ST STCF05 User Manual

High power white LED driver with I²C interface

Features

■ Boost DC-DC converter with synchronous

rectification

■ Drives 2 power white LEDs in series with a

current up to 400 mA

■ Input voltage range 2.5 V to 5.5 V

■ Needs 3 external components only

■ Output current control

■ 1.8 MHz fixed frequency PWM control

■ Peak inductor current limited to 3 A

■ Full I²C control

■ Operational modes:

– Standby mode
– Standby mode with NTC
– Flash mode: up to 400 mA
– Torch mode: up to 120 mA

■ Soft and hard triggering of flash

■ Flash and Torch dimming in 15 exponential

steps

■ 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

■ Open and shorted LED failure detection and

protection

■ Chip overtemperature detection and protection

■ Less than 1 µA standby current

■ Package 3 x 3 mm TFBGA25

Table 1. Device summary

STCF05

TFBGA25 (3 x 3 mm)

Applications

■ Cell phones and smartphones

■ Camera flashes/strobe

■ PDAs and digital still cameras

Description

The STCF05 is a high efficiency power supply
solution to drive multiple flash LEDs in camera
phones, PDAs and other hand-held devices. The
synchronous boost topology with output current
control guarantees the proper LED current over
all possible conditions of battery level and LED
forward voltage. All the functions of the device are
controlled through the I²C bus that allows to
reduce logic pins on the package and to save
PCB traces on the board. Hard and soft-triggering
of the flash are both supported. The device
includes many functions to protect the chip and
the power LEDs. These comprehend a soft-start
control, chip over temperature detection and
protection, open and shorted LEDs detection and
protection. In addition, a digital programmable
time-out function protects the LEDs in case of
wrong command from microprocessor. See
description (continued).

Order code Package Packaging

STCF05TBR TFBGA25 (3 x 3 mm) 3000 parts per reel

July 2010 Doc ID 15257 Rev 4 1/33

www.st.com

33

Contents STCF05

Contents

1 Description (continued) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2 Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

4 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

5 Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

6 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

7 Detailed description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

7.2 Boost converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

7.3 Logic pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

7.3.1 SCL, SDA pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

7.3.2 TRIG pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

7.3.3 ATN pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

7.3.4 ADD pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

7.3.5 TMSK pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

8 I²C bus interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

8.1 Data validity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

8.2 Start and stop conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

8.3 Byte format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

8.4 Acknowledge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

8.5 Interface protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

8.6 Writing to a single register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

8.7 Writing to multiple registers with incremental addressing . . . . . . . . . . . . 17

8.8 Reading from a single register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

8.9 Reading from multiple registers with incremental addressing . . . . . . . . . 18

9 Registers description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

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STCF05 Contents

9.1 PWR_ON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

9.2 TRIG_EN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

9.3 TCH_ON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

9.4 NTC_ON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

9.5 FTIM_0~3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

9.6 TDIM_0~2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

9.7 FDIM_0~2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

9.8 LDIM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

9.9 AUXI_0~3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

9.10 AUXT_0~3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

9.11 LED_S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

9.12 F_RUN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

9.13 LED_O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

9.14 NTC_W . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

9.15 NTC_H . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

9.16 OT_F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

9.17 OC_F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

9.18 VOUTOK_N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

10 Detailed description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

10.1 Power ON reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

10.2 Shutdown, shutdown with NTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

10.3 Ready mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

10.4 Single or multiple flash using external (microprocessor) temporization . . 25

10.5 External (microprocessor) temporization using TRIG_EN bit . . . . . . . . . 26

10.6 Single flash using internal temporization . . . . . . . . . . . . . . . . . . . . . . . . . 26

10.7 Multiple flash using internal temporization . . . . . . . . . . . . . . . . . . . . . . . . 26

11 Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

12 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

13 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Doc ID 15257 Rev 4 3/33

List of tables STCF05

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 read function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

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

Table 11. Dimming register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

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

Table 13. Auxiliary LED dimming table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Table 14. Torch mode and flash mode dimming registers settings . . . . . . . . . . . . . . . . . . . . . . . . . . 23

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

Table 16. Status register details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Table 17. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

4/33 Doc ID 15257 Rev 4

STCF05 List of figures

List of figures

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

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

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

Figure 4. Data validity on the I²C bus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure 5. Timing diagram on I²C bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Figure 6. Bit transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Figure 7. Acknowledge on I²C bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figure 8. Writing to a single register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 9. Writing to multiple register with incremental addressing. . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 10. Reading from a single register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 11. Reading from multiple registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 12. Current intensity vs. dimming value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Figure 13. VOUTOK_N behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Figure 14. Efficiency in flash mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Figure 15. Efficiency in torch mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Figure 16. I
Figure 17. I

Figure 18. Input current vs. input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Figure 19. Quiescent current in ready mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

LED

LED

vs. V
vs. V

at different temp.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

BAT

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

OUT

Doc ID 15257 Rev 4 5/33

Description (continued) STCF05

1 Description (continued)

An optional external NTC is supported to protect the LEDs against over heating. In mobile
phone application it is possible to reduce immediately the flash LEDs 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 to separately program the current intensity in flash and torch mode using
exponential steps by I²C. In case of insufficient power from the battery a warning is
generated. An auxiliary output can control an optional red LED to be used as a recording
indicator.

The device is packaged in BGA 3 x 3 mm with 1 mm height.

6/33 Doc ID 15257 Rev 4

STCF05 Diagram

2 Diagram

Figure 1. Block diagram

Doc ID 15257 Rev 4 7/33

Pin configuration STCF05

3 Pin configuration

Figure 2. Pin connections (top view)

1 2 3 4 5

VOUT LED LED ATN TRIG

A

VOUT ADD SDA SCL TMSK

B

PGND PGND PGND PGND AUXL

C

VLX VLX PGND VBAT NTC

D

VLX VLX PGND AGND RX

E

Table 2. Pin description

Ball n° Symbol Description

E1, D1, D2, E2 VLX Inductor connection

E5 RX Rx resistor connection

A1, B1 VOUT Output voltage

D5 NTC NTC resistor connection

C5 AUXL Auxiliary red LED connection

B4 SCL I²C clock signal

A5 TRIG Flash trigger input

E4 AGND Signal ground

B2 ADD I²C address selection

A2, A3 LED Diode cathode connection

A4 ATN Attention (open drain output, active LOW)

D4 VBAT Supply voltage

B3 SDA I²C data

B5 TMSK T-mask

C1, C2, C3, C4, D3, E3 PGND Power ground + die back connection

8/33 Doc ID 15257 Rev 4

STCF05 Maximum ratings

4 Maximum ratings

Table 3. Absolute maximum ratings

Symbol Parameter Value Unit

VBAT Signal supply voltage -0.3 to 6 V

VLX Inductor connection –0.3 to VO+0.3 V

OUT Output voltage -0.3 to 12 V

AUXL Auxiliary LED –0.3 to V

LED LEDs connection –0.3 to V

SCL, SDA, TRIG,
ATN, ADD TMSK

R

X

Logic pin -0.3 to V

Connection for reference resistor -0.3 to 3 V

NTC Connection for LED temperature sensing -0.3 to 3 V

ESD Human body model ± 2kV

P

TOT

T

OP

T

J

T

STG

1. Power dissipation is dependent on PCB. The recommended PCB design is included in the application note.

Continuous power dissipation (at TA = 70 °C)

Operating ambient temperature range -40 to 85 °C

Junction temperature -40 to 150 °C

Storage temperature range -65 to 150 °C

(1)

+0.3 V

BAT

+0.3 V

BAT

+0.3 V

BAT

800 mW

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

Functional operation under these condition is not implied.

Table 4. Thermal data

Symbol Parameter Value Unit

R

thJA

1. Using 1 inch2 of PCB area at 4-layers board.

Thermal resistance junction-ambient

(1)

56 °C/W

Doc ID 15257 Rev 4 9/33

Application STCF05

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. V

Table 5. List of external components

= 1.8 V.

ref

Component Manufacturer Part number Value Size

C

I

C

O

LTDK

TDK C1608X5R0J106M 10 µF 0603

TDK C1608X5R1A105M 1 µF 0603

VLF4014A-1R0N2R2

VLS252012T-1R0N1R7

(1)

(2)

1 µH 3.7 x 3.5 x 1.2 [mm]

1 µH 2.5 x 2 x 1.2 [mm]

NTC Murata NCP21WF104J03RA 100 kΩ 0805

R

X

RΩ MCR01MZPJ15K 15 kΩ 0402

LED Luxeon LED 2 x LXCL-PWF1 0805

1. Inductor type is recommended for high efficiency operation 85 % typ. at 400 mA output current.

2. This inductor type is recommended for the minimum app. area with typ. efficiency of the operation 77 % at 400 mA output
current

Note: Above listed components refer to typical application. Operation of the STCF05 is not limited

to the choice of these external components.

10/33 Doc ID 15257 Rev 4