Richtek RT8511BGQW Schematic [ru]

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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

FB 2

7

PWM

DIMC

3

6

VIN

GND

4

9

5

LX

WDFN-8L 2x2

Marking Information

 

0F : Product Code

0FW

W : Date Code

 

 

Copyright ©2015 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS8511B-05 February 2015

www.richtek.com

 

1

Richtek RT8511BGQW Schematic

RT8511B

Typical Application Circuit

VIN

4.2V to 24V

Chip Enable

PWM 100Hz to 8kHz

 

L

 

 

D

 

 

VOUT

 

10µH

 

 

 

 

 

6

RT8511B

 

5

R2

:

:

:

VIN

LX

3.3M

CIN

 

 

 

 

:

:

: WLEDs

 

 

 

COUT

:

:

:

1µF x 2

 

OVP

1

 

 

1µF x 2

:

:

:

8 EN

 

 

R1

 

 

 

 

 

 

 

100k

 

 

 

7 PWM

FB 2

 

 

 

 

GND

4, 9 (Exposed Pad)

 

 

3.3

3 DIMC

 

 

 

 

 

 

 

 

 

RSET

CDIMC

 

 

 

 

 

 

 

1µF

 

 

 

 

 

 

 

 

 

Figure 1. Typical Application Circuit of Normal Operation

 

 

 

 

 

 

 

L

 

 

D

 

 

VOUT

VLED

 

 

10µH

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2.7V to 24V

CLED

 

 

 

 

 

 

 

 

 

 

1µF x 2

RT8511B

 

5

R2

:

:

:

 

 

 

 

 

 

 

VIN

 

6 VIN

LX

3.3M

WLEDs

 

 

 

:

:

:

2.7V to 4.2V

 

CIN

OVP 1

COUT

:

:

:

 

Chip Enable

 

 

1µF

1µF x 2

:

:

:

 

 

 

8 EN

 

 

R1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

100k

 

 

 

 

PWM

 

 

7 PWM

FB 2

 

 

 

 

 

 

 

 

 

 

 

 

 

RSET

100Hz to 8kHz

 

 

3 DIMC

GND 4, 9 (Exposed Pad)

 

 

 

 

 

 

 

 

 

3.3

 

 

 

CDIMC

 

 

 

 

 

 

 

 

 

 

1µF

 

 

 

 

 

 

 

Figure 2. Typical Application Circuit of Low Voltage Operation

Functional Pin Description

Pin No.

Pin Name

Pin Function

1

OVP

Over Voltage Protection for Boost Converter. The detecting threshold is 1.2V.

2

FB

Feedback. Connect a resistor between this pin and GND to set the LED current.

 

 

 

3

DIMC

PWM Filter. Filter the PWM signal to a DC voltage.

4

GND

Ground.

5

LX

Switch Node for Boost Converter.

6

VIN

Power Supply Input.

7

PWM

Dimming Control Input.

8

EN

Chip Enable (Active High) for Boost Converter.

9 (Exposed Pad)

GND

The exposed pad must be soldered to a large PCB and connected to AGND for

maximum power dissipation.

 

 

Copyright ©2015 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

DS8511B-05 February 2015

2

 

RT8511B

Function Block Diagram

 

 

 

 

OVP

LX

VIN

 

 

+

1.2V

 

EN

 

 

-

 

 

 

 

 

OTP

 

OSC

 

 

 

 

S

 

Q

 

 

 

R

 

Q

OCP

 

 

 

 

 

PWM

 

 

-

 

 

Controller

 

 

+

 

PWM

D/A

+

 

 

 

DIMC

Dimming

 

 

GND

FB

 

-

 

 

 

 

 

 

 

 

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)

 

 

 

 

 

 

VIN, EN, PWM, DIMC to GND------------------------------------------------------------------------------------------

 

 

 

 

 

 

 

−0.3V to 26.5V

FB, OVP to GND ----------------------------------------------------------------------------------------------------------

 

 

 

 

 

 

 

 

−0.3V to 48V

LX to GND ------------------------------------------------------------------------------------------------------------------

 

 

 

 

 

 

 

 

−0.3V to 48V

< 500ns ----------------------------------------------------------------------------------------------------------------------

 

 

 

 

 

 

 

 

−1V to 48V

Power Dissipation, PD @ TA = 25°C

 

 

 

 

 

 

 

 

WDFN-8L 2x2 --------------------------------------------------------------------------------------------------------------

 

 

 

 

 

 

 

 

0.833W

 

Package Thermal Resistance

(Note 2)

 

 

 

 

 

 

 

 

WDFN-8L 2x2, θJA ---------------------------------------------------------------------------------------------------------

 

 

 

 

 

 

 

 

120°C/W

 

WDFN-8L 2x2, θJC ---------------------------------------------------------------------------------------------------------

 

 

 

 

 

 

 

 

8.2°C/W

 

Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------------------

 

 

 

 

 

260°C

 

Junction Temperature -----------------------------------------------------------------------------------------------------

 

 

 

 

 

 

 

150°C

 

Storage Temperature Range --------------------------------------------------------------------------------------------

 

 

 

 

 

 

 

–65°C to 150°C

ESD Susceptibility

(Note 3)

 

 

 

 

 

 

 

 

 

 

HBM (Human Body Model) ----------------------------------------------------------------------------------------------

 

 

 

 

 

 

 

2kV

 

MM (Machine Model) -----------------------------------------------------------------------------------------------------

 

 

 

 

 

 

 

200V

 

Recommended Operating Conditions

(Note 4)

 

 

 

 

 

Supply Input Voltage, VIN ------------------------------------------------------------------------------------------------

 

 

 

 

 

 

 

2.7V to 24V

Junction Temperature Range --------------------------------------------------------------------------------------------

 

 

 

 

 

 

 

40°C to 125°C

Ambient Temperature Range --------------------------------------------------------------------------------------------

 

 

 

 

 

 

 

40°C to 85°C

Electrical Characteristics

 

 

 

 

 

 

 

 

(VIN = 4.5V, TA = 25°C, unless otherwise specified)

 

 

 

 

 

 

Parameter

 

Symbol

 

 

Test Conditions

Min

Typ

Max

 

Unit

VIN Quiescent Current

 

IQ

 

VFB = 1.5V, No Switching

--

725

--

 

A

 

 

 

 

 

 

 

 

 

 

 

IQ_SW

 

VFB = 0V, Switching

--

--

2.2

 

mA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VIN Shutdown Current

 

ISHDN

 

VIN = 4.5V, VEN = 0V

--

1

4

 

A

 

 

 

 

 

 

 

 

 

 

 

 

 

Control Input

 

 

 

 

 

 

 

 

 

 

 

EN, PWM

 

Logic-High

 

VIH

 

VIN = 2.7V to 24V

1.6

--

--

 

V

Threshold Voltage

 

Logic-Low

 

VIL

 

VIN = 2.7V to 24V

--

--

0.8

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

EN Sink Current

 

 

IIH

 

VEN = 3V

 

1

--

10

 

A

 

 

 

 

 

 

 

 

 

 

 

Shutdown Delay

 

 

tSHDN

 

EN high to low

52

64

80

 

ms

 

 

 

 

 

 

 

 

 

 

 

PWM Dimming Frequency

 

 

 

 

 

0.1

--

8

 

kHz

 

 

 

 

 

 

 

 

 

 

 

 

 

Boost Converter

 

 

 

 

 

 

 

 

 

 

 

Switching Frequency

 

fOSC

 

VIN = 2.7V to 24V

0.4

0.5

0.6

 

MHz

 

 

 

 

 

 

 

 

 

 

 

 

LX On Resistance

 

 

RDS(ON)

 

VIN > 5V

 

--

0.4

0.6

 

 

(N-MOSFET)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Minimum ON Time

 

 

 

 

 

 

--

60

--

 

ns

 

 

 

 

 

 

 

 

 

 

Maximum Duty Cycle

 

DMAX

 

VFB = 0V, Switching

--

92

--

 

%

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Copyright ©2015 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

 

www.richtek.com

DS8511B-05 February 2015

4

 

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