LP8551TLXSLASHNOPB datasheet(18/47 Pages) TI1

18 / 47 page

Time

VBOOST

Driver

headroom

VBOOST

LP8551

SNVS673E – APRIL 2010 – REVISED SEPTEMBER 2014

www.ti.com

Figure 13. Boost Adaptive Control Principle with PSPWM

8.3.4 Fault Detection

The LP8551 has fault detection for LED fault, low-battery voltage, overcurrent, and thermal shutdown. The open

drain output pin (FAULT) can be used to indicate occurred fault. The cause for the fault can be read from status

external 5-V line is used to power VLDO pin.

8.3.4.1 LED Fault Detection

With LED fault detection, the voltages across the LED drivers are constantly monitored. LED fault detection is

enabled with <EN_LED_FAULT> EEPROM bit. Shorted or open LED string is detected.

If LED fault is detected:

•

The corresponding LED string is taken out of boost adaptive control loop;

•

Fault bits are set in the fault register to identify whether the fault has been open/short and how many strings

are faulty; and

•

Fault open-drain pin is pulled down.

LED fault sensitivity can be adjusted with <LED_FAULT_THR> EEPROM bit which sets the allowable variation

between LED output voltage to 3.3 V or 5.3 V. Depending on application and how much variation there can be in

normal operation between LED string forward voltages this setting can be adjusted.

Fault is cleared by setting EN pin low or by reading the fault register.

8.3.4.2 Undervoltage Detection

The LP8551 has detection for too-low VIN voltage. Threshold level for the voltage is set with EEPROM register

bits as seen in Table 2:

Table 2.

UVLO[1:0]

THRESHOLD (V)

OFF

2.7V

5.4V

8.1V

When undervoltage is detected, the LED outputs and boost shut down, the FAULT pin is pulled down, and

corresponding fault bit is set in fault register. LEDs and boost starts again when the voltage has increased above

the threshold level. Hysteresis is implemented to threshold level to avoid continuous triggering of fault when

threshold is reached.

Fault is cleared by setting EN pin low or by reading the fault register.

8.3.4.3 Overcurrent Protection

The LP8551 has detection for too-high loading on the boost converter. When overcurrent fault is detected, the

LP8551 shuts down.

Fault is cleared by setting EN pin low or by reading the fault register.

Submit Documentation Feedback

Product Folder Links: LP8551

LP8551TLX/NOPB Datasheet(PDF) 18 Page - Texas Instruments

LP8551TLX/NOPB Datasheet(HTML) 18 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

Datasheet Download

Link URL