KIT34844AEPEVBE Freescale Semiconductor, KIT34844AEPEVBE Datasheet - Page 19

• Manufacturer Part Number: KIT34844AEPEVBE
• Description: LED Lighting Development Kits IC, 10 CHANNEL LED BACKLIGHT
• Manufacturer: Freescale Semiconductor

Specifications of KIT34844AEPEVBE

• Supply Voltage: 12 V
• Supply Current: 2 uA
• For Use With/related Products: 34844A
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

required, then one 100 kohm resistor must be placed from
each channel to a diode (D2) connected to VDC2. The
resistor will provide a pull up voltage to the disconnected
channels so that they do not interfere with the DHC circuit.
The diode (D2) ensures that when the connected channels
are in PWM off state the LED strings do no conduct current
to VDC2. (See
that the failure is because of t an over-current in the Boost.
releasing the part from the over-current condition and then
shutdown the part (Refer to
Figure 7. Resistor/Diode placement for multiple open
For applications where multiple failure detection is
If the fail pin cannot be cleared by software then it indicates
Since this is a critical failure the only way to clear it is by
FUNCTIONAL DESCRIPTION
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
19
34844
Figure 6. Single Channel Disconnect Circuit.
Figure
circuit detection
7)
Table
5)
be reset by removing the failure and re-enabling the device
thru the EN pin.
OPTICAL AND TEMPERATURE CONTROL LOOP
control.
adjusted depending on the temperature of the LEDs.
closed loop backlight control, where the brightness of the
backlight is maintained at a required level by adjusting the
light output, until the desired level is achieved, or with
ambient light control, where the backlight brightness
increases as ambient light increases.
the PIN and NIN pins. Each pin supports a 0-2.048 V input
range which affects the current through the LEDs. The PIN
pin increases current as the voltage rises from 0-2.048 V.
The NIN pin reduces current as the voltage rises from 0-
2.048 V.
pin if the part is configured to use PIN+NIN control loop
functionality, the 50 mA maximum current is achieved at the
higher allowed level of PIN/NIN pins, ensuring the maximum
current of the LED Drivers are not exceeded.
by I
pins high (>2.2 V) it is called V
maximum current is set to 50 mA by using a 5.1 k resistor at
the ISET pin.
LED FAILURE PROTECTION
Open LED Protection
that channel will be pulled close to zero, which will cause the
channel to be disabled. As a result, the boost output voltage
will go to the OVP level and then come down to the regulation
level to continue powering the rest of the LED strings.
Short LED Protection
continue to operate without interruption. However, if the
If I
The 34844 supports both optical and temperature loop
For temperature loop control, the LED brightness can be
For optical loop control, the 34844 supports both optical
Both temperature and optical loops are supported through
A 10.2 k resistor or higher value must be used at the ISET
The optical and temperature control loop can be disabled
If LED fails open in any of the LED strings, the voltage in
If an LED shorted in any of the LED strings, the device will
2
C setting bits (PINEN & NINEN), or by tying PIN and NIN
Current A
2
C communication is not present, FAIL condition should
Current A
Current A
Current on LED Channel (PIN+NIN mode)
[ ]
Current on LED Channel (NIN mode)
Current on LED Channel (PIN mode)
[ ]
=
(
---------------------------------------------------------------------------------------------------------------------------------- -
2.048 VNIN
[ ]
=
(
------------------------------------------------------------------------------------------------------------ -
=
2.048 VNIN
–
(
--------------------------------------------------------------------------------------- -
VPIN
–
Analog Integrated Circuit Device Data
RSET ohms
RSET ohms
+
×
RSET ohms
SET
VPIN
ICH RegisterValue
)
×
[
[
mode, and the LED Driver
[
[
)
ICH RegisterValue
×
ICH RegisterValue
[
Freescale Semiconductor
]
]
]
×
×
×
[
2
2
2
]
)
]
]
Eqn. 3
Eqn. 4
Eqn. 5