ST STLA02 User Manual

STLA02

White LED driver for display backlight

Features

■Boost DC-DC converter

■Drives up to 6 LEDs with a total current up to 20 mA

■Output power capability up to 500 mW

■Input voltage range 2.5 V to 18 V

■Output current control

■2.3 MHz switching frequency

■PWM input for the output current dimming with 300:1 dimming range

■350 mA integrated switch

■Overvoltage protection

■Chip overtemperature detection and protection

■Soft-start implemented

■Package DFN6 2 x 2 mm

DFN6 (2 x 2 mm)

on/off by the logic signal connected to the EN pin and this pin is also dedicated for the PWM dimming of the output current. Current mode control of the regulation allows a fast response to a change of the enable pin voltage level.

Applications

■PDA and handheld devices

■Cellular phones

■MP3 players

Description

STLA02 is a boost converter that operates from 2.5 V to 18 V and can provide an output voltage as high as 27 V and can drive up to 6 white LEDs connected in series. The total output current capability is 20 mA at an output voltage of 24 V. The total output power capability is up to 500 mW. The regulation is done by the internal error amplifier which works with the feedback voltage from the sensing resistor connected in high side sensing configuration. The device can be turned

Table 1.	Device summary
	Part number	Order code	Package

	STLA02	STLA02PUR	DFN6 (2 x 2 mm)

February 2011		Doc ID 010005 Rev 1	1/23

			www.st.com

Contents	STLA02

Contents

1	Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 3
2	Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 4
3	Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	5
4	Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	6
5	Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	7
6	Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . .	8
7	Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	14
	7.1 PWM input (EN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	14
	7.2 Selection of the external components . . . . . . . . . . . . . . . . . . . . . . . . . . .	14
8	Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	18
9	Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	22

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STLA02	Diagram

1 Diagram

Figure 1.	Block diagram
	VIN			VLX
	BIAS	LOGIC		OVP	VOUT
		LOGIC		VBG
				VBG
EN/	12 V/5 V			STEP-UP
EN/	CONV			CONTROL
PWM
				ILIM
				FB SENSING	FB
					FB
	REFERENCE		VSET	VSET
	ILIM		VBG
	ILIM
				GND	AM07827v1

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Pin configuration	STLA02

2 Pin configuration

Figure 2. Pin connections (top view)

Table 2.	Pin description
Pin n°		Symbol	Name and function

1		VIN	Supply voltage pin
2		GND	Ground

3		LX	Switching pin

4		VOUT	Output voltage pin
5		FB	Feedback voltage

6		EN/PWM	Enable pin or PWM control input for dimming

Exposed pad		GND	Ground

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STLA02				Maximum ratings

3		Maximum ratings
Table 3.		Absolute maximum ratings

Symbol			Parameter	Value	Unit

VIN			Signal supply voltage	- 0.3 to 19	V
VLX			Inductor connection	- 0.3 to 30	V
FB			Feedback connection(1)	- 0.3 to 30	V
EN/PWM			Logic pin/PWM input	- 0.3 to 12	V

VOUT			Output voltage connection	- 0.3 to 30	V
P	TOT		Continuous power dissipation (at T = 70 °C)(1)	530	mW
	TOT		A
TOP			Operating ambient temperature range	- 40 to 85	°C
TJ			Junction temperature	- 40 to 150	°C
TSTG			Storage temperature range	- 65 to 150	°C

1. The maximum acceptable difference between the VOUT pin potential and feedback pin potential is 5 V.

Note:	Absolute maximum ratings are those values beyond which damage to the device may occur.
	Functional operation under these conditions is not implied.
Table 4.	Thermal data

Symbol		Parameter	Value	Unit

R		Thermal resistance junction-ambient (1)	102	°C/W
thJA

1. Power dissipation is dependent on PCB. The recommended PCB design is included in this document (TBD).

Table 5.	ESD
Symbol		Parameter	Value	Unit

HBM		Human body model	2	kV

MM		Machine model	200	V

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Application	STLA02

4 Application

Figure 3. Application schematic

VIN		VIN	VLX
VIN		VIN		VOUT
				VOUT
CIN			STLA02		R	FB
			STLA02			FB
	EN/PWM	EN/PWM		FB
		EN/PWM

			GND			ILED	COUT
						ILED	COUT

AM07828v1

Table 6.	List of external components
Component		Manufacturer	Part number	Value	Size

CIN		MURATA	GRM216R61E105KA12	1 µF / 25 V	0805
COUT		MURATA	GRM216R61E105KA12	1 µF / 25 V	0805
L		MURATA	LQH3NPN100NJ0L	10 µH	3x3x0.9 mm

		TDK	VLF3012ST-100MR59	10 µH	3x2.8x1.2 mm
		TDK	VLF3012ST-100MR59	10 µH	3x2.8x1.2 mm

RFB		TYCO	CPF0402B10RE	10 Ω	0402
LED		OSRAM	LWL283-Q1R2-3K8L-1-Z	20 mA / 3.1 V	0603

Note:	Above listed components refer to a typical application with maximum performance settings.
	Operation of the STLA02 is not limited to the choice of these external components.

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STLA02	Electrical characteristics

5 Electrical characteristics

VEN = VIN = 3 V TA = - 40 °C to 85 °C unless otherwise specified. Typical values are at TA = 25 °C, unless otherwise specified.

Table 7.

Electrical characteristics

Symbol

Parameter

Test conditions

Min.

Typ.

Max.

Unit

VIN

Input operating supply

2.5

voltage

Supply current

VEN = VIN, VOUT = 24 V, VFB = 23 V

VEN = GND

µA

Output current

VIN = 2.5 V to 18 V, RFB = 10 Ω

adjustment

VOUT

Regulated voltage range

VIN = 2.5 V to 18 V

VIN+1

IPEAK

Inductor peak current

VIN = 2.5 V

300

400

550

VFB

Feedback voltage (VOUT -

VEN = VIN, RFB = 10 Ω

190

200

210

VFB)

IFB

FB bias current

VEN = VIN, VOUT = 24 V, VFB = 24 V

µA

ILX(leak)

N-MOS leakage current

VEN = 0, VLX = VOUT = 24 V

0.1

µA

Output current tolerance

VIN = 3 V, IOUT = 0.2 V / RFB

-5

Switching frequency

VIN = 2.5 V, TA = 25 °C

1.7

2.3

MHz

DMAX

Maximum duty cycle

VEN = VIN, VOUT = 24 V, VFB = 24 V

RDSon-N

Internal N-channel RDSon

ILX = 20 mA

0.8

Efficiency of the chip itself

VIN = 10 V, IO = 20 mA, VO = 6 x

VFLED_max + VRSENSE = 24 V (1)

Efficiency of the whole

VIN = 10 V, IO = 20 mA, VO = 6 x

application

VFLED_max + VRSENSE = 24 V (1)

OVP

Output overvoltage

VIN = 3 V, no load

protection

TSHDN

Thermal shutdown

130

150

°C

THYS

Thermal shutdown

°C

hysteresis

VIL

Low and high level input

VIN = 2.5 V to 18 V, VENMAX = 12 V

1.5

VIH

logic signal on EN pin

1.8

VIN

TEN

LED current rise time ILED

VIN

= 9 V, VEN = 0 V to 3 V 6 LEDs in

0.2

= 0 to ILED = 20 mA

series

(1)

TRESPONSE

LED current rise time I

LED

= 9 V, V

= 0 V to 3 V, 6 LEDs in

µs

= 0 mA to I

(1)

LED

= 20 mA

series , V precharged

OUT

1.Guaranteed by design, but not tested in production.

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+ 16 hidden pages

ST STLA02 User Manual

1 Diagram

2 Pin configuration

Figure 2. Pin connections (top view)

Maximum ratings

4 Application

Figure 3. Application schematic

5 Electrical characteristics