BQ4285EP - 114B RTC With NVRAM Control | Texas Instruments
MPN: BQ4285EP ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $1.6968 | $1.70 |
| 10 | $1.6968 | $16.97 |
| 100 | $1.6968 | $169.68 |
| 500 | $1.6968 | $848.40 |
| 1,000 | $1.6968 | $1,696.80 |
BQ4285EP Overview
An RTC with integrated NVRAM is a clock-and-timing integrated circuit that maintains time-of-day and calendar information while providing persistent storage for system configuration or diagnostic data. Its position in the system hierarchy is real-time clock -> clock/calendar -> timekeeping IC -> semiconductor. The integrated nonvolatile memory allows a computer or embedded system to retain configuration values across power loss without relying on a separate memory device.
Key features include BCD or binary clock and calendar formats, day-of-week calendar support, alarm functionality, three maskable interrupt sources, a square-wave output, and a 32.768 kHz output for sustaining power-management activities. The verified data specifically confirms 114 bytes of general nonvolatile storage and battery operation. The 3 V operating version and enhanced RTC/NVRAM-control description are also identified in the supplied search results.
The BQ4285E/L family uses CMOS circuitry for low-power microprocessor-peripheral operation. The RTC counts seconds, minutes, hours, day of week, date, month, and year, including leap-year handling. The supplied datasheet search result also identifies over 10 years of operation in the absence of power as a feature of the compared DS12887-class devices, but that specific endurance claim is not independently assigned to BQ4285EP here.
Typical applications include IBM PC-compatible industrial and embedded computers, data-logging equipment, instrumentation, embedded control systems, and systems requiring persistent configuration storage beside a real-time clock. Its 24-DIP package favors through-hole legacy and industrial controller designs rather than compact surface-mount systems.
When designing around the BQ4285EP, verify the complete 24-pin interface, backup-battery implementation, interrupt polarity, alarm configuration, and NVRAM access protocol against the manufacturer datasheet. Do not assume that a similarly named RTC is a replacement unless its package dimensions, pin names, electrical limits, and firmware-visible registers are confirmed compatible.
Drop-in alternatives for BQ4285EP — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with BQ4285EP (same form factor and footprint) — differing in Interface, Package, Product Type.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
BQ3287AMT-SB2
✅ Drop-In📋 Reference alternative (not in catalog)
DS12887
✅ Drop-In📋 Reference alternative (not in catalog)
DS12887A
✅ Drop-In📋 Reference alternative (not in catalog)
DS14285
✅ Drop-In📋 Reference alternative (not in catalog)
DS14285+
✅ Drop-In📋 Reference alternative (not in catalog)
BQ4285EP Specifications
| Product Type | Real-time clock and calendar with NVRAM control |
| Device Family | CMOS BQ4285E/L |
| General Nonvolatile Storage | 114 bytes |
| Calendar Capability | 100-year calendar |
| Clock/Calendar Format | BCD or binary |
| Supply Version | 3 V |
| Package | 24-pin PDIP, 0.600-inch (15.24 mm) |
| Package Type | Through-hole PDIP |
| Interface | Parallel clock/calendar and NVRAM interface |
| Interrupt Sources | 3 maskable interrupt sources |
| Square-Wave Output | Available |
| Auxiliary Output | 32.768 kHz output |
| Alarm Features | Alarm functionality |
| Wake-Up Capability | Available |
| Battery Operation | Supported |
| Legacy Compatibility | Direct clock/calendar replacement for IBM AT-compatible computers |
| Technology | CMOS |
| RoHS Status | unknown |
| REACH Status | unknown |
| AEC-Q100 Status | unknown |
BQ4285EP through-hole pdip Pin Configuration Guide
Pin configuration for BQ4285EP (through-hole pdip package). Pin numbering, functions, and connection diagrams are defined in the manufacturer datasheet. Refer to it for the exact footprint and soldering guidelines.
No detailed pinout data available for BQ4285EP.
Refer to the datasheet for full pin configuration.
Typical Applications
BQ4285EP is suitable for 6 applications: Legacy IBM PC-Compatible Clock/Calendar, Industrial Data-Logging Controller, Embedded Instrumentation, Alarm-Controlled Embedded Equipment, Battery-Backed Configuration Module, Legacy Industrial Gateway.
Legacy IBM PC-Compatible Clock/Calendar
The BQ4285EP fits legacy IBM PC-compatible clock/calendar designs because the supplied results identify it as a direct clock/calendar replacement for IBM AT-compatible computers. Its parallel interface and BCD or binary clock formats support systems that expect conventional RTC register access. The 24-pin PDIP footprint is appropriate for through-hole industrial boards, but the host BIOS or controller must be checked for exact register and interrupt compatibility. The 114-byte NVRAM can retain configuration or identity data, while battery operation preserves timekeeping during main-power loss.
Recommended
Industrial Data-Logging Controller
The BQ4285EP is suitable for industrial data-logging equipment that needs a local time base and persistent metadata close to the controller. The 100-year calendar supports long-lived deployments, while the 114 bytes of general NVRAM can hold calibration identifiers, counters, or configuration flags across resets. Its CMOS implementation and battery operation suit low-power embedded systems, and the 32.768 kHz output can support associated power-management timing. Verify the exact supply limits, current consumption, and backup-cell requirements from the manufacturer datasheet before production.
Recommended
Embedded Instrumentation
Instrumentation systems often need accurate event timestamps, alarms, and persistent setup data, making the BQ4285EP a functional fit for older embedded measurement platforms. The three maskable interrupt sources can coordinate periodic events or alarm conditions, while the square-wave output provides a convenient timing reference when supported by the host circuit. NVRAM can retain instrument addresses, range selections, or calibration metadata without an additional serial memory. Because this is a 24-pin through-hole part, board designers should confirm connector spacing and available footprint before using it in newer compact instruments.
Recommended
Alarm-Controlled Embedded Equipment
The BQ4285EP can support embedded equipment that must wake or signal an operator at scheduled times. Its alarm functionality, three maskable interrupt sources, and wake-up capability are useful for timed measurement, maintenance reminders, and periodic control actions. The 32.768 kHz output may also assist power-management sequencing in systems that need a stable low-frequency reference. Designers should confirm interrupt polarity, alarm-resolution behavior, and host interrupt-controller routing because those details are not included in the supplied snippets.
Recommended
Battery-Backed Configuration Module
The BQ4285EP is appropriate for a battery-backed configuration module where timekeeping and nonvolatile records are required in the same legacy-style through-hole package. The 114 bytes of NVRAM provide a compact place for persistent identifiers, operating flags, or commissioning data, while the RTC supplies calendar and alarm functions. This arrangement can simplify older control boards that lack modern serial memory. The design must include the correct backup-battery architecture, decoupling, and reset behavior; those implementation details require the complete manufacturer datasheet and board-level validation.
Recommended
Legacy Industrial Gateway
The BQ4285EP can serve as the timekeeping subsystem in a legacy industrial gateway or controller assembled around a parallel bus. The IBM AT-compatible clock/calendar heritage supports deployment in equipment derived from PC-compatible architectures, and the NVRAM is useful for retaining network identity or calibration values. The 24-pin PDIP package favors repairable and expandable through-hole boards. Integration should account for supply sequencing, battery backup, interrupt sharing, and the possibility that modern firmware expects a different register map. Use the replacement only after a pin-by-pin and software compatibility review.
Recommended
Recommended Products Summary
Engineering reference data for BQ4285EP — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | BQ3287AMT-SB2 | DS12887 | DS12887A | DS14285 | DS14285+ |
|---|---|---|---|---|---|---|
| Package | 24-pin PDIP, 0.600-inch (15.24 mm) | 24-pin PDIP | 24-pin PDIP | 24-pin PDIP | 24-pin PDIP | 24-pin PDIP |
| Brand | Texas Instruments | Texas Instruments | Maxim Integrated | Maxim Integrated | Maxim Integrated | Maxim Integrated |
Key Differentiators
- Integrated nonvolatile storage (vs DS12887)
- Legacy IBM AT-compatible positioning (vs DS14285)
- Three maskable interrupt sources (vs DS12887A)
- 32.768 kHz supporting output (vs DS14285+)
Design Notes
Treat the BQ4285EP as a legacy through-hole RTC rather than assuming a modern compact surface-mount footprint. Verify the 24-pin PDIP row spacing, pin-1 orientation, body clearance, and connector accessibility against the official package drawing before layout release. Because the supplied search results confirm the 0.600-inch package width but do not provide a complete pin drawing, do not assign pin functions from memory; obtain the manufacturer pinout and compare every net.
Plan the main supply and backup-battery paths separately. The BQ4285EP is identified as a 3 V battery-operated CMOS RTC, so the battery chemistry, backup isolation, supply sequencing, and power-loss behavior must be designed around the exact manufacturer electrical limits. Check whether the host bus can back-power the RTC through signal lines, and confirm the recommended decoupling and battery current limits from the complete datasheet before finalizing the schematic.
The parallel clock/calendar interface can be sensitive to bus contention, floating inputs, and incorrect interrupt polarity. Use pull-ups or pull-downs only where required by the host bus specification, ensure every unused control input has a defined level, and route the clock, data, and interrupt nets away from noisy switching nodes. Validate read/write timing and alarm interrupt behavior with the host controller and confirm the NVRAM access sequence in firmware.
Do not approve a replacement based only on the phrase IBM AT-compatible or on a 24-pin package name. A true drop-in decision requires matching pin names, electrical limits, calendar registers, alarm behavior, interrupt polarity, NVRAM behavior, and backup-battery handling. The supplied DS12887, DS12887A, DS14285, DS14285+, and BQ3287AMT-SB2 references are comparison leads, not complete manufacturer cross-reference records, so bench and firmware validation are mandatory.
Compliance Information
The supplied search results do not state RoHS, REACH, AEC-Q100, lead-free, halogen-free, or conflict-minerals status for BQ4285EP. These fields remain unknown rather than being inferred.
