Driver Controller. RT8491 Datasheet

RT8491 Controller. Datasheet pdf. Equivalent

RT8491 Datasheet
Recommendation RT8491 Datasheet
Part RT8491
Description High Voltage 6-CH LED Driver Controller
Feature RT8491; ® RT8491 High Voltage 6-CH LED Driver Controller General Description The RT8491 is a 6-CH LED driv.
Manufacture Richtek
Datasheet
Download RT8491 Datasheet




Richtek RT8491
®
RT8491
High Voltage 6-CH LED Driver Controller
General Description
The RT8491 is a 6-CH LED driver controller that delivers
well matched LED current to each channel of LED string.
With external current sources, the number of LEDs per
string is only limited by the current source and the VIN/
VOUT conditions. The current mode PWM boost type
controller operates at a programmable switching
frequency of up to 1MHz, with a wide VIN range covering
from 9V to 32V. The switch driver is designed to drive
industrial grade high power MOSFETs.
The PWM loop selects and regulates the LED string with
the highest voltage string to 0.9V, thus allowing voltage
mismatches between the LED strings. The RT8491
automatically detects and excludes any open and/or
broken strings during operation from the PWM loop to
prevent VOUT from over voltage.
The RT8491 also provides LED short protection. If LED
short occurs and causes any LEDx but not all LEDx pin
voltage greater than 8V, the CAP pin is charged up by
internal 10μA. If the LED short condition lasts longer than
the CAP pin voltage reaches 3.5V, the FLAG pin will go
high and the GATE pin will be kept low immediately until
the CAP pin voltage drops below 3.5V. The delay time is
programmable by the capacitor at the CAP pin.
Features
Wide Operation Voltage Range : 9V to 32V
Programmable Channel Current
3% Current Matching Accuracy between Channels
Programmable Switching Frequency
Easy Analog and Digital Dimming Control
Programmable Soft-Start
LED Open Channel Detection and Protection
LED Short-Fault Detect Latch Off Multiple LED
Strings
Programmable Output Over Voltage Protection
Under Voltage Lockout and Thermal Shutdown
32-Lead WQFN Package
Applications
Building and Street Lighting
LED TV Backlight
LED Monitor Backlight
Industrial Display Backlight
Simplified Application Circuit
VIN
R3
12V
CIN
CVCC
CB
RT8491
VCC
CAP
VBASE
GBIAS
GATE
ISENSE
RSET
RSET
SS
CSS
GND
Chip Enable
EN
ACTL
LED1
GATE1
SENSE1
LED6
GATE6
SENSE6
L1 D1
CT
MSW
RSENSE
COUT
M1
RS1
VOUT
6 x N LEDs
M6
RS6
Copyright ©2014 Richtek Technology Corporation. All rights reserved.
DS8491-04 October 2014
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1



Richtek RT8491
RT8491
Ordering Information
RT8491
Package Type
QW : WQFN-32L 5x5 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Note :
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
RT8491GQW : Product Number
RT8491
GQW
YMDNN
YMDNN : Date Code
Pin Configurations
(TOP VIEW)
32 31 30 29 28 27 26 25
GND
ISENSE
RSET
EN
OVP
SS
VC
ACTL
1
2
3
4
5
6
7
8
24 GATE2
23 SENSE2
22 LED3
GND
21 GATE3
20 SENSE3
19 LED4
33 18 GATE4
17 SENSE4
9 10 11 12 13 14 15 16
WQFN-32L 5x5
Copyright ©2014 Richtek Technology Corporation. All rights reserved.
www.richtek.com
2
is a registered trademark of Richtek Technology Corporation.
DS8491-04 October 2014



Richtek RT8491
RT8491
Functional Pin Description
Pin No.
Pin Name
Pin Function
1,
33 (Exposed Pad)
GND
2 ISENSE
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
Switch Current Sense. Connect a sense resistor from this pin to GND. The switch
current sense signal is used for boost current mode PWM loop control and power
switch over current protection.
3
RSET
Switching Frequency Set. Put a resistor from RSET to GND to program the
switching frequency. fSW = 280kHz when RSET = 40k.
4 EN Chip Enable (Active High).
5
OVP
Over Voltage Protection. OVP pin threshold is around 1.25V. Use a resistor
divider from output to GND to program the OVP level.
6
SS
Soft-Start. Use a soft-start cap from SS pin to GND to program the soft-start time
period. Around 10A is sourcing out of SS pin.
7 VC Loop Compensation Pin.
8
ACTL
Analog/PWM Dimming Control. When used in analog dimming, ACTL control
range is from 0.4V to 1.4V.
The Fault Output. Flag pin goes high in two conditions. As the OVP pin goes
high, the FLAG pin goes high without time delay. If the LED short condition
9
FLAG
occurs and lasts longer than the CAP pin voltage reaches 3.5V, the FLAG pin will
go high and the GATE pin will be kept low immediately until the CAP pin voltage
drops below 3.5V. The delay time is programmable by the capacitor at the CAP
pin.
The LED Short Detection Time Delay Programming. If LED short occurs and
causes any LEDx but not all LEDx pin voltage greater than 8V, the CAP pin is
10
CAP
charged up by internal 10A. If the LED short condition occurs and lasts longer
than the CAP pin voltage reaches 3.5V, the FLAG pin will go high. The delay time
is programmable by the capacitor at the CAP pin. The typical delay time is 40ms
when the capacitor at CAP pin is 0.1F.
11, 14, 17,
20, 23, 26
12, 15, 18,
21, 24, 27
13, 16, 19,
22, 25, 28
SENSEx
GATEx
LEDx
Source Pin of External MOSFETx (x = 1 to 6).
The SENSEx pins are regulated around 440mV. Connect a sense resistor from
this pin to GND. The LED current is programmed by ILED = 440mV / (sense
resistance) when VACTL is greater than 1.4V.
Gate Pin for External MOSFETx (x = 1 to 6) of LED Drivers.
LEDx Pin (x = 1 to 6) is Normally Regulated Around 0.9V. If LED short occurs and
causes any LEDx but not all LEDx pin voltage greater than 8V, the LED short
protection is triggered.
29
VCC
Power Supply. For good bypass, a low ESR capacitor is needed between this pin
and GND.
The External Gate Bias Supply is Driven by an External NPN Transistor. The
30
VBASE
base of this NPN is tied to VBASE pin. The emitter of this NPN is tied to GBIAS
pin. The collector of this NPN is tied to VCC.
31
GBIAS
Internal Gate Driver Bias Voltage (around 9.5V). Need a good bypass capacitor
between this pin and GND.
32
GATE
Gate Pin for External MOSFET of Boost PWM Control.
Copyright ©2014 Richtek Technology Corporation. All rights reserved.
DS8491-04 October 2014
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
3







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