BQ4845YP-A4 - Parallel RTC with CPU Supervisor | Texas Instruments
部品番号: BQ4845YP-A4 ✗ 生産終了| 数量 | 単価 | 小計 |
|---|---|---|
| 1 | $0 | $0.00 |
| 10 | $0 | $0.00 |
| 100 | $0 | $0.00 |
| 500 | $0 | $0.00 |
| 1,000 | $0 | $0.00 |
BQ4845YP-A4 概要
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.
ドロップイン代替品: BQ4845YP-A4 — 同一パッケージでピン互換。PCBの作り直しが必要な異なるパッケージの部品は除外されています。
このシリーズのバリエーション
同一シリーズでドロップイン互換のモデル: BQ4845YP-A4 （同一形状・フットプリント） — 相違点: Interface, Mounting Type, Package.
クイック比較ツール — 並列比較する代替部品を選択:
BQ4845YP
✅ ドロップイン📋 参考代替品（カタログ未掲載）
BQ4845YS
✅ ドロップイン📋 参考代替品（カタログ未掲載）
BQ4845YP-A4 仕様
| Product Type | Parallel real-time clock and calendar with CPU supervisor |
| 電源電圧 | 5 V |
| Backup Battery Voltage | 3 V |
| Crystal Frequency | 32.768 kHz |
| Calendar Format | BCD, counting seconds through years |
| インターフェース | 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 |
| パッケージ | 28-DIP, 0.600 inch (15.24 mm) |
| 実装タイプ | Through-hole |
| Termination Count | 28 |
| RoHS Compliance | RoHS compliant |
BQ4845YP-A4 28-dip, 0.600 inch (15.24 mm) ピン配置ガイド
BQ4845YP-A4 (28-dip, 0.600 inch (15.24 mm) パッケージ) のピン配置。 ピン番号、機能、接続図はメーカーのデータシートで定義されています。正確なフットプリントとはんだ付けのガイドラインについては、データシートを参照してください。
詳細なピン配置データはありません: BQ4845YP-A4.
詳細は データシート をご参照ください。
主な用途
BQ4845YP-A4 の用途: 6 件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.
おすすめ
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.
おすすめ
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.
おすすめ
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.
おすすめ
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.
おすすめ
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.
おすすめ
おすすめ製品の概要
エンジニアリング参考データ: BQ4845YP-A4 — 比較、設計ガイダンス、コンプライアンス情報。
選定ガイド
代替品との比較
| パラメータ | この製品 | 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 |
主な差別化要因
- Integrated system supervision （vs BQ4845YP)
- External-SRAM retention control （vs BQ4845YS)
- Low-power backup operation （vs BQ4845YP)
設計ノート
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.
コンプライアンス情報
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.
