LM431ACZX Replacement: NCP431AVLPRAG, TL431CLPRPG

Original Part

LM431ACZX

onsemi

Shunt Voltage Reference IC Adjustable 2.5V 36 VV ±2% 100 mA TO-92-3

Alternative Part

NCP431AVLPRAG

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Shunt Voltage Reference IC Adjustable 2.5V 36 VV ±1% 40 µA TO-92 (TO-226)

TL431CLPRPG

onsemi

Shunt Voltage Reference IC Adjustable 2.495V 36 VV ±2.2% 100 mA TO-92 (TO-226)

1. NCP431AVLPRAG Substitution Conclusion The NCP431AVLPRAG is not a direct substitute for the LM431ACZX. While compatible in terms of reference voltage, package, and higher initial accuracy (±1%), their key operating current parameters are fundamentally opposed. The NCP431's "Current - Output" is only 40 µA, indicating an extremely weak current sourcing (pull-up) capability. It is suitable only as a voltage reference for micro-loads. In contrast, the original part's 100 mA output capability allows it to directly drive optocouplers, function as an error amplifier within the control loop, and even perform low-power linear regulation. Forcing a substitution would cause the NCP431 to fail immediately or exhibit abnormal performance in any circuit requiring appreciable output current. It is only appropriate for pure voltage reference applications with stringent quiescent current requirements and near-zero load, and cannot cover the typical applications of the original part.

2. TL431CLPRPG Substitution Conclusion The TL431CLPRPG is a functionally equivalent and essentially direct substitute for the LM431ACZX. Their core parameters are highly aligned: output current capability (100 mA), cathode operating current (1 mA), temperature coefficient, and maximum operating voltage are identical. The primary differences are a nominal reference voltage of 2.495V (0.2% lower than 2.5V) and a slightly wider initial accuracy tolerance (±2.2%). For the vast majority of applications, such as switch-mode power supply feedback or voltage monitoring, this minor voltage offset and accuracy difference typically fall within the system's design tolerance and will not impact circuit functionality or performance. The package is fully compatible. In applications not requiring stringent absolute voltage accuracy, this part is a qualified, functionally and performance-equivalent substitute.

Analysis ID: E08E-38D5000

Based on part parameters and for reference only. Not to be used for procurement or production.