FUNCTIONAL DESCRIPTION
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
will go to the OVP level and then come down to the regulation
level to continue powering the rest of the LED strings.
OTT threshold, the IC will turn off all power sources inside the
IC (LED drivers, boost and internal regulators) until the
temperature falls below the falling OTT threshold. Once it
comes back on, it will operate with the default configuration
(refer to Table 6).
Short LED Protection
If an LED shorted in any of the LED strings, the device will
continue to operate without interruption. However, if the
shorted LED happens to be in the LED string with the highest
forward voltage, the DHC circuit will automatically regulate
the output voltage with respect to the new highest LED
voltage. If more LEDs are shorted in the same LED string, it
may cause excessive power dissipation in the channel which
may cause the OTT circuit to trip which will completely
shutdown the device.
SERIAL INTERFACE CONTROL
The 34844 uses an I2C interface capable of operating in
standard (100 kHz) or fast (400 kHz) modes.
The A0/SEN pin can be used an address select pin to
allow more than 2 devices in the system. The A0/SEN pin
should be held low on all chips expect the one to be
addressed, where it is taken HIGH.
OVER-TEMPERATURE PROTECTION
The 34844 has an on-chip temperature sensor that
measures die temperature. If the IC temperature exceeds the
34844
Analog Integrated Circuit Device Data
Freescale Semiconductor
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