Electronic Components Datasheet Search |
|
A6264KLYTR-T Datasheet(PDF) 7 Page - Allegro MicroSystems |
|
A6264KLYTR-T Datasheet(HTML) 7 Page - Allegro MicroSystems |
7 / 16 page Automotive Stop/Tail LED Array Driver A6264 7 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com in the voltage drop across the LEDs, as a result of the short, the current matching in the A6264 may exceed the specified limits. A short between LEDs in different strings (figure 1D) will not result in a short fault condition. The current through the remain- ing LEDs will remain in regulation and the LEDs will be pro- tected. The current will be summed and shared by the affected strings. Current matching in the strings will then depend on the LED forward voltage differences. Open Load Detection An open load condition is detected when the voltage across the regulator, VIN – VLAx, is less than the open load detect voltage, VOCD, but greater than the output disable threshold voltage, VODIS. When this condition is present for more than the open load detect time, tOCD, then all regulators will be disabled and the fault flag allowed to go high. The regulators will remain disabled until either the power is cycled off and on, or the fault flag, FF, is pulled low. If the power is cycled, the regulators will start in the enabled state, unless disabled by tying the output to VIN, and the open load detection timer will be reset. If the open load is still present the regulators will again be disabled after the open load detect time. Pulling the fault flag low will override the open load fault action and all enabled regulators will be switched on. This state will be maintained while the fault flag is held low. If the fault flag is allowed to go high the A6264 will return to the open load fault condition and will disable all regulators. Each of the four regulators includes a limiter to ensure that the output voltage will not rise higher than the output disable threshold voltage below VIN when driven by the regulator. This means that the voltage across the regulator will not be less than the output disable voltage, unless it is forced by connecting the LAx pin to VIN. However if a load becomes disconnected, the regulator will pull the LAx pin up to the limit, which will ensure that the voltage across the regulator, VIN – VLAx, is less than the open load detect voltage, VOCD . Note that an open load may also be detected if the sum of the for- ward voltages of the LEDs in a string is close to or greater than the supply voltage on VIN. Temperature Monitor A temperature monitor function, included in the A6264, reduces the LED current as the silicon junction temperature of the A6264 increases (see figure 2). By mounting the A6264 on the same thermal substrate as the LEDs, this feature can also be used to limit the dissipation of the LEDs. As the junction temperature of the A6264 increases, the regulated current level is reduced, reducing the dissipated power in the A6264 and in the LEDs. The current is reduced from the 100% level at typically 4% per degree Celsius until the point at which the current drops to 25% of the full value, defined at TJL. Above this temperature the current will continue to reduce at a lower rate until the temperature reaches the overtemperature shutdown threshold temperature, TJF. The temperature at which this effect begins is defined as the thermal monitor activation temperature, TJM, and is specified, in the characteristics table, at the 90% cur- rent level. In extreme cases, if the chip temperature exceeds the overtem- perature limit, TJF, all regulators will be disabled. The tempera- ture will continue to be monitored and the regulators re-activated when the temperature drops below the threshold provided by the specified hysteresis. Note that it is possible for the A6264 to transition rapidly between thermal shutdown and normal operation. This can hap- pen if the thermal mass attached to the exposed thermal pad is small and TJM is increased to close to the shutdown temperature. The period of oscillation will depend on TJM, the dissipated power, the thermal mass of any heatsink present, and the ambient temperature. 100 80 60 40 20 0 TJM TJL TJF 90 25 70 90 110 Junction Temperature, TJ (°C) 130 150 170 Figure 2. Temperature monitor current reduction. |
Similar Part No. - A6264KLYTR-T |
|
Similar Description - A6264KLYTR-T |
|
|
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 |