The NUD4001 and NUD4011 are two-output, configurable constant current sources from ON Semiconductor, designed for use with SMD LEDs of size codes 3528 and 5050. The NUD4001 is ideal for driving 0.5-1W LEDs, while the NUD4011 is suitable for low-power LEDs ranging from 20mA to 60mA. These ICs offer a simple and efficient solution for LED lighting applications.
The NUD4001 comes in an S0-8 package and features a wide input voltage range (up to 30V), with a maximum output current of 500mA. It allows for easy current setting via an external resistor, simplifying the design and saving PCB space. Key parameters include a maximum output voltage of 28V, an electrostatic discharge (ESD) rating of 1000V, and an operating temperature range of -40°C to +125°C. The device also has a thermal resistance of 110°C/W and a power dissipation of 1.13W at 25°C.
The pin configuration of the NUD4001 is as follows:
| Pin | Symbol | Function |
|-----|--------|----------|
| 1 | Vin | Power input |
| 2 | Boost | Can drive an external transistor; can be left unconnected if not used |
| 3 | Rext | Connects a resistor to Vin to set the output current |
| 4 | GND | Ground |
| 5–8 | Lout | Four parallel pins connected to the anode of the LED |
The relationship between the output current (Iout) and the external resistor (Rext) is shown in the graph. At a junction temperature (Tj) of 25°C, the formula Rext = Vsense / ILED can be used. For example, if ILED is 350mA and Vsense is 0.7V, then Rext = 2.0Ω.
As the junction temperature increases, the output current decreases. This is illustrated in a graph showing how the output current varies with Tj. The maximum power dissipation (PD) is 1.13W at 25°C, but it decreases as the ambient temperature (TA) rises. For instance, at TA = 85°C, PD must be reduced to 0.6W. If the calculated PD exceeds this value, steps such as reducing the input voltage, increasing the number of LEDs, or using multiple NUD4001 devices in parallel may be necessary.
An example application involves driving three 1W LEDs with a 350mA current using a 12V battery. The calculation steps include determining Rext, VLED, Vdrop, PD_drive, PD_control, and PD_total. In this case, the total power consumption was found to be well within the allowable limit.
The NUD4001 is also used in various applications, including automotive brake lights, car headlights, and PWM-controlled brightness circuits. Each application includes specific circuit diagrams and explanations of component roles.
In contrast, the NUD4011 offers a lower maximum output current (up to 70mA), a higher input voltage (up to 200V), and a higher output voltage (up to 198V). However, it has a lower ESD rating (500V) and a different pin configuration. The fourth pin of the NUD4011 is labeled "PWM" instead of "GND," which changes its functionality depending on the output voltage. When the output voltage is above 48V, the PWM pin connects to the LED's anode; otherwise, it connects to ground.
The NUD4011 is used in AC-powered LED circuits, where the AC input is rectified and filtered before being supplied to the IC. These circuits often include a PWM signal for dimming control. The design ensures that the current through the NUD4011 flows into the LED, improving efficiency.
Both the NUD4001 and NUD4011 provide flexible and reliable solutions for LED lighting systems, with detailed datasheets and application notes available for further guidance.
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