BQ4845YP-A4E3 - 5V Parallel RTC with Supervisor | Texas Instruments
MPN: BQ4845YP-A4E3 ✓ ActiveBQ4845YP-A4E3 Overview
A real-time clock is a dedicated timekeeping and calendar integrated circuit that maintains date, day-of-week, hour, minute, and second information even when the main system supply is unavailable. The BQ4845 belongs to the RTC and clock-and-calendar IC category, within clock and timing integrated circuits and broader semiconductor timing-control devices. The BQ4845YP-A4E3 is intended for systems that retain external nonvolatile SRAM while the backup battery supplies the RTC and monitoring circuitry.
Key features include parallel BCD clock and calendar formatting, a 32.768 kHz crystal interface, backup-battery operation, an independent programmable watchdog timer, a power-fail interrupt warning, and a conditional chip-enable output. The commercial-grade device is supplied in a 28-DIP package measuring 0.600 inches, or 15.24 mm, across the row spacing. Its through-hole format is useful for industrial controllers, embedded systems, test equipment, and legacy-style equipment requiring a socketed or leaded real-time clock.
The BQ4845 architecture separates timekeeping from the host processor. The host reads and writes the parallel RTC registers, while the crystal oscillator maintains the timebase. The backup-cell path allows the clock and external SRAM write-control functions to continue during main-power loss, helping preserve system state. A programmable watchdog can reset the processor if software stops servicing the watchdog, and the power-fail warning provides an early indication that the system should enter a controlled shutdown sequence.
Typical applications include industrial data-acquisition systems, embedded controllers, telecommunications equipment, test-and-measurement instruments, and battery-backed embedded products. In a data-acquisition platform, the BQ4845YP-A4E3 can preserve event timestamps and protect external SRAM during unexpected supply interruption. In a controller, the watchdog and reset outputs improve recovery from firmware stalls or processor lockups.
Designers should verify the crystal load capacitance, oscillator layout, battery-backup implementation, and reset timing against the manufacturer datasheet. The 28-DIP footprint is not interchangeable with the surface-mount BQ4845S-A4NTR variant without PCB changes. This page combines verified manufacturer and distributor information with practical selection guidance and drop-in replacement analysis.
Drop-in alternatives for BQ4845YP-A4E3 — 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 BQ4845YP-A4E3 (same form factor and footprint) — differing in Package, Product Type, Battery Voltage Output, Conditional Chip Enable Output, External SRAM Support.
BQ4845YP-A4
✅ Drop-InContact for price
View Datasheet →BQ4845YP-A4E3
✅ Drop-In ⚠️ Specs UnverifiedContact for price
View Datasheet →BQ4845YP-A4
✅ Drop-In ⚠️ Specs UnverifiedContact for price
View Datasheet →BQ4845YP-A4
✅ Drop-In ⚠️ Specs UnverifiedContact for price
View Datasheet →BQ4845YP-A4E
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
BQ4845YP-A4E3 Specifications
| Product Type | Real-time clock and calendar IC with CPU supervisor |
| Supply Voltage Range | 4.5 V to 5.5 V |
| Clock Crystal Frequency | 32.768 kHz |
| Clock Format | BCD |
| Date Format | BCD |
| Interface Type | Parallel |
| Package | 28-DIP (0.600 in, 15.24 mm) |
| Mounting Style | Through-hole |
| Number of Pins | 28 pins |
| Operating Temperature Range | 0 °C to 70 °C |
| Temperature Grade | Commercial |
| Backup Battery Support | 3 V backup battery connection |
| Backup Mode Clock Current | Less than 500 nA |
| Watchdog Timer | Yes, programmable timeout |
| Power-Fail Warning | Yes |
| Leap-Year Feature | Yes |
| Daylight Savings Feature | Yes |
| Alarm Feature | Yes |
| Conditional Chip Enable Output | CEOUT for external SRAM write protection |
| Backup Voltage Output | VOUT for battery-voltage monitoring |
| RoHS Status | RoHS compliant |
BQ4845YP-A4E3 28-dip (0.600 in, 15.24 mm) Pin Configuration Guide
Pin configuration for BQ4845YP-A4E3 (28-dip (0.600 in, 15.24 mm) 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 BQ4845YP-A4E3.
Refer to the datasheet for full pin configuration.
Typical Applications
BQ4845YP-A4E3 is suitable for 6 applications: Industrial Data-Acquisition Systems, Embedded Control Systems, Telecommunications Equipment, Test and Measurement Instruments, Battery-Backed Embedded Products, Servers and Network Equipment.
Industrial Data-Acquisition Systems
The BQ4845YP-A4E3 fits industrial data-acquisition systems that must preserve timestamps during a mains interruption or control-system reset. Its 32.768 kHz crystal timebase maintains BCD clock and calendar information, while the 3 V backup-battery path supports RTC operation when the main 4.5 V to 5.5 V supply collapses. The CE output can hold external SRAM write lines in an inactive state during backup, reducing the chance of corrupting acquisition state. The watchdog timer and power-fail warning also give a host controller time to record a shutdown event and reduce the risk of an uncontrolled restart.
Recommended
Embedded Control Systems
The BQ4845YP-A4E3 is appropriate for legacy embedded controllers requiring a parallel real-time clock, calendar, and processor supervision in one device. The parallel interface avoids a serial bus and can connect directly to a processor's address and data lines. Its independent watchdog timer provides a recovery path when firmware stops servicing the system, while the CPU reset function is specified to remain valid as the supply approaches the lower operating limit. Backup operation preserves time and can protect external SRAM during temporary primary-power loss.
Recommended
Telecommunications Equipment
The BQ4845YP-A4E3 supports telecommunications equipment that must retain event chronology and supervise a 5 V processor rail. Its real-time clock provides BCD seconds, minutes, hours, date, and calendar information from a 32.768 kHz crystal, enabling repeatable logs and scheduled maintenance records. The power-fail warning can notify firmware before the main supply falls below its operating range, and the backup cell can maintain the RTC and SRAM write protection during the transition. The 28-DIP package is also appropriate for equipment platforms that retain through-hole memory and logic boards.
Recommended
Test and Measurement Instruments
The BQ4845YP-A4E3 is useful in test-and-measurement instruments where event logs, calibration schedules, and operator actions must remain time-aligned across a power interruption. A 32.768 kHz crystal provides the RTC timebase, while the backup-battery path keeps the clock operating with less than 500 nA clock current in backup mode. The watchdog and power-fail functions give the instrument's controller a controlled recovery mechanism rather than relying on an external operator reset. The through-hole 28-DIP format also supports repair and obsolescence-management strategies for established platforms.
Recommended
Battery-Backed Embedded Products
The BQ4845YP-A4E3 suits embedded products that use a 3 V backup cell to preserve volatile system context during main-power loss. The RTC continues counting time, the VOUT path allows the backup voltage to be monitored, and CE can prevent writes to external SRAM while primary power is unavailable. This combination supports reliable cold-start or recovery logic in controllers, instrument pods, and legacy industrial products. The principal design requirement is to follow the manufacturer battery-switchover and oscillator-layout guidance exactly.
Recommended
Servers and Network Equipment
The BQ4845YP-A4E3 can support legacy servers and network-control equipment built around 5 V logic and parallel processors. It provides a persistent calendar and clock without relying on the host operating system, plus watchdog and reset supervision for unattended operation. During power loss, the backup cell maintains the RTC and can inhibit external SRAM writes through the conditional chip-enable output. This makes the device useful for equipment that records fault sequences or uses battery-backed configuration memory. Its 28-DIP footprint is appropriate for established boards rather than new space-constrained server designs.
Recommended
Recommended Products Summary
Engineering reference data for BQ4845YP-A4E3 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | BQ4845YP-A4 | BQ4845YP-A4E3 | BQ4845YP | BQ4845YP-A | BQ4845YP-A4E |
|---|---|---|---|---|---|---|
| Package | 28-DIP (0.600 in, 15.24 mm) | 28-DIP (0.600 in, 15.24 mm) | 28-DIP (0.600 in, 15.24 mm) | 28-DIP | 28-DIP | 28-DIP |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Product Type | Parallel RTC and calendar with CPU supervisor | Parallel RTC and calendar | Parallel RTC and calendar | Parallel RTC and calendar | Parallel RTC and calendar | Parallel RTC and calendar |
| Operating Supply Voltage | 4.5 V to 5.5 V | 5 V | 4.5 V to 5.5 V | 5 V | 5 V | 5 V |
| Timebase Frequency | 32.768 kHz | 32.768 kHz | 32.768 kHz | 32.768 kHz | 32.768 kHz | 32.768 kHz |
| Clock and Date Format | BCD | BCD | BCD | BCD | BCD | BCD |
| Host Interface | Parallel | Parallel | Parallel | Parallel | Parallel | Parallel |
| Backup Battery Voltage | 3 V | 3 V | 3 V | 3 V | 3 V | 3 V |
| Special Features | Watchdog, alarm, power-fail warning, CE output, leap year, daylight savings | Watchdog, power-fail warning, SRAM backup control | Watchdog, alarm, power-fail warning, CE output, leap year, daylight savings | BQ4845 family feature set | BQ4845 family feature set | BQ4845 family feature set |
Key Differentiators
- Combines RTC and system supervision in one device (vs BQ4802YPWR)
- Supports external SRAM write protection during backup operation (vs BQ4845S-A4NTR)
- Maintains the legacy 28-DIP footprint (vs BQ4845S-A4NTR)
Design Notes
Route the 32.768 kHz crystal and its load components close to the oscillator pins, keep the loop compact, and maintain a quiet ground return. Follow the Texas Instruments BQ4845 datasheet layout guidance and keep switching-node copper and high-current paths away from the oscillator area. Crystal startup margin, load capacitance, and ESR directly affect timekeeping accuracy and should be validated on the final board.
Design the primary and backup paths separately so a 3 V backup cell cannot receive reverse voltage from the 5 V rail. Verify the backup-switchover threshold, VOUT monitoring behavior, and SRAM write-control timing against the manufacturer datasheet. Include local bulk and bypass capacitance near the supply pins, and validate startup and power-loss transitions across the full 4.5 V to 5.5 V operating range.
Do not substitute the surface-mount BQ4845S-A4NTR directly for the BQ4845YP-A4E3 because the packages and footprints differ. Also avoid assuming that every BQ4845 suffix has identical temperature, qualification, and ordering attributes. Before substitution, compare pin names, register behavior, reset timing, watchdog limits, oscillator loading, and backup current using the manufacturer datasheet for each exact MPN.
Compliance Information
The verified Ampheo product snippet identifies the BQ4845YP-A4E3 as RoHS compliant. No verified REACH, AEC-Q100, lead-free, halogen-free, or conflict-minerals statements were supplied.
