB1805-T3 supply voltage range is 1.7V ~ 3.6V, which does not include 5V operation. This part is limited to 3.3V and lower supply systems. For 5V applications, select DS1338C-33#, DS1308U-18+, or DS1337S+T&R.

Q: What packaging considerations apply when switching from 16-SOIC to 16-VFQFN (AB1805-T3)?

A: 16-VFQFN packages have smaller footprints (3x3mm vs. 7.50mm width for SOIC) and require different soldering profiles due to exposed pad thermal management. PCB layout must accommodate the smaller package and provide adequate thermal vias for the exposed pad. Reflow oven parameters may differ from SOIC requirements.

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