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PDF LT3952 Data sheet ( Hoja de datos )
| Número de pieza | LT3952 | |
| Descripción | 60V LED Driver | |
| Fabricantes | Linear | |
| Logotipo |  |
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Features
n 4000:1 True Color PWM™ Dimming
n 4A, 60V Internal DMOS Switch
n Wide Input Voltage Range: 3V to 42V
n 0V to 60V Output Current Regulation with Monitor
n PMOS Switch Driver for PWM and Output Disconnect
n LED Short-Circuit Protection and SHORTLED Flag
n Internal Spread Spectrum Frequency Modulation
n Constant-Current and Constant-Voltage Regulation
n Input Current Limit and Monitor
n Adjustable Frequency: 200kHz to 3MHz,
Synchronizable to an External Clock
n 10:1 Analog Dimming
n Programmable Open-LED Protection with
OPENLED Flag
n Programmable VIN Undervoltage and
Overvoltage Lockout
n Available in a 28-Lead TSSOP Package
Applications
n Display Backlighting
n Automotive and Avionic Lighting
n Accurate Current-Limited Voltage Regulators
LT3952
60V LED Driver with
4A Switch Current
Description
The LT®3952 is a current mode step-up DC/DC converter
with an internal, 60V, 80mΩ DMOS power switch. The
LT3952 is specifically designed to drive high power LEDs
in multiple configurations. It combines input and output
current regulation loops with output voltage regulation to
operate as a flexible current/voltage source.
Programmable switching frequency with optional spread-
spectrum modulation provides EMI reduction, while still
allowing optimization of the external components for
efficiency or component size. The LED current is program-
mable with an external sense resistor, and can be adjusted
from zero to full scale with a voltage at the CTRL pin. The
external PWM input provides LED ON/OFF control and
4000:1 dimming ratio, and an internal PWM generator
delivers the efficiency of PWM dimming to standalone
or I/O limited applications. The LT3952 is available in the
thermally enhanced 28-lead TSSOP package.
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. Patents pending
Typical Application
Short-Circuit Robust Boost LED Driver with Spread Spectrum Frequency Modulation
VIN
7V TO 42V
4.7µF
4A INPUT LIMIT
15mΩ
10µH
VIN IVINP
EN/UVLO
OVLO
IVINN
SW
GND
FB
INTVCC
PWM
ISMON
100k 100k
CTRL
VREF
PWM
ISMON
DIM
LT3952
ISP
ISN
2.2µF
100V
×2
1M
21.5k
57V OPEN LED
REGULATION
750mΩ
OPENLED
SHORTLED
OPENLED
SHORTLED
VC
3.6k IVINCOMP
8.2nF
1µF
TG
INTVCC
SYNC/SPRD
RT SS
90.9k
1MHz
100nF
INTVCC
2.2µF
16 LED (50V)
333mA
3952 TA01a
For more information www.linear.com/LT3952
Efficiency vs Input Voltage
100
90
80
70
60
0
SSFM OFF
SSFM ON
10 20 30 40 50
VIN (V)
3952 TA01b
3952f
1
1 page  
LT3952
Electrical Characteristics
The l denotes the specifications
VIN = IVINP = IVINN = 12V, ISP =
which apply over the full operating temperature range, otherwise specifications are
ISN = 24V, EN/UVLO = PWM = 3V, CTRL = 2V, OVLO = 0V unless otherwise noted
at
TA
=
25°C.
PARAMETER
CONDITIONS
MIN TYP MAX
UNITS
PWM Generator
PWM Pin Pull-Up/Pull-Down Current
PWM = 1.2V, DIM = 0.7V
l5
10 15
µA
PWM Generator Lower Threshold Offset
PWM Generator Upper Threshold Offset
0.2V < DIM < 1.2V
0.2V < DIM < 1.2V
VDIM – 15
VD8I2M5 +
VDIM + 0
VD9I5M0 +
VDIM + 15
V1D0IM75+
mV
mV
PWM Generator Frequency
DIM Pin Output Current
DIM = 0.7V, CPWM = 22nF
DIM = 0.7V
230
l 10 20 30
Hz
µA
TG Duty Cycle Using PWM Generator
DIM = 0.345V
DIM = 0.535V
DIM = 0.725V
DIM = 1.105V
1 10 21
21 30 39
42.5 50 57.5
86 90 94
%
%
%
%
Power Switch
Switch On-Resistance
Switch Leakage Current
ISW = 500mA
SW = 60V, CTRL = 0V
80
2
mΩ
µA
VC to Current Threshold Transconductance
7.5 S
Maximum Power Switch Current Limit
VC = 2V
4 4.5 5
A
Logic Inputs/Outputs
EN/UVLO Disable Threshold
EN/UVLO Falling
l 1.191 1.230 1.269
V
EN/UVLO Threshold Internal Hysteresis
75 mV
EN/UVLO Hysteresis Current
EN/UVLO = 1.25V, Device in Shutdown
EN/UVLO = 1.5V, Device in Operation
2
0 0.4
µA
µA
OVLO Threshold
OVLO Rising
l 1.191 1.230 1.269
V
OVLO Threshold Hysteresis
25 mV
OVLO Input Bias Current
OVLO = 1V
15 100
nA
SHORTLED On-Resistance
SHORTLED Output Low Voltage
SHORTLED Off-State Leakage
ISHORTLED = 1mA
ISHORTLED = 2mA
SHORTLED = 42V
60
0.3
1
Ω
V
µA
OPENLED On-Resistance
OPENLED Output Low Voltage
OPENLED Off-State Leakage
IOPENLED = 1mA
IOPENLED = 2mA
OPENLED = 42V
60
0.3
1
Ω
V
µA
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LT3952E is guaranteed to meet specified performance from
0°C to 125°C. Specifications over the –40°C to 125°C operating junction
temperature range are assured by design, characterization and correlation
with statistical process controls. The LT3952I is guaranteed to meet
performance specifications over the –40°C to 125°C operating junction
temperature range. The LT3952H is guaranteed to meet performance
specifications over the full –40°C to 150°C operating junction temperature
range. High junction temperatures degrade operating lifetimes. Operating
lifetime is derated at junction temperatures greater than 125°C.
Note 3: The LT3952 includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed the maximum operating junction temperature
when overtemperature is active. Continuous operating above the specified
maximum operating junction temperature may impair device reliability.
Note 4: Do not apply external loads to INTVCC.
Note 5: INTVCC is an output and is not meant to be externally driven.
For more information www.linear.com/LT3952
3952f
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5 Page 
LT3952
Pin Functions
CTRL (Pin 17): Output Current Sense Adjust Pin. Sets
voltage regulation threshold across ISP/ISN current sense
resistor. 0.2V to 1.2V range on CTRL adjusts ISP/ISN
threshold from 0mV to 250mV. Tie to VREF or INTVCC for
fixed 250mV threshold. Below 100mV, the CTRL pin acts
as an auxiliary PWM input for combination PWM/analog
dimming on a single pin.
VREF (Pin 18): Reference Voltage Output. This pin outputs
a fixed 2V reference, and supplies up to 100μA for use
in generating a reference voltage for the CTRL pin. When
using a resistor divider, bypass this pin with 100nF to GND.
SS (Pin 19): Soft-Start and Hiccup Control Pin. This pin
modulates oscillator frequency and VC voltage clamp when
it is below 1.7V. A capacitor on the pin sets the soft-start
interval as well as hiccup retry timing in fault mode. The
SS pin has a 25μA pull-up current in normal mode, a 2.5μA
pull-down current in hiccup mode, and a 120Ω pull-down
resistance in shutdown mode. Optional latchoff mode is
set with a 750k pull-up resistor from INTVCC to SS.
PWM (Pin 20): On/Off Control. Used for TG on/off control
and PWM dimming of the LED. Logic low idles regulator
to a lower Q current, makes the TG pin drive to ISP level,
and makes the VC pin high impedance. Logic high turns
on error amplifier, enables switching and TG. The PWM
threshold is 1.2V. Tie to VREF or INTVCC for continuous
operation. The PWM pin also supplies ±10µA switched
current sources to generate a triangle wave on external
capacitor for the PWM dimming generator. It is safe to
overdrive these currents with an external signal.
SHORTLED (Pin 21): Open-Drain Short-Circuit Indicator.
SHORTLED pulls low in the case of an LED overcurrent
fault, and releases during the start-up phase of the next
soft-start cycle. The state of SHORTLED is only updated
when the PWM pin is high. Tie this pin to desired logic
high voltage with an external resistor. The maximum
recommended sink current is 2mA to limit excess power
dissipation. Leave the pin open if unused.
OPENLED (Pin 22): Open-Drain Open-LED Indicator.
OPENLED pulls low when the voltage at the FB pin is
within 45mV of the regulation point and the LED current
has dropped to 10% of the full-scale output. OPENLED
releases when the FB voltage falls below the threshold.
The state of OPENLED is only updated when the PWM
pin is high. Tie this pin to desired logic high voltage with
an external resistor. The maximum recommended sink
current is 2mA to limit excess power dissipation. Leave
the pin open if unused.
IVINCOMP (Pin 23): Auxiliary Current Sense Amplifier
Monitor Output. The voltage at IVINCOMP is a 20× ampli-
fied and buffered version of the IVINP-IVINN differential
voltage, and the VC voltage will be reduced when IVIN-
COMP reaches its 1.2V threshold. A 1µF capacitor to GND
is suggested to filter inductor ripple and compensate the
input current loop. During PWM dimming, the IVINCOMP
pin stores the input current regulation loop value on the
capacitor during the PWM off time. Do not load this pin.
If the input current regulation loop is not used, this pin
may be connected to GND.
ISMON (Pin 24): Output Current Monitor Pin. The volt-
age at ISMON is a 4× amplified and buffered version of
the ISP, ISN differential voltage. During PWM dimming,
the ISMON voltage continues to reflect the instantaneous
output current, falling during the PWM low time.
TG (Pin 25): Top Gate Driver Output. An inverted and level-
shifted version of the PWM input signal. Drives the gate of
an external PMOS transistor between VISP and VISP – 7.5V
to provide load-side on/off control, PWM dimming, and
fault mode disconnect. Leave TG unconnected if not used.
ISN (Pin 26): Output Current Sense Amplifier Negative
Input. Connect this pin to the load side of the output cur-
rent sense resistor. If unused, tie to output voltage.
ISP (Pin 27): Output Current Sense Amplifier Positive
Input. Also serves as the positive rail for the TG driver.
Limit impedance in series with this pin.If unused, tie to
output voltage.
For more information www.linear.com/LT3952
3952f
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11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet LT3952.PDF ] | |
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