BQ4845P-A4 Parallel RTC with CPU Supervisor | Texas Instruments
N.º de pieza: BQ4845P-A4 ✓ Activo| Cant. | Precio unitario | Total |
|---|---|---|
| 1 | $0 | $0,00 |
| 10 | $0 | $0,00 |
| 100 | $0 | $0,00 |
| 500 | $0 | $0,00 |
| 1.000 | $0 | $0,00 |
BQ4845P-A4 Descripción general
A real-time clock, or RTC, is a clock-and-timing semiconductor that maintains calendar time independently of the host processor. The BQ4845 combines a time-of-day clock, 100-year calendar, CPU supervisor, watchdog timer, reset control, and nonvolatile-SRAM support in one device. It is intended for legacy embedded systems and equipment that retain time across power interruptions.
Key features include direct crystal connection, backup-battery switchover, programmable alarms, leap-year compensation, daylight-saving support, watchdog operation, CPU reset generation, and conditional chip-enable output. The parallel interface allows a host processor to read and write calendar and control information through discrete digital signals rather than a serial bus. A 3 V backup cell powers the timekeeping section and can maintain supported external SRAM data.
The device is designed for fax machines, copiers, industrial control systems, point-of-sale terminals, data loggers, and computers. Its DIP format supports through-hole legacy boards and replacement of an existing 28-pin clock-and-calendar footprint. System design must follow the manufacturer’s pin connections and ensure that the crystal, backup source, reset circuitry, and external SRAM support network are correctly connected.
Because a DIP package is specified for BQ4845P-A4, do not substitute a surface-mount SOIC variant without confirming the exact package, pin mapping, and board footprint. The product page identifies BQ4845 as available in 28-pin SOIC or DIP families, while the DigiKey result specifically identifies the A4 part as a 28-DIP device.
This page combines the verified manufacturer and distributor descriptions with application guidance and engineering considerations. For replacement decisions, verify the exact package and all electrical and functional differences; do not treat a similar RTC function as proof of pin-to-pin compatibility.
Alternativas directas para BQ4845P-A4 — mismo encapsulado, compatible pin a pin. Se excluyen las piezas de otro encapsulado que requieren retrabajo de la PCB.
Variantes de esta serie
Modelos de la misma serie compatibles directamente con BQ4845P-A4 (mismo factor de forma y huella) — difiere en Package, Product Type, Interface, Backup Battery.
Herramienta de comparación rápida — seleccione piezas alternativas para compararlas lado a lado:
BQ4845S-A4
✅ Sustitución directa✓ En stock
Consulte el precio
Ver hoja de datos →BQ4845YS-A4G4
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
BQ4845YP-A4E3
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
BQ4845YS-A4NTRG4
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
BQ4285EP
✅ Sustitución directa✓ En stock
$1.6968 / unidad
Ver hoja de datos →BQ4845P-A4 Especificaciones
| Product Type | Parallel real-time clock and calendar with CPU supervisor |
| Timekeeping | Seconds through years in BCD format |
| Calendar Range | 100 years |
| Crystal Interface | Direct connection for 32.768 kHz quartz crystal |
| Backup Battery | 3 V backup battery connection |
| Backup Current | Less than 500 nA in backup mode |
| CPU Supervision | Integrated microprocessor supervisor and reset |
| Watchdog | Watchdog timer function |
| Alarm | Alarm functionality |
| Daylight Saving | Daylight-saving support |
| Leap Year | Leap-year compensation |
| External SRAM Support | Write-protect and nonvolatile support for external SRAM |
| Conditional Chip Enable | CEOUT output |
| Battery Voltage Output | VOUT output |
| Encapsulado | 28-pin DIP, 0.600 inch / 15.24 mm pitch |
| Interfaz | Parallel |
Guía de configuración de pines de BQ4845P-A4 28-pin dip, 0.600 inch / 15.24 mm pitch
Configuración de pines para BQ4845P-A4 (encapsulado 28-pin dip, 0.600 inch / 15.24 mm pitch). La numeración de pines, las funciones y los diagramas de conexión se definen en la hoja de datos del fabricante. Consúltela para conocer el footprint exacto y las directrices de soldadura.
No hay datos detallados de patillaje disponibles para BQ4845P-A4.
Consulte la hoja de datos para ver la configuración completa de patillas.
Aplicaciones típicas
BQ4845P-A4 es adecuado para 6 aplicacións: Industrial Control Systems, Point-of-Sale Terminals, Data Loggers, Fax Machines and Copiers, Battery-Backed Embedded Products, Legacy Computer Peripherals.
Industrial Control Systems
BQ4845P-A4 fits legacy industrial controllers that need a local, battery-backed calendar rather than relying on the host processor clock. Its 100-year calendar, 32.768 kHz crystal connection, parallel interface, and CPU-supervisor function support time-stamped control events and controlled reset behavior. The less-than-500-nA backup-mode current helps maintain timekeeping during power loss, while the 28-DIP package fits through-hole legacy designs. Verify reset timing and alarm settings against the manufacturer datasheet before production.
Recomendado
Point-of-Sale Terminals
The BQ4845P-A4 is appropriate for point-of-sale equipment that maintains transaction time across power interruptions. The parallel calendar interface allows the controller to obtain seconds, calendar fields, and alarm information, while the 3 V backup battery preserves operation when the primary supply fails. Its CPU supervisor can assist with orderly processor reset, and the 100-year calendar supports long-lived deployments. Board-level validation should confirm the exact DIP pin mapping and battery isolation behavior.
Recomendado
Data Loggers
Data loggers benefit from independent timekeeping because recorded events must retain an accurate date and time even when the logging system restarts. BQ4845P-A4 provides seconds-through-years BCD timekeeping, a 100-year calendar, leap-year compensation, and daylight-saving support. The 32.768 kHz crystal connection establishes the time base, while the backup supply maintains operation during main-power loss. Use the watchdog and reset functions only after checking their timing and polarity requirements in the datasheet.
Recomendado
Fax Machines and Copiers
The BQ4845P-A4 is explicitly identified by Texas Instruments for fax machines and copiers, where event timestamps, scheduling, and system supervision are important. Its calendar functions and backup-battery support allow the equipment to retain time through short or extended power interruptions. The parallel interface can be used by legacy controller boards that are not designed around I2C or SPI. Validate crystal startup, backup-battery loading, and reset behavior in the final mechanical and electrical design.
Recomendado
Battery-Backed Embedded Products
BQ4845P-A4 is suitable for embedded products that must preserve calendar time and selected nonvolatile SRAM information when the primary supply is removed. The manufacturer describes a 3 V backup-battery connection and less-than-500-nA backup operation, which helps limit standby drain. The RTC can maintain time from seconds through years, while the CEOUT and VOUT signals provide control and battery-voltage monitoring functions for supported external SRAM arrangements. The final schematic must follow the exact manufacturer application guidance.
Recomendado
Legacy Computer Peripherals
The BQ4845P-A4 can support legacy computer peripherals that require a real-time clock, calendar, watchdog, and CPU-reset supervisor. The 28-DIP format is especially useful for older through-hole PCBs, while the parallel interface avoids introducing a new serial bus. A replacement design should preserve the original BQ4845 pinout, crystal network, backup-battery circuit, and reset polarity. Because the supplied data does not include full pin-level electrical limits, production use should rely on the TI datasheet.
Recomendado
Resumen de productos recomendados
Datos de referencia de ingeniería para BQ4845P-A4 — comparación, orientación de diseño e información de cumplimiento.
Guía de selección
Comparación con alternativas
| Parámetro | Este producto | BQ4845S-A4 | BQ4845YS-A4G4 | BQ4285EP |
|---|---|---|---|---|
| Product Type | Parallel RTC with CPU supervisor | Parallel RTC with CPU supervisor | RTC variant | RTC-related comparison candidate |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
Diferenciadores clave
- Integrated clock and power-management functions (frente a BQ4285EP)
- 100-year calendar and BCD timekeeping (frente a BQ4845YS-A4G4)
- Legacy DIP-compatible package (frente a BQ4845S-A4)
Notas de diseño
Design the backup-battery path around the BQ4845P-A4 application guidance and confirm battery polarity, isolation, and switching behavior before layout. The verified data specifies a 3 V backup battery and less than 500 nA clock-operation current in backup mode, but it does not provide the complete battery electrical limits. Confirm those values in the manufacturer datasheet and validate the system’s current budget over the intended power-loss interval.
Route the BQ4845P-A4 crystal connection and associated components according to the manufacturer pinout and layout guidance, keeping the timing path short and away from high-current switching nodes. The supplied data confirms support for a direct 32.768 kHz quartz-crystal connection but does not specify load capacitance or maximum stray capacitance. Those values must be obtained from the datasheet before final component selection and PCB release.
Do not substitute a BQ4845 family variant solely because it is also a real-time clock. The verified comparison identifies BQ4845S-A4 as SOIC while BQ4845P-A4 is a 28-DIP device, so an SOIC package cannot be treated as a same-footprint replacement on a through-hole board. Verify the exact suffix, pin mapping, reset polarity, watchdog behavior, calendar features, backup circuit, and SRAM-control signals before approving any replacement.
Use the CEOUT and VOUT functions only in the external-SRAM support arrangement described by the manufacturer. The verified product description identifies conditional chip-enable and battery-voltage outputs for write-protecting and maintaining supported external SRAM during backup operation. Validate the SRAM voltage, write timing, and control polarity in the system design because those parameters are not supplied in the verified web data.
Keep the parallel RTC interface traces away from noisy analog and switching paths where possible, even though the BQ4845P-A4 is a digital clock-and-calendar device. Maintain adequate grounding and follow the manufacturer’s recommended pin and layout arrangement. Since the supplied data does not include complete electrical timing or signal-integrity limits, treat the datasheet as the controlling source for bus timing and signal levels.
Información de cumplimiento
The supplied verified web data does not state RoHS, REACH, lead-free, halogen-free, conflict-mineral, or automotive qualification information for BQ4845P-A4. Compliance fields remain unknown rather than assumed.
