LT3795_15 Datasheet, PDF (1/30 Pages) Linear Technology – 110V LED Controller with Spread Spectrum Frequency Modulation

LT3795
110V LED Controller with
Spread Spectrum Frequency Modulation
Features
n _{3000:1 True Color PWM™ Dimming}
n _{Wide Input Voltage Range: 4.5V to 110V}
n _{Input and Output Current Reporting}
n _{PMOS Switch Driver for PWM and Output Disconnect}
n _{Internal Spread Spectrum Frequency Modulation}
n _{±2% Constant Voltage Regulation}
n _{±3% Constant Current Regulation: 0V ≤ VOUT ≤ 110V}
n _{Programmable Input Current limit}
n _{CTRL Inputs Linearly Adjust LED Current}
n _{Adjustable Frequency: 100kHz to 1MHz}
n _{Programmable Open LED Protection with OPENLED Flag}
n _{Short-Circuit Protection and SHORTLED Flag}
n _{Programmable Undervoltage Lockout with Hysteresis}
n _{Soft-Start with Programmable Fault Restart Timer}
n _{C/10 Detection for Battery Charging}
n _{Available in 28-Lead TSSOP Package}
Applications
n _{High Power LED, High Voltage LED}
n _{Battery Chargers}
n _{Accurate Current Limited Voltage Regulators}
Description
The LT^®3795 is a DC/DC controller designed to regulate a
constant-current or constant-voltage and is ideal for driv-
ing LEDs. It drives a low side external N-channel power
MOSFET from an internal regulated 7.7V supply. The fixed
frequency and current mode architecture result in stable
operation over a wide range of supply and output voltages.
Spread spectrum frequency modulation (SSFM) can be
activated for improved electromagnetic compatibility (EMC)
performance. The ground referred voltage FB pin serves as
the input for several LED protection features, and also al-
lows the converter to operate as a constant-voltage source.
The maximum output current is set by an external resistor,
and the output current amplifier has a rail-to-rail common
mode range. The LT3795 also includes a separate input
current sensing amplifier that is used to limit input current.
The TG pin inverts and level shifts the PWM signal to drive
the gate of the external PMOS. The PWM input provides
LED dimming ratios of up to 3000:1, and the CTRL inputs
provide additional analog dimming capability.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and True
Color PWM is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents, including 7199560, 7321203,
7746300.
Typical Application
Short-Circuit Robust Boost LED Driver with Spread Spectrum Frequency Modulation
V_IN
8V TO 60V
110V (TRANSIENT)
63V OVLO
2.2µF
×3
499k
15mΩ 22µH
2.2µF
1M
×4
INTV_CC
OPENLED
SHORTLED
100k
115k
12.4k
PWM
10nF
EN/UVLO V_IN IVINP
OVLO
CTRL1
CTRL2
V_REF
PWM
IVINCOMP
LT3795
IVINN
GATE
SENSE
GND
FB
ISP
RAMP
6.8nF
ISN
100k
OPENLED
SHORTLED
TG
INTV_CC
V_C RT
ISMON
SS
10k
31.6k
250kHz
0.1µF
0.1µF
6.8nF
15mΩ
13.3k
INTV_CC
4.7µF
620mΩ
87V LED
400mA
3795 TA01a
For more information www.linear.com/LT3795
Efficiency vs V_IN
100
95
90
85
80
75
70
0 10 20 30 40 50 60
V_IN (V)
3795 TA01b
3795fb
1