DS1688 Real Time Clock IC - Equivalent & Substitute Parts

Part Overview

The DS1688 is a Real Time Clock (RTC) IC with Clock/Calendar functionality in a 28-DIP (0.600", 15.24mm) through-hole package. Manufactured by Analog Devices Inc./Maxim Integrated, this component provides parallel interface timekeeping with alarm, leap year, square wave output, and unique ID features. The DS1688 is classified as obsolete, making identification of functionally equivalent substitute parts essential for system redesign, legacy system maintenance, and component sourcing continuity.

Substiute Parts

DS1688

Analog Devices Inc./Maxim IntegratedIn Stock: 2188DS1688 Datasheet

Current PartRFQ

BQ4802YDW

BenchmarqIn Stock: 1824BQ4802YDW Datasheet

MFR RecommendedRFQ

M48T02-150PC1

STMicroelectronicsIn Stock: 1525M48T02-150PC1 Datasheet

MFR RecommendedRFQ

M48T12-70PC1

STMicroelectronicsIn Stock: 2150M48T12-70PC1 Datasheet

MFR RecommendedRFQ

M48T37V-10MH1F

STMicroelectronicsIn Stock: 1945M48T37V-10MH1F Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the DS1688 is determined by the following critical parameters:

Primary Compatibility Criteria:

• Parallel interface architecture
• Time format support (12/24 hour capability)
• Date format support (YY-MM-DD minimum)
• Operating temperature range (0°C ~ 70°C)
• Supply voltage compatibility with dual-rail operation (2.7V ~ 3.3V and 4.5V ~ 5.5V)

Secondary Considerations:

• Package form factor (through-hole vs. surface mount affects PCB redesign scope)
• Memory capacity (114B baseline)
• Feature set alignment (alarm, leap year support)

The substitute parts listed below maintain functional equivalence in timekeeping, calendar, and parallel interface operation. However, package differences require PCB layout modifications. Parts are grouped by mounting technology and pin count to clarify redesign requirements.

Parameter Comparison

Engineering Selection Recommendations

For Through-Hole PCB Designs (No Layout Redesign):

M48T02-150PC1 and M48T12-70PC1 are active, through-hole mounted alternatives. Both are STMicroelectronics Timekeeper® series components with ROHS3 compliance. M48T12-70PC1 operates across 4.5V ~ 5.5V supply range and supports the full operating temperature specification. M48T02-150PC1 requires 4.75V ~ 5.5V minimum supply voltage. Both use 24-DIP Module packaging, requiring PCB pin mapping verification due to reduced pin count compared to the 28-DIP DS1688.

For Surface-Mount PCB Designs (Layout Redesign Required):

BQ4802YDW (Benchmarq, 28-SOIC) maintains 28-pin count, minimizing signal routing changes. Supports 12/24-hour time format matching DS1688 capability. Operates at 4.5V ~ 5.5V with 1.5mA typical timekeeping current. Product status is active with no RoHS compliance data provided.

M48T37V-10MH1F (STMicroelectronics, 44-BSOP) is ROHS3 compliant and active. Operates at 3V ~ 3.6V supply range, requiring voltage regulation redesign if dual-rail 2.7V ~ 3.3V and 4.5V ~ 5.5V operation is required. Includes alarm and watchdog timer features. Requires SNAPHAT socket adapter for 44-BSOP package.

Compliance Considerations:

All substitute parts except BQ4802YDW carry ROHS3 compliance certification. The DS1688 is RoHS non-compliant. Systems requiring RoHS compliance must select M48T02-150PC1, M48T12-70PC1, or M48T37V-10MH1F.

Frequently Asked Questions (FAQ)

Q: Can the DS1688 be directly replaced with a pin-compatible substitute?

A: BQ4802YDW maintains 28-pin DIP packaging, enabling direct socket replacement if PCB layout supports surface-mount conversion or if a through-hole adapter is used. M48T02-150PC1 and M48T12-70PC1 use 24-DIP packaging, requiring pin mapping verification and potential firmware adjustment for unused pins.

Q: What are the key voltage compatibility differences?

A: DS1688 supports dual-rail operation (2.7V ~ 3.3V and 4.5V ~ 5.5V). BQ4802YDW and M48T12-70PC1 operate at 4.5V ~ 5.5V only. M48T02-150PC1 requires 4.75V ~ 5.5V minimum. M48T37V-10MH1F operates at 3V ~ 3.6V, incompatible with 5.5V rail designs without voltage regulation. Verify system power architecture before selection.

Q: Does package type affect functional compatibility?

A: Package type does not affect RTC functionality but determines PCB integration method. Through-hole packages (28-DIP, 24-DIP) use traditional socket mounting. Surface-mount packages (28-SOIC, 44-BSOP) require SMD soldering and different PCB layout. Pin count differences (28-pin vs. 24-pin vs. 44-pin) require signal routing verification.

Q: Are all substitute parts currently available?

A: M48T02-150PC1, M48T12-70PC1, and M48T37V-10MH1F are active products from STMicroelectronics. BQ4802YDW is active from Benchmarq. Inventory availability varies by distributor. The DS1688 is obsolete and sourcing is limited to existing stock.

Q: What compliance certifications apply to substitute selection?

A: M48T02-150PC1, M48T12-70PC1, and M48T37V-10MH1F carry ROHS3 compliance. All listed parts are REACH Unaffected and classified as EAR99 for export control. BQ4802YDW compliance status is not specified in available data.

Q: How do time format differences affect substitution?

A: DS1688 supports 12/24-hour time format. BQ4802YDW also supports 12/24-hour format. M48T02-150PC1, M48T12-70PC1, and M48T37V-10MH1F support 24-hour format only. Systems requiring 12-hour format operation must use DS1688 or BQ4802YDW.