LTC3206EUF#TR Linear Technology, LTC3206EUF#TR Datasheet - Page 7

• Manufacturer Part Number: LTC3206EUF#TR
• Description: IC LED DRVR WT/RGB BCKLGT 24-QFN
• Manufacturer: Linear Technology
• Type: Backlight, White LED, RGB (I²C Interface)r

Specifications of LTC3206EUF#TR

• Topology: PWM, Step-Up (Boost), Switched Capacitor (Charge Pump)
• Number Of Outputs: 11
• Internal Driver: Yes
• Type - Primary: Backlight
• Type - Secondary: RGB, White LED
• Frequency: 680kHz ~ 1.36MHz
• Voltage - Supply: 2.7 V ~ 4.5 V
• Mounting Type: Surface Mount
• Package / Case: 24-QFN
• Operating Temperature: -40°C ~ 85°C
• Current - Output / Channel: 400mA
• Internal Switch(s): Yes
• Efficiency: 92%
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Voltage - Output: -

OPERATIO
The 1.5x step-up charge pump uses a patented constant
frequency architecture to combine the best efficiency with
the maximum available power at the lowest noise level.
The charge pump of the LTC3206 can be forced to come
on even if no LEDs are programmed for current. Setting bit
A3 in the I
Figure 3).
Soft-Start
To prevent excessive inrush current and supply droop
when switching into step-up mode, the LTC3206 employs
a soft-start feature on its charge pump. The current
available to the CPO pin is increased linearly over a period
of about 400µs.
Charge Pump Strength
When the LTC3206 operates in 1.5x boost mode, the
charge pump can be modeled as a Thevenin-equivalent
circuit to determine the amount of current available from
the effective input voltage, 1.5V
loop output resistance, R
R
switching term, 1/(2f
tances and the non-overlap period of the switching circuit.
However, for a given R
will be directly proportional to the advantage voltage 1.5V
– V
a 3.1V supply. If the LED forward voltage is 3.8V and the
current sources require 100mV, the advantage voltage is
3.1V • 1.5 – 3.8V – 0.1V or 750mV. Notice that if the input
voltage is raised to 3.2V, the advantage voltage jumps to
900mV—a 20% improvement in available strength.
From Figure 1, the available current is given by:
OL
I
CPO
OUT
is dependent on a number of factors including the
. Consider the example of driving white LEDs from
=
1 5 .
2
Figure 1. Equivalent Open-Loop Circuit
C serial port forces the charge pump on (see
V
IN
R
OL
–
U
V
CPO
OSC
OL
+
–
, the amount of current available
OL
• C
1.5V
R
(Figure 1).
OL
FLY
IN
3206 F01
IN
), internal switch resis-
and the effective open-
CPO
+
–
IN
Typical values of R
shown in Figure 2.
I
The LTC3206 communicates with a host (master) using
the standard I
(Figure 4) shows the timing relationship of the signals on
the bus. The two bus lines, SDA and SCL, must be high
when the bus is not in use. External pull-up resistors or
current sources, such as the LTC1694 SMBus accelerator,
are required on these lines. The LTC3206 is a receive-only
(slave) device.
Bus Speed
The I
400kHz. It has built-in timing delays to ensure correct
operation when addressed from an I
device. It also contains input filters designed to suppress
glitches should the bus become corrupted.
START and STOP Conditions
A bus-master signals the beginning of a communication to
a slave device by transmitting a START condition. A
START condition is generated by transitioning SDA from
high to low while SCL is high. When the master has
finished communicating with the slave, it issues a STOP
condition by transitioning SDA from low to high while SCL
is high. The bus is then free for communication with
another I
2
C Interface
2
C port is designed to be operated at speeds of up to
2
2.50
2.25
2.00
1.75
1.50
C device.
Figure 2. Typical R
–40
V
V
C
2
IN
CPO
IN
C 2-wire interface. The Timing Diagram
= 3V
= C
= 4.2V
–15
CPO
OL
= C
TEMPERATURE (°C)
as a function of temperature are
FLY1
10
= C
FLY2
OL
35
vs Temperature
= 1.6µF
2
60
C compliant master
LTC3206
3206 F02
85
7
3206f