KIT34844AEPEVBE Freescale Semiconductor, KIT34844AEPEVBE Datasheet - Page 45

• 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

BOOST
synchronous mode and integrates a 2.5 A FET. An integrated
sense circuit is used to sense the voltage at the LED current
mirror inputs and automatically sets the boost output voltage
(DHC) to the minimum voltage needed to keep all LEDs
biased with the required current. The DHC is designed to
operate for pulse widths > 400 ns in the LED drivers.
circuit will not operate and the voltage across the LED drivers
will increase to a value given by the OVP minus the total LED
voltage in the LED string. Therefore it is imperative to select
the proper OVP level to minimize power dissipation.
(BST[1:0]) only after the IC is powered up and before the
boost circuit is turned ON for the first time (PWM pin low to
high). This sequence avoids boost frequency to be changed
inadvertently during operation. The first I
wait for 5.0 ms after the part is turned ON, in order to allow
sufficient time for the device power up sequence to be
completed.
frequency thru I2C:
amplifier with indefinite hold time capability, to enable
immediate LED on cycles after extended off times. During
extended off times, the external LEDs cool down from their
Analog Integrated Circuit Device Data
Freescale Semiconductor
1. Take PWM pin low
2. Disable the part by software( EN bit = low)
3. Write the new Boost frequency data (BST[1:0])
4. Enable the part by software (EN bit = high)
5. Reconfigure all registers
6. Take PWM pin High
The integrated boost converter operates in non-
If the pulse widths are shorter than specified, the DHC
The user can program the boost frequency by I
Please follow this sequence in order to change the Boost
The boost controller has an integral track and hold
Table 12. Operation Current Consumption Modes
SM Bus
Manual
MODE
I
2
C
EN Pin
High
High
High
Low
Low
Low
Low
Low
2
C command has to
SCK/SDA Pins
Low (> 27 ms)
Active
Active
Low
Low
X
X
X
2
C
I
2
C Bit Command
CLRI2C bit = 0
CLRI2C bit = 0
CLRI2C bit = 0
SETI2C bit = 1
SETI2C bit = 1
SETI2C bit = 1
normal quiescent operating temperature and thereby
experience a forward voltage change, typically an increase in
the forward voltage. This change can be significant for
applications with a large number of series LEDs in a string
operating at high current. If the boost controller did not track
this increased change, the potential on the LED drivers would
saturate for a few cycles once the LED channels are re-
enabled.
HARDWARE AND SOFTWARE OVP:
maximum LED voltage over the whole temperature range. A
good practice is to set it 5.0 V or so above the max LED
voltage.
the I
present, the OVP can be controlled either by a resistor divider
connected from VOUT to GND, with its mid point tied to the
A0/SEN pin, or by a zener diode from VOUT to the A0/SEN
pin (threshold = 6.5 V). During an OVP condition, the output
voltage will go to the OVP level, which is programmed via the
I
by a zener diode. The formulas to calculate the hardware
OVP using any of the two methods are as follows:
EN bit = 0
EN bit = 0
EN bit = 1
EN bit = 0
EN bit = 0
EN bit = 1
2
C interface or settled by a resistor divider on A0/SEN pin, or
A0/SEN
The OVP value should be set to a higher value than the
The OVP can be set from 11 to 62 V, ~4.0 V spaced, using
N/A
N/A
OVP = 6.5 V [(R
2
C interface (OVP Register). If the I
Method 1
V
OUT
R LOWER
R UPPER
UPPER
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
Current Consumption
/ R
LOWER
I
2
C Low Power
Operational
Operational
(Shutdown)
Operational
Shutdown
Shutdown
) + 1] + (100E-6 x R
Mode
Sleep
Sleep
FUNCTIONAL DESCRIPTION
A0/SEN
UPPER
2
C capability is not
OVP = V
PWM pin = Low
V
Method 2
OUT
)
Part Doesn’t
Comments
Wake-up
ZENER2
V ZENER2
+ 6.5 V
34844A
45