High-Density PCB Mount DC-DC Converters

An isolated PCB mount DC-DC converter utilizes internal magnetic transformers to completely separate the primary input electrical circuit from the secondary output load. This provides galvanic isolation, eliminating common-ground loops, protecting sensitive microcontrollers from input voltage transients up to several kilovolts, generating negative output voltages, and meeting international safety isolation codes (e.g., IEC 62368-1, IEC 60601-1). A non-isolated DC-DC converter (Point of Load / POL regulator) shares a common ground pin between input and output. Non-isolated converters offer higher power efficiency (up to 96%), smaller physical dimensions, and lower unit cost, but cannot provide safety isolation or break ground loops.

Thermal derating is calculated by estimating total power dissipation inside the converter module using the efficiency formula: Pdiss = Pout * ((1 - Efficiency) / Efficiency). For example, a 10W output converter operating at 80% efficiency dissipates 10W * (0.20 / 0.80) = 2.5W as heat. Multiply Pdiss by the package thermal resistance ($\theta_{JA}$ in °C/W) to determine internal component temperature rise above ambient. In sealed enclosures where natural convection is limited, ambient internal temperatures can rise quickly. Engineers must consult the datasheet power derating curve (typically starting between +71°C and +85°C), ensuring the output power is derated by 2% to 3.3% per °C above the knee point, or add copper PCB thermal vias beneath the module pins to sink heat away.

High-frequency voltage ripple and transient spikes on DC-DC output lines are caused by transformer stray leakage inductance interacting with output diode/MOSFET parasitic capacitance ($L-C$ ringing during switching transitions) combined with output capacitor Equivalent Series Resistance (ESR) and Equivalent Series Inductance (ESL). To suppress output noise: 1) Place a low-ESR surface-mount ceramic capacitor (1µF to 10µF X7R/X5R) directly across the output pins; 2) Add a small ferrite bead in series with the positive output line followed by a secondary ceramic capacitor to create a secondary low-pass LC filter; 3) Keep PCB trace loops between the converter pins and decoupling capacitors as short and wide as possible.

The input range ratio defines the continuous DC input voltage span over which the DC-DC converter can maintain tight output voltage regulation:

• 2:1 Input Range: The maximum input voltage is twice the minimum input voltage (e.g., 9V to 18V DC, or 18V to 36V DC). Standard for fixed industrial bus architectures.
• 4:1 Input Range: The maximum input voltage is four times the minimum input voltage (e.g., 9V to 36V DC, or 18V to 75V DC). Ideal for systems powered by varying battery banks or multi-voltage power buses.
• 8:1 / 12:1 Input Range: Extremely wide input ranges (e.g., 9V to 75V DC or 14V to 160V DC continuous). Required for traction and railway systems compliant with EN 50155, where nominal battery voltages range from 24V to 110V DC including severe input dip and surge transients.

Unregulated fixed-input DC-DC converters typically require a minimum load of 10% of their rated power to stay within nominal output voltage regulation tolerances. Operating an unregulated module under zero-load conditions can cause the output voltage to rise up to 20% above nominal. In contrast, Aimtec's fully regulated DC-DC converter series feature internal feedback control loops that support true zero-load operation (0% minimum load requirement) without losing voltage regulation or risking component damage.

Yes. Aimtec offers modified standard services for OEMs needing customized output voltage trimming (e.g., non-standard 3.8V, 7.5V, or 48V outputs), specific pin lengths or pinout spacing to fit existing legacy designs, specialized conformal coating (polyurethane or silicone) for high humidity/marine applications, and custom burn-in screening. Contact Aimtec’s application team to discuss your project requirements.