BQ4845S-A4 Equivalent & Substitute Parts

Part Overview

The BQ4845S-A4 is a Real Time Clock (RTC) IC with Clock/Calendar functionality in a 28-SOIC surface mount package, manufactured by Texas Instruments. This device provides parallel interface timekeeping with alarm, daylight savings, leap year, supervisor, and watchdog timer features. The BQ4845S-A4 is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support, production continuity, and system maintenance.

Substiute Parts

BQ4845S-A4

Texas InstrumentsIn Stock: 1269BQ4845S-A4 Datasheet

Current PartRFQ

BQ4802LYDW

Texas InstrumentsIn Stock: 1993BQ4802LYDW Datasheet

MFR RecommendedRFQ

DS12885QN+T&R

Analog Devices Inc./Maxim IntegratedIn Stock: 1032DS12885QN+T&R Datasheet

MFR RecommendedRFQ

DS1556-70+

Analog Devices Inc./Maxim IntegratedIn Stock: 1564DS1556-70+ Datasheet

MFR RecommendedRFQ

DS1558Y+

Analog Devices Inc./Maxim IntegratedIn Stock: 1242DS1558Y+ Datasheet

MFR RecommendedRFQ

DS1685E-3+

Analog Devices Inc./Maxim IntegratedIn Stock: 1665DS1685E-3+ Datasheet

MFR RecommendedRFQ

DS1685EN-3+

Analog Devices Inc./Maxim IntegratedIn Stock: 2562DS1685EN-3+ Datasheet

MFR RecommendedRFQ

DS1687-5IND+

Analog Devices Inc./Maxim IntegratedIn Stock: 2010DS1687-5IND+ Datasheet

MFR RecommendedRFQ

DS1744W-120IND+

Analog Devices Inc./Maxim IntegratedIn Stock: 1518DS1744W-120IND+ Datasheet

MFR RecommendedRFQ

DS1747WP-120IND+

Analog Devices Inc./Maxim IntegratedIn Stock: 1721DS1747WP-120IND+ Datasheet

MFR RecommendedRFQ

DS17487-3+

Analog Devices Inc./Maxim IntegratedIn Stock: 1192DS17487-3+ Datasheet

MFR RecommendedRFQ

M48T201V-85MH1F

STMicroelectronicsIn Stock: 1609M48T201V-85MH1F Datasheet

MFR RecommendedRFQ

M48T58Y-70PC1

STMicroelectronicsIn Stock: 1732M48T58Y-70PC1 Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution for the BQ4845S-A4 is determined by the following critical parameters:

Primary Substitution Criteria:

• Parallel interface requirement
• Clock/Calendar functionality with time and date format support (HH:MM:SS and YY-MM-DD-dd)
• Operating temperature range compatibility (0°C ~ 70°C minimum)
• Supply voltage compatibility (4.75V ~ 5.5V primary supply)
• Battery backup voltage support (2.3V ~ 4V range)
• Surface mount packaging capability
• RoHS3 compliance

Substitution Groups:

Group 1: Direct Package Equivalents (28-SOIC Surface Mount)

• BQ4802LYDW: 28-SOIC package, active status, reduced supply voltage (2.7V ~ 3.6V), maintains parallel interface and core RTC features

Group 2: Alternative Package Surface Mount (24-TSSOP)

• DS1685E-3+: 24-TSSOP package, active status, reduced supply voltage (2.7V ~ 3.7V), includes NVSRAM and square wave output
• DS1685EN-3+: 24-TSSOP package, active status, extended temperature range (-40°C ~ 85°C), reduced supply voltage (2.7V ~ 3.7V)

Group 3: Through-Hole Alternatives (DIP Modules)

• DS17487-3+: 24-DIP module, active status, reduced supply voltage (2.7V ~ 3.7V), includes daylight savings and alarm features
• DS1687-5IND+: 24-DIP module, active status, 4.5V ~ 5.5V supply voltage, extended temperature range (-40°C ~ 85°C)
• DS1744W-120IND+: 28-DIP module, active status, reduced supply voltage (2.97V ~ 3.63V), 32KB NVSRAM
• DS1556-70+: 32-DIP module, active status, 4.5V ~ 5.5V supply voltage, 128KB NVSRAM

Group 4: Advanced Package Alternatives

• DS12885QN+T&R: 28-LCC (J-Lead) package, active status, 4.5V ~ 5.5V supply voltage, includes 114B NVSRAM
• DS1558Y+: 48-LQFP package, active status, 4.5V ~ 5.5V supply voltage, extended temperature range (-40°C ~ 85°C)
• DS1747WP-120IND+: 34-PowerCap™ module, active status, reduced supply voltage (2.97V ~ 3.63V), 512KB NVSRAM

Parameter Comparison

Engineering Selection Recommendations

For Direct Replacement (Same Package, Surface Mount 28-SOIC): BQ4802LYDW is the primary active equivalent. It maintains the 28-SOIC surface mount package and parallel interface. The reduced supply voltage range (2.7V ~ 3.6V) requires circuit design verification if the original design operates at 4.75V ~ 5.5V. This part is active status with ROHS3 compliance.

For Supply Voltage Compatibility (4.5V ~ 5.5V Range): DS12885QN+T&R, DS1556-70+, DS1558Y+, and DS1687-5IND+ maintain the 4.5V ~ 5.5V supply voltage range. DS12885QN+T&R and DS1558Y+ are surface mount options; DS1556-70+ and DS1687-5IND+ are through-hole alternatives. All are active status with ROHS3 compliance.

For Low-Power Applications (Reduced Supply Voltage): DS1685E-3+, DS1685EN-3+, DS1744W-120IND+, DS1747WP-120IND+, and DS17487-3+ operate at reduced supply voltages (2.7V ~ 3.7V or 2.97V ~ 3.63V) with lower timekeeping current consumption. These are suitable for battery-backed or low-power system designs. All are active status with ROHS3 compliance.

For Extended Temperature Range (-40°C ~ 85°C): DS12885QN+T&R, DS1558Y+, DS1685EN-3+, DS1687-5IND+, DS1744W-120IND+, and DS1747WP-120IND+ support extended operating temperatures. These are appropriate for industrial or automotive applications requiring wider temperature specifications.

For Through-Hole Mounting: DS17487-3+, DS1687-5IND+, DS1744W-120IND+, and DS1556-70+ provide DIP module packages for through-hole assembly. These are suitable for legacy board designs or applications requiring through-hole component mounting.

All substitute parts listed are active status products with ROHS3 compliance and REACH unaffected certification, ensuring regulatory compliance and long-term availability.

Frequently Asked Questions (FAQ)

Q: Can BQ4802LYDW directly replace BQ4845S-A4 in existing designs? A: BQ4802LYDW maintains the same 28-SOIC package and parallel interface. However, the supply voltage range differs (2.7V ~ 3.6V vs. 4.75V ~ 5.5V). Direct replacement requires verification that the circuit design can operate within the reduced voltage range or that voltage regulation is implemented.

Q: What is the primary difference between surface mount and through-hole substitute options? A: Surface mount substitutes (BQ4802LYDW, DS1685E-3+, DS1685EN-3+, DS1558Y+, DS1747WP-120IND+) use SOIC, TSSOP, LQFP, or PowerCap packages for PCB soldering. Through-hole substitutes (DS17487-3+, DS1687-5IND+, DS1744W-120IND+, DS1556-70+) use DIP module packages for pin insertion into PCB holes. Package selection depends on board design and assembly capability.

Q: Which substitute parts maintain the 12/24-hour time format of the BQ4845S-A4? A: BQ4802LYDW, DS1685E-3+, DS1685EN-3+, DS1687-5IND+, and DS17487-3+ support both 12-hour and 24-hour time formats. DS1556-70+, DS1558Y+, DS1744W-120IND+, and DS1747WP-120IND+ support 24-hour format only.

Q: Are all substitute parts RoHS3 compliant? A: Yes, all substitute parts listed are ROHS3 compliant and REACH unaffected, meeting current environmental and regulatory requirements.

Q: What is the key consideration when selecting a substitute for low-power applications? A: Timekeeping current consumption and supply voltage range are critical. DS1685E-3+, DS1685EN-3+, DS1744W-120IND+, DS1747WP-120IND+, and DS17487-3+ offer reduced timekeeping current (2mA ~ 3mA) at lower supply voltages (2.7V ~ 3.7V or 2.97V ~ 3.63V), making them suitable for battery-backed systems.

Q: Can substitutes with 24-hour format only replace the BQ4845S-A4 in designs requiring 12-hour format? A: No. If the application requires 12-hour time format support, only BQ4802LYDW, DS1685E-3+, DS1685EN-3+, DS1687-5IND+, or DS17487-3+ are compatible. DS1556-70+, DS1558Y+, DS1744W-120IND+, and DS1747WP-120IND+ support 24-hour format only.

Q: What is the difference between DS1685E-3+ and DS1685EN-3+? A: Both use the 24-TSSOP package and support 2.7V ~ 3.7V supply voltage with 12/24-hour time format. DS1685EN-3+ extends the operating temperature range to -40°C ~ 85°C, compared to DS1685E-3+ at 0°C ~ 70°C. Select DS1685EN-3+ for industrial or extended temperature applications.

Q: Which substitute offers the highest memory capacity? A: DS1747WP-120IND+ provides 512KB NVSRAM, the largest memory capacity among the listed substitutes. DS1556-70+ offers 128KB NVSRAM. Other parts provide smaller memory sizes or no specified NVSRAM.