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LPS4012-102NLC Datasheet(PDF) 10 Page - Skyworks Solutions Inc. |
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LPS4012-102NLC Datasheet(HTML) 10 Page - Skyworks Solutions Inc. |
10 / 17 page AAT1274 1.5A Single Flash LED Driver IC DATA SHEET 10 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 201981A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 21, 2012 Movie mode operation is controlled entirely by the AS2Cwire interface via the EN/SET pin. The FLEN signal will override movie-mode AAT1274 operation when tog- gled to a logic high level. The part will not reenter movie mode when FLEN is brought low. To reenter movie mode after a flash event the part must be cycled off and back on to reset the movie mode and reprogrammed via the AS2Cwire interface to the desired movie mode operation. Over-Voltage Protection (Open Flash LED, Open Circuit) The AAT1274 boost converter output is voltage limited by internal overvoltage protection circuitry to prevent dam- age to the device in the event an open LED or open circuit condition occurs. During an open circuit condition, the output voltage will rise to 5.5V (typical). The OVP circuit disables the boost converter to prevent the output voltage from rising above 5.5V. Once the open circuit condition is removed, normal boost operation will resume. Short Circuit Protection The AAT1274 is equipped with an auto-disable feature for the flash LED channel. After the IC is enabled and system start up commences, a test current of 2-3mA (typical) is forced through the sink channel. The channel will be disabled if the voltage of the SINK pin does not drop to a predetermined threshold. This feature is very convenient for disabling the current sink in the event the flash LED fails to a short circuit. This small test current is added to the set output current in both Flash and movie mode conditions. Over-Temperature Protection The AAT1274 has internal thermal protection circuitry to disable the device if the internal power dissipation exceeds a preset thermal limit. The junction over-temperature threshold is 140°C with 15°C of temperature hysteresis. During flash or movie-mode operation, if an environmen- tal condition, flash current sink, or the boost converter causes the internal die temperature to rise above 140°C, the boost converter will be shut down. The boost con- verter output operation will automatically recover when the over-temperature fault condition is removed. Application Information Flash Mode LED Current Flash sink current can be programmed up to a maximum of 1.5A. The maximum flash current is set by the RSET resistor. For the desired flash current, the resistor value can be calculated using the following equation: 162k Ω × A R SET 162k Ω 107k Ω I FL = = = 1.5A A flash event is initiated by asserting the FLEN pin. A flash event is automatically terminated when FLEN is deasserted. Any time that the FLINH pin is asserted, the default movie-mode current level will appear at FL chan- nel. The default movie mode current level will be main- tained on FL as long as the FLINH and FLEN pins are asserted. In addition to setting the flash current via RSET, the flash current can be changed after FLEN is asserted by programming the movie mode current register with 16 different steps. AS2Cwire Control of Movie Mode Operation In the AAT1274 control of the movie mode operation is managed by the Advanced Simple Serial Control (AS2Cwire) interface. AS2Cwire relies on the number of rising edges of the EN/SET pin to address and load internal data reg- isters. Referring to Table 1: Address 0 controls the movie mode (MM) current level as a percentage of the maximum movie mode current level. Address 3 sets the maximum possible current for movie mode operation. The maximum movie mode current is set as a fraction of the flash current with a peak value of 1/2 and default value of 1/7.3. The last column in Table 1 shows the default values for each of the address registers. |
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