BQ4845YS-A4N - Parallel RTC with CPU Supervisor | Texas Instruments
MPN： BQ4845YS-A4N ✓ 啟用中BQ4845YS-A4N 概覽
A real-time clock is a clock-and-timing integrated circuit that maintains calendar information independently of the main processor. This BQ device combines an RTC with supervisory functions, including microprocessor reset generation, watchdog timing, alarm and daylight-saving features, and nonvolatile control for external SRAM. Its conditional chip-enable output and battery-voltage output can support write-protected SRAM retention when the main supply is absent.
The parallel interface exposes clock, calendar, and control information through a processor-accessible bus. According to the Texas Instruments datasheet, the BQ4845 family is intended for systems that require reliable timekeeping, battery-backed memory retention, and orderly power-fail recovery. The verified distributor listing describes the BQ4845YS-A4N as a 28-SOIC clock/calendar part with alarm, daylight savings, leap-year, supervisor, and watchdog-timer features.
The device is appropriate for industrial controllers, embedded instruments, data-acquisition equipment, networked appliances, and other systems where time stamps and controlled reset behavior are useful. Its backup functionality helps preserve calendar data during mains or system-power interruption, while the supervisor reduces the need for separate reset and watchdog components when the system architecture allows integration.
Designers should verify the crystal load capacitance, oscillator layout, bus timing, reset polarity, and battery-backup current budget against the manufacturer datasheet. External SRAM write protection and power sequencing should be tested across normal shutdown, brownout, and battery-only transitions. The SOIC footprint also requires adequate assembly spacing and thermal-path consideration when used in compact industrial equipment.
直接替換替代品，適用於 BQ4845YS-A4N — 相同封裝，腳位對腳位相容。需重新設計 PCB 的不同封裝零件不列入。
此系列的變體
與下列產品可直接替換的同系列型號： BQ4845YS-A4N （相同外形與佔位） — 差異在於 Package, Interface, Product Type, MPN.
BQ4845YS-A4
✅ 直接替換📋 參考替代品（不在目錄中）
BQ4845YS-A4NTR
✅ 直接替換聯絡詢價
查看資料表 →DS1501YZ+
✅ 直接替換📋 參考替代品（不在目錄中）
BQ4845YS-A4G4
✅ 直接替換聯絡詢價
查看資料表 →BQ4845YS-A4N 規格
| Product Type | Parallel real-time clock and clock/calendar with CPU supervisor |
| MPN | BQ4845YS-A4N |
| Manufacturer | Texas Instruments |
| Crystal Frequency | 32.768 kHz |
| Battery Voltage Range | 2.3 V to 4 V |
| System Supply Condition | 4.5 V to 5.5 V for the stated timekeeping-current condition |
| Maximum Timekeeping Current | 1.5 mA at 4.5 V to 5.5 V |
| Backup Clock Operation Current | Less than 500 nA |
| 介面 | Parallel |
| Clock Format | BCD |
| Calendar Features | Leap year and daylight savings support |
| Supervisory Features | CPU supervisor and watchdog timer |
| Reset Features | Microprocessor reset and power-fail-related control functions |
| Nonvolatile Support | Battery-backup switchover and nonvolatile control for external SRAM |
| Backup Source | 3 V backup battery connection |
| 封裝 | 28-pin SOIC, 0.295 inch width, 7.50 mm |
| 安裝類型 | Surface mount |
| Pinout | 28-pin parallel real-time clock and supervisor pinout per manufacturer datasheet |
BQ4845YS-A4N 28-pin soic, 0.295 inch width, 7.50 mm 腳位配置指南
BQ4845YS-A4N（28-pin soic, 0.295 inch width, 7.50 mm 封裝）的腳位配置。 腳位編號、功能與連接圖定義於製造商資料手冊中。請參閱該手冊以取得確切的封裝尺寸與焊接指引。
無詳細腳位定義資料： BQ4845YS-A4N.
請參閱 資料表 以查看完整腳位配置。
典型應用
BQ4845YS-A4N 適用於 7 應用s: Industrial Data-Acquisition Controller, Battery-Backed Embedded Instrument, Networked Appliance with SRAM Retention, Alarm and Event-Logging System, Battery-Powered Sensor Gateway, Embedded Security and Access Controller, Battery-Backed Test and Measurement Equipment.
Industrial Data-Acquisition Controller
The BQ4845YS-A4N fits industrial data-acquisition equipment that must preserve a trustworthy time base while an operator or service event interrupts the main supply. Its 32.768 kHz crystal connection and parallel clock/calendar interface provide a straightforward processor-readable time source. The verified backup current is below 500 nA, helping limit battery drain while the RTC remains active. CEOUT and VOUT support power-fail control of external SRAM, while the watchdog and CPU-supervisor functions can improve recovery after a fault. The design should still validate the industrial temperature range, supply tolerances, reset timing, and battery chemistry against the manufacturer datasheet.
推薦
Battery-Backed Embedded Instrument
The BQ4845YS-A4N is suitable for instruments that retain calibration or event data during service power loss. Its less-than-500 nA backup clock operation helps preserve timekeeping without keeping the main processor active. The external-SRAM control functions can help retain data if the system uses battery-backed SRAM, while the calendar and alarm functions support timestamped records. Because the supplied data does not state the full operating-temperature range or exact reset thresholds, those values must be confirmed before selecting the part for field equipment.
推薦
Networked Appliance with SRAM Retention
The BQ4845YS-A4N can support appliances that need a stable timestamp and controlled memory retention during brownout or shutdown. The parallel interface is useful when the host processor already uses a memory-style bus, and the BQ clock/calendar format simplifies implementation of scheduled events. The backup battery powers the RTC while the system is absent, and CEOUT can assist in write-protecting external SRAM. Firmware must account for the device's operating modes and must verify power-fail timing, access restrictions, and battery current in the finished system.
推薦
Alarm and Event-Logging System
The BQ4845YS-A4N is appropriate for systems whose event log must remain time-referenced after a power interruption. Its verified feature set includes alarm, daylight-savings, leap-year, and watchdog-timer functions, and the clock/calendar provides a persistent time base for event records. The 28-SOIC package offers a conventional surface-mount footprint, while the parallel bus can be read by a host processor. Application engineers should verify alarm-resolution, timestamp-format, and interrupt details in the manufacturer datasheet because those values are not present in the supplied search excerpts.
推薦
Battery-Powered Sensor Gateway
The BQ4845YS-A4N can provide a low-power timestamp reference for a battery-powered sensor gateway that must retain configuration or event data. The verified backup clock current below 500 nA is a useful starting point for battery-life calculations, especially when the gateway spends most of its time asleep. The parallel interface and 32.768 kHz crystal support are compatible with a host microcontroller design that reads time during wake-up. Actual battery savings depend on the backup load, SRAM leakage, oscillator startup, and the gateway's communication schedule.
推薦
Embedded Security and Access Controller
The BQ4845YS-A4N is applicable to access-control and security equipment where event time stamps and controlled reset behavior are important. The backup clock can continue maintaining time during a mains interruption, while the watchdog and microprocessor-supervisor functions can help the controller recover from firmware or processor stalls. CEOUT and VOUT can support write-protected retention of external SRAM used for recent event data. Deployment engineers should verify security-related reset behavior, operating temperature, battery backup, and EMC requirements against the complete manufacturer datasheet.
推薦
Battery-Backed Test and Measurement Equipment
The BQ4845YS-A4N can support test and measurement products that need reliable event timing across power cycles. A 32.768 kHz crystal provides the RTC timebase, and the backup path allows calendar information to persist when the main instrument supply is removed. The parallel clock/calendar interface can be read during calibration or service intervals, and the supervisor/watchdog functions may simplify power-state recovery. The supplied data does not include accuracy, oscillator tolerance, or temperature-coefficient figures, so those specifications must be obtained before using it for precision timing claims.
推薦
推薦產品摘要
工程參考資料，適用於 BQ4845YS-A4N — 比較、設計指引及合規資訊。
選型指南
與替代品比較
| 參數 | 本產品 | BQ4845YS-A4 | BQ4845YS-A4NTR | DS1501YZ+ | BQ4845YS-A4G4 |
|---|---|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Maxim Integrated | Texas Instruments |
主要差異化特點
- Integrated real-time clock and CPU supervision (對比DS1501YZ+)
- External-SRAM retention support (對比DS1501YZ+)
- Low backup clock current (對比BQ4845YS-A4)
- Calendar-oriented feature integration (對比Generic basic RTC)
設計說明
Validate the complete power tree rather than only the RTC rail. The verified data specifies a 2.3 V to 4 V battery range and less than 500 nA backup clock current, but the finished current budget also includes the crystal, external SRAM, pull devices, and any supervisor leakage. Confirm battery isolation and source-selection behavior during startup, shutdown, brownout, and complete system-power removal using the manufacturer application guidance.
Place the 32.768 kHz crystal and its associated load network close to the BQ4845YS-A4N oscillator pins and keep the clock path away from switching regulators, high-current return paths, and noisy digital buses. The supplied data does not specify the required crystal load capacitance or maximum ESR, so those values must be taken from the datasheet. Confirm that the PCB layout preserves the manufacturer-recommended ground and return paths before production release.
Do not treat CEOUT as an unrestricted battery backup output. The manufacturer datasheet describes CEOUT and VOUT as part of the external-SRAM write-protection and retention arrangement, so signal polarity, access timing, and power-fail sequencing must be checked against the actual SRAM. Also verify that firmware handles the RTC's operating modes and avoids changing calendar or control registers while the interface timing is invalid.
合規資訊
The supplied verified snippets identify the component and its clock/timing features but do not provide current RoHS, REACH, AEC-Q100, lead-free, halogen-free, or conflict-minerals declarations. These fields remain unknown rather than assumed.
