|
|
PDF IS31LT3910 Data sheet ( Hoja de datos )
| Número de pieza | IS31LT3910 | |
| Descripción | UNIVERSAL HIGH BRIGHTNESS LED DRIVER | |
| Fabricantes | ISSI | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de IS31LT3910 (archivo pdf) en la parte inferior de esta página. Total 8 Páginas | ||
|
No Preview Available !
IS31LT3910
UNIVERSAL HIGH BRIGHTNESS LED DRIVER
WITH TEMPERATURE COMPENSATION
GENERAL DESCRIPTION
The IS31LT3910 is a peak current mode control LED
driver IC. The IS31LT3910 operates in constant off-time
mode. It allows efficient operation of High Brightness
(HB) LEDs with voltage sources ranging from 8VDC to
450DC or 110VAC/220VAC. The IS31LT3910 includes
a PWM dimming input that can accept an external
control signal with a duty ratio of 0 - 100% and a
frequency of up to a few kilohertz. It also includes a 0 -
240mV linear dimming input which can be used both for
linear dimming and temperature compensation of the
LED current.
The IS31LT3910 is ideally suited for buck LED drivers.
Since the IS31LT3910 operates in peak current mode
control, the controller achieves good output current
regulation without the need for any loop compensation.
It achieves good PWM dimming response because the
response time is limited only by the rate of rise and fall
of the inductor current, enabling very fast rise and fall
time.
FEATURES
November 2011
Wide input range from 8VDC to 450DC or
110VAC/220 VAC
Temperature compensation to regulate LED current
Application from a few mA to more than 1A output
Constant off-time operation
Linear and PWM dimming capability
Switch mode controller for single switch LED
drivers
Requires few external components for operation
APPLICATIONS
DC/DC or AC/DC LED driver applications
General purpose constant current source
Signal and decorative LED lighting
backlighting LED driver
APPLICATION CIRCUIT
VinDC8~450V
http://www.DataSheet4U.net/
D1
L1
Rin
IS31LT3910
VIN
R1
Cin
VREF
LD
PWMD
TOFF
C2 COFF
GATE
Q1
CS
GND
RCS
C1
LEDS
NTC
Integrated Silicon Solution, Inc. — www.issi.com
Rev.A, 11/08/2011
1
datasheet pdf - http://www.DataSheet4U.net/
1 page  
IS31LT3910
APPLICATION INFORMATION
The IS31LT3910 is optimized to drive buck LED drivers
using peak current mode control. This control method
provides fairly accurate LED current control without the
need for a high side current sensing or the design of any
additional loop compensation. The IC uses very few
external components and provides for either Linear or
PWM control of the LED current.
A capacitor connected to the Toff pin programs the off-
time of the oscillator inside. The oscillator produces
pulses at regular intervals. These pulses set the SR flip-
flop in the IS31LT3910 which causes the GATE driver to
turn on. When the MOSFET turns on, the current
through the inductor starts ramping up. This current
flows through the external sense resistor RCS and
produces a ramp voltage at the CS pin. The
comparators are constantly comparing the CS pin
voltage to both the voltage at the LD pin and the internal
240mV. Once the blanking time is complete, the output
of these comparators is allowed to reset the flip flop.
When the output of either one of the two comparators
goes high, the flip flop is reset and the GATE output
goes low. If neither of the comparator goes high，the
GATE keeps high. Assuming a 30% ripple in the
inductor, the current sense resistor RCS can be set by
using:
RCS 0.24V(orVLD)
1.15 ILED(A)
A constant off-time peak current control scheme can
easily operate at duty cycles greater than 0.5 and also
gives inherent input voltage rejection making the LED
current almost insensitive to input voltage variations.
INPUT VOLTAGE REGULATOR
When a voltage is applied through a suitable input
resistor to the VIN pin, the IS31LT3910 maintains a
constant 7.1V（typ.） at the VIN pin. This voltage is
used to power the IC. The VIN pin must be bypassed by
a low ESR capacitor to provide a low impedance path
for the high frequency current of the output GATE driver.
The input current drawn from the VIN pin is a sum of the
0.5mA(typ)current drawn by the internal circuit and the
current drawn by the GATE driver (which in turn
depends on the switching frequency and the GATE
charge of the external MOSFET).
IIN 0.5mA QG fS
In the above equation, fS is the switching frequency and
QG is the GATE charge of the external MOSFET (which
can be obtained from the datasheet of the MOSFET).
CURRENT SENSE
The current sense input of the IS31LT3910 goes to the
non-inverting inputs of two comparators. The inverting
terminal of oe comparator is tied to an internal 240mV
reference whereas the inverting terminal of the other
comparator is connected to the LD pin. The outputs of
both these comparators are fed into an OR GATE and
the output of the OR GATE is fed into the reset pin of
the flip-flop. Thus, the comparator which has the lowest
voltage at the inverting terminal determines when the
GATE output is turned off.
The outputs of the comparators also include a typical
480ns blanking time which prevents spurious turn-offs of
the external MOSFET due to the turn-on spike normally
present in peak current mode control. In rare cases, this
internal blanking time might not be enough to filter out
the turn-on spike. In these cases, an external RC filter
needs to be added between the external sense resistor
(RCS) and the CS pin.
Please note that the comparators are relatively fast with
a typical 80ns response time. A proper layout
minimizing external inductances will prevent false
triggering of these comparators.
OSCILLATOR
http://www.DataSheet4U.net/
The oscillator in the IS31LT3910 is controlled by a
single capacitor connected at the Toff pin. The equation
governing the Toff-time of oscillation period is given by:
TOFF
_ TIME
(s)
0.51 10 6
(1
COFF
10 pF
)
LINEAR DIMMING
The Linear Dimming pin is used to control the LED
current. An external voltage ranging from 50mV to
240mV can be applied to the LD pin to adjust the LED
current during operation. There are two cases when it
may be necessary to use the Linear Dimming pin.
► In some cases, it may not be possible to find the
exact RCS value required to obtain the LED current when
the internal 240mV is used. In these cases, an external
voltage divider from the Vin pin can be connected to the
LD pin to obtain a voltage (less than 240mV)
corresponding to the desired voltage across RCS.
► Linear dimming may be desired to adjust the current
level to reduce the brightness of the LEDs. Connecting
a resistor between the Vref pin and the LD pin, and also
connecting an NTC thermistor between the LD pin and
ground (refer to Application Circuit), the IS31LT3910 is
able to realize the temperature compensation function
Integrated Silicon Solution, Inc. — www.issi.com
Rev.A, 11/08/2011
5
datasheet pdf - http://www.DataSheet4U.net/
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet IS31LT3910.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| IS31LT3910 | UNIVERSAL HIGH BRIGHTNESS LED DRIVER | ISSI |
| IS31LT3916 | Offline LED driver | ISSI |
| IS31LT3918 | HIGH VOLTAGE LED LIGHTING DRIVER | ISSI |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |