Texas Instruments BQ4802LYDWR

Overview

BQ4802LYDWR from Texas Instruments is a 3.3-V parallel real-time clock IC with integrated CPU supervisor, battery-backed SRAM control, and watchdog timer. It provides BCD-formatted time-of-day/calendar (seconds to centuries), microprocessor reset with push-button override, programmable alarm/periodic interrupts, and power-fail detection. It operates in telecom base stations and medical equipment requiring nonvolatile timekeeping and system supervision.

For engineers reviewing the BQ4802LYDWR datasheet, BQ4802LYDWR pinout, BQ4802LYDWR application, or BQ4802LYDWR equivalent, key selection criteria include its 3.3-V operation, <500 nA backup current, CEOUT/VOUT-controlled external SRAM write protection, open-drain RST/INT outputs, and 28-pin SOIC package with tape-and-reel delivery (R suffix).

Technical Context

The BQ4802LYDWR integrates a temperature-compensated 32.768-kHz crystal oscillator, century-based BCD calendar engine, and dual-supply monitoring circuitry that triggers RST at VPFD = 2.53 V (typ) and switches VOUT/CEOUT between VCC and BC. Its µP bus interface uses A0–A3 address lines and DQ0–DQ7 data lines with CS/OE/WE controls, supporting read cycles as fast as 300 ns at 3.3 V.

It implements a three-level watchdog input (WDI) with programmable timeout (1.5 s default via WD0–WD2 bits), independent of main supply status; WDO and RST are asserted on timeout. Battery-low flag (BVF) and oscillator stop/start control (STOP bit) enable precise power management during extended backup operation.

Key Specifications

Pinout & Package

Package: 28-pin SOIC (DW), 3.3-V variant, tape-and-reel (R suffix). Pinout validated per TI SLUS464C Rev C (June 2002), Figure 5 (DW/PW top view).

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS12887+ and PCF8583, the BQ4802LYDWR uniquely combines 3.3-V operation, external SRAM control via CEOUT/VOUT, and integrated watchdog with µP bus compatibility-enabling drop-in replacement in space- and power-sensitive embedded systems without redesigning power or interface logic.

Availability

BQ4802LYDWR is available at Aetrix Electronics and suitable for telecom infrastructure, server management, and portable medical devices requiring stable component supply, long-life battery backup, and industrial-grade reliability.

Supply support for BQ4802LYDWR 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 delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and communications markets.

The BQ4802LYDWR belongs to TI's real-time clock and supervisor product line, designed specifically for systems needing accurate timekeeping, deterministic reset behavior, and nonvolatile memory protection during power transitions.

FAQ

What is the primary function of the BQ4802LYDWR?

The BQ4802LYDWR is a 3.3-V parallel real-time clock IC with integrated CPU supervisor and external SRAM backup control. It maintains BCD-formatted time-of-day and calendar (seconds to centuries), generates microprocessor reset on power failure, provides programmable alarm/periodic interrupts, and manages battery-backed SRAM via CEOUT/VOUT signals. Its core role is ensuring time accuracy and system reliability during power interruptions.

How does the BQ4802LYDWR handle power failure detection?

The BQ4802LYDWR monitors VCC and triggers power-fail response when voltage drops below 2.53 V (typical VPFD). At that point, it asserts INT and RST, forces CEOUT high to write-protect external SRAM, and switches VOUT to the backup cell (BC). The device sustains RTC operation and SRAM data with <0.5 µA current draw, enabling multi-year backup on a 3-V lithium cell.

Can the BQ4802LYDWR operate without an external crystal?

Yes - the BQ4802LYDWR supports external 32.768-kHz clock injection: tie X2 to ground and drive X1 with a clean square wave. However, accuracy degrades versus crystal operation (±1 min/month spec assumes DT-26 crystal). The internal oscillator circuit remains fully functional, and all RTC, supervisor, and SRAM control features operate identically regardless of clock source.

What is the purpose of the CEIN and CEOUT pins on the BQ4802LYDWR?

CEIN is an input that gates CEOUT - when VCC > VPFD, CEOUT mirrors CEIN with <25 ns propagation delay. During power failure (VCC < VPFD), CEOUT is forced high independently of CEIN to unconditionally write-protect external SRAM. This ensures data integrity even if the host µP fails to assert CEIN before brownout, making CEOUT a hardware-enforced SRAM lock.

Is the BQ4802LYDWR pin-compatible with the 5-V BQ4802Y series?

Yes - the BQ4802LYDWR shares identical pinout, register map, and interface timing with the BQ4802Y (5-V) family. Both use the same 28-pin SOIC (DW) package and support A0–A3/DQ0–DQ7 parallel bus protocol. Voltage-specific differences (VPFD = 2.53 V vs. 4.37 V, ICC = 3 mA vs. 5 mA) do not affect mechanical or logical compatibility, enabling direct substitution in 3.3-V designs.