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PDF LT3745-1 Data sheet ( Hoja de datos )
| Número de pieza | LT3745-1 | |
| Descripción | 16-Channel 50mA LED Driver | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
LT3745-1
16-Channel 50mA LED
Driver with Buck Controller
DESCRIPTION
n 6V to 55V Power Input Voltage Range
n 16 Independent LED Outputs Up to 75mA/36V
n ±4% LED Current Matching at 50mA (Typ ±1%)
n 6-Bit Dot Correction Current Adjustment
n 12-Bit Grayscale PWM Dimming
n 0.5µs Minimum LED On-Time
n Adaptive LED Bus Voltage for High Efficiency
n Cascadable 30MHz LVDS Serial Data Interface
n Full Diagnostic and Protection: Individual Open/Short
LED and Overtemperature Fault
n 40-Lead 6mm × 6mm QFN Package
APPLICATIONS
n Large Screen Display LED Backlighting
n Mono-, Multi-, Full-Color LED Displays
n LED Billboards and Signboards
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 8058810
The LT®3745-1 integrates a 16-channel LED driver with a
55V buck controller. The LED driver lights up to 75mA/36V
of LEDs in series per channel, and the buck controller gen-
erates an adaptive bus voltage supplying the parallel LED
strings. Each channel has individual 6-bit dot correction
current adjustment and 12-bit grayscale PWM dimming.
Both dot correction and grayscale are accessible via a serial
data interface in LVDS logic. A ±4% LED current match-
ing and a 0.5µs minimum LED on-time can be achieved
at 50mA per channel.
The LT3745-1 performs full diagnostic and protection
against open/short LED and overtemperature fault. The
fault status is sent back through the serial data interface.
The 30MHz fully-buffered, cascadable LVDS serial data
interface makes the chip extremely suitable for large screen
LCD dynamic backlighting and mono-, multi-, full-color
LED displays. The LT3745 uses a TTL/CMOS serial data
interface instead of LVDS.
www.DataSheet.co.kr
TYPICAL APPLICATION
16-Channel LED Driver, 1MHz Buck, 10 LEDs, 25mA to 75mA per Channel, 500Hz 12-Bit Dimming
VIN
42V TO 55V
0.47µF
4.7µF
EN
VCC
3V TO 3.6V
100k
10µF
VIN
EN/UVLO
VCC
SYNC
CAP
GATE
GND
46.4k
RT
SS
10nF
LT3745-1
ISP
ISN
FB
47µH 25mΩ
267k
47µF
×2
10k ..... ..... .....
..... .....
60.4k
32.4k
ISET
TSET
2.048MHz
LVDS CLOCK
LVDS
PWMCK+
PWMCK–
SCKI+
SCKI–
SDI+
SDI–
LDI
LED00
LED01
LED... 02
LED13
LED14
LED15
SCKO+
SCKO–
SDO+
SDO–
LVDS
37451 TA01
.....
37451f
1
Datasheet pdf - http://www.DataSheet4U.net/
1 page  
LT3745-1
TIMING CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. VIN = 12V, VCC = 3V to 3.6V, VEN/UVLO = 1.5V, VFB = 1.5V, VISP = VISN = 5V,
VLEDxx = 1V, RT = 105k, RISET = 60.4k, CCAP = 0.47µF to VIN, CSCKO+/SCKO– = CSDO+/SDO– = 15pF, unless otherwise noted.
SYMBOL
fSCKI
fPWMCK
tWH-CKI
tWL-CKI
ttWWHL--PPWWMM
tWH-LDI
tSU-SDI
tHD-SDI
tSU-LDI
tHD-LDI
tPD-SCK↑
tPD-SCK↓
∆tPD-SCK
tPD-SD
tPD-PWM
tR-SO
tF-SO
PARAMETER
Data Shift Clock Frequency
PWMCK Clock Frequency
SCKI Pulse Duration
PWMCK Pulse Duration
LDI Pulse Duration
SDI-SCKI Setup Time
SCKI-SDI Hold Time
SCKI-LDI Setup Time
LDI-SCKI Hold Time
SCKI-SCKO Propagation Delay (Rising)
SCKI-SCKO Propagation Delay (Falling)
SCK Duty Cycle Change
SCKO-SDO Propagation Delay
PWMCK-LED Propagation Delay
SCKO/SDO Rise Time
SCKO/SDO Fall Time
CONDITIONS
SCKI = H (Figure 3)
SCKI = L (Figure 3)
PWMCK = H (Figure 4)
PWMCK = L (Figure 4)
LDI = H (Figure 3)
SDI – SCKI↑ (Figure 3)
SCKI↑ – SDI (Figure 3)
SCKI↓ – LDI↑ (Figure 3)
LDI↓ – SCKI↑ (Figure 3)
SCKI↑ – SCKO↑ (Figure 3)
SCKI↓ – SCKO↓ (Figure 3)
∆tPD-SCK = tPD-SCK↑ – tPD-SCK↓
SCKO↑ – SDO (Figure 3)
PWMCK↑ – ILED (Figure 4)
CLOAD = 15pF, 10% to 90%
CLOAD = 15pF, 90% to 10%
MIN TYP MAX UNITS
l 30 MHz
l 25 MHz
l 16
l 16
ns
ns
l 20
l 20
ns
ns
l 20
ns
l5
ns
l5
ns
l5
ns
l 15
ns
l
33 50
ns
l
33 50
ns
0 ns
l2 5 8
ns
55 ns
2.6 ns
2.6 ns
www.DataSheet.co.kr
Table 1. Test Parameter Equations
∆ILEDC(%)
=
IOUTmax(0−15) – IOUTmin(0−15)
2 •IOUTavg(0−15)
•
100
∆ILEDD(%) =
IOUTavg(0−15) – IOUTcal
I OUTcal
•
100
IOUTcal
=
2500
•
1.205V
RISET
(1)
(2)
(3)
∆ILINE (% / V) =
IOUTn
VCC = 3.6V – IOUTn VCC = 3V
IOUTn VCC = 3V
•
100
0.6V
(4)
∆ILOAD (% / V) =
IOUTn
VOUTn = 3V – IOUTn VOUTn = 1V
IOUTn VOUTn = 1V
•
100
2V
(5)
VID = V(DI+ )– V(DI– )
VCM
=
V(DI+
)+
2
V(DI–
)
VOD = V(DO+ )– V(DO– )
VOS
=
V(DO+
)+
2
V(DO–
)
(6)
(7)
(8)
(9)
37451f
5
Datasheet pdf - http://www.DataSheet4U.net/
5 Page 
LT3745-1
PIN FUNCTIONS
EN/UVLO (Pin 1): Enable and Undervoltage Lockout
(UVLO) Pin. The pin can accept a digital input signal to
enable or disable the chip. Tie to 0.35V or lower to shut
down the chip or tie to 1.34V or higher for normal op-
eration. This pin can also be connected to VIN through a
resistor divider to program a power input UVLO threshold.
If both the enable and UVLO functions are not used, tie
this pin to VCC pin.
LED00 to LED15 (Pins 2 to 9, 22 to 29): LED Driver Output
Pins. Connect the cathodes of LED strings to these pins.
SCKI−, SCKI+ (Pins 10, 11): Serial Interface LVDS Logic
Clock Input Pins.
SDI−, SDI+ (Pins 12, 13): Serial Interface LVDS Logic
Data Input Pins.
LDI (Pin 14): Serial Interface TTL/CMOS Logic Latch Input
Pin. An asynchronous input signal at this pin latches the
serial data in the shift registers into the proper registers
and the status information is ready to shift out with the
coming clock pulses. See more details in the Operation
section.
VCC (Pin 15): Logic and Control Supply Pin. The pin powers
serial data interface and internal control circuitry. Must be
locally bypassed with a capacitor to ground.
PWMCK+, PWMCK− (Pins 16, 17): Grayscale PWM
Dimming LVDS Logic Clock Input Pins. Individual PWM
dimming signal is generated by counting this clock pulse
from zero to the bits in its 12-bit grayscale PWM register.
SDO+, SDO− (Pins 18, 19): Serial Interface LVDS Logic
Data Output Pins.
SCKO+, SCKO− (Pins 20, 21): Serial Interface LVDS Logic
Clock Output Pins.
SYNC (Pin 30): Switching Frequency Synchronization Pin.
Synchronizes the internal oscillator frequency to an exter-
nal clock applied to the SYNC pin. The SYNC pin is TTL/
CMOS logic compatible. Tie to ground or VCC if not used.
RT (Pin 31): Timing Resistor Pin. Programs the switching
frequency from 200kHz to 1MHz. See Table 2 for the rec-
ommended RT values for common switching frequencies.
SS (Pin 32): Soft-Start Pin. Placing a capacitor here pro-
grams soft-start timing to limit inductor inrush current
during start-up. The soft-start cycle will not begin until
all the VCC, EN/UVLO, and (VIN-VCAP) voltages are higher
than their respective UVLO thresholds.
FB (Pin 33): Feedback Pin. The pin is regulated to the
internal bang-gap reference 1.210V during start-up and
precharging phases. Connect to a resistor divider from the
buck converter output to program the maximum LED bus
voltage. See more details in the Applications Information
section.
ISN (Pin 34): Negative Inductor Current Sense Pin. The
pin is connected to one terminal of the external inductor
current sensing resistor and the buck converter output
supplying parallel LED channels.
ISP (Pin 35): Positive Inductor Current Sense Pin. The pin
is connected to the inductor and the other terminal of the
external inductor current sensing resistor.
CAP (Pin 36): VIN Referenced Regulator Supply Capacitor
Pin. The pin holds the negative terminal of an internal VIN
referenced 6.8V linear regulator used to bias the gate driver
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circuitry. Must be locally bypassed with a capacitor to VIN.
GATE (Pin 37): Gate Driver Pin. The pin drives an external
P-channel power MOSFET with a typical peak current of
1A. Connect this pin to the gate of the power MOSFET with
a short and wide PCB trace to minimize trace inductance.
VIN (Pin 38): Power Input Supply Pin. Must be locally
bypassed with a capacitor to ground.
TSET (Pin 39): Temperature Threshold Setting Pin. A
resistor to ground programs overtemperature threshold.
See more details in the Applications Information section.
ISET (Pin 40): Nominal LED Current Setting Pin. A resistor
to ground programs the nominal LED current for all the
channels. See more details in the Applications Informa-
tion section.
GND (Exposed Pad Pin 41): Ground Pin. Must be soldered
to a continuous copper ground plane to reduce die tem-
perature and to increase the power capability of the device.
37451f
11
Datasheet pdf - http://www.DataSheet4U.net/
11 Page | ||
| Páginas | Total 28 Páginas | |
| PDF Descargar | [ Datasheet LT3745-1.PDF ] | |
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