ISL97631IHTZ-T7A

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Power management integrated circuits (PMICs) are commonly used in various electronic circuits, and one of the increasingly adopted type of PMICs are LED drivers. An example of a LED driver is the ISL97631IHTZ-T7A, a high current control/constant current LED driver integrated circuit from Intersil Corporation. This article will discuss the application field and working principle of the ISL97631IHTZ-T7A.

Application Field of ISL97631IHTZ-T7A

The ISL97631IHTZ-T7A is designed to drive a single high current LED string in various applications. The ISL97631IHTZ-T7A can control the string current with very high precision and accuracy, without the need of current-sense resistors, while allowing excellent flicker and light-induced transient immunity. The ISL97631IHTZ-T7A can be used in white or RGB LED applications, such as LED lighting and LCD TV backlighting. Since its output current is digitally programmable, it is also suitable for applications where multiple LED strings can be dynamically adjusted for optimal visual performance, as well as for applications requiring LED dimming control.

Figure 1 shows a typical application circuit for driving a single LED string with the ISL97631IHTZ-T7A. The circuit includes a DC/DC converter and a LED driver IC. The DC/DC converter supplies an input voltage to the LED driver IC; the input voltage can be a regulated DC voltage, or an AC voltage rectified to DC. The LED driver IC then uses this input voltage to generate the desired output current for the LED string.

Working Principle of ISL97631IHTZ-T7A

The ISL97631IHTZ-T7A is a current-mode controlled and constant current LED driver. It adjusts its output current to the programmed setting when the voltage across the current sensing terminal (I+/I-) equals the reference voltage on VREF pin. The current then stays constant until a new setting is programed. The programming of the output current is done through an external digital input (DIN pin) that can be an I2C, SPI, or USB interface.

The ISL97631IHTZ-T7A features over-current protection (OCP) and over-temperature protection (OTP) to safeguard the IC itself and the LED string from damage. The OCP monitors the LED string current, and when the LED string current reaches a programmed over-current level, the OCP is triggered, and the LED driver output is shutdown. The OTP monitors the temperature of the IC and the LED string, and when the temperature reaches a critical level, the OTP is triggered, and the LED driver output is shutdown for a certain period of time, until the temperature drops to a safe level.

The ISL97631IHTZ-T7A also offers several additional features such as power-up/down sequencing, adjustable on-board soft-start and current-transient protection. Its on-board power-up/down sequencing allows devices to power-up or power-down in a controlled, sequenced manner to reduce in-rush current and avoid current glitches. The adjustable soft-start prevents in-rush current surges during start-up and enables the device to turn on safely and in a controlled manner. Its built-in current-transient protection ensures that the LED string current is limited during high- or low-side MOSFET switching, enabling reliable and glitch-free operation.

Conclusion

In conclusion, the ISL97631IHTZ-T7A is a high precision and high current control/constant current LED driver integrated circuit from Intersil Corporation. It is used in a wide range of applications, such as LED lighting, LCD TV backlighting and applications requiring LED dynamic dimming control. The ISL97631IHTZ-T7A utilizes current-mode control and constant current control to adjust its output current to the programmed setting. Over-current and over-temperature protection, power-up/down sequencing, adjustable on-board soft-start and current-transient protection are additional features the ISL97631IHTZ-T7A offers to ensure safe and glitch-free operation.

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