LM3554TMXSLASHNOPB datasheet(20/47 Pages) TI1

20 / 47 page

STROBE

TX1/TORCH

Timeout

Duration

Configuration Register 1 bit 7 (TX1/TORCH) = 1

(TX1/TORCH pin is a hardware torch input)

FLASH

TORCH

ILED

LM3554

SNVS549C – JUNE 2009 – REVISED FEBRUARY 2016

www.ti.com

Product Folder Links: LM3554

Submit Documentation Feedback

Feature Description (continued)

Figure 37. TX1/Torch Configured as a Hardware Torch Input

7.3.14 Flags Register and Fault Indicators

The Flags Register (0xD0) contains the Interrupt and fault indicators. Five fault flags are available in the LM3554.

These include a thermal shutdown, an LED failure flag (LEDF) , a Timeout indicator Flag (TO), a LED Thermal

Flag (NTC), and a VIN Monitor Flag. Additionally, two interrupt flag bits TX1 interrupt and TX2 interrupt indicate a

change of state of the TX1/TORCH pin (TX1 mode) and ENVM/TX2 pin (TX2 mode). Reading back a 1 indicates

the TX lines have changed state since the last read of the Flags Register. A read of the Flags Register resets

these bits.

7.3.15 Thermal Shutdown

When the device die temperature reaches 150°C the boost converter shuts down, and the NFET and PFET turn

off. Additionally, all three current sources (LED1, LED2, and LEDI) turn off. When the thermal shutdown

threshold is tripped a 1 is written to bit [1] of the Flag Register (Thermal Shutdown bit). The LM3554 starts up

again when the die temperature falls to below 135°C.

During heavy load conditions when the internal power dissipation in the device causes thermal shutdown, the

device turns off and starts up again after the die temperature cools, resulting in a pulsed on/off operation. The

OVT bit, however, is only written once. To reset the OVT bit pull HWEN low, power down the LM3554, or read

the Flags Register.

7.3.16 LED Fault

The LED Fault flag (bit 2 of the Flags Register) reads back a 1 if the part is active in flash or torch mode and

either LED1 or LED2 experience an open or short condition. An LED open condition is signaled if the OVP

threshold is crossed at OUT while the device is in flash or torch mode. An LED short condition is signaled if the

voltage at LED1 or LED2 goes below 500 mV while the device is in torch or flash mode.

There is a delay of 250 µs before the LEDF flag is valid on a LED short. This is the time from when VLED falls

below the LED short threshold of 500 mV (typical) to when the fault flag is valid. There is a delay of 2 µs from

when the LEDF flag is valid on an LED open. This delay is the time between when the OVP threshold is

triggered and when the fault flag is valid. The LEDF flag can only be reset to 0 by pulling HWEN low, removing

power to the LM3554, or reading the Flags Register.

7.3.17 Flash Timeout

The TO flag (bit [0] of the Flags Register) reads back a 1 if the LM3554 is active in flash mode and the timeout

period expires before the flash pulse is terminated. The flash pulse can be terminated before the timeout period

expires by pulling the STROBE pin low (with STR bit 0), or by writing a 0 to bit 0 or 1 of the Torch Brightness

LM3554 device, reading the Flags Register, or when the next flash pulse is triggered.

LM3554TMX/NOPB Datasheet(PDF) 20 Page - Texas Instruments

LM3554TMX/NOPB Datasheet(HTML) 20 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