BQ4845S-A4NTRG4 - 5V Parallel RTC with Supervisor | TI
MPN： BQ4845S-A4NTRG4 ✓ 啟用中BQ4845S-A4NTRG4 概覽
A real-time clock, or RTC, is a timing peripheral that retains seconds, minutes, hours, date, and calendar information independently of the main processor clock. The BQ4845 belongs to the clock and timing IC hierarchy, where it combines an RTC with voltage supervision, watchdog, reset, interrupt, and nonvolatile-memory control functions. This integration reduces the number of separate system-support components required around a microprocessor.
The BQ4845S-A4NTRG4 uses a BCD clock and calendar format and supports a parallel host interface. Its integrated 32.768 kHz crystal connections support accurate timekeeping, while the backup-cell path maintains the clock during main-power loss. The CEOUT output can write-protect external nonvolatile SRAM, and the VOUT output provides a battery-voltage signal for system monitoring.
The CPU-supervisor section adds power-fail detection, processor reset, watchdog timing, and interrupt support. According to the manufacturer datasheet, an internal approximately 100 kilohm-equivalent resistor network biases the watchdog input, while internal comparators detect the resulting level and disable the watchdog. Below the power-fail threshold, watchdog operation is disabled and the watchdog input is disconnected from the internal network.
Typical uses include industrial control systems, point-of-sale terminals, fax machines, copiers, data loggers, computers, and embedded equipment requiring calendar retention. Its 28-pin SOIC format also supports designs that need parallel access to time registers, alarm functions, supervisor status, and backup-battery information.
PCB design should place the crystal and associated load components close to the oscillator pins and keep backup-supply routing away from high-current switching nodes. Because the main supply and backup cell have separate operating ranges, designers should verify both rails under worst-case battery depletion, startup, and power-transition conditions.
This product summary consolidates the verified manufacturer and distributor information into a design-focused reference covering the BQ4845S-A4NTRG4 clock, watchdog, backup-battery, and SRAM-control functions. It also identifies same-family candidates, highlights unresolved comparison parameters, and supplies practical selection guidance beyond a basic distributor listing.
直接替換替代品，適用於 BQ4845S-A4NTRG4 — 相同封裝，腳位對腳位相容。需重新設計 PCB 的不同封裝零件不列入。
此系列的變體
與下列產品可直接替換的同系列型號： BQ4845S-A4NTRG4 （相同外形與佔位） — 差異在於 Package, Product Type, Interface, Timekeeping Format.
BQ4845S-A4NTR
✅ 直接替換聯絡詢價
查看資料表 →BQ4845YS-A4NTR
✅ 直接替換聯絡詢價
查看資料表 →BQ4845YS-A4NG4
✅ 直接替換📋 參考替代品（不在目錄中）
BQ4845YS-A4NTRG4
✅ 直接替換📋 參考替代品（不在目錄中）
BQ4845S-A4G4
✅ 直接替換聯絡詢價
查看資料表 →BQ4845S-A4NTRG4 規格
| Product Type | Parallel real-time clock and calendar with CPU supervisor |
| Main Supply Voltage Range | 4.75 V to 5.5 V |
| Backup Battery Voltage Range | 2.3 V to 4 V |
| Crystal Frequency | 32.768 kHz |
| Clock Format | BCD |
| Date Format | BCD |
| Host Interface | Parallel |
| 封裝 | 28-pin SOIC, 7.50 mm width |
| 安裝類型 | Surface mount |
| Operating Features | Alarm, daylight-saving time, leap year, watchdog timer, processor reset, interrupt, and battery-low warning |
| Calendar Range | 100 years |
| Backup Clock Operating Current | Less than 500 nA |
| Watchdog Input Bias | Approximately 1.6 V through a 100 kilohm-equivalent internal resistor network |
| Battery Voltage Output | VOUT output available |
| External SRAM Control | CEOUT write-protection output available |
| Power-Fail Behavior | Watchdog disabled and WDI disconnected from the internal resistor network below the power-fail threshold |
BQ4845S-A4NTRG4 28-pin soic, 7.50 mm width 腳位配置指南
BQ4845S-A4NTRG4（28-pin soic, 7.50 mm width 封裝）的腳位配置。 腳位編號、功能與連接圖定義於製造商資料手冊中。請參閱該手冊以取得確切的封裝尺寸與焊接指引。
無詳細腳位定義資料： BQ4845S-A4NTRG4.
請參閱 資料表 以查看完整腳位配置。
典型應用
BQ4845S-A4NTRG4 適用於 6 應用s: Industrial Control Systems, Point-of-Sale Terminals, Data Loggers, Fax Machines and Copiers, Backup-Powered Embedded Equipment, Computer and Peripheral Timing.
Industrial Control Systems
The BQ4845S-A4NTRG4 suits industrial controllers that must preserve event timestamps and calendar records during power interruptions. Its 4.75 V to 5.5 V main supply, 3 V backup-battery connection, 32.768 kHz crystal interface, and less-than-500 nA backup operating current support continuous timekeeping when VCC is removed. The parallel bus provides direct access to time, calendar, alarm, and supervisor registers, while the integrated watchdog and processor-reset functions can supervise an embedded controller without separate supervisor ICs. For an industrial design, confirm the exact operating-temperature grade and verify the watchdog thresholds against the manufacturer datasheet before release.
推薦
Point-of-Sale Terminals
Point-of-sale terminals benefit from a dedicated calendar clock that remains valid when the main system loses power. The BQ4845S-A4NTRG4 maintains BCD time and date through a 3 V backup cell, covers a 100-year calendar, and includes alarm and daylight-saving functions that can support scheduled transactions and record handling. Its parallel interface is useful with processors that already provide a bus-oriented control architecture. The CEOUT output can also control write protection for external SRAM, although the designer must confirm that the terminal's memory topology and retention requirements match the intended implementation.
推薦
Data Loggers
A data logger often needs accurate timestamps even after an unexpected power loss, making the BQ4845S-A4NTRG4's backup-powered RTC a practical timing component. The device combines a 32.768 kHz crystal oscillator with a 3 V backup battery, a 100-year calendar, alarm handling, and a low-power backup current below 500 nA. A host processor can read the parallel clock registers when the logger starts and correlate stored measurements with the retained time. Designers should allow adequate layout separation between the oscillator and backup-supply routing, and should validate clock accuracy across the intended temperature range because that limit was not included in the supplied verified snippets.
推薦
Fax Machines and Copiers
The BQ4845S-A4NTRG4 addresses the timekeeping and power-management needs identified by Texas Instruments for fax machines and copiers. It maintains date and time during main-power loss, supports alarms, and integrates watchdog and processor-reset functions for embedded print-system controllers. The 5 V main-supply range fits the documented operating environment, while the parallel interface can support deterministic access by the equipment controller. CEOUT can provide conditional write protection for external nonvolatile SRAM, helping preserve documents or settings when the primary rail collapses. Exact timer behavior and board-level integration should be checked against the complete manufacturer schematic and pin descriptions.
推薦
Backup-Powered Embedded Equipment
Equipment that must resume operations with valid timestamps after a power interruption can use the BQ4845S-A4NTRG4 as a dedicated backup time source. The RTC supports a 2.3 V to 4 V battery range, including the documented 3 V cell, and its backup operating current is less than 500 nA. The processor-reset, watchdog, battery-low, and interrupt functions provide useful fault-management signals around the host processor. Because the device is a parallel-interface part in a 28-pin SOIC package, it is best suited to boards that already have sufficient bus and routing resources and can preserve the reference clock layout without modification.
推薦
Computer and Peripheral Timing
The BQ4845S-A4NTRG4 can support legacy or industrial computer peripherals that require a dedicated parallel real-time clock. The part tracks seconds through years in BCD format, supplies a 100-year calendar, and keeps operating from a backup battery when the system supply is removed. Its alarm and watchdog capabilities allow a host processor to be scheduled or supervised independently of the main real-time operating system. Integration is most practical on custom 28-pin SOIC boards with a parallel bus, rather than on a conventional plug-in PC interface without additional glue logic. Pin-level review remains essential because the verified source did not provide a complete numbered pin table.
推薦
推薦產品摘要
工程參考資料，適用於 BQ4845S-A4NTRG4 — 比較、設計指引及合規資訊。
選型指南
與替代品比較
| 參數 | 本產品 | BQ4845S-A4NTR | BQ4845YS-A4NTR | BQ4845YS-A4NG4 | BQ4845YS-A4NTRG4 | BQ4845S-A4G4 |
|---|---|---|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Package | SOIC-28 | SOIC-28 - same | SOIC-28 - same | SOIC-28 - same | SOIC-28 - same | SOIC-28 - same |
主要差異化特點
- Combines timekeeping and CPU supervision (對比BQ4285S-SB2TR)
- Maintains time through main-power loss (對比BQ4845S-A4G4)
- Supports external SRAM retention control (對比BQ4845YS-A4NTR)
- Direct 32.768 kHz crystal interface (對比BQ4845YS-A4NG4)
設計說明
Route the 32.768 kHz crystal and its load network with short, symmetric connections to the oscillator pins, and keep the region free from switching-power traces and high-current motor or relay wiring. Place the backup-cell connection so that main-rail transients cannot couple directly into it. The supplied data confirms direct 32.768 kHz crystal and 3 V battery connections but does not provide the manufacturer layout figures, so exact guard-ring and capacitor placement should follow the TI datasheet.
Validate startup and power-loss behavior with both the main 4.75 V to 5.5 V supply and the 2.3 V to 4 V backup range. The RTC is intended to operate from a 3 V cell and continue maintaining time when VCC disappears. Check battery-low timing, the VOUT battery-voltage signal, and the power-fail threshold against the system requirements. Do not allow the backup rail to exceed its specified range during abnormal charging or transient conditions.
Do not treat every 28-pin SOIC RTC as a pin-compatible substitute. The verified candidates belong to the TI BQ4845 family, but the supplied results explicitly note that some electrical characteristics can differ. Before replacing the BQ4845S-A4NTRG4, compare the complete ordering table, pin functions, watchdog thresholds, alarm behavior, electrical limits, temperature grade, and qualification status. A matching package alone does not prove drop-in compatibility.
Account for the parallel interface when designing bus timing and firmware. The RTC supplies direct clock, calendar, alarm, supervisor, interrupt, and backup-related signals, but the verified snippets do not include complete access-time or timing-edge parameters. Confirm read and write cycle requirements, chip-select behavior, and interrupt polarity in the manufacturer datasheet. Software should also handle rollover, alarm-mask, and power-transition states rather than assuming an always-valid main supply.
合規資訊
The supplied verified snippets do not state RoHS, REACH, AEC-Q100, lead-free, halogen-free, or conflict-minerals status for this ordering code. AEC-Q100 is marked not_applicable because the device was not identified as an automotive-qualified part in the provided data; this is not an automotive-grade approval.
