LED Driver. RT8464 Datasheet

RT8464 Driver. Datasheet pdf. Equivalent

RT8464 Datasheet
Recommendation RT8464 Datasheet
Part RT8464
Description Isolated Secondary Side 6-CH LED Driver
Feature RT8464; ® RT8464 Isolated Secondary Side 6-CH LED Driver with Optocoupler Driver General Description The R.
Manufacture Richtek
Datasheet
Download RT8464 Datasheet




Richtek RT8464
®
RT8464
Isolated Secondary Side 6-CH LED Driver with Optocoupler
Driver
General Description
The RT8464 is an isolated secondary side 6-CH LED driver
that delivers well matched LED current to each channel of
LED strings. A built-in optocoupler driver supports the
transformer primary side control circuit to regulate the
LED current.
The LED current is linearly controlled by a high gain amplifier
that drives the optocoupler to control the primary side,
thus making the conventional secondary DC/DC PWM
switching stage unnecessary. The RT8464 selects and
regulates the LED strings with the highest voltage, hence
it allows voltage mismatches between LED strings. The
RT8464 automatically detects and disconnects any
unconnected and/or broken strings during operation from
the PWM loop to prevent VOUT from over voltage.
The LED currents on all channels can be simply
programmed with a resistor on each channel. Three
convenient dimming methods are provided : 1. Analog
dimming is linearly controlled by an external voltage; 2.
True digitally controlled PWM dimming controls duty cycle
of LED current; 3. PWM dimming signal can also be easily
filtered into analog dimming signal for noise-free PWM
dimming by the low pass filter with an external capacitor
at ACTL pin. Other protecting features include output over
voltage protection and thermal shutdown.
The RT8464 is available in the SOP-28 package.
Features
z High Voltage : VCC up to 32V
z Channel Current Programmable
z 3% Current Sense Threshold Voltage
z Easy Analog and Digital Dimming Control
z Adjustable Soft-Start to Avoid Inrush Current
z Automatic Detecting Unconnected Channel
z Adjustable Over Voltage Protection to Limit Output
Voltage
z Thermal Shutdown Under Voltage Lockout
z SOP-28 Package
z RoHS Compliant and Halogen Free
Applications
z Building and Street Lighting
z LED TV Backlight
z LED Monitor Backlight
z Industrial Display Backlight
Simplified Application Circuit
Isolation Barrier
VIN
Primary Side
Controller
Dimming Signal
EN RT8464
VCC
VC
SS
LEDx
GATEx
ACTL SENSEx
OPTO
GND
RSENSE
x6
x6
x6
x6
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS8464-00 November 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1



Richtek RT8464
RT8464
Ordering Information
RT8464
Note :
Package Type
S : SOP-28
Lead Plating System
G : Green (Halogen Free and Pb Free)
Richtek products are :
` RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
` Suitable for use in SnPb or Pb-free soldering processes.
Marking Information
RichTek
RT8464
GSYMDNN
RT8464GS : Product Number
YMDNN : Date Code
Pin Configurations
(TOP VIEW)
VCC
OPTO
CL
EN
OVP
SS
VC
ACTL
DCTL
SENSE6
GATE6
LED6
SENSE5
GATE5
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
SOP-28
GND
LED1
GATE1
SENSE1
LED2
GATE2
SENSE2
LED3
GATE3
SENSE3
LED4
GATE4
SENSE4
LED5
Functional Pin Description
Pin No.
1
2
Pin Name
VCC
OPTO
Pin Function
Power Supply Input of the Chip. For good bypass, a low ESR capacitor is needed
between this pin and GND.
Optocoupler Driver. It is an open collector output of the internal NPN transistor.
3 CL
4 EN
5 OVP
6 SS
Current Limit. Current limit threshold is 100mV.
Chip Enable. The chip is active when VEN > 1.4V.
Over Voltage Detection Input. OVP pin threshold is 1.2V (typ.).
Soft-Start. There is an internal constant current (6μA) to the SS pin during startup.
Connect a capacitor to set soft-start time.
7 VC
8 ACTL
9 DCTL
10, 13, 16,
19, 22, 25
11, 14, 17,
20, 23, 26
12, 15, 18,
21, 24, 27
SENSE6 to
SENSE1
GATE6 to
GATE1
LED6 to
LED1
PWM Loop Compensation.
Analog/PWM Dimming Control Input. When using in analog dimming, ACTL control
range is from 0.4V to 1.2V.
Digital Dimming Control Input. By adding a 0.1μF filter capacitor at ACTL, the digital
dimming signal at DCTL pin will be averaged out and converted into analog
dimming signal at ACTL pin.
Current Sense Input for LED Current. The threshold is 215mV and ILED = 0.215V /
RSENSE
Gate Drive Output for External Current Source MOSFETs.
LED String Voltage Sensing Input. This pin is connected to the Drain of external
current source MOSFET.
28 GND
Ground.
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
www.richtek.com
2
is a registered trademark of Richtek Technology Corporation.
DS8464-00 November 2012



Richtek RT8464
Function Block Diagram
OVP
OPTO
VC
CL
+
1.2V -
- 1.2V
+
-0.1V +
-
2.5V/6µA
- 0.7V
+ Min
Select
6
+6
-
6
SS
EN
DCTL
ACTL
1.4V +
-
1.2V
+
-
Shutdown
+
-
5V
RT8464
VCC
LEDx
GATEx
SENSEx
GND
Operation
The RT8464 regulates the lowest cathode voltage of LED strings and generates a feedback control signal to a primary
controller to regulate LED current. Each LED channel current is accurately matched and controlled by sensing an
external resistor in series with the MOSEFT. LED current dimming in all six channels can be precisely controlled by
either a PWM signal via the DCTL input pin or by an analog dimming voltage applied at the ACTL pin. Internal protection
is provided for over current and over voltage at the secondary output. The device can be operated in low current shutdown
mode by pulling the EN pin low.
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS8464-00 November 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
3







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