Adding Analog Devices ADXL343 to a PCB: layout and gate checks

The Analog Devices ADXL343 is a 3-axis digital accelerometer from Analog Devices. Its package or board interface is 14-lead 3 × 5 mm LGA, and its relevant electrical envelope is 2.0–3.6 V VS and 1.7–VS VDD I/O. It communicates or connects through I²C or SPI; two interrupts. Those fields belong together: substituting a familiar family name while changing package, voltage, sensing port, mount style, current class, or interface behavior can leave a PCB that passes ordinary net checks and still cannot be assembled or function safely.

ADXL343 is closely related to ADXL345 and supports activity, tap, free-fall, FIFO and flexible interrupts, but its exact electrical specification must drive substitution.

Common uses include low-power tilt sensing and activity and free-fall detection. Start with the manufacturer drawing and recommended application, then record the exact ordering suffix alongside the KiCad symbol and footprint. This makes the library evidence reviewable when the part is re-sourced months later.

• Copy the exact LGA land pattern, pin-one mark, and paste aperture. Similar IMUs often share body dimensions while changing pad count, center pads, orientation convention, or reserved pins.
• Place the package axes deliberately relative to the product coordinate system and record that transform in silkscreen or design notes. Keep the sensor flat, supported, and away from board flex and mounting stress.

Align axes, isolate board stress, and use interrupt outputs for event-driven operation rather than leaving the sensor at a high continuous data rate.

• Use a quiet, locally decoupled supply and keep switch nodes, inductors, high-current LED paths, speakers, and vibrating connectors away. Route clock and interrupt signals without passing beneath the sensor.
• Set I²C/SPI mode and address pins to defined states, verify I/O voltage, and expose at least one interrupt when firmware needs low-power wake or deterministic sample timing.

Put the support components where their current, thermal, optical, RF, or measurement loops are actually short—not merely where ratsnest lines look tidy. Confirm pin one from the package view used in the datasheet, distinguish top view from mating face or bottom view, and check mask, paste, drill, courtyard, enclosure, and rework access independently. A correct copper pad pattern can still be a bad production footprint when the sensing opening, connector latch, exposed pad, thermal path, or cable volume is wrong.

MakeIRL’s release gate should not stop at “the symbol has the right number of pins.” For this part, a useful gate review combines ERC/DRC with the following package- and function-specific evidence:

1. Check LGA orientation and axis convention, supply and I/O rails, decoupling, interface-mode straps, address, chip select, interrupts, and every reserved/no-connect pin.
2. Check placement for flex, vibration, heat and magnetic interference, and confirm the firmware coordinate transform matches physical rotation.
3. Check lifecycle and exact suffix because popular IMU names are often reused on breakout listings after the original IC becomes obsolete.
4. For Analog Devices ADXL343, check the exact ADXL343 order code, dual supplies, CS/address straps, interrupts, axis map, and firmware device assumptions.

Then run ERC and DRC, refill zones, and inspect the fabrication and assembly outputs. Cross-probe the exact pads named by any finding, compare the BOM MPN with the footprint and electrical limits above, and verify that a real cable, enclosure, antenna, sensor stimulus, load, or thermal path can be tested on the assembled unit. An exclusion is evidence that someone dismissed a marker; it is not evidence that the underlying condition was resolved.

The most expensive errors are usually plausible: a footprint from a sibling package, a breakout-board voltage copied to the bare IC, a headline current used without thermal analysis, or a connector family selected by pitch alone. For Analog Devices ADXL343, review these failure modes explicitly:

• Treating ADXL343 and ADXL345 as an uncontrolled generic alternate can hide subtle specification or identification differences important to validated firmware.
• Rotating the package in layout without updating firmware axes, yielding swapped or sign-inverted motion data.
• Leaving chip select or address pins floating, so the sensor changes bus mode or address during power-up.

Sourcing note. Keep the exact Analog Devices MPN in the AVL and qualify any ADXL345 cross-use explicitly rather than by distributor parametric match. The approved vendor list should preserve manufacturer, full suffix, package, voltage/range/accuracy grade, lifecycle, and mating or external components. An alternate is real only after its datasheet, land pattern, electrical behavior, firmware assumptions, and assembly process have all been compared—not because a distributor search places it in the same parametric row.