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PDF RT8497 Data sheet ( Hoja de datos )
| Número de pieza | RT8497 | |
| Descripción | Power MOSFET Integrated High Efficiency BCM LED Driver Controller | |
| Fabricantes | Richtek | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de RT8497 (archivo pdf) en la parte inferior de esta página. Total 13 Páginas | ||
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RT8497
Power MOSFET Integrated High Efficiency BCM LED Driver
Controller for High Power Factor Applications
General Description
The RT8497 integrates a power MOSFET and a
Boundary mode controller. It is used for step down
converters by well controlling the internal MOSFET and
regulating a constant output current.
The RT8497 features a ZCS detector which keeps
system operating in BCM and obtaining excellent
power efficiency, better EMI performance.
The RT8497 achieves high Power Factor Correction
(PFC) and low Total Harmonic Distortion of Current
(THDi) by a smart internal line voltage compensation
circuit which has minimized system component counts;
saved both PCB size and total system cost.
Especially, the RT8497 can use a cheap simple drum
core inductor in the system instead of an EE core to
obtain high efficiency.
The RT8497 is housed in a SOP-8 package. Thus, the
components in the whole LED driver system can be
made very compact.
Ordering Information
RT8497
Package Type
S : SOP-8
Lead Plating System
G : Green (Halogen Free and Pb Free)
MOSFET Built-In
Default : 500V/5.2
A : 500V/2
B : 600V/4.2
C : 600V/7
D : 600/3.2
Note :
Richtek products are :
RoHS compliant and compatible with the current
requirements of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes
Features
Built-In Power MOSFET
Support High Power Factor and Low THDi
Applications
Programmable Constant LED Current with
High-Precision Current Regulation
Extremely Low Quiescent Current Consumption
and 1A Shutdown Current
Compact Floating Buck Topology with Low
Component Counts, Small PCB Size, and Low
System BOM Cost
Unique Programmable AND Pin for ZVS Setting
to Achieve Best Power Efficiency
Support Off-Line Universal Input Voltage Range
Built-in Over Thermal Protection
Built-in Over Voltage Protection
Output LED String Open Protection
Output LED String Short Protection
Output LED String Over Current Protection
Applications
E27, PAR, Light Bar, Offline LED Lights
Pin Configurations
(TOP VIEW)
SGND
VC
AND
SOURCE
8
27
36
45
SOP-8
VCC
NC
DRAIN
DRAIN
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS8497-02 October 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
1 page  
RT8497
Parameter
Symbol
Test Conditions
Min Typ Max Unit
RT8497, VDS = 500V
RT8497A, VDS = 500V
Drain-Source Leakage Current IDSS
RT8497B, VDS = 600V
-- -- 10 A
RT8497C, VDS = 600V
RT8497D, VDS = 600V
Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are
stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the
operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may affect
device reliability.
Note 2. JA is measured at TA = 25C on a high effective thermal conductivity four-layer test board per JEDEC 51-7.
Note 3. Devices are ESD sensitive. Handling precaution recommended.
Note 4. The device is not guaranteed to function outside its operating conditions
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS8497-02 October 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
5 Page 
Preliminary
RT8497
L = VOUTTOFF = VPEAK VOUT TON
IPEAK
IPEAK
Where 0.5s TON 35s and 2s TOFF 30s
The frequency at the top of the sine wave can be
calculated :
fSW
=
TON
1
+ TOFF
+ TDELAY
(Tdelay is determined by the resistor connected to AND
pin , see Turn on delay time)
Turn On Delay Time
After the inductor current has reached zero, a
resonance will occur between the inductor and the
MOSFET drain-source capacitance.
In order to minimize the MOSFET switching losses,
RT8497 provides the flexibility to adjust the delay time
of next switch-on cycle in order to switch-on at the
maximum point of the resonance, which corresponds to
the minimum drain-source voltage value.
The delay time from zero current point to the maximum
of the switch resonance which can be calculated from :
Tresonance = L1CSW
where CSW is the capacitance at the switch node,
mostly determined by the MOSFET drain-source
capacitance.
The delay time TDELAY from zero current detection
point to next MOSFET switch-on cycle can be adjusted
by the resistor value R3B connected between AND pin
and IC GND
TDELAY(μs)=(-0.4 x R3B2+3500 x R3B+407500) x 10-6
R3B resister value in k.
Forward Diode Selection
When the power switch turns off, the path for the
current is through the diode connected between the
switch output and ground. This forward biased diode
must have minimum voltage drop and recovery time.
The reverse voltage rating of the diode should be
greater than the maximum input voltage and the
current rating should be greater than the maximum
load current.
VD 1.2 2 VAC(MAX) = 1.2 2 264 = 448V
The input source is universal (VIN = 85V to 264V), VD
will reach 448V.
Thermal Protection (OTP)
A thermal protection feature is included to protect the
RT8497 from excessive heat damage. When the
junction temperature exceeds a threshold of 150°C, the
thermal protection OTP will be triggered and the
internal MOSFET will be turned off.
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) / JA
where TJ(MAX) is the maximum junction temperature,
TA is the ambient temperature, and JA is the junction to
ambient thermal resistance.
For recommended operating condition specifications,
the maximum junction temperature is 125C. The
junction to ambient thermal resistance, JA, is layout
dependent. For SOP-8 package, the thermal resistance,
JA, is 188C/W on a standard JEDEC 51-7 four-layer
thermal test board. The maximum power dissipation at
TA = 25C can be calculated by the following formula :
PD(MAX) = (125C 25C) / (188C/W) = 0.53W for
SOP-8 package
The maximum power dissipation depends on the
operating ambient temperature for fixed TJ(MAX) and
thermal resistance, JA. The derating curve in Figure 2
allows the designer to see the effect of rising ambient
temperature on the maximum power dissipation.
The peak voltage stress of diode is :
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS8497-02 October 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
11
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet RT8497.PDF ] | |
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