LM3560 Datasheet, PDF(19/42 Page) Texas Instruments – LM3560 Synchronous Boost Flash Driver w/ Dual 1A High-Side Current Sources (2A Total Flash Current)

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LM3560 Datasheet, PDF (19/42 Pages) Texas Instruments – LM3560 Synchronous Boost Flash Driver w/ Dual 1A High-Side Current Sources (2A Total Flash Current)

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FIGURE 8. Message Indicator Timing Diagram

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MESSAGE INDICATOR EXAMPLE 1 (Single Pulse with

Dead Time):

As an example, to set up the message indicator for a 312 ms

ramp-up and ramp-down, 192 ms pulse width, and 1 pulse

followed by a 5s delay. The indicator settings will be as fol-

lows. tR = tF = 312 ms, tWIDTH = 192 ms (tPERIOD = 312 ms x 2

+ 192 ms x 2 = 1016 ms). BLANK# setting will be: 5s/1016

ms x 1 (PERIOD# = 1). Giving a BLANK# setting of 5. The

resulting waveform will appear as:

FIGURE 9. Message Indicator Example 1

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MESSAGE INDICATOR EXAMPLE 2 (Multiple Pulses with

Dead Time):

Another example has the same tR, tF, tPULSE, and tBLANK times

as before, but this time the PERIOD# is set to 3. Now the

tACTIVE time is tPERIOD Ã 3 = 1016 ms Ã 3 = 3048 ms. This

results in a blank time of tBLANK = tACTIVE Ã BLANK# = 3.048s

Ã 5 = 15.24s

FIGURE 10. Message Indicator Example 2

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UPDATING THE MESSAGE INDICATOR

The best way to update the message indicator is to disable

the Message Indicator output via the Enable Register bit [6],

then write the new sequence to the Indicator Register and/or

Indicator Blinking Register, and then re-enable the Message

Indicator. Updating the Indicator Registers while it is active

can lead to long delays between pattern changes. This is es-

pecially true if the PERIOD#, or BLANK# setting is changed

from a high setting to a lower setting.

NTC MODE

Writing a (1) to Configuration Register 1 bit [4] configures the

LEDI/NTC pin for NTC mode. In this mode the indicator cur-

rent source is disabled, and LEDI/NTC becomes the positive

input to the an internal comparator. NTC mode operates as a

LED current interrupt that is triggered when the voltage at

LEDI/NTC goes below 1V.

Two actions can be taken when the NTC comparator is

tripped. With Configuration Register 2 bit [1] set to â0â the NTC

interrupt will force the LED current from Flash mode into Torch

mode. With Configuration Register 2 bit [1] set to â1â, the NTC

interrupt will force the LED current into shutdown.

Whether in NTC force torch or NTC shutdown, in order to re-

enter flash mode after an NTC event, two things must occur.

First, the NTC input must be above the 1V threshold. Sec-

ondly, the Flags Register must be read.

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