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May 2011 Doc ID 12203 Rev 7 1/16

STLD40D

White LED power supply for large display backlight

Features

■ Inductor switches boost controller

■ PFM mode control

■ High efficiency over wide range of input voltage

from 3.0 V to 5.5 V

■ Over voltage protection with automatic restart

■ Adjustable peak current limit

■ Enable pin with possibility of PWM dimming

control

■ Low shutdown current < 1 µA

■ Small external component

■ Good load and line regulation

■ QFN8 3 x 3 mm

Applications

■ White LED supply for LCD backlight

■ Mobile phone

■ PDA and organizers

■ Any handsets powered form 3.0 V to 5.5 V

Description

STLD40D is a boost converter that operates from

3.0 V to 5.5 V. It can provide an output voltage as

high as 37 V and can drive up to 10 white LEDs in

series. The converter is a PFM (pulse frequency

modulation) inductor switch that can work in

discontinuous (DCM) mode operation. A minimum

OFF time of the embedded boost switch T

fixed internally and allows limiting the switching

frequency. The output current capability is 20 mA

with an output voltage of 37 V. The regulation is

done by sensing the LED current through the

resistor R

LED

. The device can be turned ON/OFF

through the logic enable signal pin EN. By

applying a low frequency PWM signal the LEDs

can be dimmed. The maximum peak inductor

current can be programmed by connected a

resistor R

SET

to the pin R

SET

QFN8 (3 x 3 mm)

Table 1. Device summary

Order code Package Packaging

STLD40DPUR QFN8 (3 x 3 mm) 3000 parts per reel

www.st.com

Summary of content (16 pages)

PAGE 1
STLD40D White LED power supply for large display backlight Features ■ Inductor switches boost controller ■ PFM mode control ■ High efficiency over wide range of input voltage from 3.0 V to 5.5 V ■ Over voltage protection with automatic restart ■ Adjustable peak current limit ■ Enable pin with possibility of PWM dimming control ■ Low shutdown current < 1 µA ■ Small external component ■ Good load and line regulation ■ QFN8 3 x 3 mm QFN8 (3 x 3 mm) resistor RLED.
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Contents STLD40D Contents 1 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 Functional description . . . . . . . . .
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STLD40D Block diagram 1 Block diagram Figure 1.
PAGE 4
Pin configuration STLD40D 2 Pin configuration Figure 2. Pin connections (top through view) Table 2. Pin description Pin n° Symbol 1 VI 2 RSET Peak inductor current adjust 3 GND Analog ground 4 FB 5 N.C.
PAGE 5
STLD40D Maximum ratings 3 Maximum ratings Table 3. Absolute maximum ratings Symbol Parameter Value Unit VBSW, VBO Breakdown voltage at VO and SW pin 44 V EN Maximum voltage applied on pin EN VI V VI Supply voltage range 6 V VESD ESD ratings - (HBM MIL STD 883C) 2 kV TOP Operating temperature - 40 to 85 °C TSTG Storage temperature range - 65 to 150 °C Value Unit 52 °C/W Table 4.
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Electrical characteristics 4 STLD40D Electrical characteristics TJ = - 40 °C to 85 °C, VI = 3.6 V, VEN = 3 V, CI = 2.2 µF, CO = 4.7 µF, L = 4.7 µH, RLED = 8 Ω VO = 32 V, typ. values @ 25 °C, unless otherwise specified. Table 5. Electrical characteristics Symbol Parameter Test conditions Min. Typ. Max. Unit VI Input voltage range 3.0 5.
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STLD40D Functional description 5 Functional description 5.1 Boost controller The STLD40D is a boost converter operating in PFM (pulsed frequency modulation) mode. The converter monitors the LED current through the resistor RLED and when the feedback voltage falls below the reference voltage REF2, the boost switch TSW turns ON and the current ramps up. The inductor current is measured by sensing the temperature compensated drain voltage of the boost MOSFET.
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Typical application STLD40D 6 Typical application Figure 3. Application circuit Table 6. External component proposal (see Figure 3) Symbol Parameter Test conditions VRRM Boost schottky diode D Typ. 40 0.5 V IR at VR = 10 V, TJ = 25 °C 30 µA 40 V VF at IF = 1 A, TJ = 25 °C RLED Feedback LED current regulation ILED = 20 mA resistor RSET Current peak setting resistor IPEAK = 0.
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STLD40D 7 Typical performance characteristics Typical performance characteristics VI = 3.6 V, VEN = 3 V, CI = 2.2 µF, CO = 4.7 µF, L = 4.7 µH, RLED = 8 Ω VO = 32 V, 10 W LEDs load (VO = 32 V) typ. values @ 25 °C, unless otherwise specified. Figure 4. ILED vs. RLED Figure 5. ILED vs. VI Figure 6. IQ vs. temperature Figure 7. ISD vs. VI Figure 8. RDSON vs.VI Figure 9. ILIMIT vs.
PAGE 10
Typical performance characteristics STLD40D Figure 10. VFB vs. temperature Figure 11. VEN vs. temperature Figure 12. Efficiency vs. VI Figure 13. VOVP vs. temperature Figure 14. ILED vs.
PAGE 11
STLD40D 8 Package mechanical data Package mechanical data In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK® packages, depending on their level of environmental compliance. ECOPACK® specifications, grade definitions and product status are available at: www.st.com. ECOPACK® is an ST trademark. Table 7. QFN8 (3 x 3 mm) mechanical data mm. Dim. Min. Typ. Max. A 0.80 0.90 1.00 A1 0 0.02 0.05 A3 0.20 b 0.25 0.30 0.35 D 2.85 3.00 3.
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Package mechanical data STLD40D Figure 15.
PAGE 13
STLD40D Package mechanical data Tape & reel QFNxx/DFNxx (3x3) mechanical data mm. inch. Dim. Min. Typ. A Max. Min. Typ. 180 13.2 7.087 C 12.8 D 20.2 0.795 N 60 2.362 T 0.504 0.519 14.4 0.567 Ao 3.3 0.130 Bo 3.3 0.130 Ko 1.1 0.043 Po 4 0.157 P 8 0.315 Doc ID 12203 Rev 7 Max.
PAGE 14
Package mechanical data STLD40D Figure 16.
PAGE 15
STLD40D Revision history 9 Revision history Table 8. Document revision history Date Revision Changes 20-Mar-2006 1 Initial release. 04-Apr-2006 2 Add RSET in table 4 and fig 2 has been updated. 27-Feb-2009 3 Modified mechanical data. 03-Mar-2009 4 Modified packaging Table 1 on page 1. 11-Mar-2009 5 Modified: Figure 2 on page 4 and added Figure 16 on page 14. 01-Jul-2010 6 Modified: Table 7 on page 11, Figure 15 on page 12 and Figure 16 on page 14.
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STLD40D Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST’s terms and conditions of sale.