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PDF RT8489 Data sheet ( Hoja de datos )
| Número de pieza | RT8489 | |
| Descripción | High Voltage 4-CH LED Driver Controller | |
| Fabricantes | Richtek | |
| Logotipo |  |
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®
RT8489
High Voltage 4-CH LED Driver Controller
General Description
The RT8489 is a 4-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 an adjustable switching frequency
of up to 1MHz, with a wide VIN range covering from 7V to
28V. 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 0.7V, thus allowing voltage
mismatches between the LED strings. The RT8489
automatically detects and excludes any open and/or
broken strings during operation from the PWM loop to
prevent VOUT from over voltage.
The LED currents on all channels are simply adjustable
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 can regulate the duty cycle of
the LED current. 3. For noise free PWM dimming, use an
on board output clamping amplifier as a low pass filter to
convert PWM dimming signals into analog dimming
signals.
Other protection features include adjustable output over
voltage protection, PWM switch current limit and thermal
shutdown.
Features
z Wide Operation Voltage Range : 7V to 28V
z Programmable Channel Current
z 3% Current Matching Accuracy between Channels
z Adjustable Switching Frequency
z Easy Analog and Digital Dimming Control
z Adjustable Soft-Start
z Adjustable Output Over Voltage Protection
z Under Voltage Lockout and Thermal Shutdown
z SOP-24 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
VIN
VCC
R3
L1
CIN
CVCC
RT8489
VCC
GATE
RSET
ISENSE
RVC
CVC
RSET
VC
SS
CSS
DCTL
LED1
GATE1
SENSE1
LED4
GATE4
ACTL
SENSE4
GND
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS8489-00 November 2012
D1
MSW
COUT
RSENSE
……
VOUT
4 x N LEDs
M1
RS1
M4
RS4
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
1 page  
RT8489
Absolute Maximum Ratings (Note 1)
z VCC --------------------------------------------------------------------------------------------------------------------------- −0.3V to 32V
z ISENSE
DC ------------------------------------------------------------------------------------------------------------------------------ −0.3V to 2V
< 20ns ------------------------------------------------------------------------------------------------------------------------ −0.3V to 6V
z GBIAS ------------------------------------------------------------------------------------------------------------------------- −0.3V to 14V
z SENSE1 to SENSE4
DC ------------------------------------------------------------------------------------------------------------------------------ −0.3V to 1V
< 20ns ------------------------------------------------------------------------------------------------------------------------ −0.3V to 6V
z LED1 - LED4 (Note 5) ---------------------------------------------------------------------------------------------------- −0.3V to 20V
z DCTL, ACTL, EN, OVP --------------------------------------------------------------------------------------------------- −0.3V to 10V
z Power Dissipation, PD@TA = 25°C
SOP-24 ----------------------------------------------------------------------------------------------------------------------- 1.3W
z Package Thermal Resistance (Note 2)
SOP-24, θJA ----------------------------------------------------------------------------------------------------------------- 77°C/W
z Junction Temperature ------------------------------------------------------------------------------------------------------ 150°C
z Storage Temperature Range --------------------------------------------------------------------------------------------- −65°C to 150°C
z Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------------------- 260°C
z ESD Susceptibility (Note 3)
HBM (Human Body Model) ----------------------------------------------------------------------------------------------- 2kV
MM (Machine Model) ------------------------------------------------------------------------------------------------------ 200V
Recommended Operating Conditions (Note 4)
z Supply Voltage, VIN ------------------------------------------------------------------------------------------------------- 7V to 28V
z Junction Temperature Range --------------------------------------------------------------------------------------------- −40°C to 125°C
z Ambient Temperature Range --------------------------------------------------------------------------------------------- −40°C to 85°C
Electrical Characteristics
(VIN = 12V, No Load, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Test Conditions
Overall
Supply Current
Shutdown Current
EN Input Voltage
EN Input Current
Logic-High
Logic-Low
LED Current Programming
SENSE1-SENSE4 Threshold
IVCC
ISHDN
VIH
VIL
IEN
SENSE Voltage CH to CH Matching
Analog Dimming ACTL Input Current IACTL
LED Current Off Threshold at ACTL VACTL_OFF
VVC ≤ 0.4V (Switching off)
VEN ≤ 1.2V
VEN ≤ 3.3V
6V > VGATEx > 2V
V(MAX) − V(MIN)
2 × V(avg)
VACTL ≤ 6V
Min Typ Max Unit
-- 5 8 mA
-- 5 -- μA
2 -- -- V
-- -- 0.5
-- 2 -- μA
214 225 236 mV
-- 1.5 3
%
-- -- 10 μA
-- 0.4 --
V
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS8489-00 November 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
5 Page 
Power On sequence
VIN
Power Off sequence
RT8489
Abnormal Power-on sequence
UVLO
PWM
EN
VIN must be turned off earlier than
EN and PWM signal
VIN must be turned on later than
EN and PWM signal
VOUT
Soft-Start
No Soft-Start
If PWM turns on late
Figure 2. Power On Sequence Control by VIN
EN/VIN
PWM
EN and/or VIN should be pulled low
once PWM pull low for over 10 ms
10ms
Figure 3. To Prevent “hard-start”Sequence
Soft-Start
The soft-start of the RT8489 can be achieved by connecting
a capacitor from the SS pin to GND. The built in soft-start
circuit reduces the start-up current spike and output
voltage overshoot. The soft-start time is determined by
the external capacitor charged by an internal 8μA constant
charging current. The SS pin directly limits the rate of
voltage rise on the VC pin, which in turn limits the peak
switch current.
The soft-start interval is set by the soft-start capacitor
stSeSlec=tioCnSSac×c3o8.rμ2dAVing t(os)the following equation :
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS8489-00 November 2012
A typical value for the soft-start capacitor is 0.1μF. The
soft-start pin reduces the oscillator frequency and the
maximum current in the switch. The soft-start capacitor
is discharged when EN/UVLO falls below its threshold,
during an over-temperature event, or during a GBIAS under
voltage event.
GBIAS Regulator Operation
The GBIAS pin requires a capacitor for stable operation
and also to store the charge for the large GATE switching
currents. Choose a 10V rated low ESR, X7R or X5R
ceramic capacitor for best performance. The value of the
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet RT8489.PDF ] | |
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