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PDF RT8576 Data sheet ( Hoja de datos )
| Número de pieza | RT8576 | |
| Descripción | High Voltage 8-CH LED Driver | |
| Fabricantes | Richtek | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de RT8576 (archivo pdf) en la parte inferior de esta página. Total 14 Páginas | ||
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RT8576
High Voltage 8-CH LED Driver
General Description
The RT8576 is an 8-CH LED driver capable of delivering
120mA for each channel. The RT8576 is a current mode
boost converter with an adjustable switching frequency
via the OSC pin from 100kHz to 1MHz and a wide VIN
range from 9V to 28V.
The PWM output voltage loop selects and regulates the
LED pin with the highest voltage string to 0.6V, hence
allowing voltage mismatches between LED strings. The
RT8576 automatically detects and disconnects any
unconnected and/or broken strings during operation from
PWM loop to prevent VOUT from over voltage.
The 3% matched LED currents on all channels are simply
programmed with a resistor. A very high contrast ratio true
digital PWM dimming can be achieved by driving the PWM
pin with a PWM signal.
When an abnormal situation (open/short/thermal) occurs,
a state signal will be sent to the system to shut down the
IC.
The RT8576 is available in TSSOP-24 (Exposed Pad) and
SOP-24 packages.
Ordering Information
RT8576
Package Type
CP : TSSOP-24 (Exposed Pad)
S : SOP-24
Lead Plating Systeme
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.
Features
z Wide Input Supply Voltage Range : 9V to 28V
z Adjustable Boost Controller Switching Frequency
from 100kHz to 1MHz
z Programmable Channel Current
z Channel Current Matching : ±3%
z External Dimming Control
z Boost MOSFET Over Current Protection
z Automatic LED Open/Short Protection to Avoid
Output Over Voltage
z VIN Under Voltage Lockout
z Adjustable Over Voltage Protection
z Under Voltage Protection
z Thermal Shutdown Protection
z Abnormal State Indicator for Open/Short/Thermal
Condition
z RoHS Compliant and Halogen Free
Applications
z LCD TV, Monitor Display Backlight
z LEDDriver Application
z General Purpose Constant Current Source
Marking Information
RT8576GCP
RT8576
GCPYMDNN
RT8576GCP : Product Number
YMDNN : Date Code
RT8576GS
RT8576
GSYMDNN
RT8576GS : Product Number
YMDNN : Date Code
DS8576-00 April 2011
www.richtek.com
1
1 page  
Function Block Diagram
EXT CS
RT8576
STATE
OSC
VIN
OVS
EN
VCCA
COMP
SS
UVLO
1.2V
0.6V
-
+
+
-
-
+
OSC
UVP
S
R
R
1.2V
-
+
5V
LDO
Shutdown
VOUT
Regulation
Unit
6µA
+
-
OVP
UVP
OTP
LED Short
+
-
5V
+
-
OUT1
OUT8
GND
PGND
PWM
ISET
DS8576-00 April 2011
www.richtek.com
5
5 Page 
where ΔVOUT is the peak-to-peak ripple voltage at the
output.
Thermal Considerations
For continuous operation, do not exceed absolute
maximum junction temperature. The maximum power
dissipation depends on the thermal resistance of the IC
package, PCB layout, rate of surrounding airflow, and
difference between junction and ambient temperature. The
maximum power dissipation can be calculated by the
following formula :
PD(MAX) = (TJ (MAX) − TA) / θJA
where TJ (MAX) is the maximum junction temperature, TA is
the ambient temperature, and θJA is the junction to ambient
thermal resistance.
For recommended operating condition specifications of
the RT8576, the maximum junction temperature is 125°C
and TA is the ambient temperature. The junction to ambient
thermal resistance, θJA, is layout dependent. For TSSOP-
24 (Exposed Pad) packages, the thermal resistance, θJA,
is 40° C/W on a standard JEDEC 51-7 four-layer thermal
test board. For SOP-24 packages, the thermal resistance,
θJA , is 90°C/W on a standard JEDEC 51-3 single-layer
thermal test board. The maximum power dissipation at TA
= 25°C can be calculated by the following formula :
PD(MAX) = (125°C − 25°C) / (40°C/W) = 2.500W for
TSSOP-24 (Exposed Pad) package
PD(MAX) = (125°C − 25°C) / (90°C/W) = 1.111W for
SOP-24 package
The maximum power dissipation depends on the operating
ambient temperature for fixed TJ(MAX) and thermal
resistance, θJA. For the RT8576 packages, the derating
curves in Figure 3 allow the designer to see the effect of
rising ambient temperature on the maximum power
dissipation.
RT8576
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0
TSSOP-24 (Exposed Pad)
SOP-24
25 50 75 100
Ambient Temperature (°C)
125
Figure 3. Derating Curve for RT8576 Packages
Layout Considerations
Careful PCB layout is very important for designing
switching power converter circuits. The following layout
guidelines should be strictly followed for best performance
of the RT8576.
` The power components L1, D1, CIN, COUT must be placed
as close as possible to the IC to reduce current loop.
The PCB trace between power components must be as
short and wide as possible.
` The compensation circuit should be kept away from
the power loops and shielded with a ground trace to
prevent any noise coupling. Place the compensation
components, RC and CC, as close as possible to pin
22.
` The exposed pad of the chip should be connected to
ground plane for thermal consideration.
DS8576-00 April 2011
www.richtek.com
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet RT8576.PDF ] | |
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