Electronic Components Datasheet Search |
|
SC619 Datasheet(PDF) 10 Page - Semtech Corporation |
|
SC619 Datasheet(HTML) 10 Page - Semtech Corporation |
10 / 13 page SC619 10 Applications Information (continued) that the voltage on the ISET pin can no longer be main- tained. After a 32ms delay (included to prevent false transitions) the charge pump will convert to 2x mode. After the charge pump switches from 1x mode to 2x mode, the device remains in 2x mode until the part is turned off. If the part is re-enabled in spotlight mode, it will begin operation in 1x mode and determine the appropriate mode of operation as previously described. Protection Circuitry The SC619 provides several protection features to safe- guard the device from catastrophic failures. These features include: Input Over-Voltage Protection (IOVP) Output Over-Voltage Protection (OVP) Over-Temperature Protection (OTP) Over-Current Protection (OCP) Short-Circuit Current Protection (SCCP) Input Over-Voltage Protection IOVP is included to prevent operation at high input volt- ages that could damage the device. The IOVP circuit senses the input voltage and determines when the supply exceeds 6V. Hysteresis is included in this circuit to avoid chattering between states. When the voltage rises above this threshold, the device is disabled until the input voltage drops to a level within the specified range. Output Over-Voltage Protection Output OVP prevents the SC619 from generating an output voltage that could damage other devices con- nected to it such as load LEDs and bypass capacitors. When the output voltage exceeds 5.5V, the OVP circuit disables the charge pump until the voltage decreases to a level within the acceptable range. This circuit allows the device to drive LEDs with high forward voltages at a reduced level without exceeding the output voltage limits specified for the device. Over-Temperature Protection The OTP circuit prevents the device from overheating and experiencing a catastrophic failure. When the junction temperature exceeds 150°C the device is disabled. It remains disabled until the junction temperature drops below this threshold. Hysteresis is included to prevent toggling between modes. • • • • • Over-Current Protection When the SC619 is in 2x mode, the input current will be approximately double the required output. When the steady-state load requires the maximum current avail- able in 2x mode, the OCP circuit prevents the device from overheating from excessive power dissipation. This feature protects the device when in 1x mode. The current limit is set lower in the 1x mode due to lower current requirements. Short-Circuit Current Protection SSCP is provided to limit the current that can be sourced when the output is shorted to ground. When a short circuit forces V OUT to drop below 2V, the SCCP detects the condition and limits the output current. Resistor Selection The ISET resistor selection is critical in generating the correct current. The value can be chosen to set the spot- light mode current or the flash mode current, and the two current settings are dependent on the same resistor. It is recommended that the resistor be selected to match the desired LED current for flash mode. This allows the designer to set the SC619’s maximum current and select the resistor package size necessary for the power dissi- pation required in flash mode. The typical application uses a 0.5Ω resistor to set a flash mode current of 500mA and spotlight mode current of 100mA. A high precision resistor should be used to ensure the specified accuracy for LED current. To avoid malfunction of the charge pump, it is recom- mended that the resistance seen at the ISET pin remain constant while the device is active (flash or spotlight mode). Changing the resistance value or the load current while the device is active could cause instability. Capacitor Selection The SC619 is designed to use low-ESR ceramic capacitors for the input and output bypass capacitors as well as the charge pump bucket capacitors. Ideal performance is achieved when C1 is exactly equal to C2. It is recom- mended that X5R or X7R ceramic capacitors be used for best performance. |
Similar Part No. - SC619_08 |
|
Similar Description - SC619_08 |
|
|
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 |