BQ4845S-A4TR - Parallel RTC with CPU Supervisor | TI
料号： BQ4845S-A4TR ✓ 量产中| 数量 | 单价 | 小计 |
|---|---|---|
| 1 | $0 | $0.00 |
| 10 | $0 | $0.00 |
| 100 | $0 | $0.00 |
| 500 | $0 | $0.00 |
| 1,000 | $0 | $0.00 |
BQ4845S-A4TR 概述
What is a parallel RTC? A real-time clock is a clock-and-timing integrated circuit that maintains time of day and calendar information when the main system supply is absent. A parallel RTC connects to a microprocessor through a parallel bus, allowing the host to read and write time data directly. A CPU supervisor adds supply monitoring, reset generation, and warning functions, making the RTC useful as a system timekeeping and power-management peripheral.
The BQ4845S-A4TR integrates a time-of-day clock, calendar, supply-voltage monitoring, interrupt warning, microprocessor reset, and battery backup functions. It connects directly to a 32.768 kHz quartz crystal and a 3 V backup battery. The backup cell powers the RTC and helps maintain external SRAM information when system voltage is absent. A battery voltage output and conditional chip-enable output can be used to control write protection for nonvolatile external SRAM.
The RTC counts seconds through years in BCD format according to the retrieved manufacturer description. It is designed for systems requiring accurate calendar time, retained data, and power-fail supervision. The device supports CPU reset and interrupt indication when the monitored supply becomes out of tolerance. These functions are useful in equipment that must restart predictably after power restoration or preserve critical records during power loss.
Typical applications include fax machines, copiers, industrial control systems, point-of-sale terminals, data loggers, and computers. The part is particularly appropriate where a host processor needs local timekeeping, calendar alarms, SRAM retention, and a supervisor signal without relying on a larger system clock module.
Designers should follow the manufacturer datasheet for crystal load capacitance, decoupling, battery connection, signal timing, and unused-pin handling. Confirm the 0°C to 70°C operating range against the system enclosure and thermal conditions. The 28-SOIC footprint requires a PCB land pattern matching the specified package width and pin arrangement.
This product page consolidates the verified manufacturer description, distributor identification, package information, and engineering considerations for the BQ4845S-A4TR. Pricing, lifecycle, and alternative availability should be checked against the cited sources because the supplied web data does not provide a complete verified pricing table or a confirmed drop-in replacement list.
直接替换替代料： BQ4845S-A4TR ——相同封装，引脚兼容。需要 PCB 改动的不同封装料号已排除。
快速对比工具——选择替代料号进行并排对比：
BQ4845YS-A4TR
✅ 直接替换📋 参考替代料（不在目录中）
BQ4845YS-A4NTRG4
✅ 直接替换📋 参考替代料（不在目录中）
BQ4845S-A4TR 规格参数
| Product Type | Parallel real-time clock (RTC) with CPU supervisor |
| Timekeeping | Time-of-day clock with 100-year calendar |
| Calendar Format | BCD format |
| Crystal Frequency | 32.768 kHz |
| Backup Battery | 3 V |
| Supply Monitoring | Temperature-compensated reference and comparator circuit |
| Supervisor Functions | Interrupt warning and microprocessor reset |
| Backup Clock Current | Less than 500 nA in backup mode |
| 封装 | 28-pin SOIC (0.295 inch, 7.50 mm width) |
| Package Type | Surface-mount SOIC |
| 工作温度 | 0°C to 70°C |
| Packaging | Tape & Reel |
| 接口 | Parallel CPU interface |
| External SRAM Support | Write-protect and nonvolatile retention control using CEOUT and VOUT pins |
| Battery Voltage Output | VOUT pin |
| Conditional Chip Enable | CEOUT pin |
BQ4845S-A4TR surface-mount soic 引脚配置指南
BQ4845S-A4TR（surface-mount soic 封装）的引脚配置。 引脚编号、功能和连接图在制造商数据手册中定义。请参阅该手册以了解确切的封装尺寸和焊接指南。
暂无详细引脚数据： BQ4845S-A4TR.
请参阅 数据手册 以查看完整引脚配置。
典型应用
BQ4845S-A4TR 适用于 6 应用s: Industrial Control Systems, Point-of-Sale Terminals, Data Loggers, Fax Machines and Copiers, Battery-Powered Embedded Systems, Computers and Embedded Platforms.
Industrial Control Systems
The BQ4845S-A4TR fits industrial controllers that need accurate calendar time alongside power-fail supervision. Its parallel RTC, 100-year calendar, 32.768 kHz crystal connection, and backup-battery support allow a controller to retain time and control external SRAM when the main supply is absent. The CPU-supervisor functions add an interrupt warning and microprocessor reset when the monitored supply moves out of tolerance. Designers should use the TI application guidance for crystal layout and power sequencing, while checking the 0°C to 70°C range against enclosure conditions.
推荐
Point-of-Sale Terminals
A point-of-sale terminal can use the BQ4845S-A4TR to maintain transaction time and calendar data while a 3 V backup cell supplies the RTC during main-power loss. The device's interrupt warning and reset functions help the host respond to supply disturbances, and the CEOUT/VOUT arrangement can help control external SRAM data retention. The parallel interface is useful when the host already uses a wired bus architecture. Firmware must accommodate the device's BCD timekeeping and power-fail event sequence documented by Texas Instruments.
推荐
Data Loggers
The BQ4845S-A4TR is suitable for data-logging equipment that must timestamp records across power interruptions. Its 100-year calendar and time-of-day clock provide a dedicated time base independent of the main processor, while the backup supply maintains RTC operation from a 3 V cell. The low backup clock current of less than 500 nA helps reduce standby consumption. The CPU supervisor's warning and reset outputs can trigger an orderly shutdown or restart, and external SRAM can be write-protected through the documented CEOUT and VOUT functions.
推荐
Fax Machines and Copiers
The BQ4845S-A4TR matches the timekeeping and supervision needs of office imaging equipment such as fax machines and copiers. A backup-powered RTC preserves calendar and transaction timestamps when the main rail drops, while the CPU supervisor can signal an impending reset or supply fault. The parallel bus permits straightforward integration with an embedded controller that reads and writes calendar data. The verified 28-SOIC package and tape-and-reel format support surface-mount manufacturing, subject to confirming the exact pin layout against the datasheet.
推荐
Battery-Powered Embedded Systems
The BQ4845S-A4TR is appropriate for embedded systems that require calendar time during main-power loss. The device operates from a 3 V backup battery for RTC retention and consumes less than 500 nA in backup clock mode, helping systems limit standby energy. A 32.768 kHz crystal provides the timebase, while the parallel host interface handles register access. Designers should account for battery chemistry, low-voltage cutoff, crystal accuracy, and the distinction between RTC backup current and total system standby current.
推荐
Computers and Embedded Platforms
The BQ4845S-A4TR can provide a dedicated time-and-calendar peripheral for computers and embedded platforms that need local timestamp retention. Its 100-year calendar, BCD format, parallel interface, and backup-battery support make it useful where the host must recover a valid time reference after power restoration. The CPU supervisor adds system-level value by monitoring the supply and issuing warning or reset signals. Integration requires verifying bus timing, address/control behavior, crystal loading, and unused-pin handling against the manufacturer documentation.
推荐
推荐产品汇总
工程参考数据： BQ4845S-A4TR ——对比、设计指导和合规信息。
选型指南
与替代料对比
| 参数 | 本产品 | BQ4845YS-A4TR | BQ4845YS-A4NTRG4 |
|---|---|---|---|
| Product Type | Parallel RTC with CPU supervisor | Parallel real-time clock | Parallel real-time clock |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments |
| Package | 28-SOIC (0.295 inch, 7.50 mm width) | 28-SOIC | 28-SOIC |
关键差异点
- CPU-supervisor integration （对比 BQ4845YS-A4TR)
- Backup current specification （对比 BQ4845YS-A4NTRG4)
- Package identification （对比 BQ4845YS-A4TR)
设计说明
Design the 3 V backup-battery path so that the RTC remains powered when the main system rail collapses, while preventing uncontrolled reverse current into the host supply. Follow the TI datasheet for the backup cell connection, supply sequencing, and decoupling. The verified backup clock current is less than 500 nA, but total standby consumption also includes leakage and any attached external circuitry.
Keep the 32.768 kHz crystal and its required load components close to the BQ4845S-A4TR oscillator pins. Route the crystal traces away from switching nodes, high-current rails, and fast digital edges to reduce noise injection and frequency disturbance. The supplied data confirms the crystal frequency but does not provide the required load capacitance or exact layout geometry, so use the manufacturer layout guidance.
Do not assume that any 28-SOIC RTC is a drop-in replacement. Verify the complete pin map, parallel-bus timing, supply thresholds, reset polarity, interrupt behavior, crystal interface, and backup-battery requirements before substitution. The BQ4845YS-A4TR and BQ4845YS-A4NTRG4 results show related parts, but the supplied snippets do not establish full pin-to-pin equivalence.
合规信息
The supplied verified data does not include compliance declarations for RoHS, REACH, AEC-Q100, lead-free status, halogen-free status, or conflict-minerals compliance.
