PCF8523T/1,118 Real Time Clock IC - Equivalent & Substitute Parts

Part Overview

The PCF8523T/1,118 is an active Real Time Clock (RTC) IC manufactured by NXP USA Inc., designed for clock/calendar applications requiring I2C serial communication. This 8-SOIC surface mount device operates across a wide supply voltage range of 1.6V to 5.5V and includes integrated alarm, leap year, and watchdog timer functionality. The part maintains active product status with 119,415 units in current inventory.

Substitute parts are identified when design requirements necessitate alternative packaging formats, different memory configurations, enhanced feature sets, or specific manufacturer preferences while maintaining core RTC functionality and I2C interface compatibility.

Key Parameters

Parameter	PCF8523T/1,118
Manufacturer	NXP USA Inc.
Package / Case	8-SOIC (0.154", 3.90mm Width)
Mounting Type	Surface Mount
Interface	I2C, 2-Wire Serial
Voltage - Supply	1.6V ~ 5.5V
Voltage - Supply, Battery	1.8V ~ 5.5V
Current - Timekeeping (Max)	0.5µA @ 2V ~ 5V
Operating Temperature	-40°C ~ 85°C
Time Format	HH:MM:SS (12/24 hr)
Date Format	YY-MM-DD-dd
Features	Alarm, Leap Year, Watchdog Timer
RoHS Status	ROHS3 Compliant
Product Status	Active

Substitute Part Grouping Explanation

Substitution logic for the PCF8523T/1,118 is determined by the following critical parameters:

Primary Compatibility Criteria:

I2C, 2-Wire Serial interface requirement
Operating temperature range: -40°C ~ 85°C
RoHS3 compliance and REACH unaffected status
Surface mount or through-hole mounting capability
Time format support: HH:MM:SS (12/24 hr)
Date format support: YY-MM-DD-dd

Secondary Differentiation Parameters:

Package format (8-SOIC, 8-DIP, 8-TSSOP, 16-SOIC, 20-DFN)
Supply voltage range (minimum 1.6V to 5.5V preferred)
Battery supply voltage range
Timekeeping current consumption
Memory size (when applicable)
Feature set (Alarm, Leap Year, Square Wave Output, Trickle-Charger, NVSRAM, SRAM)

Substitute parts are grouped by package compatibility and feature alignment. Parts maintaining 8-SOIC surface mount format with I2C interface and core RTC functionality are direct substitutes. Parts with alternative packages (8-DIP, 8-TSSOP, 16-SOIC, 20-DFN) serve as substitutes when PCB layout or design requirements permit package variation.

Parameter Comparison

Part Number	Manufacturer	Package / Case	Mounting Type	Interface	Voltage - Supply	Voltage - Battery	Current - Timekeeping (Max)	Operating Temp	Features	Memory Size	RoHS Status
PCF8523T/1,118	NXP USA Inc.	8-SOIC (0.154", 3.90mm)	Surface Mount	I2C, 2-Wire Serial	1.6V ~ 5.5V	1.8V ~ 5.5V	0.5µA @ 2V ~ 5V	-40°C ~ 85°C	Alarm, Leap Year, Watchdog Timer	-	ROHS3 Compliant
1338-31DCGI	Renesas Electronics	8-SOIC (0.154", 3.90mm)	Surface Mount	I2C, 2-Wire Serial	3.3V ~ 5.5V	1.3V ~ 3.7V	5µA @ 3.63V ~ 5.5V	-40°C ~ 85°C	Leap Year, NVSRAM, Square Wave Output	56B	ROHS3 Compliant
DS1337+	Analog Devices Inc./Maxim Integrated	8-DIP (0.300", 7.62mm)	Through Hole	I2C, 2-Wire Serial	1.8V ~ 5.5V	-	0.6µA @ 1.3V ~ 1.8V	-40°C ~ 85°C	Alarm, Leap Year, Square Wave Output	-	ROHS3 Compliant
DS1337S+	Analog Devices Inc./Maxim Integrated	8-SOIC (0.154", 3.90mm)	Surface Mount	I2C, 2-Wire Serial	1.8V ~ 5.5V	-	0.6µA @ 1.3V ~ 1.8V	-40°C ~ 85°C	Alarm, Leap Year, Square Wave Output	-	ROHS3 Compliant
DS1338U-33+T&R	Analog Devices Inc./Maxim Integrated	8-TSSOP, 8-MSOP (0.118", 3.00mm)	Surface Mount	I2C, 2-Wire Serial	3V ~ 5.5V	1.3V ~ 3.7V	125µA ~ 200µA @ 3.63V ~ 5.5V	-40°C ~ 85°C	Leap Year, NVSRAM, Square Wave Output	56B	ROHS3 Compliant
DS1339U-3+	Analog Devices Inc./Maxim Integrated	8-TSSOP, 8-MSOP (0.118", 3.00mm)	Surface Mount	I2C, 2-Wire Serial	2.7V ~ 5.5V	1.3V ~ 3.7V	150µA @ 3.3V	-40°C ~ 85°C	Alarm, Leap Year, Square Wave Output, Trickle-Charger	-	ROHS3 Compliant
DS1339U-3+T&R	Analog Devices Inc./Maxim Integrated	8-TSSOP, 8-MSOP (0.118", 3.00mm)	Surface Mount	I2C, 2-Wire Serial	2.7V ~ 5.5V	1.3V ~ 3.7V	150µA @ 3.3V	-40°C ~ 85°C	Alarm, Leap Year, Square Wave Output, Trickle-Charger	-	ROHS3 Compliant
DS1339U-33+	Analog Devices Inc./Maxim Integrated	8-TSSOP, 8-MSOP (0.118", 3.00mm)	Surface Mount	I2C, 2-Wire Serial	2.97V ~ 5.5V	1.3V ~ 3.7V	200µA @ 5.5V	-40°C ~ 85°C	Alarm, Leap Year, Square Wave Output, Trickle-Charger	-	ROHS3 Compliant
DS1340C-33#	Analog Devices Inc./Maxim Integrated	16-SOIC (0.295", 7.50mm)	Surface Mount	I2C, 2-Wire Serial	2.97V ~ 5.5V	1.3V ~ 5.5V	150µA @ 5.5V	-40°C ~ 85°C	Leap Year, Trickle-Charger	-	ROHS3 Compliant
ISL12020MIRZ	Renesas Electronics	20-PowerLFDFN	Surface Mount	I2C, 2-Wire Serial	2.7V ~ 5.5V	1.8V ~ 5.5V	14µA ~ 15µA @ 3V ~ 5V	-40°C ~ 85°C	Alarm, Daylight Savings, Leap Year, SRAM	128B	ROHS3 Compliant
ISL12022IBZ-T	Renesas Electronics	8-SOIC (0.154", 3.90mm)	Surface Mount	I2C, 2-Wire Serial	2.7V ~ 5.5V	1.8V ~ 5.5V	14µA ~ 15µA @ 3V ~ 5V	-40°C ~ 85°C	Alarm, Daylight Savings, Leap Year, SRAM	128B	ROHS3 Compliant

Engineering Selection Recommendations

All listed substitute parts maintain active product status and ROHS3 compliance with REACH unaffected designation, meeting regulatory requirements equivalent to the PCF8523T/1,118.

Direct Package Match (8-SOIC Surface Mount): The ISL12022IBZ-T and 1338-31DCGI provide identical 8-SOIC packaging, enabling direct PCB layout compatibility. The ISL12022IBZ-T offers extended memory (128B SRAM) and daylight savings functionality. The 1338-31DCGI provides 56B NVSRAM with square wave output capability.

Surface Mount Alternative Packages: The DS1337S+ maintains 8-SOIC format with lower timekeeping current (0.6µA) but requires minimum 1.8V supply voltage. The DS1338U-33+T&R and DS1339 variants use compact 8-TSSOP packaging suitable for space-constrained designs, with DS1339 variants adding trickle-charger functionality.

Through-Hole Option: The DS1337+ provides 8-DIP through-hole mounting for applications requiring traditional PCB assembly methods, with equivalent timekeeping current performance to DS1337S+.

Extended Feature Set: The ISL12020MIRZ offers 20-PowerLFDFN packaging with 128B SRAM, alarm, and daylight savings support for applications requiring enhanced calendar functionality and memory capacity.

Voltage Range Considerations: The PCF8523T/1,118 operates from 1.6V minimum supply voltage. Substitute parts with higher minimum voltage requirements (3.0V, 2.7V, 2.97V, 3.3V) require design verification when operating below their specified minimum thresholds.

Frequently Asked Questions (FAQ)

Q: Can DS1337+ (8-DIP through-hole) replace PCF8523T/1,118 (8-SOIC surface mount)?

A: DS1337+ provides equivalent I2C interface, operating temperature range, and timekeeping functionality. However, the 8-DIP through-hole package requires different PCB footprint and assembly process compared to 8-SOIC surface mount. Substitution is feasible only if PCB design accommodates through-hole mounting.

Q: What is the primary difference between ISL12022IBZ-T and 1338-31DCGI?

A: Both use 8-SOIC packaging and I2C interface. ISL12022IBZ-T provides 128B SRAM with alarm and daylight savings features, operating from 2.7V supply. The 1338-31DCGI provides 56B NVSRAM with square wave output, operating from 3.3V minimum supply. Selection depends on memory requirements and minimum supply voltage constraints.

Q: Why do DS1339 variants show higher timekeeping current than PCF8523T/1,118?

A: DS1339 variants (150µA to 200µA) include integrated trickle-charger functionality for battery backup charging, increasing standby current consumption compared to PCF8523T/1,118 (0.5µA). This trade-off provides enhanced battery management capability.

Q: Is ISL12020MIRZ suitable for applications requiring minimal PCB space?

A: ISL12020MIRZ uses 20-PowerLFDFN packaging, which is larger than 8-SOIC. This part is appropriate for designs where extended memory (128B) and enhanced features (alarm, daylight savings) justify increased package size. For space-constrained applications, 8-SOIC variants (ISL12022IBZ-T, 1338-31DCGI, DS1337S+) are preferred.

Q: What supply voltage range is common across all substitute parts?

A: No single voltage range spans all substitutes. The PCF8523T/1,118 operates from 1.6V to 5.5V. Most substitutes operate from 2.7V to 5.5V minimum. DS1337+ and DS1337S+ support 1.8V to 5.5V. Designs operating below 2.7V supply voltage are limited to PCF8523T/1,118, DS1337+, or DS1337S+.

Q: Can substitute parts with different memory sizes (56B, 128B) be used interchangeably?

A: Memory size differences indicate distinct feature sets. Parts with NVSRAM or SRAM (56B or 128B) provide non-volatile or volatile storage not present in base RTC variants. Substitution is valid only if application firmware supports the available memory configuration. Parts without specified memory size provide core RTC functionality without additional storage.

Q: What packaging options are available for space-constrained designs?

A: The DS1338U-33+T&R and DS1339 variants use 8-TSSOP/8-MSOP (0.118", 3.00mm width), the most compact option. The 8-SOIC format (0.154", 3.90mm width) is standard across PCF8523T/1,118, ISL12022IBZ-T, 1338-31DCGI, and DS1337S+. The 16-SOIC (DS1340C-33#) and 20-PowerLFDFN (ISL12020MIRZ) are larger packages for applications requiring extended functionality.

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