Rail-to-rail ESD clamp for high-speed differential ports
The Texas Instruments TPD4S010DQAR is a four-channel steering (rail-to-rail) ESD protection diode array in a 10-USON (2.5x1) package. It clamps transients on signal lines to the positive and negative supply rails rather than to ground, which keeps the protected signal's common-mode voltage undisturbed — important for differential interfaces like HDMI and Ethernet. Each of the four unidirectional channels handles a 25 W peak pulse (8/20 µs waveform), with a maximum reverse standoff voltage of 5.5 V.
25 W peak pulse — how much transient it absorbs
The 25 W peak pulse power rating tells you the maximum instantaneous energy the device can shunt per IEC 61000-4-5 surge before the junction fails. For a typical HDMI 2.0 port, the 25 W rating covers the 8 kV contact / 15 kV air-gap ESD strikes specified in IEC 61000-4-2, plus the 2 kV to 4 kV coupled surges that appear on long cable runs. If your system must survive 6 kV or higher surge levels, you would step up to a part with a higher peak pulse rating. The 5.5 V reverse standoff means the diode does not conduct at DC voltages up to 5.5 V, so it sits across a 3.3 V HDMI TMDS line or a 5 V Ethernet PHY output without loading the signal. The 9 V minimum breakdown is the voltage at which avalanche conduction starts — the gap between 5.5 V and 9 V is the transient voltage range the part absorbs before clamping fully.
10-USON package — board layout notes
The 10-USON (2.5 mm × 1.0 mm) package is a small, leadless package with a 0.50 mm pitch. It is a surface-mount package that requires a solder-paste stencil with apertures sized for the exposed pad — the centre thermal pad is not a power-dissipation path for this device (25 W is a transient, not continuous), but it does anchor the package mechanically. The 2.5 mm × 1.0 mm footprint fits under a connector or near the port edge, keeping the ESD clamp close to the transient entry point.