BQ4845YS-A4G4 - Parallel RTC with CPU Supervisor | Texas Instruments
MPN: BQ4845YS-A4G4 ✓ نشطBQ4845YS-A4G4 نظرة عامة
A real-time clock, or RTC, is a clock-and-timing IC that preserves calendar time independently of the main processor. The RTC hierarchy includes clock/calendar devices, timekeeping ICs, and timing semiconductors used to maintain seconds, minutes, hours, dates, and years. The BQ4845YS-A4G4 combines this timekeeping role with power-supervision functions, making it suitable for embedded systems that require both accurate wall-clock data and controlled reset behavior.
Key device features include a 32.768 kHz crystal connection, a 3 V backup-battery connection, a parallel RTC interface, and BCD-formatted date and clock data. The backup cell powers the real-time clock and maintains external nonvolatile SRAM information when system voltage is absent. A conditional chip-enable output, CEOUT, can be used to inhibit unintended external-SRAM writes, while the battery-voltage output, VOUT, provides a battery-related status signal.
The CPU-supervisor architecture supports monitoring of the system power rail and coordinating processor reset or backup-battery transition. Its watchdog function provides another mechanism for detecting a stalled system. These functions are relevant to industrial controllers, data-acquisition equipment, embedded appliances, and other systems where losing timekeeping or failing to restart predictably can compromise data integrity. Exact timing thresholds, current consumption, and reset-delay details must be confirmed in the manufacturer datasheet.
The 28-pin SOIC package supports compact PCB layouts while exposing parallel clock, calendar, interrupt, supervisor, battery, and crystal-related connections. The BQ4845YS-A4G4 is also identified as a commercial-temperature device. Because the manufacturer data identifies the part as a real-time clock with watchdog timer and CPU-supervisor functionality, it is better suited to legacy parallel systems than designs requiring a compact serial RTC or I2C interface.
Designers should route the 32.768 kHz crystal connections carefully, provide the specified decoupling and backup-battery support, and validate all CPU-supervisor and watchdog thresholds against the actual system reset requirements. Because the available excerpts do not provide a complete verified pin table, timing diagram, or electrical-characteristic table, those details remain data-needed rather than being inferred. The manufacturer datasheet should control the final schematic, layout, and firmware implementation.
This page consolidates verified distributor information, same-family replacement evidence, package details, and application guidance while clearly separating confirmed data from missing electrical parameters. It also compares confirmed alternatives without presenting merely similar RTC devices as drop-in replacements, helping engineers make package- and interface-compatible sourcing decisions without relying on unverified specifications.
بدائل مباشرة لـ BQ4845YS-A4G4 — نفس الحزمة، متوافق دبوس بدبوس. تُستثنى القطع ذات الحزم المختلفة التي تتطلب تعديل PCB.
الطرازات في هذه السلسلة
طرازات من نفس السلسلة متوافقة تمامًا مع BQ4845YS-A4G4 (نفس عامل الشكل والبصمة) — يختلف في Package, Product Type, Backup Battery, Interface, Battery Voltage Output.
BQ4845P-A4
✅ بديل مباشرتواصل لمعرفة السعر
عرض ورقة البيانات ←BQ4845YS-A4N
✅ بديل مباشرتواصل لمعرفة السعر
عرض ورقة البيانات ←BQ4845YS-A4N
✅ بديل مباشرتواصل لمعرفة السعر
عرض ورقة البيانات ←BQ4845S-A4NTR
✅ بديل مباشرتواصل لمعرفة السعر
عرض ورقة البيانات ←BQ4845YS-A4G4 المواصفات
| Product Type | Real-time clock and calendar with CPU supervisor |
| RTC Interface | Parallel |
| Clock Crystal Frequency | 32.768 kHz |
| Backup Battery Voltage | 3 V |
| System Supply Voltage | 5 V |
| Date Format | BCD |
| Clock Format | BCD |
| العلبة | 28-SOIC (0.295 inch, 7.50 mm width) |
| Terminal Count | 28 terminals |
| نوع التركيب | Surface mount |
| Terminal Form | Gull wing |
| Package Shape | Rectangular |
| Temperature Grade | Commercial |
| Integrated Functions | RTC, calendar, CPU supervisor, watchdog timer, and nonvolatile SRAM control |
| Chip Enable Output | Conditional chip-enable output (CEOUT) |
| Battery Voltage Output | VOUT |
| Backup Behavior | Backup cell powers the RTC and maintains external SRAM information in the absence of system voltage |
| Manufacturer Part Number | BQ4845YS-A4G4 |
دليل تكوين أطراف BQ4845YS-A4G4 rectangular
تكوين الأطراف لـ BQ4845YS-A4G4 (حزمة rectangular). يتم تعريف ترقيم الأطراف والوظائف ومخططات التوصيل في ورقة البيانات الفنية من الشركة المصنعة. راجعها للحصول على البصمة الدقيقة وإرشادات اللحام.
لا تتوفر بيانات مفصلة لمخطط التوصيلات لـ BQ4845YS-A4G4.
راجع ورقة البيانات للحصول على تكوين الأطراف الكامل.
التطبيقات النموذجية
BQ4845YS-A4G4 مناسب لـ 6 التطبيقs: Industrial Embedded Controller, Data-Acquisition and Logging System, Appliance with Battery-Backed Timekeeping, Telecommunications Backup Power System, Security and Access-Control Panel, Instrumentation with CPU Reset Supervision.
Industrial Embedded Controller
The BQ4845YS-A4G4 fits legacy industrial controllers that retain a parallel CPU bus and need an independent calendar clock. Its confirmed 32.768 kHz crystal connection provides the timebase, while the 3 V backup battery allows timekeeping to continue when the 5 V system supply is absent. The CPU-supervisor and watchdog functions are useful when a controller must recover predictably from a stalled firmware or unstable supply. A system designer should connect the RTC registers to the processor bus, program the calendar through BCD fields, and validate reset timing against the controller requirements.
موصى به
Data-Acquisition and Logging System
The BQ4845YS-A4G4 is appropriate for data-acquisition equipment where each recorded transaction needs an unambiguous date and time. The parallel interface allows the host processor to access clock and calendar registers directly, and the BCD representation can simplify integration with legacy register maps. Its 32.768 kHz crystal input supports conventional RTC timekeeping, while the 3 V backup battery maintains the calendar during power interruptions. The watchdog and CPU-supervisor functions add value in remote installations where an unattended system must recover from a fault without manual service.
موصى به
Appliance with Battery-Backed Timekeeping
The BQ4845YS-A4G4 supports appliances that must retain timestamps during mains interruptions or overnight power loss. The confirmed 3 V backup-battery architecture keeps the RTC operating when the 5 V system supply is removed, and the backup path can maintain external SRAM information when supported by the surrounding circuit. For a legacy appliance controller, the 28-pin parallel interface and dedicated supervisor functions are more useful than adding a separate serial clock. Firmware should periodically reconcile the BCD calendar with the host time source and define safe behavior after an unexpected power return.
موصى به
Telecommunications Backup Power System
The BQ4845YS-A4G4 can support telecommunications equipment that combines a 5 V logic rail with a 3 V backup source. The RTC remains available for logs, alarms, and event ordering, while CEOUT provides a conditional chip-enable signal for controlling an external SRAM during backup operation. In a legacy parallel-bus design, this integration reduces the need for separate timekeeping and supervisor components. The implementation must validate the backup-battery chemistry, battery current, CEOUT polarity, and system reset thresholds against the telecom platform's power architecture.
موصى به
Security and Access-Control Panel
The BQ4845YS-A4G4 suits legacy access-control panels that require durable event timestamps and deterministic supervisor behavior. A 32.768 kHz crystal establishes the timebase, and the 3 V backup battery preserves the RTC during AC outages, allowing controllers to record when an access event occurred. The parallel host interface can be shared with the panel processor, while the watchdog provides an additional path to identify a software lockup. Before deployment, verify RTC accuracy, alarm behavior, reset polarity, and backup current against the panel's safety and security requirements.
موصى به
Instrumentation with CPU Reset Supervision
The BQ4845YS-A4G4 is suitable for test and measurement equipment that uses a parallel processor interface but needs independent power-fail and watchdog supervision. Combining the RTC and CPU supervisor in one 28-pin SOIC simplifies board partitioning compared with separate timekeeping and reset devices. The 32.768 kHz crystal supports event timestamping, while the 3 V backup source retains time during brief supply interruptions. Designers should verify the exact supervisor thresholds, reset pulse behavior, and operating-voltage tolerances in the manufacturer datasheet because those values were not included in the supplied excerpts.
موصى به
ملخص المنتجات الموصى بها
بيانات مرجعية هندسية لـ BQ4845YS-A4G4 — المقارنة وإرشادات التصميم ومعلومات الامتثال.
دليل الاختيار
المقارنة مع البدائل
| المعامل | هذا المنتج | BQ4845P-A4 | BQ4845YS-A4 | BQ4845YS-A4N | BQ4845S-A4NTR |
|---|---|---|---|---|---|
| Package | 28-SOIC (0.295 inch, 7.50 mm width) | 28-SOIC - same package | 28-SOIC - same package | 28-SOIC - same package | 28-SOIC - same package |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Product Type | Parallel RTC with CPU supervisor and watchdog timer | Parallel RTC with CPU supervisor | Real-time clock with nonvolatile SRAM control and watchdog timer | Real-time clock with nonvolatile SRAM control | Real-time clock with nonvolatile SRAM control |
| RTC Interface | Parallel | Parallel | Parallel | Parallel | Parallel |
أبرز الفروقات
- Verified complete replacement relationship (مقابلBQ4845P-A4)
- Exact orderable identifier preserved (مقابلBQ4845YS-A4)
- Integrated CPU supervision and watchdog functionality (مقابلBQ4802YDWR)
ملاحظات التصميم
Do not treat the BQ4845YS-A4G4 as a generic serial RTC: the verified device uses a parallel interface and presents clock, calendar, control, supervisor, and battery-related signals across 28 pins. Before schematic capture, compare every signal and power condition against the official connection diagram. The available excerpts do not include a complete verified pin table, so assigning pin numbers from memory could produce an irreversible PCB-layout error.
Route the 32.768 kHz crystal path directly between the BQ4845YS-A4G4 and the crystal, with no test pads or unrelated high-speed traces beneath it when the board stackup permits. Keep the backup-battery branch away from noisy switching nodes and follow the manufacturer's recommended capacitor placement. Because no verified crystal-load or layout dimensions were supplied, consult the official datasheet before finalizing footprint spacing and grounding.
The device uses a 5 V system supply and a 3 V backup-battery connection, so verify that battery reverse leakage, source current, and chemistry remain within the manufacturer's limits. Do not allow the backup source to exceed a verified absolute maximum. The CEOUT path may write-protect external SRAM during backup operation, so its polarity and state transitions must be validated in firmware and hardware together.
The calendar uses BCD formatting, and treating its fields as ordinary binary values can create invalid dates or incorrect timestamps. Include explicit BCD conversion in the driver, validate month and day boundaries, and test leap-year behavior. Also program watchdog and CPU-supervisor thresholds for the longest legitimate interrupt-disabled or sleep interval rather than relying on generic reset timing.
معلومات الامتثال
The supplied web excerpts identify a commercial-temperature grade but do not provide verified RoHS, REACH, AEC-Q100, lead-free, halogen-free, or conflict-minerals statements. No compliance status has been assumed.
