 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
CAT4238 Datasheet(PDF) 4 Page - Catalyst Semiconductor |
|
||||||||||||||||||||||||||||||
CAT4238 Datasheet(HTML) 4 Page - Catalyst Semiconductor |
|
|
4 / 14 page  CAT4238 Doc. No. 5019 Rev. A 4 © 2006 Catalyst Semiconductor, Inc. Characteristics subject to change without notice DEVICE OPERATION The CAT4238 is a fixed frequency (1MHz), low noise, inductive boost converter that provides a constant current with excellent line and load regulation. The device uses a high-voltage CMOS power switch between the SW pin and ground to energize the inductor. When the switch is turned off, the stored energy in the inductor is released into the load via the Schottky diode. The on/off duty cycle of the power switch is internally adjusted and controlled to maintain a constant regulated voltage of 0.3V across the feedback resistor connected to the feedback pin (FB). The value of the resistor sets the LED current accordingly (0.3V/R1). During the initial power-up stage, the duty cycle of the internal power switch is limited to prevent excessive in-rush currents and thereby provide a “soft-start” mode of operation. While operating from a Li-Ion battery, the device can deliver 20mA of load current into a string of up to 10 white LEDs. For higher input voltages, the LED current can be increased. In the event of an “Open LED” fault condition, where the feedback control loop becomes open, the output voltage will continue to increase. Once this voltage exceeds 40V, an internal protection circuit will become active and place the device into a very low power safe operating mode where only a small amount of power is transferred to the output. This is achieved by pulsing the switch once every 6μs and keeping it on for about 1μs. Thermal overload protection circuitry has been included to prevent the device from operating at unsafe junction temperatures above 150ºC. In the event of a thermal overload condition the device will automatically shutdown and wait till the junction temperatures cools to 130ºC before normal operation is resumed. Light Load Operation Under light load condition (under 2mA) and with input voltage above 5.0V, the CAT4238 driving 10 LEDs, the driver starts pulse skipping. Although the LED current remains well regulated, some lower frequency ripple may appear. Switching Waveform VIN = 5.0V, ILED = 1.5mA |
Similar Part No. - CAT4238 |
|
Similar Description - CAT4238 |
|
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.COM |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
