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STLD40D
White led power supply for large display backlight
General Features
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Inductor switches boost controller PFM mode control High efficiency over wide range of input voltage from 3.0V to 5.5V Overvoltage protection with automatic restart Adjustable peak current limit Enable pin with possibility of PWM dimming control Low shutdown current <1uA Small external component Good load and line regulation QFN 3mm x 3mm x 1mm 8 leads high as 37V and can drive up to 10 white LEDs in series. The converter is a PFM (pulse frequency modulation) inductor switches and can work in discontinuous (DCM) mode operation. A minimum OFF time of the embedded boost switch TSW is fixed internally and allows limiting the switching frequency. The output current capability is 20mA with an output voltage of 37V. The regulation is done by sensing the led current through the resistor RLED. 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 RSET to the pin RSET.
QFN8 (3mm x 3mm)
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Application
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White Led supply for LCD backlight Mobile phone PDA and organizers Any handsets powered form 3.0V to 5.5V
Description
STLD40D is a boost converter that operates from 3.0V to 5.5V and can provide an output voltage as
Order code
Part number STLD40DPMR April 2006 Package QFN8L (3mm x 3mm) Rev. 2 Comments 4500 parts per reel 1/14
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Contents
STLD40D
Contents
1 2 3 4 5 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.1 5.2 5.3 5.4 Boost controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Adjustable peak inductor current limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 OVP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6 7 8
Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
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STLD40D
Pin configuration
1
Figure 1.
Pin configuration
Pin configuration (Top View )
Table 1.
PlN N 1 2 3 4 5 6 7 8 9
Pin description
SYMBOL VI RSET GND FB N/C VO EN SW PGND Supply voltage Peak inductor current adjust Analog Ground Feedback for the LED current regulation Not connected Output voltage for LED supply IC enable signal Boost switch drain Power Ground NOTE
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Maximum ratings
STLD40D
2
Table 2.
Maximum ratings
Absolute maximum ratings
Parameter Breakdown voltage at VO and SW pin Maximum voltage applied on pin EN Supply voltage range ESD ratings - (HBM MIL STD 883C) Operating temperature Storage temperature range Value 44 VI 6 2 -40 to 85 -65 to 150 Unit V V V kV C C
Symbol VBSW, VBO EN VI VESD TOP TSTG
Figure 2.
Block diagram
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STLD40D
Electrical characteristics
3
Table 3.
Electrical characteristics
Electrical characteristics (TJ=-40C to 85C, VI=3.6V, VEN=3V, CI=2.2F, CO=4.7F, L=4.7H, RLED=8 VO=32V, Typ. values @ 25C, unless otherwise specified)
Symbol VI VO IO ISD IQ
Parameter Input voltage range Output voltage range Regulated output current Stand-by current Quiescent current
Test Conditions
Min. 3.0 VI
Typ.
Max. 5.5 37
Unit V V mA
VO = 36V (10 White Leds) VEN = Low, VI = 3.6V, TJ = 25C VEN = Low, VI = 3V to 4.2V VI = 3V to 4.2V, TJ = 25C VI = 5.5V, TJ = 25C VI = 5.5V, I = 100mA VI = 4.2V, I = 100mA VI = 3.0V, I = 100mA
20 1 0.4 0.8 0.4 0.4 0.5 38 3 10 0.8 1.2
A mA
RDSON
Boost switch RDSON BVDS Breakdown voltage Maximum peak inductor limit adjust range Note: 1 Maximum peak inductor limit when RSET = VI Note: 1 Feedback voltage Line feedback voltage Maximum ON Time
V 1 1.1 A A mV mV s ns % 42 V V V
ILIM-ADJ ILIM VFB Line FB TON_MAX
RSET = 12k to 100k VI = 3V to 5.5V VI = 3.6V VI = 3V to 5.5V VI = 4.2V
0.2 0.75 130 165 5 5.5 250 75 80 36 1.5
200 35
TOFF_MIN Minimum OFF Time VI = 4.2V Efficiency at VI = 3.0VDC Note: 1 IO = 20 mA, VO = 36VDC Efficiency at VI = 5.5VDC Note: 1 IO = 20 mA, VO = 36VDC OVP OVHYS VEN Overvoltage protection Overvoltage hysteresis Enable input logic low Enable input logic high Disable Low VIL Enable High VIH
0.3 1.2
Note: 1 Guaranteed by design
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Typical performance characteristics
STLD40D
4
Typical performance characteristics
[VI=3.6V, VEN=3V, CI=2.2F, CO=4.7F, L=4.7H, RLED=8 VO=32V, 10W Leds load (VO=32V) Typ. values @ 25C, unless otherwise specified]
Figure 3.
ILED vs RLED
Figure 4.
ILED vs VI
Figure 5.
IQ vs Temperature
Figure 6.
ISD vs VI
Figure 7.
RDSON vs VI
Figure 8.
ILIMIT vs RSET
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STLD40D
Typical performance characteristics
Figure 9.
VFB vs Temperature
Figure 10. VEN vs Temperature
Figure 11. Efficiency Vs VI
Figure 12. VOVP vs Temperature
Figure 13. ILED vs Duty cycle EN pin (Dimming)
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Functional description
STLD40D
5
5.1
Functional description
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. The boost turns off when its drain voltage reaches the internally reference REF1, the main switch remains off until the minimum off time (250ns typical) has passed and the feedback voltage is below the reference again. A maximum ON time of 4s typical prevents the switch TSW to stay ON during a too long period of time.
5.2
Adjustable peak inductor current limit
The peak inductor current is monitored by sensing the drain voltage of the switch TSW. Since it exceeds the temperature compensated and supply voltage compensated reference REF1, the RS Flip flop is reset and TSW is turned OFF. By connecting a resistance to the pin RSET the peak current limit can be adjusted. from 200mA to 1A. When RSET resistor value is about 12k is connected directly to GND, the default value is 1A.
5.3
Enable
The ENABLE pin is a high logic input signal and allows turning on/off the controller without cutting the input voltage from the boost regulator circuit. The pin ENABLE can be used to dim the LED by applying a low frequency PWM signal.
5.4
OVP
If the regulation loop is cut, there is no signal at the feedback pin, the PFM controller will then continue to switch without control and generate an output voltage at the SW, and VO pin exceeding the breakdown value VBSW, and VBO. The Over Voltage Protection (OVP) senses the voltage at the VO pin. When the voltage exceed 38V Min the controller is automatically turned OFF. A hysteresis control allows the device restarting automatically since the output voltage drops down of 1.5V.
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STLD40D
Typical application
6
Typical application
Figure 14. Application circuit
Table 4.
Symbol D RLED RSET CI CO
External component proposal (see Figure 14)
Parameter Boost schottky diode Test Conditions VRRM VF at IF = 300mA, TJ = 25C IR at VR = 10V, TJ = 25C Feedback LED current regulation ILED = 20mA resistor IPEAK = 0.2A to 1A Current peak setting resistor Ceramic Type Capacitance Output capacitance: ceramic low Voltage ESR ESR Inductance DCR Boost inductor (height < 2mm) ISATRSET = GND Input filtering capacitor 8 12 2.2 4.7 35 1.6 4.7 1 1 100 Min. 40 0.5 30 Typ. Max. Unit V V A k F F V H A
L
The external components proposal should be considered as a design reference guide.The performances mentioned in the electrical characteristics table are not guaranteed for all the possible electrical parameters of the components included in this list. On an other hand the operation of STLD40D is not limited with the use of components included in this list
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Package mechanical data
STLD40D
7
Package mechanical data
In order to meet environmental requirements, ST offers these devices in ECOPACK(R) packages. These packages have a Lead-free second level interconnect. The category of second Level Interconnect is marked on the package and on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an ST trademark. ECOPACK specifications are available at: www.st.com.
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STLD40D
Package mechanical data
QFN8 (3x3) MECHANICAL DATA
DIM. A A1 A2 A3 b b1 D D2 E E2 e K L L1 L2 r r1 0.15 0.15 0.20 0.20 0.16 0.29 0.24 0.45 0.40 0.13 0.006 0.006 1.11 1.92 0.65 0.15 0.29 0.17 3.00 2.02 3.00 1.21 0.65 0.008 0.008 0.006 0.011 0.009 0.018 0.016 0.005 1.31 0.044 2.12 0.076 mm. MIN. 0.80 TYP 0.90 0.03 0.70 0.20 0.31 MAX. 1.00 0.05 0.75 0.25 0.39 0.30 0.026 0.006 0.011 0.007 0.118 0.080 0.118 0.048 0.026 0.052 0.084 MIN. 0.032 inch TYP. 0.035 0.001 0.028 0.008 0.012 MAX. 0.039 0.002 0.030 0.010 0.015 0.012
7517789
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Package mechanical data
STLD40D
Tape & Reel QFNxx/DFNxx (3x3) MECHANICAL DATA
mm. DIM. MIN. A C D N T Ao Bo Ko Po P 3.3 3.3 1.1 4 8 12.8 20.2 60 18.4 0.130 0.130 0.043 0.157 0.315 TYP MAX. 330 13.2 0.504 0.795 2.362 0.724 MIN. TYP. MAX. 12.992 0.519 inch
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STLD40D
Revision history
8
Table 5.
Revision history
Document revision history
Revision 1 2 Initial release. Add RSET in table 4 and fig 2 has been updated. Changes
Date 20-Mar-2006 04-Apr-2006
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STLD40D
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