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PDF RT8573 Data sheet ( Hoja de datos )
| Número de pieza | RT8573 | |
| Descripción | High Voltage Boost/SEPIC Controller | |
| Fabricantes | Richtek | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de RT8573 (archivo pdf) en la parte inferior de esta página. Total 17 Páginas | ||
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Preliminary
RT8573
High Voltage Boost/SEPIC Controller
General Description
The RT8573 is a current mode PWM controller designed
to drive an external MOSFET for high current LED
applications. With a low side current sense amplifier
threshold of 190mV, the LED current is programmable
with one external current sense resistor.
With programmable operating frequency up to 800kHz,
the external inductor and capacitors can be small while
maintaining high frequency.
Dimming can be done by either analog or digital. A built-in
clamping comparator and filter allow easy low noise analog
dimming conversion from digital signal with only one
external capacitor. An unique True PWM dimming control
is made easy with MOSFET under LED string. A very high
dimming ratio can be achieved by adopting both analog/
digital dimming and True PWM dimming together.
The RT8573 is available in a SOP-16 package.
Ordering Information
RT8573
Package Type
S : SOP-16
Note :
Operating Temperature Range
G : Green (Halogen Free with Commer-
cial Standard)
Richtek Green 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
RT8573
GSYMDNN
RT8573GS : Product Number
YMDNN : Date Code
Features
z High Voltage Capability : VIN Up to 36V, VOUT is
limited by External MOSFET Switch
z Boost Operation
z Current Mode PWM with Programmable Switching
Frequency
z Easy Dimming Control : Analog or Digital
Converting to Analog with One External Capacitor
z True PWM Dimming : External FET Driver is Build-
In
z Programmable Soft-Start to Avoid Inrush Current
z Programmable Over Voltage Protection
z VIN Undervoltage Lockout and Thermal Shutdown
z 16-Lead SOP Package
z RoHS Compliant and Halogen Free
Applications
z General Industrial High Power LED Lighting
z Desk Lights and Room Lighting
z Building and Street Lighting
z Industrial Display Backlight
Pin Configurations
(TOP VIEW)
GBIAS
GATE
PWMOUT
ISW
PWMDIM
ISP
ISN
VC
2
3
4
5
6
7
8
16 GND
15 VCC
14 RSET
13 OVP
12 EN
11 SS
10 DCTL
9 ACTL
SOP-16
DS8573-P00 August 2010
www.richtek.com
1
1 page  
Function Block Diagram
Preliminary
RT8573
EN
RSET
VCC
OVP
VC
SS
DCTL
1.4V
4.5V
1.2V
8.5V
+ Shutdown
-
OSC
-
+
+
-
+
-
S
R
R
RR
VCC
5V
100k
GBIAS
- 110mV
+
6µA
1.2V
+
-
-
GM
+
+
-
GBIAS
GATE
PWMOUT
PWMDIM
ISW
ISN
ISP
GND
ACTL
VISP – VISN
(mV)
190
0 0.25
1.25
VACTL (V)
DS8573-P00 August 2010
www.richtek.com
5
5 Page 
Preliminary
RT8573
Application Information
The RT8573 is a constant frequency, current mode
controller which drives an external MOSFET for PWM LED
applications, DC/DC Boost, SEPIC and Flyback converter.
When using an external load switch, the PWMDIM input
not only drives PWMOUT, but also enables controller GATE
switching and error amplifier operation. This feature provides
extremely fast, true PWM load switching with no transient
overvoltage.
In normal operation with PWMDIM high, GATE goes high
and the power MOSFET is turned on. When the oscillator
sets the PWM latch, the power MOSFET is turned off
when the VC current comparator resets the latch. When
the load current increases, a fall in the ISN voltage relative
to the reference voltage at ISP causes the VC pin to rise
and the average inductor current will therefore rise until it
equals the load current. When PWMDIM goes low,
PWMOUT goes low, VC opens and GATE switching is
disabled. Lowering PWMOUT and disabling GATE causes
the output capacitor, COUT, to hold the output voltage
constant in the absence of load current.
Input UVLO
The input operating voltage range of the RT8573 is 4.5V
to 36V. An input capacitor at the VCC pin can reduce
ripple voltage. It is recommended to use a ceramic 10μF
or larger capacitance as the input capacitor. This IC provides
an Under Voltage Lockout (UVLO) function to enhance
the stability when startup. The UVLO threshold of input
rising voltage is set at 4.5V typically with a 0.7V
hysteresis.
Power Sequence
Please refer to below Figure 6 and 7. The recommended
power-on sequence suggests the PWM to be ready before
EN and/or VIN is ready. If not, the soft-start function will
be disabled. As for power-off sequence, EN/VIN must be
pulled low within 10ms to prevent “Hard-Start” as shown
Figure 8.
Power on
sequence
VIN
Power off
sequence
Abnormal Power
on sequence
UVLO
PWM
EN
VOUT
EN must be turned
on later than VIN
and PWM signal EN must be turned
off early than VIN
Soft-Start
and PWM signal
No Soft-Start
if PWM turns
on later
Figure 6. Power On Sequence Control by EN
Power on
sequence
Power off
sequence
Abnormal Power
on sequence
VIN
UVLO
PWM
EN
VOUT
VIN must be
turned off parlier
than EN and PWM
signal
Soft-Start
VIN must be
turned on later
than EN and
PWM signal
No Soft-Start
if PWM turns
on late
Figure 7. Power On Sequence Control by VIN
EN/VIN
PWM
EN and/or VIN should
be pulled low once
PWM pulls low for
over 10ms
10ms
Figure 8. To Prevent “Hard-Start” Sequence
DS8573-P00 August 2010
www.richtek.com
11
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet RT8573.PDF ] | |
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