AB1803-T3 Real Time Clock IC Equivalent & Substitute Parts

Part Overview

The AB1803-T3 is a Real Time Clock (RTC) IC manufactured by Abracon LLC, designed for clock/calendar applications with I2C serial interface. This device integrates a 64-byte SRAM, alarm functionality, leap year support, and trickle-charger capability in a 16-VFQFN exposed pad surface mount package.

The AB1803-T3 is classified as obsolete. Identifying equivalent and substitute parts is necessary to maintain design continuity, ensure supply chain availability, and support ongoing production requirements for applications currently utilizing this component.

Key Parameters

Parameter	AB1803-T3 Specification
Manufacturer	Abracon LLC
Part Status	Obsolete
Package / Case	16-VFQFN Exposed Pad (3x3)
Type	Clock/Calendar
Interface	I2C, 2-Wire Serial
Memory Size	64B
Time Format	HH:MM:SS:hh
Date Format	YY-MM-DD-dd
Voltage - Supply	1.7V ~ 3.6V
Voltage - Supply, Battery	1.5V ~ 3.6V
Current - Timekeeping (Max)	0.17µA ~ 0.22µA @ 1.8V ~ 3V
Operating Temperature	-40°C ~ 85°C
Features	Alarm, Leap Year, SRAM, Trickle-Charger
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution of the AB1803-T3 is determined by the following critical parameters:

Primary Compatibility Criteria:

Interface type: I2C, 2-Wire Serial
Time and date format support: HH:MM:SS:hh and YY-MM-DD-dd
Operating temperature range: -40°C ~ 85°C
Supply voltage compatibility: 1.7V ~ 3.6V primary, 1.5V ~ 3.6V battery
RoHS3 compliance and MSL rating

Secondary Considerations:

Memory capacity (64B minimum for functional equivalence)
Package form factor (16-pin QFN preferred for pin-compatible replacement)
Timekeeping current consumption (ultra-low power operation)
Feature set (alarm, leap year, SRAM, trickle-charger)

Substitute parts are grouped into two categories:

Category 1: Direct Abracon Equivalent AB1805-T3 provides identical package, interface, and voltage specifications with enhanced memory (256B) and additional watchdog timer functionality. Same manufacturer ensures design continuity.

Category 2: Cross-Manufacturer Alternatives Parts from Analog Devices Inc./Maxim Integrated, Renesas Electronics, Texas Instruments, and Rohm Semiconductor provide functional RTC capability with I2C interface and compatible operating parameters. These require package and pinout verification for board-level integration.

Parameter Comparison

Parameter	AB1803-T3	AB1805-T3	DS1337U+	1337DVGI	BQ32002DR	BU9873F-GTE2	DS1307ZN+T&R	DS1308U-33+T
Manufacturer	Abracon LLC	Abracon LLC	Analog Devices/Maxim	Renesas Electronics	Texas Instruments	Rohm Semiconductor	Analog Devices/Maxim	Analog Devices/Maxim
Part Status	Obsolete	Active	Active	Active	Active	Not For New Designs	Active	Active
Package / Case	16-VFQFN (3x3)	16-VFQFN (3x3)	8-TSSOP (3.00mm)	8-TSSOP (3.00mm)	8-SOIC (3.90mm)	8-SOIC (4.40mm)	8-SOIC (3.90mm)	8-TSSOP (3.00mm)
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
Memory Size	64B	256B	—	—	—	—	56B	56B
Time Format	HH:MM:SS:hh	HH:MM:SS:hh	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 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
Voltage - Supply	1.7V ~ 3.6V	1.7V ~ 3.6V	1.8V ~ 5.5V	1.8V ~ 5.5V	3V ~ 3.6V	1.8V ~ 5.5V	4.5V ~ 5.5V	3V ~ 5.5V
Voltage - Supply, Battery	1.5V ~ 3.6V	1.5V ~ 3.6V	—	—	1.4V ~ 3.6V	—	2V ~ 3.5V	1.3V ~ 5.5V
Current - Timekeeping (Max)	0.17µA ~ 0.22µA @ 1.8V ~ 3V	0.17µA ~ 0.22µA @ 1.8V ~ 3V	0.6µA @ 1.3V ~ 1.8V	0.6µA @ 1.3V ~ 1.8V	65µA @ 3.3V	1µA ~ 1.35µA @ 3V ~ 5.5V	200µA @ 5V	125µA ~ 200µA @ 3V ~ 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
Features	Alarm, Leap Year, SRAM, Trickle-Charger	Alarm, Leap Year, SRAM, Trickle-Charger, Watchdog Timer	Alarm, Leap Year, Square Wave Output	Alarm, Leap Year, Square Wave Output	Leap Year, Square Wave Output, Trickle-Charger	Alarm, Leap Year	Leap Year, NVSRAM, Square Wave Output	Leap Year, NVSRAM, Square Wave Output
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
MSL Rating	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	3 (168 Hours)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)

Engineering Selection Recommendations

Recommended Primary Substitute: AB1805-T3

The AB1805-T3 is the optimal replacement for the obsolete AB1803-T3. Both devices share identical package geometry (16-VFQFN exposed pad, 3x3mm), interface protocol (I2C, 2-Wire Serial), supply voltage range (1.7V ~ 3.6V), and operating temperature specifications (-40°C ~ 85°C). The AB1805-T3 maintains the same ultra-low timekeeping current consumption (0.17µA ~ 0.22µA @ 1.8V ~ 3V) and MSL rating (1, Unlimited). The primary enhancement is increased SRAM capacity (256B versus 64B) and addition of watchdog timer functionality. The AB1805-T3 is currently in active production status with high inventory availability (5287 pcs), ensuring supply chain continuity. Both parts are ROHS3 compliant and REACH unaffected.

Secondary Substitutes for Alternative Package Requirements:

When package form factor change is acceptable, the following active-status alternatives provide functional RTC capability:

DS1337U+ (Analog Devices/Maxim Integrated) offers ultra-low timekeeping current (0.6µA @ 1.3V ~ 1.8V) in 8-TSSOP package with alarm and leap year support. Supply voltage range extends to 1.8V ~ 5.5V. Suitable for low-power applications with flexible voltage requirements.

DS1308U-33+T (Analog Devices/Maxim Integrated) provides 56B NVSRAM in 8-TSSOP package with extended battery voltage support (1.3V ~ 5.5V). Timekeeping current ranges 125µA ~ 200µA at 3V ~ 5.5V. Appropriate for designs requiring non-volatile memory retention.

BQ32002DR (Texas Instruments) delivers trickle-charger functionality in 8-SOIC package with supply voltage 3V ~ 3.6V and battery support 1.4V ~ 3.6V. Timekeeping current 65µA @ 3.3V. Suitable for battery-backed applications with fixed 3.3V primary supply.

Avoid for New Designs:

BU9873F-GTE2 (Rohm Semiconductor) is classified as "Not For New Designs" and should not be selected for new development projects despite active inventory availability.

Frequently Asked Questions (FAQ)

Q1: Can AB1805-T3 directly replace AB1803-T3 without PCB modification?

Yes. The AB1805-T3 maintains identical 16-VFQFN exposed pad package geometry (3x3mm), pin count, and I2C interface pinout. No PCB layout changes are required. The increased SRAM capacity (256B versus 64B) is backward compatible with firmware designed for 64B operation.

Q2: What is the primary reason to substitute the AB1803-T3?

The AB1803-T3 is classified as obsolete. Abracon LLC no longer manufactures this part. The AB1805-T3 is the direct successor in active production, ensuring long-term supply availability and design support.

Q3: Are cross-manufacturer substitutes (DS1337U+, BQ32002DR, etc.) pin-compatible with AB1803-T3?

No. Cross-manufacturer alternatives use different package types (8-TSSOP, 8-SOIC) with different pin counts and pinout configurations. These require PCB redesign and firmware adaptation. They are suitable only when package change is acceptable.

Q4: How do timekeeping current specifications affect substitute selection?

Timekeeping current directly impacts battery life in backup power scenarios. AB1803-T3 and AB1805-T3 consume 0.17µA ~ 0.22µA @ 1.8V ~ 3V, providing extended battery operation. DS1337U+ and 1337DVGI offer comparable ultra-low consumption (0.6µA @ 1.3V ~ 1.8V). DS1307ZN+T&R and DS1308U-33+T consume significantly higher current (125µA ~ 200µA), reducing battery backup duration. Select based on application power budget requirements.

Q5: What is the significance of MSL (Moisture Sensitivity Level) rating?

MSL rating indicates moisture sensitivity during storage and handling. MSL 1 (Unlimited) allows indefinite shelf storage without desiccant protection. MSL 3 (168 Hours) requires desiccant storage and limits exposure time after package opening. AB1803-T3, AB1805-T3, DS1337U+, BQ32002DR, BU9873F-GTE2, and DS1308U-33+T all carry MSL 1 rating. 1337DVGI carries MSL 3, requiring controlled storage conditions.

Q6: Can 5.5V-rated devices (DS1337U+, 1337DVGI, BU9873F-GTE2, DS1308U-33+T) substitute in 3.6V maximum supply applications?

Yes. These devices are rated for 1.8V ~ 5.5V or 3V ~ 5.5V supply ranges, which encompass the AB1803-T3 operating range of 1.7V ~ 3.6V. The higher maximum rating does not create incompatibility; the device operates safely within the lower voltage ceiling of the original application.

Q7: What is the functional difference between 64B and 256B SRAM capacity?

SRAM capacity determines available non-volatile storage for user data beyond the standard RTC registers. AB1803-T3 provides 64B; AB1805-T3 provides 256B. Applications using less than 64B of user storage are unaffected by the capacity increase. Applications requiring more than 64B benefit from AB1805-T3's expanded capacity.

Q8: Are all substitute parts ROHS3 compliant?

Yes. All listed substitute parts carry ROHS3 compliance certification, meeting EU Restriction of Hazardous Substances Directive requirements. All are REACH unaffected.

Q9: Which substitute offers the lowest timekeeping power consumption?

DS1337U+ and 1337DVGI both deliver 0.6µA @ 1.3V ~ 1.8V, matching or exceeding the AB1803-T3 specification of 0.17µA ~ 0.22µA @ 1.8V ~ 3V in their respective voltage ranges. For ultra-low-power battery-backed applications, these alternatives are optimal.

Q10: Is firmware modification required when switching from AB1803-T3 to AB1805-T3?

No firmware modification is required. Both devices use identical I2C register architecture and command protocols. The increased SRAM capacity is transparent to existing firmware. However, firmware can be enhanced to utilize the additional 192B of SRAM available in AB1805-T3.

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