Microchip Technology CDLL4621

Overview

CDLL4621 from Microsemi is a hermetically sealed, glass-encapsulated MELF (DO-213AA) Zener diode with nominal 3.6 V zener voltage, 250 µA test current, 1700 Ω maximum zener impedance at I_ZT, 7.5 µA maximum reverse leakage at 2 V, and 83 mA maximum DC zener current. It operates from –65°C to +175°C and is used for precision voltage reference and overvoltage protection in high-reliability aerospace and military power supplies.

For engineers reviewing the CDLL4621 datasheet, CDLL4621 pinout, CDLL4621 application, or CDLL4621 equivalent, key selection criteria include its ±5% zener tolerance, low-current operation at 250 µA, hermetic DO-213AA package, thermal resistance of 100 °C/W, and compliance with MIL-PRF-19500/435 for JAN/JANTXV grades.

Technical Context

The CDLL4621 functions as a two-terminal voltage reference device where the cathode band denotes the positive terminal under reverse-bias operation. Its metallurgically bonded junction ensures stable breakdown characteristics across extreme temperatures (–65°C to +175°C), and its 100 °C/W thermal resistance at L = 0 inch requires careful PCB thermal design for sustained 500 mW dissipation at T_EC = +125°C.

Zener impedance is measured with a 60 Hz RMS AC signal equal to 10% of I_ZT (250 µA), yielding 1700 Ω max - a value critical for low-noise regulation in analog sensor biasing and reference divider networks where dynamic impedance affects output stability.

Key Specifications

Pinout & Package

Package: DO-213AA (MELF, SOD-80, LL34), hermetically sealed glass case with tin/lead lead finish. Axial coefficient of expansion ≈ +6 ppm/°C; requires matched COE substrate for thermal cycling reliability.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar Zener reference applications.

Compared with CDLL4621, 1N4621UR-1 adds full military screening at higher cost and longer lead time, while CDLL4621C improves initial tolerance to ±2% without changing thermal or dynamic impedance behavior - enabling trade-offs between cost, qualification, and accuracy.

Availability

CDLL4621 is available at Aetrix Electronics and suitable for aerospace power sequencing, military radio bias networks, satellite payload reference, and downhole sensor conditioning requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for CDLL4621 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Microsemi (now part of Microchip Technology) is a U.S.-based semiconductor company specializing in high-reliability analog, mixed-signal, and radiation-hardened components for defense, aerospace, and industrial markets.

The CDLL46xx series belongs to Microsemi's legacy MIL-qualified Zener diode family, designed specifically for precision voltage reference and overvoltage protection in mission-critical systems operating under extreme environmental stress.

FAQ

What is the zener voltage tolerance for CDLL4621?

The CDLL4621 has a nominal zener voltage of 3.6 V with a tolerance of ±5%, as specified in Note 1 of the manufacturer's datasheet. This tolerance applies under thermal equilibrium at 25°C ± 3°C and is verified per MIL-PRF-19500/435 test methods. The CDLL4621 does not carry a "C" (±2%) or "D" (±1%) suffix, so tighter tolerances require selecting CDLL4621C instead of CDLL4621.

Can CDLL4621 be used in surface-mount designs?

Yes, CDLL4621 is packaged in DO-213AA (MELF), which is a leadless cylindrical surface-mount package also designated SOD-80 and LL34. Its glass body and axial geometry require compatible reflow profiles and solder paste volume control to prevent tombstoning. The CDLL4621 datasheet explicitly states "LEADLESS PACKAGE FOR SURFACE MOUNT" in the design data section.

What is the maximum power dissipation for CDLL4621 at +150°C?

At +150°C end-cap temperature (T_EC), the CDLL4621 derates linearly from 500 mW at +125°C at 10 mW/°C. Thus, maximum power dissipation is 500 mW − (150 − 125) × 10 mW = 250 mW. This value assumes no additional heatsinking and must be validated against actual board thermal performance using the stated 100 °C/W thermal resistance.

Is CDLL4621 suitable for automotive under-hood applications?

Yes, CDLL4621 supports operation from –65°C to +175°C and meets MIL-PRF-19500/435 requirements, exceeding AEC-Q200 Grade 0 (–40°C to +150°C) and Grade 1 (–40°C to +125°C) temperature ranges. Its hermetic glass package and metallurgically bonded junction provide robustness against thermal shock and humidity ingress typical in under-hood environments, making CDLL4621 appropriate for engine control module references.

How does the zener impedance of CDLL4621 affect low-noise applications?

The CDLL4621 has a maximum zener impedance of 1700 Ω at 250 µA test current, measured with a 60 Hz RMS AC signal equal to 10% of I_ZT. In low-noise applications like sensor excitation or ADC reference buffering, this impedance contributes directly to output voltage ripple and noise gain - requiring careful filtering or supplemental regulation if sub-mV stability is required. The CDLL4621 datasheet Figure 3 confirms impedance decreases with increasing current, suggesting operation above 250 µA may improve dynamic performance.