LM3560 Datasheet, PDF (22/42 Pages) Texas Instruments – LM3560 Synchronous Boost Flash Driver w/ Dual 1A High-Side Current Sources (2A Total Flash Current)

FIGURE 14. VIN Flash Monitor Example
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LED VOLTAGE MONITOR
The LM3560 includes a 4-bit ADC which monitors the LED
forward voltage (VLED) and stores the digitized value in bits
[3:0] of the VLED Monitor Register. The highest voltage of
VLED1 or VLED2 is automatically sensed, and that becomes
the sample point for the ADC. Bit 5, the ADC shutdown bit,
enables/disables the ADC with the default state set to enable
(bit [5] = 0).
AUTOMATIC CONVERSION MODE
With the ADC enabled, a conversion is performed each time
a flash pulse is started. When a flash pulse is started bit [6] of
the VLED Monitor Register (End of Conversion bit) is auto-
matically written with a ‘0’. At the end of the conversion, bit [6]
will go high signaling that the VLED data is valid. A readback
of the VLED Monitor register will clear bit [6]. Figure 15 details
the VLED Monitor Automatic Conversion.
MANUAL CONVERSION MODE
The VLED Monitor can be set up for manual conversion mode
by setting bit [4] of the VLED Monitor Register to '1'. When
this bit is set high the EOC bit (bit [6]) goes low, and a con-
version is performed. When the conversion is complete, the
EOC bit goes high again. Subsequent conversions are per-
formed in manual mode by reading back the VLED Monitor
register. This resets the EOC bit and starts another conver-
sion (see Figure 16).
ADC DELAY
The ADC Delay register provides for a programmable delay
from 250 µs to 8ms in steps of 250 µs. This delay is the delay
from when the EOC bit goes low to when the VLED Monitor
samples the LED voltage. In Automatic Mode the EOC bit
goes low when the Flash LED current hits its target. In Manual
mode the EOC bit goes low at the end of a readback of the
VLED Monitor Register (or when the manual mode bit (bit 4)
is re-written with a 1).
FIGURE 15. VLED Monitor Automatic Mode
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