BQ4845S-A4NG4 - Parallel RTC with NVSRAM Control | TI
Teilenummer: BQ4845S-A4NG4 ✗ AbgekündigtBQ4845S-A4NG4 Übersicht
A real-time clock, or RTC, is a clock-and-timing IC that keeps track of calendar time independently of the system processor. The BQ4845 family combines an RTC with CPU-supervision features in the broader category of clock and timing ICs, providing a system-specific hardware solution for embedded equipment. Its backup-battery connection allows the clock and external SRAM information to remain maintained when the main system supply is absent.
The BQ4845S-A4NG4 includes a 100-year calendar, BCD clock and date formats, alarm capability, daylight-saving support, leap-year handling, watchdog timing, processor reset, interrupt generation, and battery-low warning. Its parallel interface provides direct access to calendar, alarm, and control registers. The 32.768 kHz crystal connection provides the timekeeping reference, while the separate backup-battery path supports retention of real-time-clock and external nonvolatile SRAM data during main-power loss.
The integrated CPU-supervisor functions provide a hardware-level response to power-condition events. The device is intended to combine timekeeping with reset generation, watchdog control, interrupt signaling, and write protection for external SRAM. According to the Texas Instruments product page, CEOUT conditionally enables or write-protects the external nonvolatile SRAM, while VOUT provides a battery-related voltage output. These functions allow the RTC to participate directly in system power management rather than serving only as a passive timekeeping device.
Typical uses include industrial control systems, point-of-sale terminals, data loggers, fax machines, copiers, and embedded computer equipment. The device is particularly relevant where a system needs persistent timestamps, reliable calendar scheduling, processor-reset supervision, and nonvolatile memory retention across a main-power interruption. The 5 V supply and parallel interface are appropriate for systems designed around a conventional microprocessor bus rather than a low-voltage serial RTC architecture.
When laying out the board, place the 32.768 kHz crystal and its associated load components close to the oscillator pins and maintain the layout and grounding guidance in the manufacturer datasheet. Route backup-battery and power-supervisor traces to limit switching noise and unwanted coupling. Because the exact pin mapping was not included in the supplied source excerpts, engineers should verify all 28 connections against the official Texas Instruments datasheet before fabrication.
This product page combines verified manufacturer and distributor information, package details, application guidance, and cross-reference results. It also distinguishes verified drop-in candidates from unavailable alternatives so procurement and engineering teams can assess fit without treating electrically similar but unverified parts as true replacements.
Drop-in-Alternativen für BQ4845S-A4NG4 – gleiches Gehäuse, Pin-kompatibel. Bauteile mit anderem Gehäuse, die eine PCB-Überarbeitung erfordern, sind ausgeschlossen.
Varianten dieser Serie
Modelle derselben Serie, die drop-in-kompatibel sind mit BQ4845S-A4NG4 (gleiche Bauform und Footprint) – abweichend in Package, Product Type, Backup Battery, External SRAM Support.
BQ4845P-A4
✅ Drop-InPreis auf Anfrage
Datenblatt ansehen →BQ4845S-A4G4
✅ Drop-InPreis auf Anfrage
Datenblatt ansehen →BQ4845YP-A4E3
✅ Drop-InPreis auf Anfrage
Datenblatt ansehen →BQ4845S-A4NG4 Technische Daten
| Device Type | Parallel real-time clock with CPU supervisor |
| Clock IC Type | Real-time clock (RTC) |
| Schnittstellentyp | Parallel |
| Clock Format | BCD |
| Date Format | BCD |
| Calendar | 100-year calendar |
| Crystal Frequency | 32.768 kHz |
| System Supply Voltage | 5 V |
| Backup Battery Voltage | 3 V |
| Gehäuse | 28-pin SOIC, 7.50 mm width |
| Pin-Anzahl | 28 pins |
| Betriebstemperatur | -40°C to +85°C |
| Integrated Functions | NVSRAM control, watchdog timer, CPU reset, interrupts, and battery-low warning |
| External SRAM Support | Conditional chip enable output (CEOUT) and battery voltage output (VOUT) |
| Alarm Capability | Supported |
| Daylight Saving Support | Supported |
| Leap-Year Handling | Supported |
BQ4845S-A4NG4 28-pin soic, 7.50 mm width Pinbelegungsleitfaden
Pinbelegung für BQ4845S-A4NG4 (28-pin soic, 7.50 mm width-Gehäuse). Pin-Nummerierung, Funktionen und Anschlussdiagramme sind im Herstellerdatenblatt definiert. Entnehmen Sie diesem den genauen Footprint und Lötrichtlinien.
Keine detaillierten Pinbelegungsdaten verfügbar für BQ4845S-A4NG4.
Siehe die Datenblatt für die vollständige Pin-Konfiguration.
Typische Anwendungen
BQ4845S-A4NG4 ist geeignet für 6 Anwendungs: Industrial Control Systems, Point-of-Sale Terminals, Data Loggers, Fax Machines and Copiers, Embedded Computers and Instrumentation, Battery-Backed Security and Access Systems.
Industrial Control Systems
The BQ4845S-A4NG4 fits industrial controllers that need accurate calendar records and deterministic power supervision. Its 100-year BCD calendar and direct 32.768 kHz crystal connection provide timekeeping independent of the main processor, while the 5 V system supply suits conventional embedded control hardware. The watchdog timer, CPU reset, interrupts, and battery-low warning can support recovery and diagnostic functions. A 3 V backup battery maintains RTC and external SRAM information when main power disappears. The -40°C to +85°C rating also makes the device suitable for many industrial environments, although enclosure temperature and regulator dissipation must be checked.
Empfohlen
Point-of-Sale Terminals
Point-of-sale terminals benefit from a dedicated 100-year calendar, alarm scheduling, and persistent external SRAM support. The BQ4845S-A4NG4 connects to a 32.768 kHz quartz crystal for stable timekeeping and uses a 3 V backup cell to retain calendar data and external nonvolatile SRAM information during a power interruption. Its parallel interface allows a host processor to access time, calendar, and control registers directly. Integrated watchdog and processor-reset functions add system robustness, while the 28-pin SOIC package is practical for a conventional point-of-sale main board.
Empfohlen
Data Loggers
A data logger often needs timestamps that survive battery changes or unintended power loss, making the BQ4845S-A4NG4 appropriate for time-of-day and calendar management. The device's 100-year BCD calendar, alarm function, and 3 V backup-battery connection preserve timing information while the 5 V main supply is absent. CEOUT can conditionally enable or write-protect an external nonvolatile SRAM, allowing retained records to be isolated during backup operation. The watchdog timer and CPU reset functions also support long-running field deployments by helping recover unattended embedded systems after faults.
Empfohlen
Fax Machines and Copiers
Fax machines, copiers, and document-processing equipment can use the BQ4845S-A4NG4 for calendar scheduling, alarm functions, and system recovery. The parallel interface supports direct host-processor access to timekeeping and supervisor registers, while the 100-year calendar handles recurring document and maintenance schedules. Backup operation from a 3 V cell preserves RTC and external SRAM contents if mains-derived power fails. The integrated watchdog, reset, interrupt, and battery-low warning functions complement the copying workflow by providing hardware-level health monitoring during extended unattended operation.
Empfohlen
Embedded Computers and Instrumentation
The BQ4845S-A4NG4 is suitable for embedded computers and instrumentation requiring independent calendar time, CPU supervision, and retained data. A 32.768 kHz crystal maintains a stable reference, while the 100-year BCD calendar supports timestamped measurements and scheduled events. The 5 V operating supply is compatible with systems that already use a conventional processor rail. If an external nonvolatile SRAM is used, CEOUT supports controlled access or write protection, and the 3 V backup source preserves the RTC and SRAM data during main-power loss. The wide -40°C to +85°C range supports industrial and commercial equipment.
Empfohlen
Battery-Backed Security and Access Systems
The BQ4845S-A4NG4 can support access-control and security equipment that records time and must retain configuration or event data through a mains interruption. Its 100-year calendar provides timestamp reference, and the 3 V backup cell keeps the RTC operational while the 5 V system supply is removed. Conditional external-SRAM control through CEOUT can help protect retained records during backup operation. Alarm and interrupt outputs can initiate host-side event handling, while the watchdog and processor-reset functions improve fault recovery. The package and temperature rating suit many indoor industrial installations.
Empfohlen
Zusammenfassung der empfohlenen Produkte
Technische Referenzdaten für BQ4845S-A4NG4 – Vergleich, Designhinweise und Compliance-Informationen.
Auswahlhilfe
Vergleich mit Alternativen
| Parameter | Dieses Produkt | BQ4845P-A4 | BQ4845S-A4G4 | BQ4845YP-A4E3 |
|---|---|---|---|---|
| Package | 28-pin SOIC | 28-pin SOIC | 28-pin SOIC | 28-pin SOIC |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Device Type | Parallel RTC with NVSRAM control and CPU supervisor | Parallel RTC with NVSRAM control and CPU supervisor | Parallel RTC with NVSRAM control and CPU supervisor | Parallel RTC with NVSRAM control and CPU supervisor |
| Interface Type | Parallel | Parallel | Parallel | Parallel |
| System Supply Voltage | 5 V | 5 V | 5 V | 5 V |
| Backup Battery Voltage | 3 V | 3 V | 3 V | 3 V |
| Crystal Frequency | 32.768 kHz | 32.768 kHz | 32.768 kHz | 32.768 kHz |
| Integrated Functions | NVSRAM control, watchdog timer, CPU reset, interrupts, battery-low warning | NVSRAM control, watchdog timer, CPU reset, interrupts, battery-low warning | NVSRAM control, watchdog timer, CPU reset, interrupts, battery-low warning | NVSRAM control, watchdog timer, CPU reset, interrupts, battery-low warning |
Wichtigste Unterscheidungsmerkmale
- Integrated calendar, memory-control, and CPU-supervisor functions (vs. BQ4845P-A4)
- Direct 32.768 kHz crystal and 3 V backup-battery support (vs. BQ4845S-A4G4)
- Parallel interface in a 28-pin SOIC package (vs. BQ4845YP-A4E3)
Designhinweise
Place the 32.768 kHz crystal and its load network close to the oscillator pins, following the exact topology and grounding arrangement in the manufacturer datasheet. Keep high-current switching-node copper and fast digital clocks away from the oscillator and backup-battery traces. Because the supplied source excerpts do not contain the complete pinout or recommended layout, the official BQ4845 datasheet must govern pad assignment and routing rather than an inferred schematic.
Separate the 5 V system-supply path from the 3 V backup-battery path and account for both states when selecting capacitors and protection devices. The RTC and external SRAM data are intended to remain available during backup operation, so the design should prevent unintended battery drain and verify CEOUT behavior during both main-powered and battery-powered intervals. Consult the manufacturer datasheet for capacitor values, battery current, and absolute-maximum limits because those values were not present in the supplied excerpts.
Do not treat an electrically similar RTC as a drop-in replacement without checking the complete 28-pin connection and operating limits. BQ4845P-A4 is the best-supported candidate because the supplied comparison reports consistent terminals and packages, while suffix variants may differ in temperature grade, packaging, qualification, or ordering information. Confirm the complete pin table, 5 V and 3 V operating limits, oscillator requirements, reset timing, and backup behavior against the official manufacturer documentation before production substitution.
The parallel bus should be routed with a continuous ground reference, and unused inputs should be handled according to the datasheet rather than left floating. Avoid routing the clock and data bus beneath or immediately adjacent to the crystal, backup-battery connection, and switching-supply return currents. Because bus timing, setup, and hold limits were not included in the supplied sources, the processor and RTC must be checked against the official electrical-characteristics tables for the intended clock rate.
Compliance-Informationen
The supplied verified excerpts do not state compliance declarations for the BQ4845S-A4NG4. The -40°C to +85°C operating-temperature specification does not by itself establish AEC-Q100 qualification.
