From automotive headlights to cab backlight control panels, LED technology is very common in the automotive industry. Due to the fixed form factor, some automotive LED applications such as scintillator signals are subject to severe restrictions. Therefore, a simple device with a smaller number of pins and a smaller size is required. However, since these systems are still connected to the car's battery, they must be able to handle higher voltages to withstand load dumping. Finding a buck converter with 40V voltage processing capability and good performance and small size is not an easy task. The LMR14006 is a new device in the SIMPLE SWITCHER® family of buck converters that is ideal for scintillator/turn signal applications with rated voltages and currents of 40V and 600mA respectively.
Traditional LED drivers are more suitable for LED applications than voltage regulators because they enable higher turn-on and turn-off rates, which require minimal soft-start time and are very useful in devices using buck topologies. Less or no output capacitors at all. The higher opening and closing rates dynamically reduce the current flowing through the LEDs without the human eye being aware of the opening and closing operations. However, in order for the LED to flash, the user will have to turn the power on and off at a relatively low frequency, requiring a regulator with a relatively long soft-start time.
Voltage regulators such as the LMR14006 operate in peak current mode. Due to the rigorous electromagnetic interference (EMI) requirements of automotive designs, frequency-fixed DC/DC regulators make EMI migration easier. The LMR14006 features a 2.1MHz switching frequency option, which allows for smaller component sizes and helps keep switching noise out of the AM band. The LMR14006 also has a very low bill of materials (BOM) quantity, which simplifies its design.
The LMR14006 has a SHDN pin. When this pin is pulled low, the device is disabled and the device is enabled when pulled up to above 2.1V. To make the LED flash, you only need to input a pulse waveform of the desired threshold to the SHDN pin. You can also achieve the same effect with the VIN pin. However, since the VIN pin is the power supply input to the regulator, switching the VIN pin means that the input current to the IC is also turned on and off. Due to the size limitations of the scintillator, this can cause problems when the board layout is not optimal, such as a large voltage spike on the input. Keeping large spikes on the input can cause damage to the IC and can affect the stability of the device's normal operation; suppressing these spikes may require additional circuitry. At the same time, there is no large current on the SHDN pin, and the on/off switching of this pin does not cause any problems related to voltage spikes. Figure 1 shows the LMR14006 in an LED scintillator application.
Figure 1: LMR14006 as an LED scintillator.
The LRS14006's RSNS resistor and feedback reference voltage control the current flowing through the LED. The LMR14006 has a reference voltage of 765mV, which is much lower than the voltage reference of conventional voltage regulators. Equation 1 represents the power dissipation in the sense resistor:
(1)
Therefore, a lower reference voltage will result in lower power dissipation in the sense resistor and ultimately higher efficiency.
Therefore, for simple LED scintillator applications, the SIMPLE SWITCHER buck regulator with low pin count and low BOM count is more advantageous. Devices such as the LMR14006 and LMR16006 are small, efficient, and have a low component count. If you need a device that meets AEC-Q100 requirements, the LMR16006Y-Q1 is an alternative to the LMR14006 pin and footprint.
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Original link:
https://e2e.TI.com/blogs_/b/behind_the_wheel/archive/2015/09/04/automotive-led-blinkers-made-simple
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