ST QFN20 Manuale utente

September 2008 Rev 5 1/35

STCF03

High power white LED driver with I²C interface

Features

■Buck-boost dc/dc converter

■Drives one power white LED up to 800 mA from

2.7 V to 5.5 V in QFN

■Drives one power white LED up to 800 mA from

3.3 V to 5.5 V in BGA

■Efficient up to 92%

■Output current control

■1.8 MHz typ. fixed frequency PWM

■Synchronous rectification

■Full I²C control

■Operational modes:

– Shutdown mode

– Shutdown + NTC

– Ready mode + auxiliary red LED

– Flash mode: up to 800 mA

– Torch mode: up to 200 mA

■Soft and hard triggering of flash

■Flash and torch dimming with 16 exponential

values

■Dimmable red LED indicator auxiliary output

■Internally or externally timed flash operation

■Digitally programmable safety time-out in flash

mode

■LED overtemperature detection and protection

with external NTC resistor

■Opened and shorted LED failure detection and

protection

■Chip over temperature detection and protection

■< 1 µA shutdown current

■Packages:

– QFN20 (4x4)

– TFBGA25 (3x3)

Applications

■Cell phone and smart phone

■Camera flashes/strobe

■PDAs and digital still cameras

Description

The STCF03 is a high efficiency power supply

solution to drive a single flash LED in camera

phone, PDAs and other hand-held devices. It is a

buck - boost converter to guarantee a proper LED

current control over all possible conditions of

battery voltage and output voltage; the output

current control ensure a good current regulation

over the forward voltage spread characteristics of

the flash LED.

Thanks to the high efficiency of the converter

allows having the input current taken from the

battery remain under 1.5 A. (See 1: Description

(continued))

TFBGA25 (3x3)

QFN20 (4x4)

Table 1. Device summary

Order code Package Packaging

STCF03PNR QFN20 (4x4 mm) 4500 parts per reel

STCF03TBR (1) TFBGA25 (3x3 mm) 3000 parts per reel

1. Available on request.

www.st.com

Contents STCF03

2/35

Contents

1 Description (continued) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2 Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

5 Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

6 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

7 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

7.1 Buck-Boost converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

7.2 Logic pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

7.2.1 SCL, SDA pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

7.2.2 TRIG pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

7.2.3 ATN pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

7.2.4 ADD pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

7.2.5 TMSK pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

7.3 I²C bus interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

7.4 Data validity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

7.5 Start and stop conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

7.6 Byte format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

7.7 Acknowledge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

7.8 Writing to a single register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

7.9 Interface protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

7.10 Writing to multiple registers with incremental addressing . . . . . . . . . . . . 18

7.11 Reading from a single register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

7.12 Reading from multiple registers with incremental addressing . . . . . . . . . 19

8 Description of internal registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

8.1 PWR_ON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

8.2 TRIG_EN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Contents STCF03

3/35

8.3 TCH_ON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

8.4 NTC_ON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

8.5 FTIM_0~3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

8.6 TDIM_0~3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

8.7 FDIM_0~3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

8.8 AUXI_0~3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

8.9 AUXT_0~3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

8.10 F_RUN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

8.11 LED_F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

8.12 NTC_W . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

8.13 NTC_H . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

8.14 OT_F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

8.15 VOUTOK_N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

9 Detailed description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

9.1 PowerON reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

9.2 Shutdown, shutdown with NTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

9.3 Ready mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

9.4 Single or multiple Flash using external (µP) temporization . . . . . . . . . . . 25

9.5 External (µP) temporization using TRIG_EN bit . . . . . . . . . . . . . . . . . . . . 26

9.6 Single Flash using internal temporization . . . . . . . . . . . . . . . . . . . . . . . . 26

9.7 Multiple Flash using internal temporization . . . . . . . . . . . . . . . . . . . . . . . 26

10 Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

11 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

12 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

List of tables STCF03

4/35

List of tables

Table 1. Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Table 2. Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Table 3. Absolute maximum ratings (see Note:). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Table 4. Thermal data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Table 5. List of external components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Table 6. Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Table 7. Address table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Table 8. Interface protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Table 9. I²C register mapping function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Table 10. Command register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Table 11. Dimming register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Table 12. Auxiliary register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Table 13. Auxiliary LED dimming table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Table 14. Torch mode and Flash mode dimming registers settings . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Table 15. Status register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Table 16. Status register details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Table 17. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

List of figures STCF03

5/35

List of figures

Figure 1. Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Figure 2. Pin connections (bottom view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Figure 3. Application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Figure 4. Procedure for assigning a non-default I²C address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Figure 5. Data validity on the I²C Bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure 6. Timing diagram on I²C Bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure 7. Bit transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Figure 8. Acknowledge on I²C Bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Figure 9. Writing to a single register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figure 10. Writing to multiple register with incremental addressing. . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 11. Reading from a single register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 12. Reading from multiple registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 13. Flash and Torch current vs. dimming value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Figure 14. VOUTOK_N behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Figure 15. Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 16. IOTORCH vs T_DIMM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 17. IOFLASH vs F_DIMM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 18. IOAUX vs AUXI. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 19. IOFLASH vs Temp. VI= 3.3 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 20. VFB2 vs Temp. at IO= 800 mA, VI= 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 21. IQvs Temp. VI= 5.5 V ready-mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Figure 22. Start-up in Flash mode 800 mA at VI= 3.6 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Figure 23. Line transient in Flash mode 800 mA, change of VIfrom 2.7 V to 3.3 V in 10 µs. . . . . . . . 28

Description (continued) STCF03

6/35

1 Description (continued)

All the functions of the device are controlled through the I²C which helps bus that allows to

reduce logic pins on the package and to save PCB tracks on the board. Hard and soft-

triggering of flash are both supported. The device includes many functions to protect the

chip and the power LED such as: a soft start control, chip over temperature detection and

protection as well as opened and shorted LED detection and protection. Besides, a digital

programmable time out function protects the LED in case of a wrong command from the µP.

An optional external NTC resistor is supported to protect the LED against over heating.

In mobile phone applications it is possible to reduce immediately the flash LED current

during the signal transmission using the TMSK pin. This saves battery life and gives more

priority to supply RF transmission instead of flash function.

It is possible by I²C to separately program the current intensity in flash and torch mode using

exponential steps. An auxiliary output can control an optional red LED to be used as a

recording indicator.

The device is packaged in QFN 4x4 20L with a height less than 1 mm and in TFBGA25 3x3.

Diagram STCF03

7/35

2 Diagram

Figure 1. Block diagram

Pin configuration STCF03

8/35

3 Pin configuration

Figure 2. Pin connections (bottom view)

TFBGA25 (3x3)

QFN20 (3x3)

Table 2. Pin description

Pin n° for

QFN20

Pin n° for

TFBGA25 Symbol Name and function

1 E1, D2 VLX2 Inductor connection

2 B3 RX Rx resistor connection

3 A4 NTC NTC resistor connection

4 D1, C2 VOUT Output voltage

5 B5 FB1 Feedback pin [ILED*(RFL+RTR)]

6A5FB2R

TR bypass

7 B4 FB2S Feedback sensing pin [ILED*RFL]

8 E2 GND Signal ground

9 D4 ADD I²C address selection

10 D5 AUXL Auxiliary LED output

11 C5 TMSK TX mask input.

12 B1, C1 PVBAT Power supply voltage

13 A3 VBAT Supply voltage

14 A2 VLX1A Inductor connection

15 A1, B2 VLX1B Inductor connection

16 E5 SCL I²C clock signal

17 E3 SDA I²C data

18 C3, D3 PGND Power ground

19 E4 ATN Attention (open drain output, active LOW)

20 C4 TRIG Flash trigger input

Exposed pad PGND To be connected to the PCB ground plane for optimal electrical and

thermal performance

Maximum ratings STCF03

9/35

4 Maximum ratings

Note: Absolute maximum ratings are those values beyond which damage to the device may occur.

Functional operation under these condition is not implied.

Table 3. Absolute maximum ratings (see Note:)

Symbol Parameter Value Unit

VBAT Signal supply voltage -0.3 to 6 V

PVBAT Power supply voltage -0.3 to 6 V

VLX1A, VLX1B Inductor connection 1 –0.3 to VI+0.3 V

VLX2 Inductor connection 2 –0.3 to VO+0.3 V

VOUT Output voltage -0.3 to 6 V

AUXL Auxiliary LED –0.3 to VI+0.3 V

FB1, FB2, FB2S Feedback and sense voltage -0.3 to 3 V

SCL, SDA, TRIG,

ATN, ADD TMSK Logic Pin -0.3 to VI+0.3 V

RXConnection for reference resistor -0.3 to 3 V

NTC Connection for LED Temperature sensing -0.3 to 3 V

ESD Human body model ±2kV

PTOT (BGA) (1)

1. Power dissipation is related parameter to used PCB. The recommended PCB design is included in the application note.

Continuous power dissipation (at TA=70°C) 800 mW

TOP Operating junction temperature range -40 to 85 °C

TJJunction temperature -40 to 150 °C

TSTG Storage temperature range -65 to 150 °C

Table 4. Thermal data

Symbol Parameter QFN20 TFBGA25 Unit

RthJA Thermal resistance junction-ambient 59 150 °C/W

Application STCF03

10/35

5 Application

**: Connect to VI, or GND or SDA or SCL to choose one of the 4 different I²C Slave Addresses.

***: Optional components to support auxiliary functions.

Note: All of the above listed components refer to typical application. Operation of the STCF03 is

not limited to the choice of these external components.

Figure 3. Application schematic

Table 5. List of external components

Component Manufacturer Part number Value Size

CITDK X5R0J106M 10 µF 0603

COTDK X5R0J105M 1 µF 0603

L (IFLASH = 0.5A) TDK VLF3012ST-4R7MR91 4.7 µH 2.6 x 2.8 x 1.2 mm

L (IFLASH = 0.8A) TDK VLF4012AT-4R7M1R1 4.7 µH 3.7 x 3.5 x 1.2 mm

NTC Murata NCP21WF104J03RA 100 kΩ0805

RFL 0.27 Ω0603

RTR 1.8 Ω0402

RX15 kΩ0402

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