Transient DAC Glitch

The most significant glitch energy occurs during a major carry transition, such as when the digital input code changes from 0111 to 1000. At this boundary, multiple internal current switches must change state simultaneously. Timing skews between these switches cause a momentary period where all switches are briefly on or off, creating a narrow, high-amplitude voltage spike at the output summing node.

The glitch impulse is the primary fingerprinting metric, defined as the integrated voltage-time product of the transient spike. It is measured in picovolt-seconds (pV·s). This area is highly sensitive to:

• Switch mismatch: Transistor threshold voltage variations
• Interconnect delay: Parasitic capacitance differences in the routing
• Clock distribution: Skew in the latch timing signals

In a differential current-steering DAC, the glitch appears as a common-mode spike when both complementary outputs momentarily deviate in the same direction. The differential output may show a doublet pulse (positive then negative excursion) as the switches settle. The exact shape of this doublet—its amplitude, width, and ringing—is a unique hardware signature.

Following the initial glitch spike, the DAC output exhibits a characteristic settling trajectory back to the final analog value. This trajectory is dominated by:

• Slew rate limiting: The op-amp's finite current to charge the output capacitance
• Linear settling: The exponential RC decay of the output network
• Thermal tails: Slow components from die heating during the current surge

The glitch energy is not constant but code-dependent. A transition from 0011 to 0100 produces a different glitch than 0111 to 1000. This creates a glitch energy map across all possible code transitions, forming a high-dimensional fingerprint. The worst-case glitch typically occurs at the mid-scale transition where the most switches toggle.

A secondary artifact is clock feedthrough, where the digital latch clock signal capacitively couples into the analog output path. This appears as small, periodic spikes synchronized to the DAC update clock. The amplitude of this feedthrough is determined by the parasitic gate-drain capacitance of the switch transistors, a parameter with significant manufacturing variance.

The brief, non-ideal electromagnetic signature emitted when a radio frequency transmitter is initially energized. This period contains unique hardware-specific artifacts, including the Transient DAC Glitch, which are used for device fingerprinting. The glitch is a key component of the overall turn-on signature, revealing the digital-to-analog converter's switching behavior.

The measurement of the duration required for a transmitter's frequency and amplitude to stabilize within a specified tolerance after the initial turn-on event. The Transient DAC Glitch directly extends the settling time, as the momentary voltage spike must dissipate before the output reaches a steady state. This analysis reveals phase-locked loop dynamics and DAC performance.

The timing uncertainty in the digital clock edges during the power-up sequence. This jitter is a primary cause of the Transient DAC Glitch, as timing skews between internal DAC switches during a major code transition lead to the unintended voltage spike. Analyzing this jitter provides a unique fingerprint of the clock distribution network.

The quantification of the transient amplitude excursion beyond the steady-state level during the ramp-up phase. The Transient DAC Glitch manifests as a sharp, momentary overshoot caused by an underdamped response in the DAC's output buffer or the power amplifier control loop. Its peak amplitude and decay rate are distinct hardware signatures.

The non-linear amplitude and phase distortion generated by the power amplifier when driven through its non-linear region during a rapid ramp-up. The Transient DAC Glitch can excite these non-linearities, creating a cascade of distortion products that are highly specific to the amplifier's transistor physics and biasing network.

Broadband spectral noise generated by the rapid switching of the transmitter. The Transient DAC Glitch, being a fast voltage spike, is a significant contributor to this splatter. The specific spectral shape of the glitch-induced interference in adjacent channels serves as a unique, unclonable identifier of the transmitter's digital-to-analog converter.