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CAT3614HV2-T2 Datasheet(PDF) 10 Page - ON Semiconductor |
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CAT3614HV2-T2 Datasheet(HTML) 10 Page - ON Semiconductor |
10 / 13 page CAT3614 Doc. No. MD-5035, Rev. C 10 © 2008 SCILLC. All rights reserved. Characteristics subject to change without notice LED Current Setting Figure 1 shows the timing diagram necessary at the EN/DIM input for setting the LED currents. The EN/DIM set up time requires the signal to be held high for 10µs or longer to ensure the initialization of the driver at power-up. Each subsequent pulse on the EN/DIM (300ns to 200µs pulse duration) steps down the LED current from full scale of 31mA to zero with a 1mA resolution. Consecutive pulses should be separated by 300ns or longer. Pulsing beyond the 0mA level restores the current level back to full scale and the cycle repeats. Pulsing frequencies from 5kHz up to 1MHz can be supported during dimming operations. When the EN/DIM is held low for 1.5ms or more, the CAT3614 enters the shutdown mode and draws “zero” current. For applications with three LEDs or less, any unused LED pins should be tied to VOUT, as shown on Figure 3. Protection Mode If an LED becomes open-circuit, the output voltage VOUT is internally limited to about 5.5V. This is to prevent the output pin from exceeding its absolute maximum rating. The driver enters a thermal shutdown mode as soon as the die temperature exceeds about +165ºC. When the device temperature drops down by about 20ºC, the device resumes normal operation. External Components The driver requires a total of four external 1µF ceramic capacitors: two for decoupling input and output, and two for the charge pump. Both capacitor types X5R and X7R are recommended for the LED driver application. In the 1.5x charge pump mode, the input current ripple is kept very low by design, and an input bypass capacitor of 1µF is sufficient. In 1x mode, the device operating in linear mode does not introduce switching noise back onto the supply. Recommended Layout In 1.5x charge pump mode, the driver switches internally at a high frequency of 1MHz. It is recommended to minimize trace length to all four capacitors. A ground plane should cover the area under the driver IC as well as the bypass capacitors. Short connection to ground on capacitors Cin and Cout can be implemented with the use of multiple vias. A copper area matching the TDFN exposed pad (GND) must be connected to the ground plane underneath. The use of multiple vias improves the package heat dissipation. GND VIN LED2 LED3 LED1 LED4 EN/DIM CAT3614 VIN VOUT 1µF 1µF CIN 3V to 5.5V C1- C1+ C2- C2+ 1µF 1µF COUT ENABLE/ DIMMING Figure 3. Three LED Application GND VIN LED2 LED3 LED1 LED4 EN/DIM CAT3614 VIN VOUT 1µF 1µF CIN 3V to 5.5V C1- C1+ C2- C2+ 1µF 1µF COUT Flash LED ENABLE/ DIMMING 120mA Figure 4. Single Flash LED Application |
Similar Part No. - CAT3614HV2-T2 |
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Similar Description - CAT3614HV2-T2 |
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