LT3519IMS-1#TRPBF Linear Technology, LT3519IMS-1#TRPBF Datasheet - Page 9

• Manufacturer Part Number: LT3519IMS-1#TRPBF
• Description: LED DRIVER WITH INTEGRATED SCHOT
• Manufacturer: Linear Technology
• Type: High Power, Constant Currentr

Specifications of LT3519IMS-1#TRPBF

• Constant Current: Yes
• Constant Voltage: Yes
• Topology: PWM, SEPIC, Step-Down (Buck), Step-Up (Boost)
• Number Of Outputs: 1
• Internal Driver: Yes
• Type - Primary: Automotive
• Frequency: 800kHz ~ 1.10MHz
• Voltage - Supply: 3 V ~ 30 V
• Mounting Type: Surface Mount
• Package / Case: 16-MSOP
• Operating Temperature: -40°C ~ 125°C
• Current - Output / Channel: 750mA
• Internal Switch(s): Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Efficiency: -

APPLICATIONS INFORMATION
Dimming Control
There are two methods to control the current source for
dimming using the LT3519/LT3519-1/LT3519-2. The fi rst
method, PWM Dimming, uses the PWM pin to modulate
the current source between zero and full current to achieve
a precisely programmed average current. To make this
method of current control more accurate, the switch de-
mand current is stored on the internal V
quiescent phase when PWM is low. This feature minimizes
recovery time when the PWM signal goes high. To obtain
best PWM dimming performance, it is necessary to use
an external disconnect switch in the LED current path to
prevent the output capacitor from discharging during the
PWM signal low phase. For best product of analog and PWM
dimming, the minimum PWM low or high time should be at
least six switching cycles (3μs for f
PWM period is determined by the system. The maximum
PWM dimming ratio (PWM
the maximum PWM period (t
pulse width (t
Example:
The second method of dimming control, Analog Dim-
ming, uses the CTRL pin to linearly adjust the current
sense threshold during the PWM high state. When the
CTRL pin voltage is less than 1V but more than 100mV,
the LED current is:
t
PWM
PWM
I
MAX
LED
=
= 9ms, t
RATIO
RATIO
V
CTRL
4 • R
MIN
=
=
MIN
– 100mV
9ms
t
SENSE
) as follows:
t
3µs
MAX
MIN
= 3μs (f
= 3000:1
RATIO
SW
MAX
= 2MHz)
) and the minimum PWM
) can be calculated from
SW
= 2MHz). Maximum
C
node during the
When V
to be:
When V
LED current is in the nonlinear region of V
Threshold vs V
Characteristics.
The LED current programming feature through the CTRL
pin possibly increases the total dimming range by a factor
of ten. In order to have the accurate LED current, precision
resistors are preferred (1% is recommended). The CTRL
pin should not be left open. Tie to V
Programming Output Voltage (Constant Voltage
Regulation) or Open LED/Overvoltage Threshold
For a boost application, the output voltage can be set by
selecting the values of R1 and R2 (see Figure 1) according
to the following equation:
I
V
LED
LT3519/LT3519-1/LT3519-2
OUT
Figure 1. FB Resistor Divider for Boost LED Driver
CTRL
=
CTRL
=
R
250mV
⎛
⎜
⎝
SENSE
R2
R1
is higher than 1.2V, the LED current is clamped
is more than 1V but less than 1.2V, the
CTRL
+1
⎞
⎟ • 1.22V
⎠
as shown in the Typical Performance
LT3519-1/
LT3519-2
LT3519/
FB
V
OUT
R1
R2
3519 F01
REF
if not used.
ISP
-V
3519fa
9
ISN