CMHZ5242B-TR-TIN - 12V 500mW SOD-123 Zener Diode | Central Semiconductor
MPN: CMHZ5242B-TR-TIN β End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.18 | $0.18 |
| 10 | $0.14 | $1.40 |
| 100 | $0.09 | $9.00 |
| 500 | $0.06 | $30.00 |
| 1,000 | $0.04 | $40.00 |
CMHZ5242B-TR-TIN Overview
A Zener diode is a silicon diode operated in reverse breakdown: above the Zener voltage it conducts while holding the voltage across its terminals nearly constant, making it a simple two-terminal voltage regulator. In the power-management hierarchy, a Zener sits at the simplest end of voltage regulators - before shunt references and LDO linear regulators - and is widely used for bias generation, transient clamping, and low-cost reference levels.
Key features of the CMHZ5242B include a 12 V nominal breakdown, a 500 mW power dissipation rating, a 5% voltage tolerance (B-suffix), and a compact SOD-123 footprint compatible with high-density surface-mount assembly. The tin/lead finish supports traditional soldering processes where lead-bearing finishes remain permitted; for RoHS-focused builds, Central offers the otherwise-identical CMHZ5242B TR PBFREE variant.
According to the manufacturer datasheet, the CMHZ5221B Series is manufactured as a high-quality voltage regulator in a surface-mount package, and the CMHZ5242B is rated 12 V at 500 mW in the SOD-123 case.
Typical applications include 12 V rail clamping, input overvoltage protection for microcontroller GPIO lines, supply-rail bias generation, and consumer/computer board-level voltage reference duties where a discrete two-terminal solution is preferred over an IC reference.
Design consideration: the 500 mW rating applies only with adequate PCB copper to keep junction temperature within limits - derate power as ambient temperature rises, and always verify the tolerance band (11.4 V to 12.6 V) against the protection threshold of the circuit being clamped.
This page synthesizes distributor pricing, drop-in alternatives, lifecycle status, and practical design notes not found in the manufacturer datasheet, as of 2026-09-14.
Drop-in alternatives for CMHZ5242B-TR-TIN β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
CMHZ5242B TR PBFREE
β Drop-Inπ Reference alternative (not in catalog)
CMHZ5242B BK
β Drop-Inπ Reference alternative (not in catalog)
CMHZ5242B-TR-TIN Maximum Ratings & Electrical Characteristics
| Zener Voltage (Nominal) | 12 V |
| Zener Voltage Range (at IZT) | 11.4 V to 12.6 V |
| Zener Voltage Tolerance | +/-5% |
| Power Dissipation | 500 mW |
| Test Current (IZT) | 20 mA |
| Configuration | Single Zener |
| Mounting Type | Surface Mount |
| Package | SOD-123 |
| Finish / Plating | Tin/Lead (TIN/LEAD) |
| Packaging | Tape and Reel (TR) |
| Series | CMHZ5221B |
| RoHS Status | Non-compliant (tin/lead finish); lead-free variant CMHZ5242B TR PBFREE available |
CMHZ5242B-TR-TIN Pin Configuration
| Pin 1 | Cathode β Cathode terminal; reverse-biased in Zener regulation mode (bar/marking side) |
| Pin 2 | Anode β Anode terminal; forward conduction mode when positive relative to cathode |
Typical Applications
CMHZ5242B-TR-TIN is suitable for 6 applications: 12 V Rail Voltage Regulation, Input Overvoltage Clamping, Consumer Entertainment Electronics, Computer Board Reference Levels, Bias Supply for Sensor Circuits, Reverse Polarity and Transient Protection.
12 V Rail Voltage Regulation
The CMHZ5242B's 12 V nominal breakdown at 20 mA test current and 500 mW dissipation rating make it a compact, low-cost shunt regulator for 12 V auxiliary rails in industrial and computer boards. Placed across the rail with a series current-limiting resistor, it holds the node within the 11.4 V to 12.6 V band for light loads. Unlike an LDO, it needs no feedback network or output capacitor, trading precision (5% tolerance) and efficiency for simplicity. Keep operating current between roughly 5 mA and 20 mA so dissipation stays well below the 500 mW limit.
Recommended
Input Overvoltage Clamping
In industrial environments where wiring faults or inductive kicks can push a node above its safe level, the CMHZ5242B clamps the voltage to approximately 12.6 V maximum at its tolerance ceiling. Its 500 mW rating absorbs moderate continuous overvoltage energy, and its SOD-123 body fits directly across input terminals or connector pins. The engineer must series-limit fault current so the diode stays within 500 mW, and should account for the 11.4 V worst-case knee if the protected node must operate near 12 V without leakage.
Recommended
Consumer Entertainment Electronics
Central Semiconductor positions the CMHZ5221B Series for entertainment applications - set-top boxes, audio accessories, and small appliances - where a two-terminal 12 V reference or bias level is needed at minimum cost. The 5% B-grade tolerance is sufficient for bias generation and level shifting, and the surface-mount SOD-123 case supports automated high-volume assembly. Because it adds no switching artifacts and requires no external components, it suits noise-sensitive bias nodes, though regulation accuracy (11.4 V to 12.6 V) must be acceptable to the circuit.
Recommended
Computer Board Reference Levels
For computer peripheral and adapter boards, the CMHZ5242B provides a stable 12 V-banded reference for comparator thresholds, indicator biasing, and legacy interface level detection. At 20 mA test current the dynamic impedance is low, giving a stiff reference for low-current sense inputs. The part's surface-mount footprint fits dense PCBs, and the tape-and-reel format supports pick-and-place throughput. Designers should budget for tolerance drift across temperature, as the 5% band is specified at the test current rather than across the full operating range.
Recommended
Bias Supply for Sensor Circuits
Sensor front ends frequently need a modest bias rail derived from a higher supply; the CMHZ5242B shunt regulator creates a nominal 12 V node from a higher bus with one series resistor. Its 500 mW capability supports bias currents into the tens of milliamps, adequate for powering low-drift signal-conditioning stages or setting an ADC reference offset. The two-terminal topology means zero quiescent-circuit complexity - current not drawn by the load flows through the diode - so the series resistor must be sized for worst-case no-load condition to keep dissipation under 500 mW.
Recommended
Reverse Polarity and Transient Protection
Wired in series (forward conduction) or shunt (reverse breakdown), the CMHZ5242B protects low-voltage inputs from reverse battery connection and moderate transients. In the shunt configuration it clamps negative-going surges at its forward diode drop and positive excursions near 12.6 V, protecting downstream ICs rated for lower maxima. Its 500 mW steady-state rating plus surge capability handles common automotive and industrial abuse events when paired with a series resistor or fuse. Verify pulse-energy limits in the Central Semiconductor datasheet for the specific transient waveform.
Recommended
Recommended Products Summary
Engineering reference data for CMHZ5242B-TR-TIN β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | CMHZ5242B TR PBFREE | CMHZ5242B BK |
|---|---|---|---|
| Package | SOD-123 | SOD-123 - same | SOD-123 - same |
| Brand | Central Semiconductor | Central Semiconductor | Central Semiconductor |
| Zener Voltage (Nominal) | 12 V | 12 V | 12 V |
| Voltage Tolerance | +/-5% | +/-5% | +/-5% |
| Power Dissipation | 500 mW | 500 mW | 500 mW |
| Test Current (IZT) | 20 mA | 20 mA | 20 mA |
| Packaging Format | Tape & Reel | Tape & Reel | Bulk |
Key Differentiators
- Tin/lead finish for legacy solder processes (vs CMHZ5242B TR PBFREE)
- Tighter banding than standard C-grade parts (vs CMHZ5242C-type (non-B) equivalents)
- Tape-and-reel delivery for automated assembly (vs CMHZ5242B BK)
Design Notes
Estimated: the 500 mW rating at 12 V nominal implies an absolute maximum continuous Zener current of approximately 41.7 mA (0.5 W / 12 V). Size the series resistor so worst-case current (maximum supply voltage, no load) keeps dissipation below 500 mW with temperature derating applied. The 20 mA test current is where the 11.4 V to 12.6 V band is specified - operating well below it widens the effective tolerance band.
The SOD-123 package dissipates its 500 mW rating only with adequate pad copper. Use the standard SOD-123 land pattern with at least the recommended pad dimensions from the Central Semiconductor datasheet and connect both pads to copper pour where possible. For clamping applications near the power limit, thermal relief on the cathode pad will raise junction temperature and accelerate leakage drift.
Do not treat the 12 V value as exact: the B-grade tolerance is +/-5%, so conduction can begin anywhere from 11.4 V to 12.6 V. Using this part to clamp a nominal 12 V rail causes parasitic current at the tolerance low end. Also note the part is discontinued under Central Semiconductor PDN01284 - release the lead-free CMHZ5242B TR PBFREE or a qualified SOD-123 equivalent into your AVL before stock runs out.
Compliance Information
The -TIN suffix denotes a tin/lead (TIN/LEAD) plating finish, so this variant is not RoHS compliant and is not lead-free. The lead-free alternative is CMHZ5242B TR PBFREE. Part is covered by Central Semiconductor discontinuation notice PDN01284.
