Texas Instruments BQ2204APN

Overview

BQ2204APN from Texas Instruments is a CMOS SRAM nonvolatile controller unit that converts up to four banks of standard CMOS SRAM into battery-backed nonvolatile memory. It provides power-fail detection (VPFD = 4.62 V typical), <10 ns CE propagation delay, and dual 3V primary-cell backup inputs (BC1/BC2) for industrial data retention in systems like programmable logic controllers and real-time clocks.

For engineers reviewing the BQ2204APN datasheet, BQ2204APN pinout, BQ2204APN application, or BQ2204APN equivalent, key selection criteria include its 5V supply operation with 5% tolerance, THS-selectable power-fail threshold, conditioned CE outputs (CECON1–CECON4), and support for hardware-based SRAM bank decoding via A/B inputs.

Technical Context

The BQ2204APN implements a precision comparator-based power-fail detection circuit with user-selectable VPFD (4.62 V at THS = VSS or 4.37 V at THS = VCC). Its internal switching logic routes VOUT to BC1 or BC2 based on voltage comparison with VBSO = 0.4 V typical, enabling sequential battery use without manual intervention.

During power-down, CECON outputs are forced high within tWPT = 100 µs typical after VCC falls below VPFD, unconditionally write-protecting SRAM. During power-up, CECON outputs remain inactive for tCER = 120 ms max after VCC exceeds VPFD to ensure processor stabilization before memory access resumes.

Key Specifications

Pinout & Package

Package: 16-pin narrow-body PDIP (Plastic Dual In-line Package), 0.3-inch width, commercial temperature range (0°C to 70°C).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar SRAM nonvolatile controller applications.

Compared with DS1230Y-120 and MAX690A, the BQ2204APN uniquely integrates hardware-based four-bank SRAM decoding, dual-primary-cell switchover, and conditioned CE outputs-making it the only direct solution for scalable, field-serviceable nonvolatile memory expansion in industrial control systems.

Availability

BQ2204APN is available at Aetrix Electronics and suitable for industrial PLC data retention, real-time clock backup, and medical device configuration storage requiring stable component supply and long-term obsolescence support.

Supply support for BQ2204APN 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 company headquartered in Dallas, Texas, delivering analog and embedded processing solutions for industrial, automotive, and consumer markets.

The BQ2204APN belongs to TI's legacy battery-management and nonvolatile memory controller product line, designed specifically to enable robust, hardware-governed SRAM backup in mission-critical industrial systems where firmware-based solutions introduce reliability risk.

FAQ

What is the function of the THS pin on the BQ2204APN?

The THS pin on the BQ2204APN selects the power-fail detection threshold: when tied to VSS, VPFD is 4.62 V typical for 5% supply tolerance; when tied to VCC, VPFD is 4.37 V typical for 10% tolerance. The BQ2204APN requires THS to be hard-wired to either VSS or VCC-floating or intermediate voltages cause undefined behavior and must be avoided in production designs.

How does the BQ2204APN manage dual backup batteries on BC1 and BC2?

The BQ2204APN continuously compares BC1 and BC2 voltages and routes VOUT to the higher source when their difference exceeds VBSO = 0.4 V. This automatic switchover allows one battery to be replaced while the other sustains memory retention. The BQ2204APN does not charge batteries and is intended only for non-rechargeable 3V lithium primary cells.

What happens to CECON outputs during power-up of the BQ2204APN?

After VCC rises above VPFD, the BQ2204APN holds CECON1–CECON4 inactive for tCER = 120 ms maximum-regardless of CE input state-to allow microcontroller stabilization. Only after this interval does the BQ2204APN resume transparent CE-to-CECON routing. This prevents spurious memory accesses during processor reset and boot sequences.

Can the BQ2204APN support more than four SRAM banks?

No-the BQ2204APN provides exactly four conditioned chip-enable outputs (CECON1–CECON4) and a two-input decoder (A/B), limiting hardware-based bank selection to four SRAM devices. Expanding beyond four banks requires cascading multiple BQ2204APN units or adding external decoding logic, which is not supported by the BQ2204APN's architecture or timing specifications.

Is the BQ2204APN pin-compatible with other members of the bq2204 family?

Yes-the BQ2204APN shares identical pinout and electrical behavior with BQ2204ASN (SOIC-16) and earlier bq2204 variants. All share the same 16-pin DIP/SOIC footprint, VCC/VSS placement, and functional assignment for CE, A, B, BC1, BC2, THS, VOUT, and CECON1–CECON4. Designers may substitute packages without PCB revision, provided thermal and layout constraints are met.