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PDF LT3965 Data sheet ( Hoja de datos )
| Número de pieza | LT3965 | |
| Descripción | 8-Switch Matrix LED Dimmer | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
n Eight Independent 17V 330mΩ NMOS Switches
n Independent On/Off/Dimming Control of up to 4 LEDs
for Each Switch
n I2C Multidrop Serial Interface with Open LED and
Shorted LED Fault Reporting
n 16 Unique I2C Addresses
n VDD Range: 2.7V to 5.5V and VIN Range: 8V to 60V
n Digital Programmable 256:1 PWM Dimming
n Fade Transition Between PWM Dimming States
n Optional Internal Clock Generator or External Clock
Source for PWM Dimming
n Open LED Overvoltage Protection
n Programmable Open LED and Shorted LED Threshold
n Flicker Free PWM Dimming
APPLICATIONS
n Automotive LED Headlight Clusters
n Large LED Displays
n Automated Camera Flash Equipment
n RGBW Color Mixing Lighting
Electrical Specifications Subject to Change
LT3965
8-Switch Matrix LED
Dimmer
DESCRIPTION
The LT®3965 is an LED bypass switching device for dim-
ming individual LEDs in a string using a common current
source. It features eight individually controlled floating
source N-channel MOSFET switches rated for 17V/330mΩ.
The eight switches can be connected in parallel and/or in
series to bypass current around one or more LEDs in a
string. The LT3965 as a slave uses the I2C serial interface
to communicate with the master. Each of eight channels
can be independently programmed to bypass the LED
string in constant on, constant off, dimming without fade
transition or dimming with fade transition mode. The
LT3965 provides an internal clock generator and also
supports external clock source for PWM dimming. The
LT3965 reports fault conditions for each channel such as
open LED and shorted LED. The four address select pins
allow 16 LT3965 devices to share the I2C bus. The device
is available in a 28-lead TSSOP package
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Matrix LED Dimmer Powered by a Buck Mode LED Driver
750Ω
Q1
Q2
1k
1k M1
VIN 0.5Ω
40V
D4 SKYHOOK
1µF
100V
SKYHOOK
10k
LED+
499k
Q3
EN/UVLO
93.1k
VIN ISP
EN/UVLO
ISN
INTVCC
PWM
PWMOUT
2.2µF
SYNC
VREF
LT3955
VMODE
FB
CTRL
1µF
50V
PGND
GND
GNDK
SW
RT DIM/SS VC
20k
28.7k
375kHz
0.1µF
0.01µF
IN4148 28k
D2 D3
LED+
0.1µF
100V
1µF
500mA
DRN8
SRC8
DRN7
SRC7
DRN6
SRC6
DRN5
SRC5
VIN VDD
LT3965
SDA
SCL
ALERT
EN/UVLO
VCC
0.1µF
10k
10k
5V
10k
SDA
SCL
ALERT
EN/UVLO
VLED
26V
DRN4
SRC4
DRN3
RTCLK
28k
500Hz DIMMING FREQUENCY
SRC3
ADDR1
D1
L1
33µH
DRN2
SRC2
DRN1
ADDR2
ADDR3
ADDR4
L1: WE744066330
D1: DFLS260
D2, D3: CMSD6263S 2 IN 1 PACKAGE
D4, D5: PMEG6010CEH
D5
LED–
SRC1
GND LEDREF
M1: VISHAY Si7309DN
Q1, Q3: ZETEX FMMT 593
Q2: ZETEX FMMT 493
3965 TA01
PRERELEASEFor more information www.linear.com/LT3965
3965p
1
1 page  
LT3965
ELECTRICAL CHARACTERISTICS
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 LT3965E is guaranteed to meet performance specifications
from the 0°C to 125°C junction temperature. Specifications over the –40°C
to 125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LT3965I is guaranteed over the full –40°C to 125°C operating junction
temperature range. High junction temperatures degrade operating
lifetimes. Operating lifetime is derated at junction temperatures greater
than 125°C.
Note 3: VOTH[1:0] and VSTH[1:0] register bits are set by LT3965 I2C
commands. VOTH/VSTH programmed by VOTH[1:0]/VSTH[1:0] refer to the
open/shorted LED threshold between DRN and SRC of a channel. For
a channel, VIN > VSRC + VOTH + 2.5V is required for accurate open LED
detection.
Note 4: Rise and fall times are measured at 30% and 70% levels.
Note 5: I2C interface timing diagram.
SDA
SCL
tHD,STA
REPEATED START
CONDITION
tSU,DAT
tHD,DATO
tHD,DATI
tSU,STA tHD,STA tSP
tSP
tSU,STO
tBUF
3965 TD
REPEATED START
CONDITION
STOP
CONDITION
START
CONDITION
TYPICAL PERFORMANCE CHARACTERISTICS
VDD Quiescent Current
vs Temperature
1.8 VDD = 5V
1.6
ALL SWITCHES ARE ON
1.4
1.2
ALL SWITCHES ARE OFF
1.0
0.8
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3965 G01
VIN Quiescent Current
vs Temperature
2.4 VIN = 40V, LEDREF = 3V
2.2
2.0 VOTH[1:0] = VSTH[1:0] = 11,
1.8 SWITCHES ARE ON
1.6
1.4
VOTH[1:0] = 11, VSTH[1:0] = 00,
SWITCHES ARE OFF
1.2
1.0 VOTH[1:0] = VSTH[1:0] = 00,
SWITCHES ARE OFF
0.8
0.6
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3965 G02
EN/UVLO Threshold
vs Temperature
1.27
1.26
1.25 RISING
1.24
FALLING
1.23
1.22
1.21
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3965 G03
PRERELEASEFor more information www.linear.com/LT3965
3965p
5
5 Page 
LT3965
APPLICATIONS INFORMATION
POWER-ON RESET AND DIMMING CYCLE
INITIALIZATION
When the LT3965 is powered on or the EN/UVLO pin is
toggled HIGH, an internal power-on reset (POR) signal is
generated to set all registers to their default states. The
eight channel switches are in off state (all channel LEDs
are on) upon the POR. The POR also initializes each chan-
nel’s dimming counter with one-eighth dimming cycle
shift, which can avoid simultaneous channel switching
at the beginning of dimming cycle to reduce switching
noises (see Figure 2). When in dimming mode (with or
without fade transition), the channel LED string is always
being turned on at the beginning of its dimming cycle. The
channel LED string will be turned off if the value of the
channel counter, which is clocked by the internal oscilla-
tor or an external clock source, equals the dimming value
stored in the channel SCMREG command register. Once
the channel LED string is turned off, it remains off until
its next dimming cycle starts.
DIMMING WITHOUT FADE TRANSITION VS DIMMING
WITH FADE TRANSITION
Each channel of the LT3965 can be independently pro-
grammed to perform dimming without fade transition or
dimming with fade transition. For dimming without fade
transition, the dimming changes from the initial value to
the target value in one dimming cycle. For dimming with
fade transition, the dimming changes transitionally from the
initial value to the target value step by step in multiple dim-
ming cycles, following a predetermined logarithmic curve.
The number of the transitional steps depends on the
distance between the initial value and the target value.
The maximum number of transitional steps from 1(/256)
dimming to 255(/256) dimming is 100 (see Figure 3) and
the maximum number of transitional steps from 255(/256)
dimming to 1(/256) dimming is 92 (see Figure 4). Each
step runs 4 PWM dimming cycles, and each dimming
cycle consists of 2048 RTCLK clock cycles. Then TSTEP =
TPWM • 4 = TRTCLK • 8192
256
224
192
160
128
96
64
32
0
0 20 40 60 80 100
NUMBER OF STEPS
3865 F03
Figure 3. LT3965 Up Transition Dimming Curve
POR
1 DIMMING CYCLE = 2048 RTCLK CLOCK CYCLES
1/256 DIMMING (8 CLOCK CYCLES)
CH1
PHASE SHIFT OF 1/8 DIMMING CYCLE = 256 CLOCK CYCLES
CH2
CH3
CH4
CH5
CH6
CH7
CH8
3965 F02
Figure 2. POR Dimming Cycle Initialization Diagram
PRERELEASEFor more information www.linear.com/LT3965
3965p
11
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LT3965.PDF ] | |
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