Richtek RT8561CGQW Schematic [ru]

High Voltage 8-CH LED Driver

RT8561C

General Description

The RT8561C is a 40V 8-CH LED driver capable of

delivering 30mA to each channel with 10 LEDs (3.6V per

diode), for a total of 80 LEDs with one driver. The RT8561C

is a current mode boost converter that operates at 1MHz,

with a wide V

range from 4.5V to 24V and an on chip

IN

current switch rated at 2.5A.

The PWM output voltage loop regulates the LED pins to

0.6V with an auto adjustment circuit allowing voltage

mismatches between LED strings. The RT8561C automati

cally detects and disconnects any unconnected and/or

broken strings during operation from the PWM loop to

prevent V

from over voltage.

OUT

The 1.5% matched LED currents on all channels can be

simply programmed with a resistor or a current sink. A

very high contrast ratio true digital PWM dimming can be

achieved by driving the PWM pin with a PWM signal.

Other protection features include programmable output

over voltage protection, LED current limit, PWM switch

current limit and thermal shutdown.

The RT8561C is available in a WQFN-24L 4x4 package.

Ordering Information

RT8561C

Package Type
QW : WQFN-24L 4x4 (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.

Marking Information

E4= : Product Code

E4=YM

DNN

YMDNN : Date Code

Features

z High Voltage : V
z Programma ble Channel Current from 10mA to 30mA

and Matched to 1.5%

z Current Mode PWM 1MHz Boost Converter
z Easy and High Accuracy Digital Dimming by PWM

Signal

z Programmable Soft-Start
z Automatic Detection of Unconnected and/or Broken

Channel

z Programmable Over Voltage Protection
z Disconnects LED in Shutdown
z No Power Sequence Concern
z V

Under Voltage Lockout

IN

zz

z Over Temperature Protection

zz

zz

z Current Limiting Protection

zz

zz

z Small 24-Lead WQFN Package

zz

zz

z RoHS Compliant and Halogen Free

zz

up to 24V, V

IN

up to 40V

OUT

Applications

z UMPC and Notebook Computer Backlight

z GPS, Portable DVD Backlight

z Desk Lights and Room Lighting

Pin Configurations

(TOP VIEW)

RISET GND

LX

LX

18

VCC

17

CREG

16

LED8

15

LED7

14

NC

LED6

13

EN

25

11

ACTL

LED1

LED2

LED3

LED4

LED5

OVP

GND

GND

24 2223

1

2

3

4

5

6

7

8 9 10 12

VC

NC

WQFN-24L 4x4

GND

21 20 19

GND

SS

DS8561C-00 April 2011 www.richtek.com

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RT8561C

Typical Application Circuit

L1

VCC

EN5V

ACTL

7

VC

CREG

9

SS

GND

10µH

RT8561C

LX

LED1

LED2

LED7

LED8

OVP

RISET

...

19, 20

1

2

15

16

6

10

I

LED

V

4.5V to 24V

C8

IN

PWM Signal

R1

1.8k

C2

3.9nF

C1

R4

10µF

10

C6

1µF

R5
1k

1k

R6

C3

4.7µF

C4

0.1µF

21, 22, 23, 24,

25 (Exposed Pad)

18

13

11

17

Note :

Due to the limitation of maximum duty, 5V input can support typically to V

D1

R7

R

ISET

4.75k

(mA) =

C5
10µF

C7

...

R(k)

= 33V.

OUT

R2

R3

20 x 4.75

ISET

:
:
:
:

Ω

V

OUT

40V MAX

:

:

...

:

:

:

:

:

:

V

OUT

:

8 x 10 LED String

:
:
:

Figure 1. 1MHz, 20mA Full Scale Current PWM Dimming Control

Function Block Diagram

VCC

OVP

EN

CREG

VC

SS

ACTL

GND

4.2V

1.2V

1.6V

LDO

5V

5µA

­+

+

-

­+

Shutdown

OSC

S

R

R

+

-

V

OUT

Regulation

Unit

LX

+

-

+

-

LED1

LED2

.
.
.

+

5V

+

-

-

+

-

LED7

LED8

RISET

DS8561C-00 April 2011www.richtek.com

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Functional Pin Description

Pin No. Pi n Na m e Pin Fun c tion

LED1, LED2,

1, 2, 3, 4, 5

6 OVP

7 VC PWM boost converter loop compensation node.

8 NC No Internal Connection.

9 SS Soft Start Pin, a capacitor of at least 10nF is required for soft start.

10 RISET A resistor or a current from DAC on this pin programs the full LED current.

LED3, LED4,
LED5

Channel 1 to Channel 5 LED current sink. Leave the pin unconnected if not
used.

Over Voltage Protection. PWM boost converter turns off when V
higher than 1.2V.

RT8561C

goes

OVP

11 ACTL

12 NC No Internal Connection.

13 EN Chip enable pin, when pulled low, chip is in shutdown mode.

14, 15, 16

17 CREG

18 VCC Power supply of the chip. For good bypass, a low ESR capacitor is required.

19, 20 LX PWM boost converter switch node.

21, 22, 23, 24,

25 (Exposed Pad)

LED6, LED7,
LED8

GND

Analog/Digital dimming control. When using analog dimming,

I ( mA) = for V 1.2V .

LED ACTL

Channel 6 to Channel 8 LED current sink. Leave the pin unconnected if not
used.

4.7μF capacitor should be placed on this pin to stabilize the 5V output of the
internal regulator. This regulator is for chip internal use only.

Ground pin of the chip. The exposed pad mus t be soldered to a large PCB
and connected to GND for maximum power dissipation.

20 x 4.75

R(k)

ISET

Ω

≥

DS8561C-00 April 2011 www.richtek.com

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RT8561C

Absolute Maximum Ratings (Note 1)

z Supply Voltage, VCC ----------------------------------------------------------------------------------------------------- 28V

z LX Pin Voltage at Switching Off ---------------------------------------------------------------------------------------- 50V

z LED1 to LED8 Pin--------------------------------------------------------------------------------------------------------- 50V

z ACTL, EN ------------------------------------------------------------------------------------------------------------------- 24V

z OVP -------------------------------------------------------------------------------------------------------------------------- −0.3V to 5.5V

z Power Dissipation, P

WQFN-24L 4x4 ------------------------------------------------------------------------------------------------------------ 1.923W

z Package Thermal Resistance (Note 2)

WQFN-24L 4x4, θJA------------------------------------------------------------------------------------------------------- 52°C/W

WQFN-24L 4x4, θJC------------------------------------------------------------------------------------------------------ 7°C/W

z Junction Temperature ----------------------------------------------------------------------------------------------------- 150°C

z Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------- 260°C
z Storage Temperature Range -------------------------------------------------------------------------------------------- −65°C to 150°C

z ESD Susceptibility (Note 3)

HBM (Human Body Mode) ---------------------------------------------------------------------------------------------- 2kV

MM (Machine Mode) ------------------------------------------------------------------------------------------------------ 200V

@ TA = 25°C

D

Recommended Operating Conditions (Note 4)

z Supply Input Voltage, VCC---------------------------------------------------------------------------------------------- 4.5V to 24V

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

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

−40°C to 125°C

−40°C to 85°C

Electrical Characteristics

(VCC = 17V, T

Supply Current I

VIN Under Voltage Lockout
Threshold

Shutdown Current I

EN Threshold
Voltage

ACTL Threshold
Voltage

EN Pin Input Current IEN VEN ≤ 5V -- -- 0.1 μA

LED Curre nt Programming

LED Curr ent I

LEDs Current Matching

RISET Pin Voltage V

Input Current of ACTL I

V

Threshold Un-connection -- 0.1 -- V

LED

= 25°C, unless otherwise specified)

A

Parameter Symbol Test Conditions Min Typ Max Unit

VC ≤ 0.2V (Switching off) -- 3 5 mA

VCC

VIN Rising -- 4.2 4.5

Hysteresis -- 0.3 --

VEN = 0V -- -- 10 μA

1.6 -- 5

-- -- 0.65

1.3 -- 5

-- -- 0.65

2V > V

2V > V
Calculating
(I

(MAX)

3.6kΩ ≤ R

V

ACTL

> 0.6V, R

LED

> 0.6V, R

LED

= 4.75kΩ 19 20 21 mA

ISET

= 4.75kΩ

ISET

-- -- 1.5 %

− I

) / I

(MIN)

≤ 9.6kΩ, V

ISET

Average

x 100%

> 1.2V 1.17 1.2 1.23 V

ACTL

= 1.3V -- 1 2 μA

Logic-High V

Logic-Low

Logic-High V

Logic-Low

V

UVLO

SHDN

EN_H

V

EN_L

ACTL_H

V

ACTL_L

LED

RISET

ACTL

To be continued

V

V

V

DS8561C-00 April 2011www.richtek.com

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RT8561C

Parameter Symbol Test Conditions Min Typ Max Unit

P W M Boos t Conv e r t er

Switching Frequency 0.8 1 1.2 MHz

Minimum On Time -- 100 -- ns

Regulated V

Highest Voltage LED String 0.5 0.6 0.7 V

LED

Amplifier (gm) Output Current 2.4V > VC > 0.2V -- ±15 -- μA

VC Threshold PW M Switch Off 0.1 0.2 -- V

LX R

LX Current Limit I

-- 0.3 0.5 Ω

DS(ON)

2.5 -- -- A

LIM

O VP & So f t St art

OVP Threshold V

OVP Input Curr ent I

1.1 1.2 1.3 V

OVP

V

OVP

≤ 3V -- -- 50 nA

OVP

Soft Start Current ISS VSS ≤ 2.5V 3 5 8 μA

Thermal Shutdown
Temperat ure

-- 150 -- °C

T

SD

Thermal Shutdown Hysteresis -- 20 -- °C

Note 1. Stresses listed as the above “Absolute Maximum Ratings” may cause permanent damage to the device. These are for

stress ratings. 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 for extended

periods may remain possibility to affect device reliability.

Note 2. θ

Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.

is measured in the natural convection at TA = 25°C on a high effective four layers thermal conductivity test board of

JA

JEDEC 51-7 thermal measurement standard. The case point of θ

is on the expose pad for the WQFN package.

JC

DS8561C-00 April 2011 www.richtek.com

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