®
RT8511B
43V Asynchronous Boost WLED Driver
General Description
The RT8511B is an LED driver IC that can support up to 10 WLED in series. It is composed of a current mode boost converter integrated with a 43V/2.2A power switch running at a fixed 500kHz frequency and covering a wide VIN range from 2.7V to 24V.
The white LED current is set with an external resistor, and the feedback voltage is regulated to 200mV (typ.). During operation, the LED current can be controlled by the PWM input signal in which the duty cycle determines the feedback reference voltage.
For brightness dimming, the RT8511B is able to maintain steady control of the LED current. Therefore, no audible noises are generated on the output capacitor. The RT8511B also has programmable over voltage pin to prevent the output from exceeding absolute maximum ratings during open LED conditions. The RT8511B is available in WDFN-8L 2x2 package.
Features
Wide Input Voltage Range : 2.7V to 24V
High Output Voltage : up to 43V
Direct PWM Dimming Control and Frequency from 100Hz to 8kHz
Internal Soft-Start and Compensation
200mV Reference Voltage
PWM Dimming with Internal Filter
Programmable Over Voltage Protection
Over Temperature Protection
Current Limit Protection
Thin 8-Lead WDFN Package
RoHS Compliant and Halogen Free
Applications
UMPC and Notebook Computer Backlight
GPS, Portable DVD Backlight
Ordering Information
RT8511B 
Package Type
QW : WDFN-8L 2x2 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
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.
Pin Configurations
(TOP VIEW)
OVP 1 |
GND |
8 |
EN |
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FB 2 |
7 |
PWM |
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DIMC |
3 |
6 |
VIN |
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GND |
4 |
9 |
5 |
LX |
WDFN-8L 2x2
Marking Information
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0F : Product Code |
0FW |
W : Date Code |
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Copyright ©2015 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
DS8511B-05 February 2015 |
www.richtek.com |
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1 |
RT8511B
Typical Application Circuit
VIN
4.2V to 24V
Chip Enable
PWM 100Hz to 8kHz
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L |
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D |
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VOUT |
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10µH |
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6 |
RT8511B |
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5 |
R2 |
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VIN |
LX |
3.3M |
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CIN |
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: WLEDs |
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COUT |
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1µF x 2 |
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OVP |
1 |
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1µF x 2 |
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8 EN |
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R1 |
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100k |
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7 PWM |
FB 2 |
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GND |
4, 9 (Exposed Pad) |
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3.3 |
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3 DIMC |
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RSET |
CDIMC |
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1µF |
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Figure 1. Typical Application Circuit of Normal Operation |
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L |
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D |
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VOUT |
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VLED |
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10µH |
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2.7V to 24V |
CLED |
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1µF x 2 |
RT8511B |
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5 |
R2 |
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VIN |
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6 VIN |
LX |
3.3M |
WLEDs |
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2.7V to 4.2V |
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CIN |
OVP 1 |
COUT |
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Chip Enable |
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1µF |
1µF x 2 |
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8 EN |
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R1 |
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100k |
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PWM |
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7 PWM |
FB 2 |
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RSET |
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100Hz to 8kHz |
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3 DIMC |
GND 4, 9 (Exposed Pad) |
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3.3 |
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CDIMC |
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1µF |
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Figure 2. Typical Application Circuit of Low Voltage Operation
Functional Pin Description
Pin No. |
Pin Name |
Pin Function |
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1 |
OVP |
Over Voltage Protection for Boost Converter. The detecting threshold is 1.2V. |
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2 |
FB |
Feedback. Connect a resistor between this pin and GND to set the LED current. |
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3 |
DIMC |
PWM Filter. Filter the PWM signal to a DC voltage. |
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4 |
GND |
Ground. |
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5 |
LX |
Switch Node for Boost Converter. |
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6 |
VIN |
Power Supply Input. |
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7 |
PWM |
Dimming Control Input. |
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8 |
EN |
Chip Enable (Active High) for Boost Converter. |
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9 (Exposed Pad) |
GND |
The exposed pad must be soldered to a large PCB and connected to AGND for |
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maximum power dissipation. |
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Copyright ©2015 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
www.richtek.com |
DS8511B-05 February 2015 |
2 |
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RT8511B
Function Block Diagram
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OVP |
LX |
VIN |
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+ |
1.2V |
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EN |
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- |
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OTP |
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OSC |
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S |
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Q |
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R |
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Q |
OCP |
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PWM |
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- |
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Controller |
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+ |
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PWM |
D/A |
+ |
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DIMC |
Dimming |
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GND |
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FB |
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- |
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Copyright ©2015 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
DS8511B-05 February 2015 |
www.richtek.com |
|
3 |
RT8511B
Absolute Maximum Ratings |
(Note 1) |
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VIN, EN, PWM, DIMC to GND------------------------------------------------------------------------------------------ |
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−0.3V to 26.5V |
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FB, OVP to GND ---------------------------------------------------------------------------------------------------------- |
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−0.3V to 48V |
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LX to GND ------------------------------------------------------------------------------------------------------------------ |
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−0.3V to 48V |
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< 500ns ---------------------------------------------------------------------------------------------------------------------- |
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−1V to 48V |
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Power Dissipation, PD @ TA = 25°C |
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WDFN-8L 2x2 -------------------------------------------------------------------------------------------------------------- |
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0.833W |
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Package Thermal Resistance |
(Note 2) |
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WDFN-8L 2x2, θJA --------------------------------------------------------------------------------------------------------- |
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120°C/W |
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WDFN-8L 2x2, θJC --------------------------------------------------------------------------------------------------------- |
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8.2°C/W |
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Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------- |
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260°C |
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Junction Temperature ----------------------------------------------------------------------------------------------------- |
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150°C |
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Storage Temperature Range -------------------------------------------------------------------------------------------- |
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–65°C to 150°C |
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ESD Susceptibility |
(Note 3) |
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HBM (Human Body Model) ---------------------------------------------------------------------------------------------- |
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2kV |
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MM (Machine Model) ----------------------------------------------------------------------------------------------------- |
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200V |
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Recommended Operating Conditions |
(Note 4) |
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Supply Input Voltage, VIN ------------------------------------------------------------------------------------------------ |
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2.7V to 24V |
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Junction Temperature Range -------------------------------------------------------------------------------------------- |
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−40°C to 125°C |
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Ambient Temperature Range -------------------------------------------------------------------------------------------- |
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−40°C to 85°C |
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Electrical Characteristics |
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(VIN = 4.5V, TA = 25°C, unless otherwise specified) |
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Parameter |
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Symbol |
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Test Conditions |
Min |
Typ |
Max |
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Unit |
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VIN Quiescent Current |
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IQ |
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VFB = 1.5V, No Switching |
-- |
725 |
-- |
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A |
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IQ_SW |
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VFB = 0V, Switching |
-- |
-- |
2.2 |
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mA |
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VIN Shutdown Current |
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ISHDN |
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VIN = 4.5V, VEN = 0V |
-- |
1 |
4 |
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A |
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Control Input |
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EN, PWM |
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Logic-High |
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VIH |
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VIN = 2.7V to 24V |
1.6 |
-- |
-- |
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V |
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Threshold Voltage |
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Logic-Low |
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VIL |
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VIN = 2.7V to 24V |
-- |
-- |
0.8 |
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EN Sink Current |
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IIH |
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VEN = 3V |
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1 |
-- |
10 |
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A |
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Shutdown Delay |
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tSHDN |
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EN high to low |
52 |
64 |
80 |
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ms |
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PWM Dimming Frequency |
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0.1 |
-- |
8 |
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kHz |
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Boost Converter |
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Switching Frequency |
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fOSC |
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VIN = 2.7V to 24V |
0.4 |
0.5 |
0.6 |
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MHz |
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LX On Resistance |
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RDS(ON) |
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VIN > 5V |
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-- |
0.4 |
0.6 |
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(N-MOSFET) |
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Minimum ON Time |
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-- |
60 |
-- |
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ns |
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Maximum Duty Cycle |
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DMAX |
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VFB = 0V, Switching |
-- |
92 |
-- |
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% |
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Copyright ©2015 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
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www.richtek.com |
DS8511B-05 February 2015 |
4 |
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