BQ4845YP-A4 - Parallel RTC with CPU Supervisor | Texas Instruments
料号： BQ4845YP-A4 ✗ 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 |
BQ4845YP-A4 概述
A real-time clock, or RTC, is a clock-and-timing semiconductor that maintains calendar information independently of the system processor. It counts seconds through years, supplies time to embedded equipment, and commonly wakes or resets a host controller after power restoration. An RTC with CPU-supervisor functions adds power-failure detection, restart timing, and watchdog monitoring, allowing a system to distinguish a normal shutdown from an uncontrolled loss of control.
The BQ4845YP-A4 combines timekeeping with support functions for external nonvolatile SRAM. Its conditional chip-enable output, CEOUT, can control SRAM write protection, while VOUT provides a battery-voltage output used by the backup-power subsystem. According to the manufacturer datasheet, the on-chip backup switchover circuit allows the backup cell to power the RTC and preserve SRAM information when system voltage is absent.
The clock section accepts a direct 32.768 kHz quartz crystal, a standard frequency for calendar-counting RTCs because the divider can derive a one-second update from 32,768 cycles. The part records calendar information through years in BCD format and includes leap-year logic plus daylight-saving correction. These features suit meters, data loggers, industrial controllers, embedded products, and access-control equipment that must retain accurate wall-clock time.
The watchdog timer and microprocessor-reset function support dependable recovery from firmware hangs or abnormal operating conditions. Battery backup allows continued counting and external-SRAM retention while the main supply is removed, although total retention time depends on the backup cell, SRAM characteristics, leakage current, and supply conditions. Precise battery-life calculations therefore require component-specific values beyond the supplied source material.
PCB implementation should reserve the specified 28-DIP footprint and route the crystal, backup supply, reset, alarm, watchdog, and SRAM-control signals according to the manufacturer datasheet. Keep crystal traces short and decouple supply pins close to the device. Because this is a through-hole DIP package, verify board spacing and mechanical clearance rather than assuming a surface-mount land pattern.
This page combines the verified distributor identity, package information, manufacturer features, application guidance, and replacement limitations. The supplied evidence does not establish five pin-to-pin alternatives, so an engineering replacement should not be approved solely from a general functional similarity.
直接替换替代料： BQ4845YP-A4 ——相同封装，引脚兼容。需要 PCB 改动的不同封装料号已排除。
本系列中的变体
可与以下型号直接替换的同系列型号： BQ4845YP-A4 （相同外形与封装尺寸） ——差异在于 Interface, Mounting Type, Package.
快速对比工具——选择替代料号进行并排对比：
BQ4845YP
✅ 直接替换📋 参考替代料（不在目录中）
BQ4845YS
✅ 直接替换📋 参考替代料（不在目录中）
BQ4845YP-A4 规格参数
| Product Type | Parallel real-time clock and calendar with CPU supervisor |
| 电源电压 | 5 V |
| Backup Battery Voltage | 3 V |
| Crystal Frequency | 32.768 kHz |
| Calendar Format | BCD, counting seconds through years |
| 接口 | Parallel |
| Real-Time Clock Count | 1 timer |
| Backup Operating Current | Less than 500 nA |
| Alarm Function | Yes |
| Daylight Savings Correction | Yes |
| Leap-Year Calculation | Yes |
| Watchdog Timer | Yes |
| Microprocessor Reset | Yes |
| Battery Low Warning | Yes |
| External SRAM Control | Nonvolatile write-protect and backup-retention control |
| Conditional Chip Enable Output | CEOUT |
| Battery Voltage Output | VOUT |
| 封装 | 28-DIP, 0.600 inch (15.24 mm) |
| 安装类型 | Through-hole |
| Termination Count | 28 |
| RoHS Compliance | RoHS compliant |
BQ4845YP-A4 28-dip, 0.600 inch (15.24 mm) 引脚配置指南
BQ4845YP-A4（28-dip, 0.600 inch (15.24 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： BQ4845YP-A4.
请参阅 数据手册 以查看完整引脚配置。
典型应用
BQ4845YP-A4 适用于 6 应用s: Battery-Backed Industrial Data Logger, Metering and Utility Data Equipment, Embedded Access-Control Controller, Process-Control and Automation Equipment, Alarm and Event-Notification System, Network Appliance with Persistent Event Logs.
Battery-Backed Industrial Data Logger
The BQ4845YP-A4 fits a data logger that must preserve timestamps while recording or idle during a mains outage. Its 32.768 kHz crystal input maintains calendar time in BCD format through years, while the 3 V backup source supports continued counting and external-SRAM retention. The below-500 nA backup clock specification helps limit drain, although calculated battery life must include the external SRAM and control-logic loads. Use the watchdog and reset functions to ensure the host records an orderly shutdown and resumes reliably when power returns.
推荐
Metering and Utility Data Equipment
The BQ4845YP-A4 supports metering equipment that must retain an accurate calendar across scheduled service windows and unintended outages. Alarm, leap-year, and daylight-saving functions assist long-duration timestamp management, while CPU reset and watchdog supervision improve recovery after a controller fault. CEOUT can control external SRAM write protection, helping preserve collected records during backup operation. The design must verify local daylight-saving rules and configure the device correctly rather than assuming calendar corrections are universally identical.
推荐
Embedded Access-Control Controller
The BQ4845YP-A4 is appropriate for access-control equipment that timestamps grants and maintains state through a temporary power loss. Its calendar, alarm, and backup functions support time-based authorization, while the watchdog and microprocessor-reset outputs help recover an embedded controller that stops responding. External SRAM retention through CEOUT is useful for transaction records, subject to correct battery backup and memory-cell behavior. Firmware should define time-zone and daylight-saving policy and test restart sequences around battery depletion.
推荐
Process-Control and Automation Equipment
The BQ4845YP-A4 can add dependable timekeeping and supervision to industrial control equipment. A 32.768 kHz crystal supplies the RTC time base, and the backup path supports time retention when the main rail fails. The watchdog and reset functions coordinate host recovery, while CEOUT assists with retaining external SRAM. Because a controller may also need deterministic communication, the parallel RTC bus should be isolated from switching-node and high-current traces according to the manufacturer layout guidance.
推荐
Alarm and Event-Notification System
The BQ4845YP-A4 suits alarm equipment that needs a persistent time base and host-fault recovery. Its alarm function can initiate scheduled events, while watchdog and reset outputs help distinguish controller stalls and restart the system. The 3 V backup connection allows timekeeping to continue during short supply interruptions, and the below-500 nA backup clock current reduces idle drain. Validation should include alarm behavior after reset, oscillator startup, backup switching, and recovery from complete battery discharge.
推荐
Network Appliance with Persistent Event Logs
The BQ4845YP-A4 can support event timestamping in an embedded network appliance that must retain records through power loss. Parallel calendar data, backup operation, and external-SRAM control provide a compact implementation for embedded logs or configuration data. Watchdog and reset functions improve recovery after firmware lockups. The PCB should keep the 28-DIP oscillator and backup circuitry away from high-speed communication and power-conversion stages, while grounding and decoupling strategy follows the manufacturer requirements.
推荐
推荐产品汇总
工程参考数据： BQ4845YP-A4 ——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 | BQ4845YP | BQ4845YS |
|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | Texas Instruments |
| Product Type | Parallel RTC with CPU supervisor | Real-time clock family variant | Real-time clock family variant |
关键差异点
- Integrated system supervision （对比 BQ4845YP)
- External-SRAM retention control （对比 BQ4845YS)
- Low-power backup operation （对比 BQ4845YP)
设计说明
Reserve the exact 28-DIP footprint and verify mechanical clearance before layout because this is a 0.600 inch (15.24 mm) through-hole package rather than a surface-mount device. Keep the 32.768 kHz crystal and associated pins close to the BQ4845YP-A4, minimize loop area, and avoid routing backup-clock signals beside high-current switching nodes. The complete pin map must be taken from the official datasheet because the supplied search excerpts do not contain all numbered assignments.
Design the 5 V main supply and 3 V backup path as a coordinated switchover network around the manufacturer reference circuit. Verify backup-source polarity, source impedance, decoupling, and the behavior of CEOUT and VOUT during normal operation, main-power loss, and battery depletion. The stated clock current below 500 nA does not equal complete battery life; an Estimated: capacity calculation would also need backup-cell capacity, SRAM leakage, and all peripheral standby currents.
Do not treat every RTC with a 28-DIP footprint as a substitute. Validate pin names, supply levels, oscillator connection, alarm polarity, watchdog behavior, reset timing, SRAM write protection, and daylight-saving logic before replacement. Also test what the processor bus reads during backup operation, because write protection can change if the main rail disappears. The verified search results identify related TI orderable codes but do not provide enough complete electrical data to waive this review.
合规信息
The Ampheo product listing explicitly identifies BQ4845YP-A4 as RoHS compliant. No verified REACH, AEC-Q100, lead-free, halogen-free, or conflict-minerals declarations were supplied.
