LTC3783
PWM LED Driver and Boost,
Flyback and SEPIC Controller
U
FEATURES
DESCRIPTIO
The LTC®3783 is a current mode LED driver and boost,
flybackandSEPICcontrollerthatdrivesbothanN-channel
power MOSFET and an N-channel load PWM switch.
When using an external load switch, the PWMIN input not
only drives PWMOUT, but also enables controller GATE
switching and error amplifier operation, allowing the con-
troller to store load current information while PWMIN is
low.Thisfeature(patentpending)providesextremelyfast,
true PWM load switching with no transient overvoltage or
undervoltageissues;LEDdimmingratiosof3000:1canbe
achieved digitally, avoiding the color shift normally asso-
ciated with LED current dimming. The FBP pin allows
analog dimming of load current, further increasing the
effective dimming ratio by 100:1 over PWM alone.
True Color PWMTM Delivers Constant Color with
■
3000:1 Dimming Ratio
■
Fully Integrated Load FET Driver for PWM Dimming
Control of High Power LEDs
■
100:1 Dimming from Analog Inputs
■
Wide FB Voltage Range: 0V to 1.23V
■
Constant Current or Constant Voltage Regulation
■
Low Shutdown Current: IQ = 20µA
■
1% 1.23V Internal Voltage Reference
■
2% RUN Pin Threshold with 100mV Hysteresis
■
Programmable Operating Frequency (20kHz to
1MHz) with One External Resistor
■
Synchronizable to an External Clock Up to 1.3fOSC
■
Internal 7V Low Dropout Voltage Regulator
■
Programmable Output Overvoltage Protection
In applications where output load current must be re-
turned to VIN, optional constant current/constant voltage
regulation controls either output (or input) current or
output voltage and provides a limit for the other. ILIM
provides a 10:1 analog dimming ratio.
■
Programmable Soft-Start
Can be Used in a No RSENSETM Mode for VDS < 36V
■
■
16-Lead DFN and TSSOP Packages
U
APPLICATIO S
For low- to medium-power applications, No RSENSE mode
can utilize the power MOSFET’s on-resistance to eliminate
the current-sense resistor, thereby maximizing efficiency.
■
High Voltage LED Arrays
■
Telecom Power Supplies
■
42V Automotive Systems
■
The IC’s operating frequency can be set with an external
resistor over a 20kHz to 1MHz range and can be synchro-
nized to an external clock using the SYNC pin.
24V Industrial Controls
■
IP Phone Power Supplies
, LTC and LT are registered trademarks of Linear Technology Corporation.
True Color PWM and No R
are trademarks of Linear Technology Corporation.
SENSE
All other trademarks are the property of their respective owners. Patent pending.
The LTC3783 is available in the 16-lead DFN and TSSOP
packages.
U
TYPICAL APPLICATIO
350mA PWM LED Boost Application
Typical Waveforms
V
IN
6V TO 16V
10µF
×2
(< TOTAL V OF LEDs)
F
V
2.2µH
PWMIN
1M
5V/DIV
ZETEX ZLL51000
V
OUT
<25V
LTC3783
RUN
PWMIN OV/FB
PWMOUT
V
OUT
0.2V/DIV
237k
V
IN
AC COUPLED
LED*
STRING
I
TH
SS
I
L
I
LIM
2.5A/DIV
105k
C
OUT
M1
M2
V
GATE
REF
10µF
0.1µF
10µF
FBP
SENSE
I
FBN
FREQ
SYNC
INTV
CC
GND
LED
4.7µF
0.5A/DIV
10k
6k
0.05Ω 12.4k
0.3Ω
3783 TA01b
GND
1µs/DIV
3783 TA01a
M1, M2: SILICONIX Si4470EY *LUMILEDS LHXL-BW02
3783f
1
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