LM3559TLX National Semiconductor Corporation, LM3559TLX Datasheet - Page 22

• Manufacturer Part Number: LM3559TLX
• Description: Synchronous Boost Flash Driver With Dual 900 Ma High Side Current Sources 1.8a Total Flash Current
• Manufacturer: National Semiconductor Corporation

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FLAGS REGISTER AND FAULT INDICATORS
Eight fault flags are available in the LM3559. These include:
a Flash Timeout, a Thermal Shutdown, an LED Failure Flag
(LEDF), an LED Thermal Flag (NTC), a VIN Monitor Flag, and
a VIN Flash Monitor Flag. Additionally, two LED interrupt flag
bits (TX1 interrupt and TX2 interrupt) are set when the corre-
sponding interrupt is activated. Reading back a "1" indicates
the flagged event has happened. A read of the Flags Register
resets these bits.
FLASH TIMEOUT
The Timeout or (TO flag), (bit [0] of the Flags Register), reads
back a (1) if the LM3559 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 Enable Register
bit [5] = 0), or by writing a (0,0) to bits [1:0] of the Enable
Register. The TO flag is reset to (0) by pulling HWEN low,
removing power to the LM3559, reading the Flags Register,
or when the next Flash pulse is triggered.
FIGURE 13. VLED Monitor Automatic Mode
FIGURE 14. VLED Monitor Manual Mode
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THERMAL SHUTDOWN
When the LM3559’s die temperature reaches +150°C, the
boost converter shuts down, and the NFET and PFET turn off.
Additionally, the active current source (LED1 and/or LED2)
turn off. When the thermal shutdown threshold is tripped a (1)
gets written to bit [1] of the Flags Register (Thermal Shutdown
bit). The LM3559 will not start up again until the die temper-
ature falls to below +135°C and the Flags Register is read
back, or when the device is shut down and started up again.
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 the
OUT pin 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. In
an LED open condition there is a 2 µs deglitch time from when
the output voltage crosses the OVP threshold to when the
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