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PDF RT8572 Data sheet ( Hoja de datos )
| Número de pieza | RT8572 | |
| Descripción | High Voltage 8-CH LED Driver | |
| Fabricantes | Richtek | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de RT8572 (archivo pdf) en la parte inferior de esta página. Total 13 Páginas | ||
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RT8572
High Voltage 8-CH LED Driver
General Description
The RT8572 is an 8-CH LED driver capable of delivering
60mA for each channel. The RT8572 is a current mode
boost converter with an adjustable switching frequency
via the RT 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
RT8572 automatically detects and disconnects any
unconnected and/or broken strings during operation from
PWM loop to prevent VOUT from over voltage. The 1.5%
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 status signal will be sent to the system to shut down
the IC.
The RT8572 is available in an SOP-24 package.
Ordering Information
RT8572
Package Type
S : SOP-24
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
RT8572
GSYMDNN
RT8572GS : Product Number
YMDNN : Date Code
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 : ±1.5%
z External Dimming Control
z Boost MOSFET Over Current Protection
z Automatic LED Open/Short Protection to Avoid
Output Over Voltage
z VCC Under Voltage Lockout
z Adjustable Over Voltage Protection
z Under Voltage Protection
z Thermal Shutdown Protection
z Abnormal Status 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
Pin Configurations
(TOP VIEW)
LED1
OVP/UVP
RISET
NC
PWM
NC
STATUS
RT
VC
SS
EN
SEN
2
3
4
5
6
7
8
9
10
11
12
24 LED2
23 LED3
22 LED4
21 LED5
20 LED6
19 LED7
18 LED8
17 GND
16 VCC
15 CREG
14 DRV
13 PGND
SOP-24
DS8572-01 March 2011
www.richtek.com
1
1 page  
Function Block Diagram
DRV SEN
RT8572
STATUS
RT
VCC
OVP/UVP
EN
CREG
VC
SS
PWM
6V
1.2V
0.6V
-
+
+
-
-
+
OSC
UVP
S
R
R
1.2V
-
+
5V
LDO
Shutdown
VOUT
Regulation
Unit
6µA
+
-
OVP
UVP
OTP
LED Short
+
-
+
5V -
LED1
LED8
GND
PGND
RISET
DS8572-01 March 2011
www.richtek.com
5
5 Page 
It is recommended to choose a ceramic capacitor based
on the output voltage ripple requirements. The minimum
value of the output capacitor, COUT, can be calculated by
the following equation :
COUT
=
IOUT ×D
ΔVOUT × f
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 RT8572, the maximum junction temperature is 125°C
and TA is the ambient temperature. The junction to ambient
thermal resistance, θJA, is layout dependent. 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) / (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 RT8572 package, the derating
curve in Figure 3 allows the designer to see the effect of
rising ambient temperature on the maximum power
dissipation.
RT8572
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0
Single-Layer PCB
25 50 75 100
Ambient Temperature (°C)
125
Figure 3. Derating Curve for RT8572 Packages
Layout Considerations
PCB layout is very important for designing switching power
converter circuits. The following layout guides should be
strictly followed for best performance of the RT8572.
` The power components L1, D1, CIN, COUT must be placed
as close to the chip as possible 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 as close to pin 9 as possible, regardless
of whether it is RC or CC.
DS8572-01 March 2011
www.richtek.com
11
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet RT8572.PDF ] | |
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