Texas Instruments LM8333FLQ8Y/NOPB

Overview

LM8333FLQ8Y/NOPB from Texas Instruments is a mobile I/O companion IC that offloads keypad scanning and I/O expansion from the host processor in portable electronics. It supports up to 72-key matrix (8×8 standard + 8 special-function keys), provides a 15-byte FIFO for key event buffering, delivers <2 µA standby current, and communicates via I²C-compatible ACCESS.bus at up to 400 kHz - enabling low-power operation in smartphones and handheld media players.

For engineers reviewing the LM8333FLQ8Y/NOPB datasheet, LM8333FLQ8Y/NOPB pinout, LM8333FLQ8Y/NOPB application, or LM8333FLQ8Y/NOPB equivalent, key selection considerations include its dual-mode GPIOs with external interrupt capability, programmable 16-bit PWM output, hardware watchdog timer (WD_OUT → RESET), and Halt mode entry after configurable inactivity (default 500 ms).

Technical Context

The LM8333FLQ8Y/NOPB integrates a fully static architecture with an internal RC oscillator (nominal 1 MHz, ±30% variation) and automatic Halt mode activation when no keypad, I/O, or bus activity occurs. Its 15-byte FIFO buffers key-press/release events encoded as 8-bit codes (MSB=1 for press, 0 for release), with error reporting for FIFO overrun, keypad overrun (>2 keys), and invalid commands.

It implements a two-wire ACCESS.bus interface compliant with I²C standards, operating as a slave device at 400 kHz with fixed 7-bit address 0xA2 (write)/0xA3 (read). The IRQ output signals key events, errors, or GEN_IO_0/GEN_IO_1 edge transitions, remaining asserted until cleared via READ_INT (0xD0) command.

Key Specifications

Pinout & Package

LM8333FLQ8Y/NOPB is packaged in a 32-pin WQFN (Package Number NJE0032A), 5 mm × 5 mm, 0.5 mm pitch, with exposed thermal pad. Pin functions are validated per TI SNLS246K datasheet Figures 1 and signal descriptions (pp. 4–5).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar I/O companion applications.

Compared with TCA6424A and PCA9555, the LM8333FLQ8Y/NOPB uniquely integrates dedicated keypad scanning, 15-byte FIFO buffering, hardware watchdog, and programmable PWM - delivering higher functional integration and lower system-level power in mobile UI applications.

Availability

LM8333FLQ8Y/NOPB is available at Aetrix Electronics and suitable for smartphone UI subsystems, PDA input expansion, handheld gaming console interfaces, and portable media player control requiring stable component supply and long-term lifecycle support.

Supply support for LM8333FLQ8Y/NOPB 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 specializing in analog, embedded processing, and digital signal processing technologies with broad industrial and consumer applications.

The LM8333FLQ8Y/NOPB belongs to TI's Mobile I/O Companion product line, designed specifically to reduce host processor overhead and power consumption in portable devices with physical keypads and limited I/O resources.

FAQ

What is the function of the WD_OUT pin on the LM8333FLQ8Y/NOPB?

The WD_OUT pin on the LM8333FLQ8Y/NOPB is the mandatory watchdog timer output. It must be connected directly to the system RESET input. The hardware watchdog is always enabled and cannot be disabled; if not periodically refreshed via I²C commands, WD_OUT asserts to reset the host system. This ensures fail-safe operation in battery-powered mobile devices where software hangs could otherwise cause unrecoverable lockups. The LM8333FLQ8Y/NOPB relies on this connection for system-level reliability.

How does the LM8333FLQ8Y/NOPB handle simultaneous key presses?

The LM8333FLQ8Y/NOPB detects and reports simultaneous key presses beyond two keys as a keypad overrun error (KEYOVR bit in error register). When more than two keys are pressed concurrently, the resulting matrix pattern becomes ambiguous, so the device asserts the IRQ output and sets the KEYOVR flag. The host must read the error code via READ_ERROR (0xF0) and decide whether to discard or interpret the partial FIFO contents. This behavior prevents false key interpretations and is documented in the SNLS246K datasheet section "Keypad Scanning".

Can the PWM output of the LM8333FLQ8Y/NOPB be used as a general-purpose digital output?

Yes, the PWM output of the LM8333FLQ8Y/NOPB can be used as a general-purpose digital output. When the PWM_CTL command disables the timer (MOD bit = 0), the PWM pin operates in TRI-STATE® (high-impedance), drive-low, or drive-high mode depending on OUT_DIR and PWM_DIR bits. This allows it to serve as a configurable GPIO without requiring additional hardware. The LM8333FLQ8Y/NOPB thus provides functional flexibility - using the same pin for either precision PWM generation or simple level control based on host configuration.

What is the minimum debounce time configurable for the LM8333FLQ8Y/NOPB keypad scanner?

The minimum debounce time for the LM8333FLQ8Y/NOPB keypad scanner is 3 ms, set by writing 0x01 to the DEBOUNCE command (0x22). The debounce value is multiplied by 3 ms (n × 3 ms), with valid range n = 1–255, yielding 3 ms to ~765 ms. This fine-grained adjustment enables reliable scanning of mechanical key switches with varying contact bounce characteristics. The LM8333FLQ8Y/NOPB applies this delay automatically after detecting a state change, ensuring robust key detection across diverse switch types.

Does the LM8333FLQ8Y/NOPB support both 3.3V and 2.5V supply rails?

Yes, the LM8333FLQ8Y/NOPB supports supply voltages from 2.25 V to 2.9 V, making it compatible with both 2.5 V and 3.3 V systems when operated within specification. The DC Electrical Characteristics table specifies VCC min = 2.25 V and max = 2.9 V at TA = –40°C to +85°C. Operation outside this range - including standard 3.3 V rails - is not guaranteed and may cause malfunction or damage. The LM8333FLQ8Y/NOPB is optimized for low-voltage mobile platforms and must be powered accordingly.