ST STCF03 User Manual

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

STCF03

QFN20 (4 x 4)

■ Packages:

–QFN20 (4 x 4)
– TFBGA25 (3 x 3)

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.

TFBGA25 (3 x 3)

Table 1. Device summary

Order codes Packages Packaging

STCF03PNR QFN20 (4 x 4 mm) 4500 parts per reel

STCF03TBR TFBGA25 (3 x 3 mm) 3000 parts per reel

February 2011 Doc ID 13169 Rev 7 1/35

www.st.com

35

Contents STCF03

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

2/35 Doc ID 13169 Rev 7

STCF03 Contents

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

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 (microprocessor) temporization . 25

9.5 External (microprocessor) 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

Doc ID 13169 Rev 7 3/35

List of tables STCF03

List of tables

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

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

Table 3. Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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. QFN20 (4 x 4 mm.) mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Table 18. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

4/35 Doc ID 13169 Rev 7

STCF03 List of figures

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. I
Figure 17. I

OTORCH

OFLASH

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

Figure 19. I

OFLASH

Figure 20. VFB2 vs. temp. at I
Figure 21. I

Q

Figure 22. Start-up in flash mode 800 mA at V
Figure 23. Line transient in flash mode 800 mA, change of V

Figure 24. QFN20 (4 x 4 mm.) drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

vs. T_DIMM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

vs. F_DIMM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

vs. temp. VI = 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

= 800 mA,VI = 3.3 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

O

vs. temp. VI = 5.5 V ready-mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

= 3.6 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

I

from 2.7 V to 3.3 V in 10 µs . . . . . . . . 28

I

Doc ID 13169 Rev 7 5/35

Description (continued) STCF03

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 soft­triggering 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
microprocessor. 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 (4 x 4 mm) 20L with a height less than 1 mm and in
TFBGA25 (3 x 3 mm).

6/35 Doc ID 13169 Rev 7

STCF03 Diagram

2 Diagram

Figure 1. Block diagram

Doc ID 13169 Rev 7 7/35

Pin configuration STCF03

3 Pin configuration

Figure 2. Pin connections (bottom view)

QFN20 (4x4)

Table 2. Pin description

Pin n° for

QFN20

Pin n° for
TFBGA25

Symbol Name and function

1 E1, D2 VLX2 Inductor connection

2B3RXR

resistor connection

X

3 A4 NTC NTC resistor connection

4 D1, C2 VOUT Output voltage

5 B5 FB1 Feedback pin [I

6A5FB2R

bypass

TR

7 B4 FB2S Feedback sensing pin [I

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

*(RFL+RTR)]

LED

LED*RFL

TFBGA25 (3x3)

]

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

8/35 Doc ID 13169 Rev 7

STCF03 Maximum ratings

4 Maximum ratings

Table 3. Absolute maximum ratings

(1)

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 V

VLX2 Inductor connection 2 –0.3 to V

+0.3 V

I

+0.3 V

O

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

R

X

Logic pin -0.3 to V

Connection for reference resistor -0.3 to 3 V

+0.3 V

I

NTC Connection for LED temperature sensing -0.3 to 3 V

ESD Human body model ±2kV

(2)

(BGA)

P

TOT

T

OP

T

J

T

STG

1. Absolute maximum ratings are those values beyond which damage to the device may occur. Functional operation under
these condition is not implied.

2. 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

Operating junction temperature range -40 to 85 °C

Junction temperature -40 to 150 °C

Storage temperature range -65 to 150 °C

Table 4. Thermal data

Symbol Parameter QFN20 TFBGA25 Unit

R

thJA

Thermal resistance junction-ambient 59 150 °C/W

Doc ID 13169 Rev 7 9/35

Application STCF03

5 Application

Figure 3. Application schematic

**: 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.

Table 5. List of external components

Component Manufacturer Part number Value Size

L (I

L (I

C

I

C

O

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

FLASH

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

FLASH

TDK X5R0J106M 10 µF 0603

TDK X5R0J105M 1 µF 0603

NTC Murata NCP21WF104J03RA 100 kΩ 0805

R

FL

R

TR

R

X

0.27 Ω 0603

1.8 Ω 0402

15 kΩ 0402

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.

10/35 Doc ID 13169 Rev 7

STCF03 Electrical characteristics

6 Electrical characteristics

TJ = 25 °C, VI = 3.6 V, 2 x CI = 10 µF, CO = 1 µF, L = 4.7 µH, RFL = 0.27 Ω, R
R

= 15 kΩ, Typ. values @ 25 °C, unless otherwise specified.

X

Table 6. Electrical characteristics

= 1.8 Ω,

TR

Symbol Parameter Test condition Min. Typ. Max. Unit

V

Input operation supply voltage 2.7 5.5 V

I

V

PW_ON

RESET

V

Power ON reset threshold VI rising 2.3 V

Flash mode for VI = 2.7 V to 5.5 V
(STCF03PNR)

Output current adjustment
range I

FLASH

I

O

Output current adjustment
range I

TORC H

Auxiliary LED output current
adjustment range I

Regulated voltage range 2.5 5.3 V

O

AUXLED

Flash mode for V

= 2.7 V to 3.3 V

I

(STCF03TBR)

Flash mode for V

=3.3 V to 5.5 V

I

(STCF03TBR)

Torch mode VI = 2.7 V to 5.5 V 15 200

Ready mode, VI = 3.3 V to 5.5 V 0 20

60 800

60 600

60 800

FB1 Feedback voltage Torch mode 30 250 mV

FB2 Feedback voltage Flash mode 30 250 mV

mA

ΔI

R

Output current tolerance Flash mode, IO = 160 mV/R

O

FB1-FB2 ON resistance Torch mode, IO = 200 mA 90 mΩ

ON_

Quiescent current in
SHUTDOWN mode

I

Q

NTC_ON=0 1

NTC_ON=1 1

FL

Quiescent current in ready ­mode

Frequency VI = 2.7 V 1.8 MHz

f

s

= 3.2 to 4.2 V, flash mode,

V

Efficiency of the chip itself

ν

Efficiency of the whole
application

I

= 800 mA

I

O

V

= 3.2 to 4.2 V, flash mode,

I

IO = 800 mA, VO=V

fLED_max

+ V

FB2

5.02 V
See the typical application schematic

-10 10 %

1.8 mA

87

=

76

It is included losses of inductor and
sensing resistor

OVP Output over voltage protection V

OV

Over voltage hysteresis VI = 5.5 V, No Load 0.3 V

HYST

OTP Over temperature protection V

OT

R

ON

Over temperature hysteresis VI = 5.5 V 20 °C

HYST

T1 RX-NTC switch ON resistance Ready mode 25 Ω

= 5.5 V, No Load 5.3 V

I

= 5.5 V 140 °C

I

µA

%

Doc ID 13169 Rev 7 11/35