Richtek RT8510GQW Schematic [ru]

RT8510

43V 4-CH LED Driver

General Description

The RT8510 is a high efficiency driver for white LEDs. It is designed for LCD panels that employ an array of LEDs as the lighting source. An integrated switch current mode boost controller drives four strings in parallel and supports up to 12 pieces of LED per string. The internal current sinks support a maximum of ±2% current mismatching for excellent brightness uniformity in each string of LED. To provide enough headroom for current sink operation the boost controller monitors the minimum voltage of feedback pins and regulates an optimized output voltage for power efficiency.

The RT8510 has a wide input voltage range from 4.2V to 24V and provide an adjustable 10mAto 40mALEDcurrent. The internal 200mΩ, 43V power switch with current-mode control provides cycle-by-cycle over current protection. RT8510 also integrates PWM dimming function for accurate LED current control. The input PWM dimming frequency can operate from 120Hz to 30kHz without inducing any inrush current through the LED or inductor. The switching frequency of the RT8510 is adjustable from 500kHz to 2MHz, allowing the user flexibility between efficiency and component size.

The RT8510 is available in a WQFN-16L 3x3 package.

Ordering Information

RT8510

Package Type

QW : WQFN-16L 3x3 (W-Type)

Lead Plating System

G : Green (Halogen Free and Pb Free) Z : ECO (Ecological Element with

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.

Features

zWide Input Voltage : 4.2V to 24V

zHigh Output Voltage : Up to 43V

zAdjustable Channel Current : 10mA to 40mA

zChannel Current Accuracy : ±3%

zChannel Current Matching : ±2%

zPWM Dimming Frequency : 120Hz to 30kHz

zAdjustable Switching Frequency : 500kHz to 2MHz

zBuilt-In Soft-Start

zDisconnects LED in Shutdown

zOpen Current Sink Detection

zAdjustable Over Voltage Protection

zOver Temperature Protection

zCurrent Limit Protection

zThin 16-Lead WQFN Package

zRoHS Compliant and Halogen Free

Applications

zUMPC and Notebook Computer Backlight

zGPS, Portable DVD Backlight

Pin Configurations

(TOP VIEW)

		CH4	CH3	CH2	CH1
		16	15	14	13
	AGND	1			12	OVP
	COMP	2	GND		11	PGND
	ISET	3			10	PGND
	RT			17		LX
		4			9
		5	6	7	8
		PWM	EN	VIN	LX
		WQFN-16L 3x3

DS8510-03 June 2011	www.richtek.com
	1

RT8510

Marking Information

HU= : Product Code

YMDNN : Date Code

HU=YM

DNN

Typical Application Circuit

VOUT

L

D1

43V MAX

VIN

10µH

4.2V to 24V

CIN

R2

10µF

10

RT8510

8, 9

ROVP2

:

:

:

:

7

VIN

LX

2M

10 LED String

C2

:

:

:

:

COUT

:

:

:

:

Chip Enable

1µF

OVP

12

6 EN

10µF

:

:

:

:

ROVP1

100k

62k

PWM Dimming

5

PWM

CH1

13

2

COMP

CH2

14

C4

R3

4 RT

CH3

15

10k

3

ISET

CH4

16

1nF

C3

RRT

AGND

PGND

51k

RISET

10nF

10, 11

1

4.75k

Figure 1. General Application Circuit

VOUT

23V MAX

L

D1

(VOUT depends on DMAX)

VBATT

10µH

2.7V to 24V

CIN

10µF

RT8510

7

8, 9

ROVP2

:

:

:

:

5V

VIN

LX

2M

10 LED String

C2

COUT

:

:

:

:

10µF

:

:

:

:

Chip Enable

1µF

6 EN

OVP 12

:

:

:

:

ROVP1

100k

62k

PWM Dimming

5 PWM

CH1 13

2 COMP

CH2 14

C4

R3

4 RT

CH3 15

10k

3

ISET

CH4 16

1nF

C3

RRT

AGND

PGND

51k

RISET

10nF

10, 11

1

4.75k

Figure 2. Low Input Voltage Application Circuit

www.richtek.com

DS8510-03 June 2011

2

RT8510

Function Pin Description

Pin No.

Pin Name

Pin Function

1

AGND

Analog Ground of LED Driver.

2

COMP

Compensation Pin

for Error Amplifier. Connect a compensation network to

ground.

LED Current Set Pin. LED current is set by the value of the resistor RISET

connected from the ISET pin to ground. Do not short the ISET pin. VISET is

3

ISET

typically 0.6V.

95

I =

LED

RISET

4

RT

Frequency Adjust Pin. This pin allows setting the switching frequency with a

resistor to 500kHz to 2MHz.

5

PWM

Dimming Control Input.

6

EN

Chip Enable (Active High). Note that this pin is high impedance. There should be

a pull low 100kΩ resistor connected to GND when the control signal is floating.

7

VIN

Power Supply Input.

8, 9

LX

Switching Pin of Boost Converter.

10, 11

PGND

Power Ground of Boost Converter.

12

OVP

Sense Input for Over Voltage Protection. The detecting threshold is 1.2V.

13, 14, 15, 16

CH1 to CH 4

Current Sink for LED. Leave the pin unconnected, if not used.

17 (Exposed Pad)

GND

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

maximum power dissipation.

Function Block Diagram

OVP

LX

EN VIN

+

1.2

-

RT

OSC

Regulator

S

Q

R

Q

OCP

OTP

PWM

+

PGND

Controller

-

0.4V

COMP

EA+

4

-

LED

PWM

Detection

CH1

CH2

CH3

+

CH4

+

+

: :

+	0.6V	-	-	-
-
ISET

AGND

DS8510-03 June 2011

www.richtek.com

3

RT8510

Absolute Maximum Ratings (Note 1)

z Supply Input Voltage to GND ------------------------------------------------------------------------------------------	−0.3V to 26.5V
z EN, PWM, ISET, COMP, RT to GND --------------------------------------------------------------------------------	−0.3V to 26.5V
z LX, OVP, CH1, CH2, CH3, CH4 to GND ----------------------------------------------------------------------------	−0.3V to 48V
z Power Dissipation, PD @ TA = 25°C
WQFN-16L 3x3 -----------------------------------------------------------------------------------------------------------	1.471W
z Package Thermal Resistance (Note 2)
WQFN-16L 3x3, θJA -----------------------------------------------------------------------------------------------------	68°C/W
WQFN-16L 3x3, θJC -----------------------------------------------------------------------------------------------------	7.5°C/W
z Lead Temperature (Soldering, 10 sec.) -----------------------------------------------------------------------------	260°C
z Junction Temperature ---------------------------------------------------------------------------------------------------	150°C
z Storage Temperature Range -------------------------------------------------------------------------------------------	−65°C to 150°C
z ESD Susceptibility (Note 3)
HBM ------------------------------------------------------------------------------------------------------------------------	2kV
MM --------------------------------------------------------------------------------------------------------------------------	200V

Recommended Operating Conditions	(Note 4)
z Supply Input Voltage, VIN ----------------------------------------------------------------------------------------------	4.2V to 24V
z Junction Temperature Range ------------------------------------------------------------------------------------------	−40°C to 125°C
z 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	VCOMP = 0V, No Switching	--	1	1.5	mA
				VCOMP = 2V, Switching		2	3
	VIN Shutdown Current		ISHDN	VIN = 4.5V, EN = 0V	--	--	10	μA
	VIN Under Voltage Lockout		UVLO	Rising	--	2.2	--	V
				Falling	--	2.1	--
	Control Input
	EN, PWM Threshold	Logic-High	VIH	VIN = 4.2V to 24V	2	--	--	V
	Voltage	Logic-Low	VIL		--	--	0.8
	PWM Dimming Frequency		fPWM		120	--	30k	Hz
	EN, PWM Leakage Current		ILKG		2	--	6	μA
	EN Shutdown Delay		tEN	RRT = 51kΩ	--	32	--	ms
	Boost Converter
				RRT = 25kΩ	--	2	--
	Switching Frequency		fOSC	RRT = 51kΩ	--	1	--	MHz
				RRT = 102kΩ	--	0.5	--
	LX On Resistance (N-MOSFET)		RDS(ON)_N	VIN > 4.5V	--	0.2	0.32	Ω
	Minimum ON Time		tMON		--	120	--	ns
	Maximum Duty		DMAX	VCOMP = 2V, Switching	--	90	--	%
	LX Current Limit		ILIM		--	2	--	A

	To be continued
www.richtek.com	DS8510-03 June 2011
4