Texas Instruments LM8333FLQ8X/NOPB

Overview

LM8333FLQ8X/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, features an I²C-compatible ACCESS.bus interface (slave address 0xA2), and delivers <2 µA standby current in Halt mode.

For engineers reviewing the LM8333FLQ8X/NOPB datasheet, LM8333FLQ8X/NOPB pinout, LM8333FLQ8X/NOPB application, or LM8333FLQ8X/NOPB equivalent, key selection considerations include its dual wake-up-capable GPIOs (GEN_IO_0/GEN_IO_1), programmable 16-bit PWM output, hardware-enforced watchdog timer (WD_OUT → RESET), and fixed 4-ms keypad scan interval with configurable debounce (1–255 × 3 ms) and active time (1–255 × 3 ms).

Technical Context

The LM8333FLQ8X/NOPB implements a fully static architecture with hardware-controlled Halt mode entry after configurable inactivity (default 500 ms), reducing supply current to <2 µA. Its internal RC oscillator (nominal 1 MHz, ±30% variation) drives keypad scanning at ~4 ms intervals and supports host-programmable timing via ACTIVE and DEBOUNCE commands.

Communication occurs exclusively over a two-wire ACCESS.bus interface compliant with I²C standards (up to 400 kHz), where the device operates as a slave with fixed 7-bit address 0xA2 (MSB-aligned). Key events, GPIO interrupts, and error conditions trigger the open-drain IRQ output, which remains asserted until cleared by READ_INT (0xD0); the first bus cycle after wake-up from Halt mode returns a NACK, requiring host retry.

Key Specifications

Pinout & Package

LM8333FLQ8X/NOPB is packaged in a 32-pin WQFN (Package Number NJE0032A), 5 mm × 5 mm, 0.5 mm pitch, wettable flank, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TCA6408A and PCA9555, the LM8333FLQ8X/NOPB uniquely integrates keypad scanning, SF-key wake-up prioritization, programmable PWM, and hardware-enforced watchdog-all in a single 32-pin WQFN package with <2 µA Halt-mode current, making it irreplaceable for space-constrained, battery-sensitive handheld UI subsystems.

Availability

LM8333FLQ8X/NOPB is available at Aetrix Electronics and suitable for mobile phones, PDAs, smart handheld devices, and personal media players requiring stable component supply across long production lifecycles.

Supply support for LM8333FLQ8X/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 and embedded processing technologies, with leadership in low-power interface solutions and automotive-grade reliability.

The LM8333 product line was designed specifically for mobile UI subsystems, integrating keypad scanning, I/O expansion, and power-aware operation to reduce host processor overhead in battery-powered handheld devices.

FAQ

What is the function of the WD_OUT pin on the LM8333FLQ8X/NOPB?

The WD_OUT pin on the LM8333FLQ8X/NOPB is a mandatory watchdog timer output that must be connected directly to the system RESET input. It asserts low on timeout to force a hardware reset-there is no software disable or configuration option. This ensures fail-safe recovery if the host fails to service the LM8333FLQ8X/NOPB within expected timing windows, and it is active in all operating modes including Halt.

How does the LM8333FLQ8X/NOPB handle simultaneous key presses?

The LM8333FLQ8X/NOPB detects and reports simultaneous key presses beyond two keys as a KEYOVR (keypad overrun) error condition. When this occurs, the IRQ output is asserted, and the error flag is set in the error register (readable via READ_ERROR command 0xF0). The FIFO continues storing valid events, but the host must interpret or discard ambiguous patterns-no automatic resolution or ghosting suppression is implemented in hardware.

Can the LM8333FLQ8X/NOPB operate without an external clock source?

Yes, the LM8333FLQ8X/NOPB operates using an internal RC oscillator and requires no external crystal or clock source. The CLK_IN pin must be connected to GND through a 68 kΩ resistor to set the nominal oscillator frequency (~1 MHz, ±30% variation). This self-contained timing eliminates BOM cost and layout complexity while enabling guaranteed Halt-mode entry and consistent 4-ms scan intervals.

What happens during I²C communication when the LM8333FLQ8X/NOPB is in Halt mode?

When the LM8333FLQ8X/NOPB is in Halt mode, the first I²C bus cycle initiated by the host receives a NACK because the internal clock is disabled and the device cannot respond immediately. The host must abort the transaction and retry the command; the second attempt succeeds as the device wakes into Active mode. Alternatively, sending a START byte (0x01) before the main transaction reliably wakes the LM8333FLQ8X/NOPB without requiring retries.

Is the LM8333FLQ8X/NOPB pin-compatible with other members of the LM8333 family?

No, the LM8333FLQ8X/NOPB is not pin-compatible with other LM8333 variants such as the 49-ball csBGA (LM8333GGR8AXS). It uses the 32-pin WQFN package (NJE0032A) with distinct pin assignments-including dedicated WAKE_INx and K_OUTx signals mapped to different pads than the csBGA version. PCB layout must match the specific package; migration requires board redesign.