CD1A50

Introduction
The Microchip Technology CD1A50 is a 1 A, 50 V Schottky barrier rectifier diode supplied in bare die form for hybrid microcircuit and high-reliability applications. Fabricated with metallurgically bonded construction and qualified under MIL-PRF-19500/586, this device belongs to the CD series of small-signal and power Schottky rectifiers. The bare-die configuration (CD1A50) enables direct die attach in custom assemblies, offering the same electrical performance as the packaged CDLL1A50 variant while providing maximum design flexibility in space-constrained or high-density modules. It features low forward voltage drop, extremely low reverse leakage, and inherent radiation hardness, making it ideal for military, aerospace, and high-reliability systems requiring efficient rectification with minimal power loss.

Key Features
The CD1A50 delivers outstanding performance for a Schottky rectifier in die format. It provides a working peak reverse voltage of 50 V with a maximum forward voltage of 0.36 V at 0.1 A and 0.60 V at 1.0 A. Reverse leakage current remains tightly controlled at 0.10 mA maximum at 25 °C and 5.0 mA at 100 °C (rated voltage). Junction capacitance is only 0.9 pF typical at 5 V reverse bias and 1 MHz. The device supports an average rectified output current of 1.0 A and a non-repetitive surge peak forward current of 25 A. Additional strengths include non-sensitivity to electrostatic discharge per MIL-STD-750 Method 1020 (human body model), metallurgical bonding for superior reliability, and full military-grade screening options (JAN, JANTX, JANTXV, JANS). The bare-die format eliminates package parasitics, allowing direct integration into hybrids with custom thermal and mechanical interfaces while maintaining RoHS compliance options for commercial variants.

Applications
The CD1A50 is optimized for high-reliability rectification in demanding environments. Primary uses include power supplies and DC-DC converters in military and aerospace systems, high-density hybrid microcircuits, radiation-hardened instrumentation, low-leakage protection diodes, and switching regulators where low forward drop improves efficiency. It excels in space-constrained modules, battery-powered equipment, and RF/microwave assemblies requiring fast switching and minimal capacitance. The die form supports custom packaging or direct bonding in MCMs (multi-chip modules), making it suitable for legacy upgrades and new high-rel designs in avionics, satellites, and defense electronics.

Package and Ordering Information
The CD1A50 is supplied as an unpackaged silicon die for wire-bond or flip-chip assembly. Die dimensions follow standard microcircuit formats with metallized anode and cathode contacts optimized for eutectic or epoxy attach. No external leads or encapsulation are present, allowing users to define the final mechanical outline. Ordering code CD1A50 specifies the 50 V rating and bare-die configuration. Related packaged equivalents include CDLL1A50 in the DO-213AB (MELF) glass package. Military screening levels (JANS highest) and RoHS variants (commercial only) are available through standard Microchip high-reliability channels. Marking on the die follows internal high-rel conventions for traceability.

Absolute Maximum Ratings
These ratings apply at 25 °C unless otherwise noted and represent limits beyond which permanent damage may occur. Working peak reverse voltage (VRWM), repetitive peak reverse voltage, and DC blocking voltage are all 50 V. Average rectified forward current (IO) reaches 1.0 A at TA = 55 °C (PCB-mounted reference). Non-repetitive peak surge forward current (IFSM) is 25 A for 8.3 ms half-sine wave. Operating and storage junction temperature range extends from –65 °C to +125 °C for this variant. Solder temperature for die attach processes is limited to 260 °C for 10 seconds. Repetitive ratings are pulse-width limited by maximum junction temperature. For bare-die applications, users must ensure junction temperature never exceeds +125 °C through proper thermal design.

Thermal Characteristics
Thermal performance for the bare die depends on the assembly method and heatsinking. Junction-to-lead thermal resistance in packaged equivalents is 40 °C/W, while junction-to-ambient reaches 220 °C/W. In die form, effective thermal resistance is significantly lower when bonded to a high-thermal-conductivity substrate or heat spreader, allowing full 1 A operation with proper mounting. Transient thermal impedance curves from the family datasheet confirm safe operation under pulsed conditions. Derating is required above 55 °C ambient to maintain junction temperature limits. The metallurgically bonded die construction provides excellent thermal stability across the full temperature range.

DC Electrical Characteristics
All parameters are measured at TA = +25 °C unless otherwise noted, with a 300 µs pulse width and low duty cycle. Maximum instantaneous forward voltage (VF) is 0.36 V at 0.1 A and 0.60 V at 1.0 A, ensuring low conduction losses. Maximum reverse leakage current (IRM) at rated voltage is 0.10 mA at 25 °C and 5.0 mA at 100 °C. These values remain stable across the military temperature range, minimizing standby power dissipation in high-reliability circuits. Forward voltage temperature coefficient is negative, typical of Schottky devices, further improving efficiency at elevated temperatures.

Capacitance and Dynamic Characteristics
Junction capacitance (CT) is 0.9 pF maximum at VR = 5 V and f = 1.0 MHz. This extremely low capacitance supports high-frequency switching and RF applications with minimal parasitic effects. Reverse recovery time is inherently fast for Schottky technology (typically under 500 ns), eliminating the need for snubbers in many circuits. The device exhibits soft recovery characteristics that reduce EMI generation during commutation.

Surge and Reliability Considerations
The 25 A surge rating handles short-duration overloads typical of power-up or fault conditions without degradation. Combined with MIL-PRF-19500/586 qualification, the CD1A50 undergoes rigorous screening for temperature cycling, burn-in, and hermeticity (in packaged equivalents). Inherent radiation hardness makes it suitable for space and nuclear environments. ESD classification exceeds standard military requirements, and the bare-die format allows full electrical testing prior to assembly.

Application Considerations
For optimal performance, the CD1A50 die requires careful attachment using conductive epoxy or gold eutectic bonding to a suitable substrate with matched thermal expansion. Wire bonding or ribbon leads connect the anode and cathode pads. PCB or hybrid layout should minimize loop inductance and provide adequate heat spreading to achieve the 1 A rating. When used in parallel or series configurations, matched forward voltages ensure current sharing. The low VF and capacitance directly contribute to higher system efficiency and faster response in switching power supplies. Designers should reference the full family datasheet for thermal impedance curves and derating information when implementing custom packaging. The CD1A50 remains a proven choice for high-reliability rectification where packaged devices cannot meet size or thermal constraints.