Richtek RT8561CGQW Schematic [ru]

Loading...

RT8561C

High Voltage 8-CH LED Driver

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 VIN range from 4.5V to 24V and an on chip 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 VOUT from over voltage.

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 requirements of IPC/JEDEC J-STD-020.

`Suitable for use in SnPb or Pb-free soldering processes.

Marking Information

E4= : Product Code

E4=YM YMDNN : Date Code

DNN

Features

zHigh Voltage : VIN up to 24V, VOUT up to 40V

zProgrammable Channel Current from 10mA to 30mA and Matched to 1.5%

zCurrent Mode PWM 1MHz Boost Converter

zEasy and High Accuracy Digital Dimming by PWM Signal

zProgrammable Soft-Start

zAutomatic Detection of Unconnected and/or Broken Channel

zProgrammable Over Voltage Protection

zDisconnects LED in Shutdown

zNo Power Sequence Concern

zVIN Under Voltage Lockout

zOver Temperature Protection

zCurrent Limiting Protection

zSmall 24-Lead WQFN Package

zRoHS Compliant and Halogen Free

Applications

zUMPC and Notebook Computer Backlight

zGPS, Portable DVD Backlight

zDesk Lights and Room Lighting

Pin Configurations

(TOP VIEW)

 

GND

GND

GND

GND

LX

LX

 

 

 

24

23

22

21

20

19

 

 

LED1

1

 

 

 

 

 

18

VCC

LED2

2

 

 

 

 

 

17

CREG

LED3

3

 

GND

 

 

16

LED8

LED4

4

 

 

 

15

LED7

 

 

 

 

 

LED5

5

 

 

 

 

 

14

LED6

OVP

6

 

 

 

 

25

13

EN

 

 

 

 

 

 

7

8

9

10

11

12

 

 

 

VC

NC

SS

RISET

ACTL

NC

 

 

 

 

WQFN-24L 4x4

 

 

DS8561C-00 April 2011

www.richtek.com

1

Richtek RT8561CGQW Schematic

RT8561C

 

 

 

 

 

 

 

 

 

 

 

 

 

Typical Application Circuit

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VOUT

 

 

 

 

 

 

 

 

L1

 

D1

 

 

 

40V MAX

 

 

 

VIN

 

 

 

10µH

 

 

 

 

 

 

 

 

4.5V to 24V

 

C1

 

 

 

C5

 

 

 

 

 

 

R4

 

 

 

 

 

 

 

 

 

 

 

10µF

RT8561C

 

10µF

:

:

:

 

 

 

10

 

 

 

 

 

:

 

 

 

 

 

 

18

VCC

LX

19, 20

 

:

:

... :

:

8 x 10 LED String

 

 

 

 

 

 

 

 

:

:

:

:

 

 

 

C6

 

 

 

 

 

R7

C7

:

:

:

:

 

 

 

1µF

R5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

 

 

 

 

 

 

 

5V

 

1k

13 EN

LED1

 

 

 

 

 

 

 

 

R6 1k

 

11 ACTL

LED2

2

 

 

 

 

 

 

 

PWM Signal

 

 

...

...

 

 

 

 

 

 

 

 

7 VC

LED7

15

 

 

 

 

 

 

 

 

 

 

LED8

16

 

R2

 

 

 

 

 

R1

 

 

 

17

 

6

 

 

 

 

 

C8

 

 

 

CREG

OVP

 

 

VOUT

 

 

1.8k

 

 

 

 

 

 

 

 

 

 

C2

C3

C4

 

9 SS

RISET

10

 

R3

 

 

 

 

 

4.7µF

 

 

 

 

RISET

 

 

 

 

 

 

3.9nF

 

0.1µF

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4.75k

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

21, 22, 23, 24,

 

 

ILED (mA) =

20 x 4.75

 

 

 

 

 

 

25 (Exposed Pad)

GND

 

RISET (kΩ)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Note :

Due to the limitation of maximum duty, 5V input can support typically to VOUT = 33V.

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

Function Block Diagram

 

 

 

 

LX

 

 

 

VCC

 

-

OSC

 

 

 

 

 

S

 

LED1

 

 

 

4.2V

+

+

 

 

 

 

R

 

 

 

OVP

 

+

-

 

 

 

 

R

 

 

 

1.2V

 

 

 

 

 

-

 

 

 

 

 

EN

 

-

+ -

 

LED2

 

 

 

1.6V

+

 

+

 

 

 

Shutdown

.

 

 

 

5V

 

 

-

 

 

CREG

 

 

 

.

 

 

LDO

 

 

 

 

 

 

 

 

VOUT

 

.

 

 

VC

 

 

 

 

 

 

 

 

Regulation

+

LED7

 

 

 

 

 

Unit

 

 

 

 

 

 

 

-

 

 

 

 

5µA

 

 

5V

 

 

 

 

 

 

 

 

 

 

SS

 

 

 

 

 

 

 

 

 

 

 

+

LED8

 

 

ACTL

 

 

+

 

 

 

 

 

-

 

 

 

GND

 

 

-

 

 

 

 

 

 

 

 

 

 

 

 

 

RISET

 

 

 

www.richtek.com

 

 

 

 

DS8561C-00

April

2011

2

 

 

 

 

 

 

 

 

 

 

 

RT8561C

Functional Pin Description

Pin No.

Pin Name

 

 

Pin Function

 

 

 

 

 

 

LED1, LED2,

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

1, 2, 3, 4, 5

LED3, LED4,

 

LED5

used.

 

 

 

 

6

OVP

Over Voltage Protection. PWM boost converter turns off when VOVP goes

higher than 1.2V.

 

 

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.

 

 

 

11

ACTL

Analog/Digital dimming control. When using analog dimming,

ILED (mA) =

20 x 4.75

for VACTL ≥ 1.2V.

 

 

 

 

 

 

 

 

RISET(kΩ)

12

NC

No Internal Connection.

 

 

 

13

EN

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

 

 

 

14, 15, 16

LED6, LED7,

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

LED8

used.

 

17

CREG

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.

 

 

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,

GND

Ground pin of the chip. The exposed pad must be soldered to a large PCB

25 (Exposed Pad)

and connected to GND for maximum power dissipation.

 

 

 

 

 

 

DS8561C-00 April 2011

www.richtek.com

3

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, PD @ TA = 25°C

 

 

 

 

 

 

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

 

 

Recommended Operating Conditions (Note 4)

 

 

 

 

 

z Supply Input Voltage, VCC ----------------------------------------------------------------------------------------------

 

 

 

 

4.5V to 24V

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

 

 

 

 

−40°C to 125°C

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

 

 

 

 

−40°C to 85°C

Electrical Characteristics

 

 

 

 

 

 

(VCC = 17V, TA = 25°C, unless otherwise specified)

 

 

 

 

 

Parameter

Symbol

Test Conditions

Min

Typ

Max

 

Unit

 

 

 

 

 

 

 

 

 

 

Supply Current

 

IVCC

VC ≤ 0.2V (Switching off)

--

3

5

 

mA

VIN Under Voltage Lockout

VUVLO

VIN Rising

--

4.2

4.5

 

V

Threshold

 

Hysteresis

--

0.3

--

 

 

 

 

 

Shutdown Current

 

ISHDN

VEN = 0V

--

--

10

 

μA

EN Threshold

 

Logic-High

VEN_H

 

1.6

--

5

 

V

Voltage

 

Logic-Low

VEN_L

 

--

--

0.65

 

 

 

 

 

ACTL Threshold

 

Logic-High

VACTL_H

 

1.3

--

5

 

V

Voltage

 

Logic-Low

VACTL_L

 

--

--

0.65

 

 

 

 

 

EN Pin Input Current

IEN

VEN ≤ 5V

--

--

0.1

 

μA

LED Current Programming

 

 

 

 

 

 

 

LED Current

 

ILED

2V > VLED > 0.6V, RISET = 4.75kΩ

19

20

21

 

mA

LEDs Current Matching

 

2V > VLED > 0.6V, RISET = 4.75kΩ

--

--

1.5

 

%

 

Calculating

 

 

 

 

 

(I(MAX) − I(MIN)) / IAverage x 100%

 

 

 

 

 

RISET Pin Voltage

 

VRISET

3.6kΩ ≤ RISET ≤ 9.6kΩ, VACTL > 1.2V

1.17

1.2

1.23

 

V

Input Current of ACTL

IACTL

VACTL = 1.3V

--

1

2

 

μA

VLED Threshold

 

 

Un-connection

--

0.1

--

 

V

 

 

 

 

 

 

 

To be continued

 

 

 

 

 

 

 

 

 

 

www.richtek.com

 

 

 

 

DS8561C-00

April 2011

4

RT8561C

Parameter

Symbol

Test Conditions

Min

Typ

Max

Unit

 

 

 

 

 

 

 

PWM Boost Converter

 

 

 

 

 

 

Switching Frequency

 

 

0.8

1

1.2

MHz

Minimum On Time

 

 

--

100

--

ns

Regulated VLED

 

Highest Voltage LED String

0.5

0.6

0.7

V

 

 

 

 

 

 

 

Amplifier (gm) Output Current

 

2.4V > VC > 0.2V

--

±15

--

μA

 

 

 

 

 

 

 

VC Threshold

 

PWM Switch Off

0.1

0.2

--

V

LX RDS(ON)

 

 

--

0.3

0.5

Ω

LX Current Limit

ILIM

 

2.5

--

--

A

OVP & Soft Start

 

 

 

 

 

 

OVP Threshold

VOVP

 

1.1

1.2

1.3

V

OVP Input Current

IOVP

VOVP ≤ 3V

--

--

50

nA

Soft Start Current

ISS

VSS ≤ 2.5V

3

5

8

μA

Thermal Shutdown

TSD

 

--

150

--

°C

Temperature

 

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. θJA is measured in the natural convection at TA = 25°C on a high effective four layers thermal conductivity test board of JEDEC 51-7 thermal measurement standard. The case point of θJC is on the expose pad for the WQFN package.

Note 3. Devices are ESD sensitive. Handling precaution is recommended.

Note 4. The device is not guaranteed to function outside its operating conditions.

DS8561C-00 April 2011

www.richtek.com

 

5

+ 9 hidden pages