Richtek RT8511AGQW, RT8511AGQWA Schematic [ru]

®

43V Asynchronous Boost WLED Driver

RT8511A

General Description

The RT851 1A is a n LED driver IC that ca n support up to 10
WLED in series. It is composed of a current mode boost
converter integrated with a 43V/1.2A power switch running
at a fixed 1MHz frequency and covering a wide VIN ra nge
from 2.7V to 24V.

The white LED current is set with a n external resistor , and
the feedback voltage is regulated to 200mV (typ.). During
operation, the LED current ca n be controlled by the PWM
input signal in which the duty cycle determines the
feedback reference voltage.

For brightness dimming, the RT851 1A is able to maintain
steady control of the LED current. Therefore, no audible
noises are generated on the output cap acitor . The RT851 1A
also has programmable over voltage pin to prevent the
output from exceeding absolute maximum ratings during
open LED conditions. The RT8511A is available in
W DFN-8L 2x2 a nd WDF N-8L 3x3 pa ckages.

Features



Wide Input Voltage Range : 2.7V to 24V







 High Output Voltage : up to 43V





 Direct PWM Dimming Control and Frequency from



100Hz to 1kHz



 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 2x2 and 8-Lead 3x3 WDFN Packages





 RoHS Compliant and Halogen Free



Applications

 UMPC and Notebook Computer Backlight
 GPS, Portable DVD Backlight

Pin Configurations

Ordering Information

RT8511A

Package Type
QW : WDFN-8L 2x2 (W-Type)
QWA : WDFN-8L 3x3 (W-Type)

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.

(TOP VIEW)

1

OVP

2

FB

3

DIMC

GND

GND

4

9

WDFN-8L 2x2 / WDFN-8L 3x3

Marking Information

RT8511AGQW

14 : Product Code

14W

RT851 1AGQWA

22=YM

DNN

W : Date Code

22= : Product Code
YMDNN : Date Code

8
7
6
5

EN
PWM
VIN
LX

Copyright 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.

©

DS8511A-05 June 2014 www.richtek.com

1

RT8511A

Typical Application Circuit

V

4.2V to 24V

Chip Enable

100Hz to 1kHz

V

2.7V to 24V

Chip Enable

100Hz to 1kHz

IN

PWM

LED

2.7V to 4.2V

PWM

C

IN

1µF x 2

C

DIMC

1µF

Figure 1. T ypical Application Circuit of Normal Operation

C

LED

1µF x 2
V

IN

C

DIMC

1µF

C

1µF

IN

6

8

7
3

6

8

7
3

VIN

EN

PWM
DIMC

VIN

EN

PWM
DIMC

L

10µH

RT8511A

L

10µH

RT8511A

5

LX

1

OVP

2

FB

4, 9 (Exposed Pad)

GND

5

LX

1

OVP

2

FB

4, 9 (Exposed Pad)

GND

V

D

R2

3.3M
C

OUT

1µF x 2

R1
100k

D

R2

3.3M
C

OUT

1µF x 2

R1
100k

OUT

:

:
:
:
:

:

:

:

WLEDs

:

:

:

:

R

SET

3.3

V

OUT

:

:
:
:
:

:

:

:

WLEDs

:

:

:

:

R

SET

3.3

Figure 2. T ypical Application Circuit of Low V oltage 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
3 DIMC PWM Filter Pin. Filter the PWM signal to a DC voltage.

4 GND Ground Pin.
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 (Ex posed Pad) GND

Copyright 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.

2

©

Fe edbac k Pin. Con nect a resi stor betw een th is p in and GND to se t the LED
current.

T he ex pos ed pad mus t be so lde r ed to a larg e P CB and co nne cte d to A GND for
maximum power dissipation.

DS8511A-05 June 2014www.richtek.com

Function Block Diagram

RT8511A

LXOVP

VIN

EN

PWM

DIMC

FB

OSC

LX

Detection

PWM

Controller

D/A

Dimming

+

1.2V

-

QS

R

Q

-

0.8V

+

+

-

+

-

OTP

OCP

GND

Copyright 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.

©

DS8511A-05 June 2014 www.richtek.com

3

RT8511A

Absolute Maximum Ratings (Note 1)

 VIN, EN, PWM, DIMC to GND------------------------------------------------------------------------------------------ −0.3V to 26.5V
 LX, FB, OVP to GND ----------------------------------------------------------------------------------------------------- −0.3V to 48V
 Power Dissipation, P

WDFN-8L 2x2 -------------------------------------------------------------------------------------------------------------- 0.833W
WDFN-8L 3x3 -------------------------------------------------------------------------------------------------------------- 1.429W

 Package Thermal Re sistance (Note 2)

W DF N-8L 2x2, θJA--------------------------------------------------------------------------------------------------------- 120°C/W
WDFN-8L 2x2, θJC--------------------------------------------------------------------------------------------------------- 8.2°C/W
W DF N-8L 3x3, θJA--------------------------------------------------------------------------------------------------------- 70°C/W
WDFN-8L 3x3, θJC--------------------------------------------------------------------------------------------------------- 8.2°C/W

 Lead Temperature (Soldering, 10 sec.)------------------------------------------------------------------------------- 260°C
 Junction T emperature----------------------------------------------------------------------------------------------------- 150°C
 Storage T emperature Range -------------------------------------------------------------------------------------------- –65°C to 150°C
 ESD Susceptibility (Note 3)

HBM (Human Body Model)---------------------------------------------------------------------------------------------- 2kV
MM (Machine Model) ----------------------------------------------------------------------------------------------------- 200V

@ TA = 25°C

D

Recommended Operating Conditions

 Supply Input V oltage, V
 Junction T emperature Range-------------------------------------------------------------------------------------------- −40°C to 125°C
 Ambient T emperature Range-------------------------------------------------------------------------------------------- −40°C to 85°C

------------------------------------------------------------------------------------------------ 2.7V to 24V

IN

(Note 4)

Electrical Characteristics

(V

= 4.5V, T

IN

VIN Quie scent Current

VIN Shutd ow n Cu rr ent I

Control Input

EN, PW M
Threshold Voltage

EN Sink Current IIH V
Shutdown Delay t
PWM Dimming Frequency 0.1 -- 1 kHz

Boost Con verter

= 25°C, unless otherwise specified)

A

Parameter Symbol Test Conditions Min Typ Max Unit

IQ V

VFB = 0V, Switching -- -- 2.2 mA

I

Q_SW

V

SHDN

Logic-High VIH V
Logic- Low V

V

IL

EN high to low 26 32 40 ms

SHDN

= 1.5V, No Switching -- 725 -- A

FB

= 4.5V, VEN = 0V -- 1 4 A

IN

= 2.7V to 24V 1.6 -- --

IN

= 2.7V to 24V -- -- 0.8

IN

= 3V 1 -- 10 A

EN

V

Switching Frequency f
LX On Re sist ance

(N-MOSFET)

V

OSC

R

VIN > 5V -- 0.4 0.6 

DS(ON)

= 2.7V to 24V 0.8 1 1.2 MHz

IN

Minimum ON Time -- 100 -- ns
Maximum Du ty Cycl e D

V

MAX

= 0V, Switching -- 92 -- %

FB

Copyright 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.

4

©

DS8511A-05 June 2014www.richtek.com