Renesas RD56F

Overview

RD56F from Renesas Electronics is a 1 W planar-type silicon Zener diode with a nominal zener voltage of 56 V (B grade: 53–60 V), dynamic impedance of 50 Ω at 10 mA, and temperature coefficient of +43 mV/°C (typical). It features DO-41 glass-sealed DHD (Double Heatsink Diode) packaging and is used for precision voltage regulation and surge absorption in industrial power supplies and analog reference circuits.

For engineers reviewing the RD56F datasheet, RD56F pinout, RD56F application, or RD56F equivalent, this page provides verified electrical specifications, thermal derating curves, JEDEC DO-41 terminal mapping, real-world use cases in voltage clamping and constant-current biasing, and two validated alternative Zener diodes with documented voltage and impedance differences.

Technical Context

The RD56F operates as a reverse-biased voltage reference device with a specified zener test current of 10 mA and maximum reverse current of 5 μA at VR = 43 V. Its positive temperature coefficient (+43 mV/°C typ.) indicates increasing VZ with rising junction temperature - critical for thermal stability analysis in linear regulator feedback paths.

It employs a planar diffusion process in a glass-hermetic DO-41 package, enabling 175°C maximum junction temperature and 400 W surge reverse power handling for t = 10 μs pulses. Thermal resistance is dependent on PCB copper area, ranging from 240°C/W (5 mm²) to 80°C/W (20 mm²).

Key Specifications

Pinout & Package

RD56F uses the JEDEC-standard DO-41 axial glass package (3.0 mm Ø × 5.0 mm L), with cathode indicated by a black band. The device has two terminals: anode and cathode - no internal circuitry or additional pins.

Key Features

Applications

Equivalent & Alternatives

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

Compared with RD56F, the 1N5255B offers lower dynamic impedance but lacks its positive temperature coefficient for drift compensation, while the BZX55-C56 uses a smaller DO-35 package with reduced surge capacity - making RD56F preferable for industrial-grade 1 W clamping where thermal stability and pulse robustness are prioritized.

Availability

RD56F is available at Aetrix Electronics and suitable for industrial power supplies, analog sensor interfaces, and surge-protected control modules requiring stable component supply and long-term obsolescence management.

Supply support for RD56F 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

Renesas Electronics Corporation is a Japanese semiconductor manufacturer formed in 2010 via merger of NEC Electronics and Renesas Technology, specializing in microcontrollers, analog, and discrete power devices.

The RD56F belongs to the RD2.0F–RD82F planar Zener diode family designed for standardized voltage regulation and transient suppression in industrial, computing, and communications equipment under the "Standard" quality grade.

FAQ

What is the exact zener voltage tolerance for RD56F?

The RD56F is specified with a B-grade zener voltage range of 53 V to 60 V at IZ = 10 mA, corresponding to ±6.25% tolerance around the nominal 56 V value. This tolerance is measured after 40 ms power-on stabilization per datasheet Note 1, and applies across the full operating temperature range of −65°C to +175°C.

Does RD56F have a cathode marking, and how is polarity identified?

Yes, RD56F uses a black band on the glass body to indicate the cathode terminal, consistent with JEDEC DO-41 standard marking. The unmarked end is the anode. This marking is visible under standard visual inspection and must be oriented correctly in PCB layout to ensure proper reverse-bias operation during voltage regulation or clamping.

What is the maximum allowable surge reverse power for RD56F, and under what conditions?

The RD56F supports a surge reverse power of 400 W for pulse width t = 10 μs at TA = 25°C, as defined in Absolute Maximum Ratings. This rating assumes non-repetitive operation and is validated per Figure 7 in the datasheet. Exceeding this limit - either in energy (W·s) or repetition rate - risks irreversible junction damage.

How does the +43 mV/°C temperature coefficient affect RD56F in precision reference designs?

The +43 mV/°C typical temperature coefficient means RD56F's zener voltage increases by approximately 43 mV per degree Celsius rise in junction temperature. In precision reference designs, this drift must be compensated - for example, by pairing with a negative-TC component or using it in temperature-stabilized enclosures - especially where regulation accuracy better than ±1% over −40°C to +85°C is required.

Is RD56F RoHS compliant, and what is its lead-free status?

RD56F was originally released prior to RoHS enforcement (2006 datasheet), and Renesas documentation does not explicitly declare RoHS compliance for this legacy DO-41 part. Customers requiring RoHS-compliant Zener diodes should consult Renesas' current product matrix or consider modern equivalents such as the RZ560BN (lead-free, DO-213AA) - RD56F itself is not certified RoHS-compliant per EU Directive 2011/65/EU.