Nexperia USA Inc. NCR321ZX

Overview

NCR321ZX from Nexperia is a resistor-equipped NPN transistor-based constant-current LED driver in SOT223 (SC-73) package, integrating two diodes on-chip. It delivers stabilized 10 mA output without external components and up to 250 mA with an external resistor (e.g., 3 Ω), features digital PWM dimming support up to 10 kHz, and maintains ±1% current accuracy over supply voltage variation. It is AEC-Q101 qualified for automotive interior lighting and instrumentation.

For engineers reviewing the NCR321ZX datasheet, NCR321ZX pinout, NCR321ZX application, or NCR321ZX equivalent, key selection considerations include its 1.4 V low voltage overhead, 3.3 V enable threshold, 250 mA max adjustable output, thermal performance on 4-layer PCB (70 K/W R_th(j-a)), and PWM-compatible enable input for microcontroller-driven dimming.

Technical Context

The NCR321ZX implements a monolithic current-regulating architecture combining an NPN transistor, internal bias resistor (1.5 kΩ), and two integrated diodes - enabling stable current source behavior independent of V_CC fluctuations. Its enable input operates at TTL/CMOS logic levels (V_EN ≤ 4.5 V max), supporting direct microcontroller interfacing.

Current regulation relies on internal feedback via the R_EXT terminal, where output I_OUT = V_BE/R_EXT ≈ 0.95 V / R_EXT, delivering 250 mA at R_EXT = 3 Ω. The device exhibits –0.27 %/K temperature coefficient and 1 %/V supply sensitivity, validated across –40 °C to +85 °C ambient.

Key Specifications

Pinout & Package

SOT223 (SC-73) plastic surface-mounted package with increased heatsink; 4 leads. Exposed collector pad provides primary thermal path to PCB copper.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar constant-current LED driver applications.

Compared with NSI45020AZT1G and NCR320Z, the NCR321ZX uniquely balances microcontroller-ready enable logic, 10 kHz PWM dimming, and 250 mA scalability - making it optimal for automotive human-machine interface (HMI) lighting where both precision and controllability are required.

Availability

NCR321ZX is available at Aetrix Electronics and suitable for automotive interior lighting, dashboard instrumentation, license plate illumination, and parallel high-current LED arrays requiring stable component supply and AEC-Q101 compliance.

Supply support for NCR321ZX 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

Nexperia is a global semiconductor expert specializing in high-volume, high-reliability discrete and logic devices, with leadership in automotive-qualified components and energy-efficient power management.

The NCR321ZX belongs to Nexperia's resistor-equipped transistor (RET) LED driver family, designed specifically for cost-sensitive, thermally constrained automotive HMI lighting where integration, qualification, and ease of MCU control are essential.

FAQ

What is the maximum continuous output current for NCR321ZX?

The NCR321ZX delivers up to 250 mA continuous output current when configured with a 3 Ω external resistor (R_EXT) and mounted on a 4-layer FR4 PCB with adequate copper area. This rating assumes T_amb ≤ 25 °C and accounts for its 1250 mW power dissipation limit and 70 K/W thermal resistance. Derating is required above 25 °C ambient per the published power derating curve.

Can NCR321ZX be used with a 3.3 V microcontroller GPIO?

Yes - the NCR321ZX's enable input (VEN) has a maximum threshold of 4.5 V and draws only ~1.2 mA at 3.3 V, allowing direct connection to standard 3.3 V MCU GPIO pins without series resistors or level shifters. Its enable current remains stable across temperature (–40 °C to +85 °C), ensuring reliable on/off and PWM dimming control.

How does the internal 1.5 kΩ resistor affect operation?

The internal 1.5 kΩ bias resistor sets a default stabilized output current of ~10 mA when R_EXT is left unconnected (open). This eliminates the need for external components in low-current indicator applications. When an external resistor is added between REXT and GND, it overrides the internal resistor and determines I_OUT ≈ 0.95 V / R_EXT, enabling precise current scaling up to 250 mA.

Is thermal design guidance available for NCR321ZX on PCB?

Yes - Nexperia specifies R_th(j-a) = 70 K/W for a 4-layer FR4 PCB with tin-plated finish and standard SOT223 footprint, and 100 K/W for single-sided copper. Recommended layout includes ≥1 cm² copper pour connected to the exposed collector pad (Pin 4), thermal vias under the pad, and avoidance of signal traces beneath the device to maximize heat transfer to inner layers or ground plane.