Texas Instruments BQ4802YPW

Overview

BQ4802YPW from Texas Instruments is a parallel real-time clock IC with integrated CPU supervisor and external SRAM nonvolatile memory backup capability. It operates at 5 V, delivers BCD-formatted time-of-day and century-based calendar data, consumes less than 500 nA in battery-backup mode, and provides microprocessor reset with push-button override. It is used in telecom base stations and industrial control systems requiring persistent timekeeping during power loss.

For engineers reviewing the BQ4802YPW datasheet, BQ4802YPW pinout, BQ4802YPW application, or BQ4802YPW equivalent, key selection criteria include its 28-pin TSSOP package, 5-V operation, CEOUT/VOUT-controlled SRAM write-protection, programmable watchdog timeout (default 1.5 s), and battery-low flag support in backup mode.

Technical Context

The BQ4802YPW integrates a temperature-compensated 32.768-kHz crystal oscillator, a 16-byte BCD register map for time/calendar/alarm/control, and dual-supply switchover logic that routes VOUT to the higher of VCC or BC (3-V lithium cell). Its CEOUT output asserts low only when CEIN is low and VCC exceeds VPFD (4.37 V typical), enabling conditional write-protection of external SRAM.

It implements an open-drain RST output with 200-ms active-low hold after VCC crosses VPFD, a three-level WDI input supporting programmable watchdog timeout via WD0–WD2 bits (register B), and interrupt generation for power-fail, alarm, and periodic events - all functional in battery-backup mode.

Key Specifications

Pinout & Package

Package: 28-pin TSSOP (PW), RoHS-compliant, 4.4 mm × 9.7 mm body, 0.65 mm pitch.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar real-time clock with supervisor applications.

Compared with DS12887A+ and M41T81SM6, the BQ4802YPW uniquely combines 5-V parallel SRAM timing, integrated VOUT/CEOUT SRAM power-and-write-control, and programmable watchdog - making it the only option for compact, high-reliability 5-V systems needing coordinated RTC, supervisor, and nonvolatile memory backup.

Availability

BQ4802YPW is available at Aetrix Electronics and suitable for telecom base stations, industrial control systems, and medical instrumentation requiring stable component supply, long-lifecycle support, and guaranteed traceable sourcing.

Supply support for BQ4802YPW includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader focused on analog, embedded processing, and connectivity technologies, serving industrial, automotive, and communications markets.

The BQ4802YPW belongs to TI's real-time clock and supervisor product line, designed specifically for systems requiring synchronized timekeeping, deterministic reset behavior, and seamless nonvolatile memory backup during power transitions.

FAQ

What is the primary function of the BQ4802YPW in a system?

The BQ4802YPW serves as an integrated real-time clock with CPU supervisor and external SRAM backup controller. It maintains accurate time-of-day and calendar data in BCD format, monitors VCC for power-fail conditions, asserts RST and INT outputs, and manages VOUT/CEOUT to protect external SRAM during power loss - all within a single 28-pin TSSOP device.

Does the BQ4802YPW support battery-backed operation, and what is its typical backup current?

Yes, the BQ4802YPW supports battery-backed operation via the BC pin, accepting a 3-V lithium cell. Its typical backup current is 0.3 µA at 25°C with no load on VOUT or CEOUT, enabling multi-year runtime on a standard CR2032 cell while preserving both RTC accuracy and SRAM data integrity.

How does the BQ4802YPW interface with external SRAM for nonvolatile backup?

The BQ4802YPW interfaces with external SRAM using two dedicated pins: VOUT supplies the higher of VCC or BC to the SRAM's VCC pin, and CEOUT drives the SRAM's chip-enable input. When VCC falls below VPFD, CEOUT goes high (deasserted), write-protecting the SRAM - eliminating need for external logic or diodes in the backup path.

Can the BQ4802YPW generate interrupts in battery-backup mode, and which types are supported?

Yes, the BQ4802YPW can generate interrupts in battery-backup mode. Supported types include power-fail (PWRIE), programmable alarm (AIE), and periodic (PIE) interrupts - all routed to the open-drain INT pin. This allows wake-up or status signaling even when main power is absent, critical for unattended equipment like data loggers and telecom nodes.

What is the default watchdog timeout period for the BQ4802YPW, and how is it configured?

The default watchdog timeout period for the BQ4802YPW is 1.5 seconds, set by WD0–WD2 bits (000) in register B. These bits are programmable via the parallel interface and retain their value across power cycles. The watchdog is disabled if WDI is left floating, as an internal 100-kΩ divider biases it to ~1.6 V, disabling the timer without external components.