ST STCF05 User Manual

STCF05

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

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).

Table 1.	Device summary
	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

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

10.4Single 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

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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

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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. ILED vs. VBAT at different temp.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Figure 17. ILED vs. VOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Figure 18. Input current vs. input voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

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

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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.

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STCF05	Diagram

2 Diagram

Figure 1. Block diagram

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Pin configuration	STCF05

3 Pin configuration

Figure 2. Pin connections (top view)

		1	2	3	4	5
	A	VOUT	LED	LED	ATN	TRIG
	B	VOUT	ADD	SDA	SCL	TMSK
	C	PGND	PGND	PGND	PGND	AUXL
	D	VLX	VLX	PGND	VBAT	NTC
	E	VLX	VLX	PGND	AGND	RX

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

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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 VBAT+0.3	V
LED			LEDs connection	–0.3 to VBAT+0.3	V
SCL, SDA, TRIG,			Logic pin	-0.3 to VBAT+0.3	V
ATN, ADD TMSK
RX			Connection for reference resistor	-0.3 to 3	V
NTC			Connection for LED temperature sensing	-0.3 to 3	V
ESD			Human body model	± 2	kV
P	TOT		Continuous power dissipation (at T = 70 °C) (1)	800	mW
			A
TOP			Operating ambient temperature range	-40 to 85	°C
TJ			Junction temperature	-40 to 150	°C
TSTG			Storage temperature range	-65 to 150	°C

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

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		Thermal resistance junction-ambient (1)	56	°C/W
thJA

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

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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. Vref = 1.8 V.

Table 5.	List of external components
Component		Manufacturer	Part number	Value	Size
CI		TDK	C1608X5R0J106M	10 µF	0603
CO		TDK	C1608X5R1A105M	1 µF	0603
L		TDK	VLF4014A-1R0N2R2 (1)	1 µH	3.7 x 3.5 x 1.2 [mm]
			VLS252012T-1R0N1R7 (2)	1 µH	2.5 x 2 x 1.2 [mm]
NTC		Murata	NCP21WF104J03RA	100 kΩ	0805
RX		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.

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