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LP8866S-Q1 Datasheet(PDF) 34 Page - Texas Instruments |
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LP8866S-Q1 Datasheet(HTML) 34 Page - Texas Instruments |
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34 / 82 page  7.3.9.2.5 FSET Resistor Missing Faults (FSET) The FSET resistor missing or invalid for both BOOST_FSET and PWM_FSET is detected if any one of them is not assembled or not a valid value as requested during the initialization. LP8866S-Q1 defaults the switching frequency of boost to 400 kHz if BOOST_FSET resistor is missing or invalid, or PWM dimming frequency to 305 Hz if PWM_FSET resistor is missing or invalid. The FSET_STATUS fault bit is set in the BOOST_FAULT_STATUS register. The FSET resistor missing or invalid fault is not monitored after initialization, so that the LP8866S-Q1 device operates at the boost switching frequency and the PWM dimming frequency determined during initialization even though the FSET resistor is missing or invalid after initialization. 7.3.9.2.6 ISET Resistor Out of Range Faults (ISET) If the ISET pin resistor is shorted to GND during normal operation, the maximum current for each LED channel can be calculated in Equation 20 : § · u ¨ ¸ © ¹ LED_ISET_FAULT LED _ LIMIT LED_CURRENT[11:0] I = I 4095 (20) where • ILED_LIMIT = 280 mA LED_CURRENT[11:0] register will be automatically modified to 1/4 of latest programmed data. if it is not programmed after device enabling, the default value of LED_CURRENT[11:0] register is 0xFFF and automatically modified to 0x3FF after the fault occurs. If ISET pin voltage returns back to above 1.1 V, the LED_CURRENT[11:0] register data automatically returns to latest programmed data. The ISET_STATUS fault bit will be set in the BOOST_FAULT_STATUS register and the INT pin is triggered. 7.3.9.2.7 Thermal Shutdown Faults (TSD) If the die temperature of LP8866S-Q1 reaches the thermal shutdown threshold TSD, the boost, power-line FET, and LED outputs on LP8866S-Q1 shuts down to protect the device from damage. Fault status bit TSD_STATUS bit will be set, and the INT pin will be triggered. The device restarts the power-line FET, the boost, and LED outputs when temperature drops by TSD_HYS amount. 7.3.9.3 LED Faults 7.3.9.3.1 Open LED Faults (OPEN_LED) During normal boost operation, boost voltage is raised if any of the used LED outputs falls below the LED_DRV_HEADROOM threshold level. Open LED fault is detected if boost output voltage has reached the maximum and at least one LED output is still below the threshold. The open string is then disconnected from the boost adaptive control loop and its output is disabled. Any LED fault sets the status bit LED_STATUS and an interrupt is generated unless LED interrupt is disabled. The detail of open LED faults can be read from bits OPEN_LED and LEDx_FAULT (x = 1...6). These bits maintain their value until device power-down. But the LED_STATUS bit could be cleared by the interrupt clearing procedure. If a new LED fault is detected, LED_STATUS is set and an interrupt generated again. LP8866S-Q1 SNVSBD1A – AUGUST 2020 – REVISED FEBRUARY 2021 www.ti.com 34 Submit Document Feedback Copyright © 2021 Texas Instruments Incorporated Product Folder Links: LP8866S-Q1 |
Similar Part No. - LP8866S-Q1_V01 |
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Similar Description - LP8866S-Q1_V01 |
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