BQ4845P-A4 Parallel RTC with CPU Supervisor | Texas Instruments
料号： BQ4845P-A4 ✓ 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 |
BQ4845P-A4 概述
A real-time clock, or RTC, is a clock-and-timing semiconductor that maintains calendar time independently of the host processor. The BQ4845 combines a time-of-day clock, 100-year calendar, CPU supervisor, watchdog timer, reset control, and nonvolatile-SRAM support in one device. It is intended for legacy embedded systems and equipment that retain time across power interruptions.
Key features include direct crystal connection, backup-battery switchover, programmable alarms, leap-year compensation, daylight-saving support, watchdog operation, CPU reset generation, and conditional chip-enable output. The parallel interface allows a host processor to read and write calendar and control information through discrete digital signals rather than a serial bus. A 3 V backup cell powers the timekeeping section and can maintain supported external SRAM data.
The device is designed for fax machines, copiers, industrial control systems, point-of-sale terminals, data loggers, and computers. Its DIP format supports through-hole legacy boards and replacement of an existing 28-pin clock-and-calendar footprint. System design must follow the manufacturer’s pin connections and ensure that the crystal, backup source, reset circuitry, and external SRAM support network are correctly connected.
Because a DIP package is specified for BQ4845P-A4, do not substitute a surface-mount SOIC variant without confirming the exact package, pin mapping, and board footprint. The product page identifies BQ4845 as available in 28-pin SOIC or DIP families, while the DigiKey result specifically identifies the A4 part as a 28-DIP device.
This page combines the verified manufacturer and distributor descriptions with application guidance and engineering considerations. For replacement decisions, verify the exact package and all electrical and functional differences; do not treat a similar RTC function as proof of pin-to-pin compatibility.
直接替换替代料： BQ4845P-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： BQ4845P-A4 （相同外形与封装尺寸） ——差异在于 Package, Product Type, Interface, Backup Battery.
快速对比工具——选择替代料号进行并排对比：
BQ4845S-A4
✅ 直接替换✓ 有现货
联系询价
查看数据手册 →BQ4845YS-A4G4
✅ 直接替换📋 参考替代料（不在目录中）
BQ4845YP-A4E3
✅ 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）
BQ4845P-A4 规格参数
| Product Type | Parallel real-time clock and calendar with CPU supervisor |
| Timekeeping | Seconds through years in BCD format |
| Calendar Range | 100 years |
| Crystal Interface | Direct connection for 32.768 kHz quartz crystal |
| Backup Battery | 3 V backup battery connection |
| Backup Current | Less than 500 nA in backup mode |
| CPU Supervision | Integrated microprocessor supervisor and reset |
| Watchdog | Watchdog timer function |
| Alarm | Alarm functionality |
| Daylight Saving | Daylight-saving support |
| Leap Year | Leap-year compensation |
| External SRAM Support | Write-protect and nonvolatile support for external SRAM |
| Conditional Chip Enable | CEOUT output |
| Battery Voltage Output | VOUT output |
| 封装 | 28-pin DIP, 0.600 inch / 15.24 mm pitch |
| 接口 | Parallel |
BQ4845P-A4 28-pin dip, 0.600 inch / 15.24 mm pitch 引脚配置指南
BQ4845P-A4（28-pin dip, 0.600 inch / 15.24 mm pitch 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： BQ4845P-A4.
请参阅 数据手册 以查看完整引脚配置。
典型应用
BQ4845P-A4 适用于 6 应用s: Industrial Control Systems, Point-of-Sale Terminals, Data Loggers, Fax Machines and Copiers, Battery-Backed Embedded Products, Legacy Computer Peripherals.
Industrial Control Systems
BQ4845P-A4 fits legacy industrial controllers that need a local, battery-backed calendar rather than relying on the host processor clock. Its 100-year calendar, 32.768 kHz crystal connection, parallel interface, and CPU-supervisor function support time-stamped control events and controlled reset behavior. The less-than-500-nA backup-mode current helps maintain timekeeping during power loss, while the 28-DIP package fits through-hole legacy designs. Verify reset timing and alarm settings against the manufacturer datasheet before production.
推荐
Point-of-Sale Terminals
The BQ4845P-A4 is appropriate for point-of-sale equipment that maintains transaction time across power interruptions. The parallel calendar interface allows the controller to obtain seconds, calendar fields, and alarm information, while the 3 V backup battery preserves operation when the primary supply fails. Its CPU supervisor can assist with orderly processor reset, and the 100-year calendar supports long-lived deployments. Board-level validation should confirm the exact DIP pin mapping and battery isolation behavior.
推荐
Data Loggers
Data loggers benefit from independent timekeeping because recorded events must retain an accurate date and time even when the logging system restarts. BQ4845P-A4 provides seconds-through-years BCD timekeeping, a 100-year calendar, leap-year compensation, and daylight-saving support. The 32.768 kHz crystal connection establishes the time base, while the backup supply maintains operation during main-power loss. Use the watchdog and reset functions only after checking their timing and polarity requirements in the datasheet.
推荐
Fax Machines and Copiers
The BQ4845P-A4 is explicitly identified by Texas Instruments for fax machines and copiers, where event timestamps, scheduling, and system supervision are important. Its calendar functions and backup-battery support allow the equipment to retain time through short or extended power interruptions. The parallel interface can be used by legacy controller boards that are not designed around I2C or SPI. Validate crystal startup, backup-battery loading, and reset behavior in the final mechanical and electrical design.
推荐
Battery-Backed Embedded Products
BQ4845P-A4 is suitable for embedded products that must preserve calendar time and selected nonvolatile SRAM information when the primary supply is removed. The manufacturer describes a 3 V backup-battery connection and less-than-500-nA backup operation, which helps limit standby drain. The RTC can maintain time from seconds through years, while the CEOUT and VOUT signals provide control and battery-voltage monitoring functions for supported external SRAM arrangements. The final schematic must follow the exact manufacturer application guidance.
推荐
Legacy Computer Peripherals
The BQ4845P-A4 can support legacy computer peripherals that require a real-time clock, calendar, watchdog, and CPU-reset supervisor. The 28-DIP format is especially useful for older through-hole PCBs, while the parallel interface avoids introducing a new serial bus. A replacement design should preserve the original BQ4845 pinout, crystal network, backup-battery circuit, and reset polarity. Because the supplied data does not include full pin-level electrical limits, production use should rely on the TI datasheet.
推荐
推荐产品汇总
工程参考数据： BQ4845P-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 | BQ4845S-A4 | BQ4845YS-A4G4 | BQ4285EP |
|---|---|---|---|---|
| Product Type | Parallel RTC with CPU supervisor | Parallel RTC with CPU supervisor | RTC variant | RTC-related comparison candidate |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
关键差异点
- Integrated clock and power-management functions （对比 BQ4285EP)
- 100-year calendar and BCD timekeeping （对比 BQ4845YS-A4G4)
- Legacy DIP-compatible package （对比 BQ4845S-A4)
设计说明
Design the backup-battery path around the BQ4845P-A4 application guidance and confirm battery polarity, isolation, and switching behavior before layout. The verified data specifies a 3 V backup battery and less than 500 nA clock-operation current in backup mode, but it does not provide the complete battery electrical limits. Confirm those values in the manufacturer datasheet and validate the system’s current budget over the intended power-loss interval.
Route the BQ4845P-A4 crystal connection and associated components according to the manufacturer pinout and layout guidance, keeping the timing path short and away from high-current switching nodes. The supplied data confirms support for a direct 32.768 kHz quartz-crystal connection but does not specify load capacitance or maximum stray capacitance. Those values must be obtained from the datasheet before final component selection and PCB release.
Do not substitute a BQ4845 family variant solely because it is also a real-time clock. The verified comparison identifies BQ4845S-A4 as SOIC while BQ4845P-A4 is a 28-DIP device, so an SOIC package cannot be treated as a same-footprint replacement on a through-hole board. Verify the exact suffix, pin mapping, reset polarity, watchdog behavior, calendar features, backup circuit, and SRAM-control signals before approving any replacement.
Use the CEOUT and VOUT functions only in the external-SRAM support arrangement described by the manufacturer. The verified product description identifies conditional chip-enable and battery-voltage outputs for write-protecting and maintaining supported external SRAM during backup operation. Validate the SRAM voltage, write timing, and control polarity in the system design because those parameters are not supplied in the verified web data.
Keep the parallel RTC interface traces away from noisy analog and switching paths where possible, even though the BQ4845P-A4 is a digital clock-and-calendar device. Maintain adequate grounding and follow the manufacturer’s recommended pin and layout arrangement. Since the supplied data does not include complete electrical timing or signal-integrity limits, treat the datasheet as the controlling source for bus timing and signal levels.
合规信息
The supplied verified web data does not state RoHS, REACH, lead-free, halogen-free, conflict-mineral, or automotive qualification information for BQ4845P-A4. Compliance fields remain unknown rather than assumed.
