 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
ISL78100 Datasheet(PDF) 12 Page - Intersil Corporation |
|
||||||||||||||||||||||||||||||
ISL78100 Datasheet(HTML) 12 Page - Intersil Corporation |
|
|
12 / 19 page  12 FN6626.0 December 17, 2007 . Bias Current Dimming Current in the LED load is determined by the value of the feedback resistor and the target feedback regulation voltage as shown in Equation 1: With MODE tied to VDC, voltage across the feedback resistor is set by VLEVEL as shown in Equation 2: The value of VFB should be limited to between 50mV and 450mV for linear operation. For minimum light output, VFB may be set below 50mV. With MODE tied to GND, voltage across the feedback resistor is set at ~400mV via an internal reference. In either operating mode, if LED temperature control is enabled, the value of VFB will be reduced when maximum LED temperature is exceeded. Input Overvoltage For automotive applications, an external high voltage NFET driven by the FAULT pin disconnects the device from the input supply in response to voltage spikes on the input supply. During start-up, an internal charge pump drives the FAULT pin above the input voltage, ensuring the NFET is fully enhanced and powering up the device. In normal operation, the switching node of the boost regulator or the floating supply of the buck regulator is used to pump FAULT above VIN. On detection of an overvoltage, the FAULT pin is discharged to GND. The gate to source voltage of the NDMOS is internally limited to ±15V to prevent voltage stress. Fault Protection The external NFET is also used as a fault protection switch, disconnecting the input supply if a fault occurs for more than 50ms. The system monitors feedback voltage regulation, output overvoltage and input overvoltage. For applications not requiring input voltage or fault protection, connect VBAT and VIN directly together. All faults except input supply overvoltage latch the ISL78100 into an off-state that can be cleared by either power cycling the input supply or the EN/PWM pin. Connecting the TMAX pin to VDC disables the fault latch function (LED over-temperature control is also disabled). Output Overvoltage Protection (OVP) If the FB pin is shorted to ground or an LED fails open circuit, output voltage in BOOST mode can increase to potentially damaging voltages. An optional overvoltage protection circuit can be enabled by connection of the OVP pin to the output voltage. The device will stop switching if the output voltage exceeds OVPH and re-start when the output voltage falls below OVPL. During sustained OVP fault conditions, VOUT will saw-tooth between the upper and lower threshold voltages at a frequency determined by the magnitude of current available to discharge the output capacitor and the value of output capacitor used. The OVP threshold can be set to a lower value by using an external zener diode and resistor, as shown in Figure 33. R1 should be adjusted to minimize offset in the FB voltage due to FB pin input current. A value of 100 Ω is recommended. FIGURE 31. OPERATION WITH ENL CONTROLLED FET FIGURE 32. OPERATION WITH NO ENL CONTROLLED FET I LED V FB R SENSE ----------------------- = (EQ. 1) V FB V LEVEL 5 ---------------------- = (EQ. 2) ISL78100 |
Similar Part No. - ISL78100 |
|
Similar Description - ISL78100 |
|
|
|
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
