ltc3210-1 Linear Technology Corporation, ltc3210-1 Datasheet - Page 11

• Manufacturer Part Number: ltc3210-1
• Description: Main/cam Led Controller With 64-step Brightness Control In 3mm X 3mm Qfn
• Manufacturer: Linear Technology Corporation

OPERATIO
From Figure 2, for 1.5x mode the available current is
given by:
For 2x mode, the available current is given by:
Notice that the advantage voltage in this case is 3.1V • 2
– 3.8V – 0.1V = 2.3V. R
nifi cant overall increase in available current is achieved.
Typical values of R
shown in Figure 3 and Figure 4.
Shutdown Current
In shutdown mode all the circuitry is turned off and the
LTC3210-1 draws a very low current from the V
ply. Furthermore, CPO is weakly connected to V
LTC3210-1 enters shutdown mode when both the ENM
and ENC pins are brought low at 150μs (typ). ENM and
ENC have 250k internal pull down resistors to defi ne the
shutdown state when the drivers are in a high imped-
ance state.
I
I
OUT
OUT
=
=
Figure 3. Typical 1.5x R
( .
(
1 5
2
V
3.8
3.6
3.4
3.2
3.0
2.6
2.4
2.8
BAT
V
–40
BAT
V
V
C2 = C3 = C4 = 2.2μF
R
BAT
CPO
R
U
OL
–
OL
= 3V
= 4.2V
OL
–
V
–15
CPO
V
as a function of temperature are
CPO
OL
TEMPERATURE (˚C)
)
is higher in 2x mode but a sig-
10
)
OL
35
vs Temperature
60
32101 F03
85
BAT
BAT
. The
sup-
Thermal Protection
The LTC3210-1 has built-in overtemperature protection.
At internal die temperatures of around 150°C thermal shut
down will occur. This will disable all of the current sources
and charge pump until the die has cooled by about 15°C.
This thermal cycling will continue until the fault has been
corrected.
Mode Switching
The LTC3210-1 will automatically switch from 1x mode
to 1.5x mode and subsequently to 2x mode whenever a
dropout condition is detected at an LED pin. Dropout occurs
when a current source voltage becomes too low for the
programmed current to be supplied. The time from drop-
out detection to mode switching is typically 0.4ms.
The part is reset back to 1x mode when the part is shut
down (ENM = ENC = Low) or on the falling edge of ENC.
An internal comparator will not allow the main switches to
connect V
CPO pin has decayed to less than or equal to the voltage
at the V
BAT
BAT
Figure 4. Typical 2x R
pin.
4.6
4.4
4.2
4.0
3.8
3.6
3.4
3.2
and CPO in 1x mode until the voltage at the
–40
V
V
C2 = C3 = C4 = 2.2μF
BAT
CPO
= 3V
= 4.8V
–15
TEMPERATURE (˚C)
10
OL
35
vs Temperature
LTC3210-1
60
32101 F04
85
11
32101fb