BQ4845S-A4 - Parallel RTC with CPU Supervisor | Texas Instruments
MPN: BQ4845S-A4 ✓ NakahandaBQ4845S-A4 Ulas
A real-time clock is a timekeeping peripheral that maintains calendar information independently of the system processor. The BQ4845S-A4 combines a low-power RTC with a CPU supervisor, allowing a system to detect power faults, monitor operating intervals, receive reset signaling, and preserve external SRAM contents during primary-power loss. This integration reduces the number of discrete supervisory components required in embedded equipment.
The device provides an on-chip battery-backup switchover circuit and nonvolatile control for external SRAM through the conditional chip enable output, CEOUT, and battery voltage output, VOUT. Its backup clock current is less than 500 nA, while the parallel interface and BCD calendar support microprocessor-based timekeeping. The 28-SOIC package is designed for conventional surface-mount assembly, and the verified distributor listing identifies a 7.50 mm-wide, 0.295-inch body.
The BQ4845S-A4 is suitable when the system requires more than a basic clock. Its watchdog timer can initiate reset or interrupt behavior when software stops responding, while the CPU supervisor provides power-monitoring signals during startup and shutdown. Backup support can maintain RTC operation and external SRAM information when the system supply is absent, assuming the backup battery remains within the manufacturer-specified operating limits.
Typical designs place the RTC beside the processor and nonvolatile SRAM, connect a 32.768 kHz crystal to the oscillator inputs, and route CEOUT and VOUT to the memory-control interface. The parallel bus simplifies firmware access to time and calendar registers. Designers should follow the manufacturer datasheet for crystal load capacitance, decoupling, signal timing, reset polarity, and battery connection details.
This page combines verified manufacturer and distributor information with engineering guidance for RTC integration, power-fail control, watchdog validation, and PCB layout. The available data does not provide a current unit-price table, so pricing fields are not fabricated here. Verify distributor availability and lifecycle status before committing a production design.
Mga alternatibo na pwedeng ilagay na BQ4845S-A4 — parehas na package, pin-to-pin na katugmang. Hindi kasama ang mga bahagi ng iba't-ibang package na nangangailangan ng pagpapaayos ng PCB.
Variante sa Seri na ito
Katulad na modelo sa serye na katugma sa pagpasok BQ4845S-A4 (parehas na form factor at footprint) — pagkakaiba sa Package, Product Type, Backup Battery, Battery Voltage Output.
BQ4845S-A4NTRG4
✅ Drop-InMagkontak para sa presyo
Tingnan ang Datasheet →BQ4845YS-A4NTRG4
✅ Drop-In📋 Alternatibo na Reference (hindi sa katalogo)
BQ4845YS-A4NTR
✅ Drop-InMagkontak para sa presyo
Tingnan ang Datasheet →BQ4845S-A4 Mga Spesipikasyon
| Product Type | Parallel real-time clock with CPU supervisor |
| Timekeeping Format | BCD, seconds through years |
| Crystal Frequency | 32.768 kHz |
| Backup Battery | 3 V |
| Backup Clock Current | Less than 500 nA |
| Interface | Parallel |
| Integrated Functions | RTC, CPU supervisor, watchdog timer, reset, interrupts, battery-low warning |
| Nonvolatile SRAM Control | External SRAM write protection and switchover control |
| Battery-Backup Switchover | On-chip |
| CEOUT Function | Conditional chip enable output |
| VOUT Function | Battery voltage output |
| Packhaging | 28-pin SOIC |
| Package Body Width | 7.50 mm |
| Package Length | 0.295 inch |
| Uri ng Pagpapasok | Surface mount |
| Application Categories | Industrial control systems, point-of-sale terminals, data loggers, computers, fax machines, copiers |
Gabay sa Pin Configuration ng BQ4845S-A4 0.295 inch
Pin configuration para sa BQ4845S-A4 (0.295 inch package). Ang pagnunumero ng pin, mga function, at connection diagram ay tinukoy sa datasheet ng manufacturer. Sumangguni dito para sa eksaktong footprint at mga alituntunin sa soldering.
Wala ng detalyadong pinout data na magagamit para sa BQ4845S-A4.
Sumangguni sa datasheet para sa buong pin configuration.
Tipikal na mga Gamit
BQ4845S-A4 ay nararapat para sa 6 aplikasyons: Industrial Control Systems, Point-of-Sale Terminals, Data Loggers, Fax Machines and Copiers, Computer Peripheral Equipment, Battery-Powered Embedded Equipment.
Industrial Control Systems
The BQ4845S-A4 fits industrial controllers that need persistent calendar time and supervised processor power. It combines a 32.768 kHz crystal interface with BCD time and calendar registers, while its CPU supervisor and reset functions help the controller respond to power faults. The 3 V backup path and external-SRAM control features can preserve system state when the main rail fails. Compared with a basic software timestamp, the integrated RTC continues timing independently of the processor. Designers should verify supervisor thresholds, reset polarity, bus timing, and crystal loading in the TI datasheet.
Inirekomenda
Point-of-Sale Terminals
A point-of-sale terminal can use the BQ4845S-A4 to maintain transaction time through power interruptions and system resets. The parallel interface provides direct access to seconds, calendar, and alarm information, while the watchdog and CPU-supervisor functions support recovery from a stalled controller. External SRAM can be write-protected through CEOUT during power transitions, helping protect transaction records when VOUT reports backup-battery status. The part is appropriate when the design values reliable timestamps more than a minimal RTC-only solution.
Inirekomenda
Data Loggers
The BQ4845S-A4 is useful in data loggers that must timestamp measurements during normal operation and after short power interruptions. Its low-power backup clock current of less than 500 nA helps preserve RTC operation, while the 3 V backup-battery connection supports continued calendar tracking. CEOUT and VOUT can coordinate write protection for external SRAM, reducing the risk of corrupting buffered records during a power failure. Firmware should use the watchdog and reset outputs to mark interrupted logging sessions and synchronize newly collected data.
Inirekomenda
Fax Machines and Copiers
The BQ4845S-A4 can provide time and calendar functions in office equipment that must retain operational timing across power cycles. The integrated CPU supervisor and reset functions are useful for system initialization after brownout or supply interruption, while the watchdog helps recover embedded firmware that stops responding. The parallel RTC architecture and external-SRAM control make the device relevant to older control boards with processor-managed memory. Designers should confirm logic-level compatibility, bus timing, backup-battery chemistry, and package footprint against the original design.
Inirekomenda
Computer Peripheral Equipment
The BQ4845S-A4 suits computer peripherals that need an independent time base, power-fail detection, and controlled reset behavior. A 32.768 kHz crystal supports conventional RTC operation, and the backup battery can maintain timekeeping while the system is unpowered. CEOUT and VOUT allow an external SRAM to be protected before its contents become uncertain during supply loss. In a new design, the RTC should be placed close to the crystal and backup source, with careful routing of reset and supervisory signals to prevent false trip events.
Inirekomenda
Battery-Powered Embedded Equipment
The BQ4845S-A4 can support portable or intermittently powered equipment that must retain real-time information between active operating periods. The verified backup-current value of less than 500 nA is relevant to battery-life calculations, although actual consumption depends on battery voltage, leakage, temperature, and the selected crystal and external components. The CPU supervisor provides a hardware basis for orderly shutdown or restart, and the RTC preserves time independently of the main processor. Engineers should validate the full power budget rather than treating the clock-current specification as the complete system standby current.
Inirekomenda
Buod ng mga Inirekomendang Produkto
Impormasyon ng Talumpati sa Engineering for BQ4845S-A4 — ikabit, gabay sa disenyo, at impormasyon ng pagsunod sa kautusan.
Paunawang Hanapin
Ikabit sa Mga Alternatibo
| Parametro | Ito ang Producto | BQ4845S-A4NTRG4 | BQ4845YS-A4NTRG4 | BQ4845YS-A4NTR |
|---|---|---|---|---|
| Package | 28-SOIC | 28-SOIC | 28-SOIC | 28-SOIC |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
Pangunahing mga Pagkakaiba
- Integrated RTC and CPU supervision (kumpara saBQ4845YS-A4NTRG4)
- External SRAM retention support (kumpara saBQ4845S-A4NTRG4)
- Low-power backup operation (kumpara saBQ4845YS-A4NTR)
Talaan ng Disenyo
Route the 32.768 kHz crystal connections as short as possible and keep the oscillator loop away from switching nodes, high-current rails, and the parallel bus. Preserve the manufacturer-recommended ground and decoupling layout around the RTC, backup battery, and supervisor inputs. Crystal placement, grounding, and shielding are especially important because the RTC’s timing accuracy depends on oscillator noise and load conditions.
Design the power-fail path around the verified CEOUT and VOUT functions and ensure the backup battery is isolated from the primary rail as specified by the manufacturer. Confirm that the external SRAM receives write protection before its supply becomes indeterminate. Validate startup, brownout, and battery-only behavior with the actual supply ramps and load currents rather than relying only on nominal voltage values.
Do not infer pin compatibility from the BQ4845 family name or from a distributor cross-reference result alone. Compare the complete pinout, parallel-bus timing, reset polarity, watchdog limits, supervisor thresholds, battery handling, and package dimensions against the TI datasheet. The supplied data identifies related variants, but it does not quantify every electrical difference, so production substitution requires a documented engineering review.
Impormasyon ng Pagsunod sa Kautusan
Compliance information was not present in the supplied verified web data. Confirm RoHS, REACH, AEC-Q100, lead-free, halogen-free, and conflict-minerals status using the current manufacturer product documentation or supplier declaration.