BQ4845S-A4G4 - Parallel RTC with CPU Supervisor | TI
料号： BQ4845S-A4G4 ✗ 停产| 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-A4G4 概述
A real-time clock, or RTC, is a clock-and-timing semiconductor that maintains time independently of the main processor. The BQ4845S-A4G4 adds calendar and supervisory functions, placing it between a basic RTC, a clock-and-calendar IC, and a system timing peripheral. Its battery-backed operation allows timekeeping to continue when system power is absent, while the CPU supervisor helps a controller recover from unstable supply conditions.
Verified manufacturer information identifies time-of-day clocking, a 100-year calendar, a CPU supervisor, a watchdog timer, interrupt support, and controls for external nonvolatile SRAM. The device provides a conditional chip-enable output, CEOUT, and a battery-voltage output, VOUT. CEOUT can control write-protect behavior for external SRAM, while the backup cell supplies the RTC and preserves retained system information.
The parallel interface provides a straightforward connection to a microprocessor or controller bus rather than requiring a serial RTC protocol. A 32.768 kHz crystal supplies the timekeeping reference, while the 3 V backup source preserves clock state during main-power loss. This arrangement separates calendar continuity from volatile processor state and supports controlled recovery after power restoration.
Typical uses include industrial control systems, point-of-sale terminals, data loggers, computers, fax machines, and copiers, as identified by the Texas Instruments product page. These systems benefit from persistent timestamps, reset control, and battery-backed external memory. The combination of RTC and supervisor functions can also reduce the number of separate timing and reset components on a control board.
The primary design task is preserving signal and power behavior across normal operation, backup mode, and power restoration. Place the crystal and associated components according to the manufacturer layout guidance, maintain the specified backup-battery connection, and verify the system’s reset, alarm, interrupt, and SRAM-control requirements. The 28-SOIC footprint allows conventional surface-mount assembly while supporting a mixed analog-timing and digital-control system.
This page consolidates verified manufacturer and distributor information with selection guidance, application context, and design considerations for engineers evaluating the BQ4845S-A4G4. Parameter values not stated in the supplied source data remain explicitly marked as needed rather than inferred or estimated.
直接替换替代料： BQ4845S-A4G4 ——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-A4G4
✅ 直接替换📋 参考替代料（不在目录中）
BQ4845S-A4NTRG4
✅ 直接替换📋 参考替代料（不在目录中）
BQ4845S-A4G4 规格参数
| Product Type | Real-time clock and calendar IC with CPU supervisor |
| Clock Interface | Parallel |
| Timekeeping Crystal Frequency | 32.768 kHz |
| Backup Battery | 3 V |
| Calendar Range | 100 years |
| 封装 | 28-SOIC, 0.295 inch width, 7.50 mm |
| 安装类型 | Surface mount |
| Supervisor Functions | CPU supervisor and watchdog timer |
| Alarm and Interrupt Functions | Alarm and interrupt functions |
| External Memory Control | Conditional chip-enable output CEOUT |
| Battery Monitoring | Battery voltage output VOUT |
| Backup Retention | Maintains external SRAM information in the absence of system voltage |
| System-Level Use | Battery-backed system timing and power-failure monitoring |
BQ4845S-A4G4 28-soic, 0.295 inch width, 7.50 mm 引脚配置指南
BQ4845S-A4G4（28-soic, 0.295 inch width, 7.50 mm 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-A4G4.
请参阅 数据手册 以查看完整引脚配置。
典型应用
BQ4845S-A4G4 适用于 7 应用s: Industrial Control Systems, Point-of-Sale Terminals, Data Loggers, Computers and Embedded Equipment, Copiers and Printers, Fax Machines and Office Equipment, Battery-Backed Instrumentation.
Industrial Control Systems
The BQ4845S-A4G4 fits industrial controllers that need a battery-backed time base, calendar information, and power supervision in one peripheral. Its 32.768 kHz crystal interface and 3 V backup connection support persistent timestamps after the main supply disappears, while the CPU supervisor helps the controller detect abnormal supply conditions. The parallel interface is useful in systems where a microprocessor bus is already present and a serial RTC would add another communication path.
推荐
Point-of-Sale Terminals
The BQ4845S-A4G4 is appropriate for point-of-sale equipment where transaction time must remain available through brief or complete power interruptions. Its 100-year calendar helps organize dated records, and the backup battery preserves RTC operation when system voltage is removed. The supervisor and watchdog functions add recovery value in embedded terminals that must restart predictably after brownout, power loss, or processor lockup.
推荐
Data Loggers
The BQ4845S-A4G4 provides a persistent time reference for data loggers that must timestamp samples outside normal power conditions. A 32.768 kHz crystal drives the time-of-day clock, while the 3 V backup source preserves timing during field deployments where the main supply can be intermittent. CEOUT can assist with controlling external SRAM retention, helping a designer protect records that must not disappear during a power interruption.
推荐
Computers and Embedded Equipment
The BQ4845S-A4G4 is useful in computers and embedded equipment that need timekeeping separate from the main processor. The backup battery maintains RTC and calendar state during shutdown, while the CPU supervisor assists system recovery from unstable power. Its 28-SOIC package and parallel interface support designs that favor conventional surface-mount assembly and direct microprocessor connection over a serial bus.
推荐
Copiers and Printers
The BQ4845S-A4G4 can support copiers and printers that maintain event, maintenance, and job-related timestamps across power interruptions. Its 100-year calendar and backup-powered RTC provide continuity for system logs, while the supervisor functions help the embedded controller respond to supply faults. The parallel interface can be attractive in legacy or industrial equipment that already uses a parallel peripheral bus.
推荐
Fax Machines and Office Equipment
The BQ4845S-A4G4 suits office equipment requiring persistent date and time information plus controlled power-state behavior. A 32.768 kHz crystal maintains the reference clock, and the 3 V backup battery allows the RTC to continue when the equipment is unplugged or its supply drops. The integrated supervisor and watchdog functions are useful when reliable reset behavior is needed in a long-running embedded controller.
推荐
Battery-Backed Instrumentation
The BQ4845S-A4G4 can be used in instrumentation that records the time of measurements and must preserve context after a power interruption. The backup cell maintains the RTC, while CEOUT can be used in a controlled SRAM-retention scheme. The 28-SOIC format is suitable for boards that need a discrete timing and supervisor function without adding a serial communication protocol.
推荐
推荐产品汇总
工程参考数据： BQ4845S-A4G4 ——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-A4G4 | BQ4845S-A4NTRG4 |
|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | Texas Instruments |
关键差异点
- Combines calendar timing and CPU supervision （对比 BQ4845YS-A4G4)
- Supports battery-backed SRAM retention control （对比 BQ4845S-A4NTRG4)
- Uses a documented parallel RTC architecture （对比 BQ4845YS-A4G4)
设计说明
Design the main supply and 3 V backup path so the RTC remains powered when system voltage disappears, while preventing unintended backfeeding of the backup source. Verify the manufacturer’s absolute maximum and recommended operating limits before selecting capacitors or protection components. The verified material confirms a 3 V backup connection but does not provide the complete supply-current limits, so those values must be taken directly from the TI datasheet.
Keep the 32.768 kHz crystal connection short and follow the TI reference layout, including the recommended load network and ground return. Crystal stability depends on mechanical layout, stray capacitance, grounding, and the selected crystal’s load and ESR requirements. Because those component values are not included in the supplied verified data, do not invent them; extract the values from the manufacturer datasheet and validate startup and frequency accuracy on the assembled board.
Do not assume that a related BQ4845 suffix is automatically interchangeable. Confirm the complete ordering table, pin names, electrical limits, timing, temperature range, and package drawing for BQ4845YS-A4G4 or BQ4845S-A4NTRG4 before substituting either part. A distributor cross-reference result identifies candidates but does not prove that CEOUT, VOUT, reset, watchdog, or SRAM-retention behavior matches exactly.
合规信息
The supplied verified sources identify the Texas Instruments product and datasheet but do not state RoHS, REACH, lead-free, halogen-free, conflict-minerals, or automotive qualification status.
