PCAL6408AHK - 8-Bit I2C I/O Expander, XQFN-16 | NXP
MPN: PCAL6408AHK ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0 | $0.00 |
| 10 | $0 | $0.00 |
| 100 | $0 | $0.00 |
| 500 | $0 | $0.00 |
| 1,000 | $0 | $0.00 |
PCAL6408AHK Overview
An I/O expander is a peripheral IC that adds extra general-purpose input/output pins to a microcontroller or embedded processor over a serial bus such as I2C or SMBus. In the system hierarchy, it sits within the interface IC family, under mixed-signal peripheral devices, and complements microcontrollers whose native GPIO count is exhausted. Expanders offload GPIO expansion while consuming only two bus wires (SDA, SCL), conserving processor pins and board routing.
Key features include a wide supply range of 1.65 V to 5.5 V, dual power rails for true voltage level translation between logic domains, programmable output drive strength, and latchable inputs. The interrupt output and active-low reset provide robust event-driven and fault-recovery behavior in multi-slave I2C systems.
The Agile I/O feature set - configurable output drive, input latch, and pull-up/pull-down enable - allows system designers to tune signal integrity and power per pin, which is significant in mixed-voltage designs where a 1.8 V MCU must safely drive 3.3 V or 5 V peripherals. Open-drain and push-pull operating modes over I2C/SMBus at 400 kHz provide flexible bus integration.
Typical applications include GPIO expansion in portable and battery-powered devices, level translation between low-voltage processors and legacy 5 V peripherals, sensor and keypad scanning, LED control, and backplane status monitoring in industrial systems.
Design consideration: because the XQFN-16 package measures only 1.8 x 2.6 mm, the exposed pad must be soldered to a grounded PCB land pattern for reliable thermal and mechanical performance; verify land-pattern tolerances before assembly.
This page synthesizes distributor pricing context, drop-in alternatives, practical design notes, and AEO-optimized FAQs not found in the NXP datasheet.
Drop-in alternatives for PCAL6408AHK — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PCA6408AHK
✅ Drop-In📋 Reference alternative (not in catalog)
PCAL6408AHK Specifications
| Product Type | 8-bit I2C-bus/SMBus level translating I/O expander |
| Number of I/O Pins | 8 |
| Interface | I2C, SMBus |
| Maximum Bus Clock Frequency | 400 kHz |
| Supply Voltage Range (VDD) | 1.65 V to 5.5 V |
| Level Translation | Yes (dual power rail) |
| Agile I/O Features | Programmable output drive strength, latchable inputs |
| Interrupt Output | Yes (open-drain) |
| Reset Input | Yes (active-low reset) |
| Configuration Registers | Yes |
| Package | XQFN-16 (1.8 x 2.6 mm) |
| Mounting Type | Surface Mount |
| Lifecycle Status | Active |
| Drop-in Compatibility | Pin-to-pin replacement, software backward-compatible with PCA6408A |
PCAL6408AHK xqfn-16 (1.8 x 2.6 mm) Pin Configuration Guide
Pin configuration for PCAL6408AHK (xqfn-16 (1.8 x 2.6 mm) package). Pin numbering, functions, and connection diagrams are defined in the manufacturer datasheet. Refer to it for the exact footprint and soldering guidelines.
No detailed pinout data available for PCAL6408AHK.
Refer to the datasheet for full pin configuration.
Typical Applications
PCAL6408AHK is suitable for 6 applications: Portable and Battery-Powered Devices, Voltage Level Translation between Logic Domains, Keypad and Switch Scanning, Industrial Backplane Status Monitoring, LED Control and Indication, Consumer Electronics Peripheral Expansion.
Portable and Battery-Powered Devices
The PCAL6408AHK suits portable electronics because its XQFN-16 package measures only 1.8 x 2.6 mm and its 1.65 V to 5.5 V supply range allows direct operation from a single lithium-ion cell or a 1.8 V rail. In a smartphone accessory or wearable, the expander adds eight GPIOs for button sensing, LED indicators, and peripheral enables while consuming only two I2C wires on the main processor. The Agile I/O input latch captures short key-press pulses between bus polls, and programmable output drive strength minimizes EMI in compact enclosures. Battery life benefits from event-driven interrupt operation instead of continuous polling.
Recommended
Voltage Level Translation between Logic Domains
Because the PCAL6408AHK provides dual power rails, it functions as both a GPIO expander and a voltage translator: an MCU side running at 1.65 V to 1.8 V can drive or read I/O ports referenced to 3.3 V or 5 V rails. This eliminates a separate bidirectional translator chip in mixed-voltage systems such as a 1.8 V Cortex-M design interfacing with legacy 5 V sensors, relays, or industrial indicators. Per the NXP datasheet, the wide VDD range of 1.65 V to 5.5 V supports nearly any common logic family pairing, and the interrupt output crosses domains safely, reducing component count and board area in mixed-voltage signal chains.
Recommended
Keypad and Switch Scanning
The PCAL6408AHK reads up to eight switches or a small keypad matrix over I2C at 400 kHz, fast enough to scan several times per millisecond. The open-drain interrupt output asserts on any input change, so the host MCU sleeps until a key press occurs, reducing power in battery-operated terminals and appliances. The latchable input feature (Agile I/O) guarantees that short pulses are not lost between read cycles, while the active-low reset allows recovery from bus lockups without power cycling. The I2C address selection permits multiple expanders on one bus for larger keypads, keeping wiring harnesses short and cost-effective.
Recommended
Industrial Backplane Status Monitoring
In industrial controllers and backplanes, the PCAL6408AHK aggregates eight status flags - card presence, fuse alarms, fan-fail signals, door switches - onto a single I2C segment. The interrupt output provides immediate fault notification, and the input latch ensures glitchy alarms are captured before the host reads them. The wide 1.65 V to 5.5 V supply tolerates noisy rail excursions, and the reset pin restores known-good configuration after a brownout. Its XQFN-16 (1.8 x 2.6 mm) footprint fits dense monitoring cards, and Agile I/O pull-up/pull-down control removes external bias resistors, simplifying BOM management across multiple card variants.
Recommended
LED Control and Indication
The PCAL6408AHK drives indicator LEDs through its push-pull outputs, with programmable output drive strength allowing designers to limit sink/source current per pin for efficient low-current LED indication without external series resistors in some designs. Configuration registers set each pin as input or output independently, so a single expander can mix LEDs and switches. The 400 kHz I2C interface updates all eight outputs in one write transaction, enabling rapid status changes on instrument panels, network equipment front panels, and set-top boxes. The XQFN-16 package's 1.8 x 2.6 mm size fits behind a light pipe on space-limited front-panel PCBs.
Recommended
Consumer Electronics Peripheral Expansion
Set-top boxes, routers, white goods, and audio equipment frequently exhaust the host SoC's GPIO pins. The PCAL6408AHK restores eight configurable pins over I2C/SMBus for power-enable lines, mode strapping, sensor inputs, and indicator control, while its dual-rail level translation bridges a 1.8 V SoC to 3.3 V board-level signals. NXP states the PCAL6408A is a pin-to-pin, software backward-compatible upgrade from the PCA6408A, so existing consumer platforms can adopt it without firmware changes. The Agile I/O drive-strength control helps meet EMI/EMC pre-compliance in plastic enclosures by slowing edge rates on long indication lines.
Recommended
Recommended Products Summary
Engineering reference data for PCAL6408AHK — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PCA6408AHK |
|---|---|---|
| Package | XQFN-16 (1.8 x 2.6 mm) | XQFN-16 (1.8 x 2.6 mm) - same |
| Brand | NXP Semiconductors | NXP Semiconductors |
| I/O Count | 8 | 8 |
| Supply Voltage Range | 1.65 V to 5.5 V | 1.65 V to 5.5 V |
| Bus Interface | I2C, SMBus (400 kHz) | I2C, SMBus (400 kHz) |
| Level Translation | Yes (dual power rail) | Yes (dual power rail) |
| Agile I/O (drive strength, input latch) | Yes | No |
| Software Compatibility | Fully backward-compatible with PCA6408A (per NXP) | Baseline register set |
| Interrupt / Reset | Yes / Yes (active-low) | Yes / Yes |
Key Differentiators
- Agile I/O feature set (vs PCA6408AHK)
- True dual-rail level translation (vs PCA6408AHK)
- Software backward compatibility enables risk-free upgrades (vs PCA6408AHK)
Design Notes
The XQFN-16 package measures only 1.8 x 2.6 mm with fine-pitch perimeter lands and an exposed center pad. Solder the exposed pad to the PCB land pattern (typically grounded) for mechanical reliability and heat dissipation, and verify that your assembly house supports XQFN reflow with appropriate solder paste aperture design. Use the land pattern in the NXP PCAL6408A datasheet rather than generic QFN footprints - the ultra-small body requires tighter tolerances than standard 3x3 mm QFN packages.
Exploit the dual power rails for level translation: connect VDD(I2C) to the host logic rail (e.g., 1.8 V) and VDD(P) to the peripheral voltage domain (3.3 V or 5 V). Ensure both rails are decoupled with 0.1 uF ceramic capacitors placed close to their respective pins. Because supply range spans 1.65 V to 5.5 V, avoid powering the peripheral rail above the absolute maximum of the connected loads, and sequence rails so the I2C side is not back-driven through the expander during power-up.
Size I2C pull-up resistors for the 400 kHz Fast-mode bus: lower values (e.g., 2.2k to 4.7k) improve edge rates on longer or higher-capacitance buses, while higher values save power on short buses. Use the Agile I/O programmable output drive strength to slow edges on long LED or indicator lines and reduce EMI. Enable the input latch for signal lines that may glitch, ensuring short pulses are held until the host reads them via I2C.
Compliance Information
Compliance details not stated in the verified web data. NXP product page lists an 'Environmental Quality' section for PCAL6408AHK - consult nxp.com/part/PCAL6408AHK for official RoHS/REACH status.
