ST STCF04 User Manual

High power white LED SuperCap™ driver with I²C interface

Features

■ Buck-boost converter with 1.5 A peak current

limiting and synchronous rectification

■ Burst mode operation when output is charged

■ Input voltage range 2.5 V to 5.5 V

■ Programmable output charging voltage up to

5.5 V

■ Full I²C control

■ Operation modes:

– Shutdown mode
– Monitoring mode with NTC and SuperCap

monitoring
– Idle mode
–Flash mode
– Torch mode: up to 320 mA

■ Controlled LED current in all modes

■ Soft and hard triggering of Flash, Torch and

Picture light modes

■ Torch dimming in 12 exponential steps

■ Flash dimming in 8 steps

■ Active balancing of SuperCap voltage

■ SuperCap status flag

■ Internally or externally timed flash operation

■ Digitally programmable safety timeout in Flash

mode

■ Torch mode safety timeout

■ LED overtemperature detection and protection

with external NTC resistor

■ Shorted LED failure detection and protection

■ Chip overtemperature detection and protection

STCF04

Datasheet − production data

TFBGA25 (3 x 3 mm)

Applications

■ Cell phones and smartphones

■ Camera flashes/strobe

■ PDAs and digital still cameras

Description

The STCF04 is a dedicated and space optimized
high efficiency solution for driving a flash LED
module in cameras, phones, PDAs and other
handheld devices using the SuperCap
technology. It is based on a DC-DC buck-boost
converter, which ensures a proper and efficient
charging control and monitoring of the SuperCap
in the whole battery voltage range. The output
current control ensures a good current regulation
over the forward voltage spread characteristics of
the flash LEDs in Torch and Flash mode
operation. The SuperCap charging current is
limited to a defined value which avoids overload of
the battery. The SuperCap discharge current
flows through the LEDs and the external
MOSFET which must be chosen according to the
desired flash current.

Table 1. Device summary

Order code Package Packaging

STCF04TBR TFBGA25 (3 x 3 mm) 3000 parts per reel

May 2012 Doc ID 022927 Rev 2 1/43

This is information on a product in full production.

www.st.com

43

Contents STCF04

Contents

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

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

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

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

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

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

7 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

8 Detailed description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

8.1 Logic pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

8.1.1 SCL, SDA pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

8.1.2 FLASH pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

8.1.3 TORCH pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

8.1.4 RESET pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

8.1.5 ATN pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

8.1.6 ADD pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

8.1.7 READY pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

8.1.8 Data validity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

8.1.9 START and STOP conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

8.1.10 Byte format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

8.1.11 Acknowledge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

8.1.12 Interface protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

8.1.13 Writing to a single register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

8.1.14 Writing to multiple registers with incremental addressing . . . . . . . . . . . 20

8.1.15 Reading from a single register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

8.1.16 Reading from multiple registers with incremental addressing . . . . . . . . 21

9 Description of the internal registers . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

9.1 Commands (CMD_REG) 00(hex) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

2/43 Doc ID 022927 Rev 2

STCF04 Contents

9.1.1 PWR_ON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

9.1.2 FLASH_ON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

9.1.3 TCH_ON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

9.1.4 NTC_ON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

9.1.5 TCHV_H . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

9.1.6 CHRG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

9.1.7 MONTR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

9.2 Flash register (FL_REG) 01(hex) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

9.3 AUX LED (AUX_REG) 02(hex) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

9.4 Status (STAT_REG) 03(hex) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

9.5 Feature (FTR_REG) 04(hex) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

9.6 Torch register (TRCH_REG) 05(hex) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

10 Theory of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

10.1 The state machine diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

10.2 Power-ON reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

10.2.1 RESET pin function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

10.3 Shutdown mode and NTC mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

10.4 Monitoring mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

10.5 Idle mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

10.6 AUX LED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

10.7 Single or multiple flash using external (microprocessor) temporization . . 30

10.8 External (microprocessor) temporization using the FLASH_ON bit . . . . . 31

10.9 Single flash using internal temporization . . . . . . . . . . . . . . . . . . . . . . . . . 31

10.10 Light sensor feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

11 Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

12 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

13 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Doc ID 022927 Rev 2 3/43

List of tables STCF04

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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Table 6. Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Table 7. I²C address table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Table 8. Interface protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Table 9. I²C register mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Table 10. Command register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Table 11. Flash register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Table 12. Flash mode dimming registers settings (EXT_REG = 0) . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Table 13. Flash time dimming register settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Table 14. AUX LED register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Table 15. Auxiliary LED dimming table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Table 16. Auxiliary LED timing table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Table 17. Status register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Table 18. Status register details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Table 19. Feature register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Table 20. Light sensor reference dimming register settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Table 21. DC-DC converter output voltages (V

Table 22. DC-DC converter coil peak current limit values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Table 23. Torch register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Table 24. Torch mode dimming registers settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Table 25. The safety timeout for Torch mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Table 26. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

OUT

4/43 Doc ID 022927 Rev 2

STCF04 List of figures

List of figures

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

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

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

Figure 4. Behavior of the READY pin in different modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figure 5. Data validity on the I²C bus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 6. Timing diagram on I²C bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 7. Bit transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 8. Acknowledge on I²C bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 9. Writing to a single register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Figure 10. Writing to multiple registers with incremental addressing . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Figure 11. Reading from a single register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Figure 12. Reading from multiple registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Figure 13. State machine diagram of the STCF04 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Figure 14. Reset timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Figure 15. Flash current vs. input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Figure 16. Torch current vs. input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Figure 17. Aux LED current vs. input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Figure 18. Charging efficiency vs. V

Figure 19. Torch time - settings compared to real values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Figure 20. Torch current - settings compared to real values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Figure 21. Flash time - settings compared to real values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Figure 22. Flash current - settings compared to real values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Figure 23. Aux LED time - settings compared to real values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Figure 24. Aux LED current- settings compared to real values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Figure 25. Operation in Flash mode - single flash pulse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Figure 26. Operation in Flash mode - multiple flash pulses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Figure 27. Operation in Torch mode with TCHV_H bit = 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Figure 28. Operation in Torch mode with TCHV_H bit = 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

voltage (VIN = 3.6 V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

OUT

Doc ID 022927 Rev 2 5/43

Description (continued) STCF04

1 Description (continued)

All the functions of the device are controlled through the I²C bus which reduces the number
of logic pins of the package and saves PCB tracks on the application board. Hard and soft­triggering of flash and torch are both supported. The device includes many functions to
protect the chip and the power LEDs. These include a soft-start control, chip
overtemperature detection and protection, and shorted LED detection and protection. In
addition, a digital programmable timeout function protects the LEDs in case of a wrong
command issued by the microprocessor. An optional external NTC is supported to protect
the LEDs against overheating. It is possible to separately program the current intensity in
Flash and Torch mode through I²C. In order to guarantee the proper function of Flash mode,
the SuperCap voltage should be monitored by the microprocessor using the READY pin
feature. In case of insufficient power from the SuperCap, a warning is generated. The device
is packaged in BGA 3 x 3 mm with 1 mm height.

6/43 Doc ID 022927 Rev 2

STCF04 Diagram

2 Diagram

Figure 1. Block diagram

LSIN

NTC_ON

NTC_ON

LSIN

AUXLED

AUXLED

READY

READY

TORCH

TORCH

FLASH

FLASH

ATN

ATN

RESET

RESET

SCL

SCL

SDA

SDA

ADD

ADD

AUXLED

AUXLED

VBAT

VBAT

PREREG

PREREG

& BIAS

& BIAS

CONTROL

CONTROL

LOGIC

LOGIC

I²C

I²C

INTERF

INTERF

LSCON

LSCON

PVBAT

PVBAT

CONVERTER

CONVERTER

FLASH

FLASH

FLASH

FLASH

TRIGGERING

TRIGGERING

TRIGGERING

TRIGGERING
&CURRENT

&CURRENT

&CURRENT

&CURRENT

LIMITITING

LIMITITING

LIMITITING

LIMITITING

OSCILLATOR & TIME

OSCILLATOR & TIME

COUNTER

COUNTER

PROTECTIONS &

PROTECTIONS &

DIAGNOSTICS

DIAGNOSTICS

ON - CHIP

ON - CHIP

TEMP

TEMP

BUCK

BUCK

VLX1

VLX1

OVER -

OVER -

CURRENT

CURRENT

LED

LED

FAIL

FAIL

VLX2

VLX2

BOOST

BOOST

CONVERTER

CONVERTER

TORCH

TORCH

TORCH

TORCH

DIMMING

DIMMING

DIMMING

DIMMING

NTC_W

NTC_W

NTC_H

NTC_H

+

+

-

-

+

+

-

-

SUPERCAP

SUPERCAP

BALANCING &

BALANCING &

SUPERCAP

SUPERCAP

VOLTAGE

VOLTAGE

BALANCING &

BALANCING &

CONTROL

CONTROL

VOLTAGE

VOLTAGE
CONTROL

CONTROL

REF4

REF4

NTC_ON

NTC_ON

REF5

REF5

CURRENT

CURRENT
SENSING

SENSING

NTC

NTC

BIAS

BIAS

REF

REF
120 mV..1.2 V

120 mV..1.2 V

MX

MX

MX

MX

ENABLE/

ENABLE/

1.8 V REF

1.8 V REF

VOUT

VOUT

VMID

VMID

DRIVE

DRIVE

LED

LED

PGND

PGND

ISENS

ISENS

NTCRXPGND AGND

NTCRXPGND AGND

Doc ID 022927 Rev 2 7/43

Pin configuration STCF04

3 Pin configuration

Figure 2. Pin connection (top view)

Table 2. Pin description

Pin Symbol Description

A1 VLX1 Inductor connection 1

E1 VLX2 Inductor connection 2

D5 R

D1 VOUT SuperCap connection

C1 VMID SuperCap middle pin connection

E5 NTC NTC resistor connection

A3 READY SuperCap status flag pin

B3 SCL I²C clock signal

A4 FLASH Flash trigger input

E2 AGND Signal ground

B5 TORCH Torch trigger input

B4 RESET External reset input

D4 ISENS Flash regulator sensing connection

C3 ADD I²C address selection

E4 LED Diode module cathode connection

C4 ATN Attention (open drain output, active LOW)

B1 PVBAT Supply voltage

A5 SDA I²C data

E3 AUXLED Auxiliary red LED connection

B2 LSCON Light sensor capacitor connection

X

RX resistor connection

D3 VBAT Signal supply voltage

A2 LSIN Light sensor input

C5 DRIVE MOSFET driver output

C2, D2 PGND Power ground + die back connection

8/43 Doc ID 022927 Rev 2

STCF04 Maximum ratings

4 Maximum ratings

Table 3. Absolute maximum ratings

Symbol Parameter Value Unit

VBAT, PVBAT Signal supply voltage - 0.3 to 6 V

VLX Inductor connection - 0.3 to 6 V

VOUT SuperCap connection - 0.3 to 6 V

VDCDC DC-DC converter output - 0.3 to 6 V

VMID SuperCap middle pin connection - 0.3 to 6 V

AUXLED AUXLED connection - 0.3 to 6 V

LED LED connection - 0.3 to 6 V

SCL, SDA, ATN, ADD,

READY, TORCH,

FLASH, RESET

Logic pins - 0.3 to V

+ 0.3 V

BAT

PVBAT Power supply voltage - 0.3 to V

+ 0.3 V

BAT

DRIVE External MOSFET drive - 0.3 to 6 V

LSIN Light sensor input - 0.3 to 6 V

LSCON Light sensor capacitor connection - 0.3 to 6 V

R

X

Connection for reference resistor - 0.3 to 3 V

NTC Connection for LED temperature sensing - 0.3 to 3 V

ISENS Flash regulator sensing connection - 0.3 to 3 V

ESD Human body model ± 2kV

P

T

T

STG

TOT

OP

T

J

Continuous power dissipation (at TA=70 °C) 1 W

Operating junction temperature range - 40 to 85 °C

Junction temperature - 40 to 150 °C

Storage temperature range - 65 to 150 °C

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

Functional operation under these conditions is not implied.

Table 4. Thermal data

Symbol Parameter Value Unit

R

thJA

1. This parameter corresponds to the PCB board, 8 layers with 1 inch² of cooling area.

Thermal resistance junction-ambient

(1)

56 °C/W

Doc ID 022927 Rev 2 9/43

Application STCF04

5 Application

Figure 3. Application schematic

Note: **: 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 are highlighted with blue
rectangles.

Note: The anode of the AuxLED should be also connected to the V

OUT

.

10/43 Doc ID 022927 Rev 2

STCF04 Application

Table 5. List of external components

Component Manufacturer Part number Value Size

L

Murata LQM2HPN1R0MJC 1 µH / 1.5 A 2.5 x 2.0 x 1.1 mm

TDK VLS252012T-1R0N1R7 1 µH / 1.7 A 2.5 x 2.0 x 1.2 mm

CIN, COUT TDK C1608X5R0J106MT 10 µF / 6.3 V 0603

Rx Rohm MCR01MZPJ15K 15 kΩ 0402

NTC Murata NCP21WF104J03RA 100 kΩ 0805

Murata DME2W5R5K404M 400 mF / 5.5 V 20.5 x 18.5 x 3 mm

EDLC152344 550 mF / 5.5 V 44 x 23 x 1.5 mm

CSUP

TDK

EDLC272020 500 mF / 5.5 V 20 x 20 x 2.7 mm

CAP-xx GS 2 19F 1.6 F / 5 V 40 x 17 mm

LED MODULE Luxeon 4x LXCL-PWF4 White LED 0805

T

FL

R

FL

(1)

C

INT

R

* Tyco 0402

LIGHT

T

* Vishay TEMT6000 4 x 2 x 1 mm

FOTO

STMicroelectronics STL8NH3LL 8 A / 12 kΩ 3.3 x 3.3 x 0.9 mm

Tyco TL2BR01FTE 0R01 1206

TDK 10 µF / 6.3 V 0402

AUXLED Red LED 0603

C

R

1. Optional components for the auxiliary light sensor feature.

100 nF 0402

Note: The components listed above refer to a typical application. However, STCF04 operation is

not limited to the choice of these external components.

Doc ID 022927 Rev 2 11/43

Electrical characteristics STCF04

6 Electrical characteristics

TA = 25 °C, V

= 15 kΩ, V

R

X

Table 6. Electrical characteristics

= 3.6 V connected to V

IN

= 4.2 V/10 A. Unless otherwise specified, typical values are at 25 °C.

FLED

BAT

and P

VBAT

, C

IN

= 10 µF, C

= 1.6F/5 V L = 1 µH,

SUP

Symbol Parameter Test conditions Min. Typ. Max. Unit

V

V

PW_ON

RESET

IN

Operating input supply
voltage

Power-ON reset
threshold

2.5 5.5 V

VIN rising 2.3 V

Output current

Torch mode VIN=2.7 V to 5.5 V 15 320

Idle mode, VI or VO=3.3 V to 5.5 V 0 100

=2.7 V to 5.5 V, I

V

IN

= 10 mΩ

R

FL

V

=2.7 V to 5.5 V, IDC0=0 1.45

IN

=2.7 V to 5.5 V, IDC0=1 1.80

V

IN

LED

= 12 A

108 120 132 mV

V

ISENS

I

PEAK

adjustment range
I

I

O

TORCH

Auxiliary LED output
current adjustment
range I

AUXLED

Current sensing input

Switch peak current limit

Regulated voltage
range optimized for

V

=2.7 V to 5.5 V 4.5 5.5 V

IN

Flash mode

mA

A

V

OUT

I

MID

ΔI

Regulated voltage
range optimized for
Torch mode

V

tolerance

OUT

V

=2.7 V to 5.5 V

IN

Percentage with respect to
programmed voltage

V

+

FLED

0.25

-5 +5 %

V

Active balancing output VIN=2.7 V to 5.5 V -400 400 mA

Output current variation Torch mode I

O

Quiescent current in
Shutdown mode

Quiescent current in
Shutdown mode

I

Q

Quiescent current in
Monitoring mode

Quiescent current in Idle
mode

f

s

Switching frequency VIN=2.7 V 1.8 MHz

=2.7 to 5.5 V, NTC_ON=0 1

V

IN

VIN=2.7 to 5.5 V, NTC_ON=1 2

NTC_ON=0, SuperCap monitoring=1 45

NTC_ON, CHRG=0 1 mA

= 300 mA -10 10 %

LED

µA

12/43 Doc ID 022927 Rev 2

STCF04 Electrical characteristics

Table 6. Electrical characteristics (continued)

Symbol Parameter Test conditions Min. Typ. Max. Unit

Efficiency of the
converter

ν

Efficiency in Torch mode
operation

=3.7 V, VDC_0,1=1, IDC0=1 85

V

IN

=2.7 V to 4.2 V, IDC_0=1,

V

IN

TCHV_H=1 I

=2.7 V to 4.2 V, IDC_0=1,

V

IN

TCHV_H=0 I

V

SUPMAX

V

SUPHYST,

FLASH_ON=1

V

SUPMAX

V

SUPHYST,

FLASH_ON=1

V

SUPMAX

V

SUPHYST

V

SUPHYST

SuperCap regulated
voltage hysteresis

FLASH_ON=1

V

SUPMAX

V

SUPHYST

V

MONIREADY

OTP

OTHYST

SuperCap voltage ready
hysteresis

Overtemperature
protection

Overtemperature
hysteresis

PWR_ON=0, VDC_0 or/and VDC_1=1 0.2 V

=5.5 V 140 C

V

IN

=5.5 V 20 C

V

IN

V_NTCW NTC threshold warning Idle mode, I

V_NTCH NTC threshold hot Idle mode, I

VOL

Output logic signal level
low ATN, READY

I

ATN, READY

=320 mA

TORC H

=320 mA

TORC H

=5.5 V, V

SUPMIN

=5.5 V-

TCHV_H=1 or

=5.0 V, V

SUPMIN

=5.0 V-

TCHV_H=1 or

=4.5 V, V

SUPMIN

=4.5 V-

, TCHV_H=1 or

=4.2 V, V

SUPMIN

=4.2 V-

, TCHV_H=0

=2 mA max. 0.56 V

NTC

=2 mA max. 1.2 V

NTC

50

70

1.3

0.8

0.3

0.2

=+10 mA 0.3 V

%

V

I

OZ

V

IL

V

IH

I

LSCON

V

LSIN

V

DRIVE

T

ON

Output logic leakage
current ATN, READY

V

ATN, READY

=3.3 V 1 mA

Input logic signal level
SCL, SDA, TEST,
RESET, SCHRG,

=2.7 V to 5.5 V

V

IN

FLASH, TORCH, ADD

Input reset current VIN=2.7 V to 5.5 V, V

Analog input signal
range

MOSFET driver output

Reference voltage
range

LED current rise time
I

LED

=0 to I

LED

=max.

V

=2.7 V to 5.5 V 0.1 1.6 V

IN

Source: I

Sink: I

DRIVE

EXT_REG=1

= -8 mA 4.27 V

DRIVE

= +8 mA 1.05 V

(1)

Flash triggered by external trig 0.3 ms

Doc ID 022927 Rev 2 13/43

00.4

1.4 3.0

=1.6 V 10 mA

REF

0.12 1.2 V

V

Electrical characteristics STCF04

Table 6. Electrical characteristics (continued)

Symbol Parameter Test conditions Min. Typ. Max. Unit

T

RESMIN

T

LSCAPRES

Minimum RESET time VIN=2.7 V to 5.5 V 1 µs

Reset time of the light
sensor capacitor

200 µs

14/43 Doc ID 022927 Rev 2

STCF04 Introduction

7 Introduction

The STCF04 is a high efficiency buck-boost converter with input current limitation dedicated
to managing the power for Flash/Torch mode operations using the SuperCap technology
and to control the high current white LEDs in cell phone cameras and portable applications
in general.

The device operates in Free-running mode with a coil peak current limiter. It charges and
stores the energy on the SuperCap from a single cell lithium-Ion battery (2.5 V to 4.2 V). The
device contains an active balancer circuit able to regulate the middle pin of the SuperCap,
therefore guaranteeing the reliability of the SuperCap component. The device operation and
diagnostic are controlled by the I²C bus. Torch current is adjustable from 15 mA to 320 mA.
The maximum flash current is set by choosing the R
using a dedicated register. The device operates as a standalone flash SuperCap controller
able to drive one external MOSFET.

The device has two modes of managing the energy in the SuperCap during Torch mode
operation, both adjustable by I²C:

1. Torch mode 1: in this case the output current in Torch mode is regulated from V
which is set by VDC bits in the feature register (R4). This mode is optimized to give the
possibility of triggering the flash without any delay caused by a recharging of the
SuperCap.

2. Torch mode 2: in this case the output current in Torch mode is regulated from V
V

+ 0.25 V. This mode is optimized for maximum efficiency in Torch mode. The

FLED

SuperCap must be recharged after the end of Torch mode operation.

resistor and it can be adjusted by I²C

FL

OUT,

OUT

=

The device uses an external NTC resistor to sense the temperature of the white LEDs and
light sensor management to optimize the flash duration in Flash mode. These last two
functions are optional so they may not be needed in all applications, and, in such cases, the
relevant external components can be omitted. In Monitoring mode, when the voltage
Monitoring mode of the SuperCap is active, the device is working with low consumption.
When the READY pin goes HIGH, meaning that the SuperCap has been self-discharged,
the P should initiate a re-charge of the SuperCap, for example, by entering Charge mode.

Doc ID 022927 Rev 2 15/43

Detailed description STCF04

8 Detailed description

8.1 Logic pins

8.1.1 SCL, SDA pins

These are the standard CLOCK and DATA pins as defined in the I²C bus specifications.
External pull-ups are required according to I²C bus specifications.

8.1.2 FLASH pin

This input pin is internally AND-ed with the FLASH_ON bit to generate the internal signal
that activates the flash operation. This gives the user the possibility to accurately control the
flash duration using a dedicated pin, avoiding the I²C bus latencies (hard-triggering). Neither
internal pull-up nor pull-down is provided.

8.1.3 TORCH pin

This input pin is internally AND-ed with the TCH_ON bit to generate the internal signal that
activates the torch operation. Neither internal pull-up nor pull-down is provided.

8.1.4 RESET pin

This pin works as an external reset input. The microprocessor can use this pin to reset the
STCF04 at any time. Neither internal pull-up nor pull-down is provided. This pin is active
LOW.

8.1.5 ATN pin

This output pin (open drain, active LOW) is provided to better manage the information
transfer from the STCF04 to the microprocessor. Because of the limitations of a single
master I²C bus configuration, the microprocessor should regularly communicate with the
STCF04 to verify if certain operations have been completed, or to check diagnostic
information. Alternatively, the microprocessor can use the ATN pin to be advised that a new
data is available in the STAT_REG register, therefore avoiding continuous communication.
The information may then be read in the STAT_REG by a read operation via I²C which also
automatically resets the ATN pin to HIGH. The STAT_REG is also reset to 0. No internal
pull-up is provided.

8.1.6 ADD pin

This pin offers the opportunity of selecting one of the 4 possible I²C slave addresses.
Neither internal pull-up nor pull-down is provided. The pin must be connected to GND, VBAT,
SCL or SDA to select the desired I²C slave address (see
floating.

Ta bl e 7

). This pin cannot be left

16/43 Doc ID 022927 Rev 2

STCF04 Detailed description

Table 7. I²C address table

ADD pinA7A6A5A4A3A2A1A0

GND0110000R/W

VBAT0110001R/W

SDA0110010R/W

SCL0110011R/W

8.1.7 READY pin

This pin can be used to monitor the voltage on the SuperCap by the microprocessor. The
status of this pin has different meanings according to the current mode of operation of the
STCF04.

- Idle, Monitoring, Torch mode with TCHV_H=1:

The READY pin goes LOW when the SuperCap voltage reaches the threshold voltage set
by the V
voltage - 0.2 V of hysteresis. When READY is HIGH it means that it is necessary to recharge
the SuperCap in order to be able to make a flash.

- Torch mode with TCHV_H=0:

The READY pin goes LOW when the SuperCap reaches 4.2 V and is HIGH when the
SuperCap is below 4.2 V and Torch mode is not active.

register, otherwise the READY pin is HIGH when V

DC

SuperCap

goes below VDC

- FLASH:

The READY pin goes LOW as soon as the SuperCap voltage reaches the threshold voltage
set by the V

register. It stays LOW until the SuperCap voltage decreases below 4.2 V and

DC

Flash mode is not active. This feature allows the user to perform multiple flashes.

See

Figure 4

below for details.

Figure 4. Behavior of the READY pin in different modes

Doc ID 022927 Rev 2 17/43

Detailed description STCF04

Data transmission from the main microprocessor to the STCF04 and vice versa takes place
through the 2 I²C bus interface wires, consisting of the two lines SDA and SCL (pull-up
resistors to a positive supply voltage must be externally connected).

8.1.8 Data validity

As shown in

Figure 5

, the data on the SDA line must be stable during the high period of the
clock. The HIGH and LOW state of the data line can only change when the clock signal on
the SCL line is LOW.

Figure 5. Data validity on the I²C bus

8.1.9 START and STOP conditions

Both data and clock lines remain HIGH when the bus is not busy. As shown in
START condition is a HIGH to LOW transition of the SDA line while SCL is HIGH. The STOP
condition is a LOW to HIGH transition of the SDA line while SCL is HIGH. A STOP condition
must be sent before each START condition.

CS11340

Figure 6

, a

Figure 6. Timing diagram on I²C bus

18/43 Doc ID 022927 Rev 2

STCF04 Detailed description

8.1.10 Byte format

Every byte transferred to the SDA line must contain 8 bits. Each byte must be followed by an
acknowledge bit. The MSB is transferred first. One data bit is transferred during each clock
pulse. The data on the SDA line must remain stable during the HIGH period of the clock
pulse. Any change in the SDA line at this time is interpreted as a control signal.

Figure 7. Bit transfer

AM11867v 1

8.1.11 Acknowledge

The master (microprocessor) puts a resistive HIGH level on the SDA line during the
acknowledge clock pulse (see
pull down (LOW) the SDA line during the acknowledge clock pulse, so that the SDA line is
stable LOW during this clock pulse. The peripheral which has been addressed must
generate an acknowledge pulse after the reception of each byte, otherwise the SDA line
remains at the HIGH level during the ninth clock pulse duration. In this case, the master
transmitter can generate the STOP information in order to abort the transfer. The STCF04
does not generate the acknowledge bit if the V

Figure 8. Acknowledge on I²C bus

8.1.12 Interface protocol

Figure 8

). The peripheral (STCF04) that acknowledges must

supply is below 2.7 V.

I

The interface protocol is composed of (

- A START condition (START)

- A device address + R/W bit (read =1 / write =0)

- A register address byte

Doc ID 022927 Rev 2 19/43

Ta bl e 8

):

Detailed description STCF04

- A sequence of data n* (1 byte + acknowledge)

- A STOP condition (STOP)

The register address byte determines the first register in which the read or write operation
takes place. When the read or write operation is finished, the register address is
automatically incremented.

Table 8. Interface protocol

Device address + R/W bit Register address Data

76543210 76543210 76543210

S
T

M

A

S

R

B

L
S
B

W

A

R

M

C

S

K

B

T

8.1.13 Writing to a single register

Writing to a single register starts with a START bit followed by the 7-bit device address of the
STCF04. The 8
operation. The master then waits for an acknowledgement from the STCF04. The 8-bit
register address is then sent to the STCF04. It is also followed by an acknowledge pulse.
The last transmitted byte is the data to be written to the register. It is again followed by an
acknowledge pulse from the STCF04. The master then generates a STOP bit and the
communication is over. See

Figure 9. Writing to a single register

th

bit is the R/W bit, which is 0 in this case. R/W = 1 means a reading

Figure 9

DEVICE

ADDRESS

7 bits

W

R

I
T
E

below.

ADDRESS OF

REGISTER

L

A

M

S

C

S

B

K

B

DATA

L
S
B

AM11863v1

S

A

T

C

O

K

P

L

A

S

M

T

S

A

B
R
T

L

R

M

A

S

/

S

C

B

W

B

K

SDA LINE

M

A

S

C

S

C

B

K

B

K

8.1.14 Writing to multiple registers with incremental addressing

It would be impractical to send the device address and the address of the register when
writing to multiple registers several times. The STCF04 supports writing to multiple registers
with incremental addressing. When data is written to a register, the address register is
automatically incremented, so the next data can be sent without sending the device address
and the register address again. See

20/43 Doc ID 022927 Rev 2

Figure 10

below.

L

S

A

S

T

C

B

O

K

P

STCF04 Detailed description

Figure 10. Writing to multiple registers with incremental addressing

DEVIC E

ADDRESS

7 bits

W
R

ADDRESS OF

I

T

REGISTER i

E

DATA i

DATA i +1

DA TA i +2

DA TA i+ 2

DA TA i +n

L

M

A

S

M

T

S

A

B

R
T

M

R

L

A

S

/

S

C

B

W

B

K

M

A

S

S

C

S

C

B

B

K

B

K

L

M

A

S

S

C

B

B

K

SDA LINE

8.1.15 Reading from a single register

The reading operation starts with a START bit followed by the 7-bit device address of the
STCF04. The 8
the address + R/W bit by an acknowledge pulse. The address of the register that should be
read is sent afterwards and confirmed again by an acknowledge pulse of the STCF04 again.
Then the master generates a START bit again and sends the device address followed by the
R/W bit, which is now 1. The STCF04 confirms receipt of the address + R/W bit by an
acknowledge pulse and starts to send the data to the master. No acknowledge pulse from
the master is required after receiving the data. Then the master generates a STOP bit to
terminate the communication. See

Figure 11. Reading from a single register

th

bit is the R/W bit, which is 0 in this case. The STCF04 confirms receipt of

Figure 11

D EVICE

ADDRESS

7 bits

W

ADDRESS

R

T
E

OF

I

REGISTER

M

L

A

S

S

C

B

B

K

.

D EVICE

ADDRESS

7 bits

A

M

L

A

S

S

C

B

B

K

R
E

DATA

A
D

M

L

C

S

S

K

B

B

L

A

S

C

B

K

AM11864v1

S

T
O
P

S

M

T

S

A

B

R
T

R

A

L

M

/

C

S

S

W

K

B

B

S

A

L

T

C

S

A

K

B

R
T

SDA LINE

A

R

C

/

K

W

N

L

O

S

B

A
C

K

AM11865v1

S

T
O
P

8.1.16 Reading from multiple registers with incremental addressing

Reading from multiple registers starts in the same way as reading from a single register. As
soon as the first register is read, the register address is automatically incremented. If the
master generates an acknowledge pulse after receiving the data from the first register, then
reading of the next register can start immediately without sending the device address and
the register address again. The last acknowledge pulse before the STOP bit is not required.
See

Figure 12

.

Doc ID 022927 Rev 2 21/43

Detailed description STCF04

Figure 12. Reading from multiple registers

DEVIC E

ADDRESS

7 bits

W
R

I
T
E

ADDRESSOF

REGISTER i

DEVICE

ADDRESS

7 bits

R
E

DATA i

A
D

DA TA i +1

DA TA i +2

DATA i+2

DATA i +n

S

M

T

S

A

B
R
T

R

M

A

L

/

S

C

S

W

B

K

B

S

A

L

T

C

S

A

K

B

R
T

A

R

C

/

K

W

L

S

B

SDA LINE

M

A

S

C

B

K

M

A

L

S

C

S

B

K

B

M

A

L

S

C

S

B

K

B

M

A

L

S

C

S

B

K

B

L

N

S

S

O

T

B

O

A

P
C
K

AM11866v1

22/43 Doc ID 022927 Rev 2

STCF04 Description of the internal registers

9 Description of the internal registers

Table 9. I²C register mapping

Register name SUB address (hex) Operation Description

CMD_REG 00 R / W Commands

FL_REG 01 R / W Flash register

AUX_REG 02 R / W Auxiliary LED

STAT_REG 03 R only Status register

FTR_REG 04 R / W Features

TRCH_REG 05 R / W Torch register

Note: All the registers can be read only when the PWR_ON bit is 1. Reading any register when

PWR_ON = 0, gives 0 regardless of the real value of the register. This concerns command
and feature registers in Monitoring mode and Shutdown + NTC mode.

9.1 Commands (CMD_REG) 00(hex)

Table 10. Command register

CMD_REG

(Write mode)

SUB ADD=00 PWR_ON FLASH_ON TCH_ON NTC_ON TCHV_H CHRG MONTR N/A

Power-ON

RESET value

9.1.1 PWR_ON

9.1.2 FLASH_ON

MSB LSB

0 0 00000 0

When set, it activates all analog and power internal blocks including the NTC supporting
circuit, and the device is ready to operate (Idle mode). As long as PWR_ON=0, only the I²C
interface is active, minimizing Shutdown mode power consumption.

This bit is AND-ed with the FLASH pin to generate the internal signal FL_ON that activates
Flash mode. In this way, both soft-triggering and hard-triggering of the flash are possible. If
soft-triggering (through I²C) is chosen, the FLASH pin is not used and must be kept HIGH
(tied to VBAT). If hard-triggering is chosen, then the FLASH pin must be connected to a
microprocessor I/O devoted to flash timing control, and the FLASH_ON bit must be set in
advance. Both triggering modes can benefit from the internal flash time counter, which uses
the FLASH_ON bit and can work either as a safety shutdown timer or as a flash duration
timer. Flash mode can start only if PWR_ON=1. The LED current is controlled by the value
set by the FDIM_0~2 of the DIM_REG.

9.1.3 TCH_ON

Torch on: when set to 1 from Idle mode, the STCF04 enters Torch mode. The LED current is
controlled by the value set by the TDIM_0~3 of the TORCH_REG.

Doc ID 022927 Rev 2 23/43

Description of the internal registers STCF04

9.1.4 NTC_ON

This bit activates the comparators that monitor the LED temperature. NTC-related blocks
are always active regardless of this bit in Torch mode and Flash mode.

9.1.5 TCHV_H

Torch voltage HIGH: when set to 1, the SuperCap voltage is maintained to the value set by
the feature register (VDC_0~1) during Torch mode. If this bit is set to 0, voltage on the
SuperCap is regulated to maintain the desired torch current and optimize the efficiency in
Torch mode.

9.1.6 CHRG

This bit enables the charging of the SuperCap, when set to 1, the device starts to charge the
SuperCap by the limited current from the PVBAT. During this operation the active balancing
circuit is enabled.

9.1.7 MONTR

When this bit is set and the VDC voltage in the feature register is set to a non-zero value at
the same time, the device enters Monitoring mode.

9.2 Flash register (FL_REG) 01(hex)

Table 11. Flash register

(Write mode)

SUB ADD=01 FTIM_4 FTIM_3 FTIM_2 FTIM_1 FTIM_0 FDIM_2 FDIM_1 FDIM_0

Power-ON, Shutdown

mode RESET value

Table 12. Flash mode dimming registers settings (EXT_REG = 0)

F_DIM (hex)01234567

DRIVE voltage

LED current [A]*

Example LED

current (A) for

RFL = 10 mΩ

CL_REG

MSB LSB

00000000

FDIM_0~2: these 3 bits define the LED current in Flash mode with 8 values.

FTIM_0~4: these 5 bits define the flash duration timer value in Flash mode with 32 values.

[mV]**

12 48 60 72 84 96 108 120

0.012 V /
R

1.2 4.8 6 7.2 8.4 9.6 10.8 12

FL

0.048 V /
R

FL

0.060 V /
R

FL

0.072 V /
R

FL

0.084 V /
R

FL

0.096 V /
R

FL

0.108 V /
R

FL

0.120 V /
R

FL

Note: RFL is the external sensing resistor, external MOS transistor connected, see Figure 3.

24/43 Doc ID 022927 Rev 2

STCF04 Description of the internal registers

FTIM_0~4: these 5 bits define the maximum flash duration. It is intended to limit the energy

dissipated by the LED to a maximum safe value or to leave the control of the flash duration
to the STCF04 during normal operation. Values from 0~31 correspond to 0~410 ms
(according to

Ta bl e 1 3

). The timing accuracy is related to the internal oscillator frequency
that clocks the flash time counter (+/- 20%). Entering Flash mode (either by soft or hard
triggering) activates the flash time counter, which begins counting down from the value
loaded in the F_TIM register. When the counter reaches zero, Flash mode is stopped by
resetting the TRIG_EN bit, and simultaneously, the ATN pin is set to true (LOW) to alert the
microprocessor that the maximum time has been reached. The FTIM value remains
unaltered at the end of the count.

Table 13. Flash time dimming register settings

FTIM_DIM(hex)0123456789ABCDEF

Flash length[ms] 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 90

FTIM_DIM(hex)101112131415161718191A1B1C1D1E1F

Flash length[ms] 110 130 150 170 190 210 230 250 270 290 310 330 350 370 390 410

9.3 AUX LED (AUX_REG) 02(hex)

Table 14. AUX LED register

AUX_REG

(Write mode)

SUB ADD = 02 AUXI_3 AUXI_2 AUXI_1 AUXI_0 AUXT_3 AUXT_2 AUXT_1 AUXT_0

Power-ON,

Shutdown mode

RESET value

MSB LSB

00000000

AUXI_0~3: this 4-bit register defines the AUX LED current from 0 to 100 mA. See

Ta b le 1 5

AUX LED dimming for reference. Loading any value between 1 and 11 also starts the AUX
LED current source timer, if enabled. The AUX LED current source is active only in Idle
mode, and is deactivated in any other mode.

AUXT_0~3: this 4-bit register controls the timer that defines the ON-time of the AUX LED
current source. ON-time starts when the AUXI register is loaded with any value other than
zero, and stops after the time defined in the AUXT register. Values from 0 to 14 of the AUXT
register correspond to an ON-time of the AUX LED ranging from 100 to 1500 ms in 100 ms
steps. The value 15 puts the AUX LED into the continuous light mode. The
activation/deactivation of the AUX LED current source is controlled using only the AUXI
register.

Table 15. Auxiliary LED dimming table

AUXI (hex) 0123456789AB

AUX LED current

[mA]

0 6 10 15 20 25 33 40 53 67 80 100

Doc ID 022927 Rev 2 25/43

Description of the internal registers STCF04

Table 16. Auxiliary LED timing table

AUXT (hex)0123456789ABCDEF

AUX LE D

time [s]

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4

∞

9.4 Status (STAT_REG) 03(hex)

Table 17. Status register

(Read mode)

SUB ADD=03 N/A F_RUN FL_R NTC_W NTC_H OT_F FL_OVR LTH

Power-ON, Shutdown

mode RESET value

STAT_REG

MSB LSB

0000000 0

F_RUN: this bit is kept HIGH by the STCF04 during Flash mode. By checking this bit, the
microprocessor can verify if the Flash mode is running or has been terminated by the time
counter.

FL_R: (FLASH ready) this bit is set to 0 if the SuperCap voltage is not high enough to make
a flash.

NTC_W: this bit is set HIGH by the STCF04 and the ATN pin is pulled down, when the
voltage seen on the pin R

exceeds V

X

= 0.56 V. This threshold corresponds to a

REF4

warning temperature value at the LED measured by the NTC. The device is still operating,
but a warning is sent to the microprocessor. This bit stays high until the temperature goes
below the threshold.

NTC_H: this bit is set HIGH by the STCF04 and the ATN pin is pulled down, when the
voltage seen on the pin R

exceeds V

X

= 1.2 V. This threshold corresponds to an excess

REF5

temperature value at the LED measured by the NTC. The device is put into Idle mode to
avoid damaging the LED. This bit is reset by the STCF04 following a read operation of the
STAT_REG.

OT_F: this bit is set HIGH by the STCF04 and the ATN pin is pulled down, when the chip
overtemperature protection (~140 °C) has put the device into Idle mode. This bit is reset by
the STCF04 following a read operation of the STAT_REG.

FL_OVR: this bit is set HIGH, if the flash operation is terminated by the light sensor.

LTH: this bit is set HIGH when the local temperature protection for the SuperCap charging

circuit is activated.

26/43 Doc ID 022927 Rev 2

STCF04 Description of the internal registers

Table 18. Status register details

Bit name

F_RUN

(STAT_REG)

FL_R

NTC_W

(STAT_REG)

NTC_H

(STAT_REG)

OT_F

(STAT_REG)

FL_OVR LTH

Default value 0 0 0 0 0 0 0

Latched

(1)

Forces Idle

mode when set

Sets ATN LOW

when set

1. YES means that the bit is set by internal signals and is reset to default by an I²C read operation of STAT_REG. NO means
that the bit is set and reset by internal signals in real-time.

NO NO YES YES YES NO NO

NO NO NO YES YES NO NO

NO YES YES YES YES YES NO

9.5 Feature (FTR_REG) 04(hex)

Table 19. Feature register

(Write mode)

SUB ADD=04 IDC_0 N/A VDC_1 VDC_0 EN_LS LS_2 LS_1 LS_0

Power-ON, Shutdown

mode RESET value

LS_REG

MSB LSB

00000000

LS_0~2: these 3 bits define the value of the internal reference voltage for the light sensor
comparator. The EN_LS bit must be set to 1 to activate the internal reference for the light
sensor comparator.

EN_LS: this bit enables the light sensor function when set HIGH.

Table 20. Light sensor reference dimming register settings

LS_DIM(hex) 0123 4 5 6 7

LSREF[mV] 200 400 600 800 1000 1200 1400 1600

VDC_0~1: these 2 bits define the output voltage of the DC-DC converter.

Table 21. DC-DC converter output voltages (V

VDC_1 VDC_0 V

OUT

)

OUT

004.5 V

015.0 V

105.5 V

Note: See Section 10.4.

IDC_0: this bit defines the peak current limit value of the DC-DC converter.

Doc ID 022927 Rev 2 27/43

Description of the internal registers STCF04

Table 22. DC-DC converter coil peak current limit values

IDC_0 I

COIL (PEAK)

01.45 A

11.80 A

9.6 Torch register (TRCH_REG) 05(hex)

Table 23. Torch register

(Read mode)

SUB ADD=05 TTRCH1 TTRCH0 TDIM_3 TDIM_2 TDIM_1 TDIM_0 N/A N/A

Power-ON, Shutdown

mode RESET value

Table 24. Torch mode dimming registers settings

VRID_REG

MSB LSB

0000000 0

TTRCH_0~1: these bits define the Torch mode time.

TDIM_0~3: these 4 bits define the LED current in Torch mode with 12 values.

TDIM (hex) 0123456789AB

LED current [mA] 15 20 30 45 60 75 100 120 160 200 240 320

Internal step 1 2 3 4 5 6 7 8 9 10 11 12

Table 25. The safety timeout for Torch mode

TTRCH1 TTRCH0 Torch time

0 0 Infinity

01 5s

10 10s

11 15s

28/43 Doc ID 022927 Rev 2

STCF04 Theory of operation

10 Theory of operation

10.1 The state machine diagram

The state machine diagram of the device describes the overall function of the logic part of
the device. It helps with the understanding of all the working modes of the complex and
efficient management of the stored energy.

Figure 13. State machine diagram of the STCF04

NTC

Status _Register

LOCK

ALARM

Fromany states

Fromany states

!P WR_ON & NTC

Aux
LED

On

read

CHRG
+ NTC

!PWR_ON || !RESET

!P WR_ON & ! NTC

NTC

!NTC & PWR_O N

AuxLed_ON

MaxTimeLed

Flash

+

MaxTimeFlash

FLASH_ ON
& READY

Shutdown

PWR_O N

CHRG
|| FLA SH_ON
|| TCH_O N

FLASH_ ON
&READY&
LS

Flash

+
CHRG
+ NTC

+ LS

Battery plug-in

IDLE

!CHRG
|| ( READY
&!FLASH_ON &
!TCH_ON )

CHRG

TCH_ON
& READY
&TCHV_H

!P WR_ON || !MONTR

!TCH_ ON

TCH_ON
&READY
&!TCHV_H

!P WR_ON & MONTR

Torch

eff.

+

CHRG

+ NTC

Torch

+
CHRG
+ NTC

Monitoring

PWR_ON = Power ON
MONTR = Monitoring ON
LS_ON = Light Sensor ON
CHRG = Charging ON
FLASH_ON = bit Flash_ON & pin Flash ON
TCH_ON = bit TCH_ON & pin Torch ON
AuxLED_ON = Auxiliary led ON
READY= Ready Pin

AM11887v1

Doc ID 022927 Rev 2 29/43

Theory of operation STCF04

10.2 Power-ON reset

This mode is initiated by applying a supply voltage above the V
value. An internal timing (~1 µs) defines the duration of this status. The logic blocks are
powered, but the device doesn't respond to any input. The registers are reset to their default
values, the ATN and SDA pins are in high-Z, and the I²C slave address is internally set by
reading the ADD pin configuration. After the internally defined time has elapsed, the
STCF04 automatically enters Shutdown mode. For the additional reset of the device, it is
also possible to use the RESET pin.

10.2.1 RESET pin function

The device is put into Reset mode when the logic level on the RESET pin is 0. The logic
blocks are powered, but the device doesn't respond to any input. The registers are reset to
their default values; the ATN and SDA pins are in high-Z. The RESET pin must stay in LOW
level for T
reset function driven by the RESET pin is not needed, the RESET pin must be connected to
the V

Figure 14. Reset timing

BAT

RESMIN

= VIN.

time (1 µs) at least to guarantee correct resetting of the device. When the

PW_ON RESET

threshold

10.3 Shutdown mode and NTC mode

In Shutdown mode only the I²C interface is live, accepting I²C commands and register
settings. The device enters this mode automatically after reset or by resetting the PWR_ON
bit from other operation modes. Power consumption is at the minimum (1 µA typ.), if NTC is
not activated (NTC_ON = 0). If the NTC_ON is set, the µP can measure the LED
temperature through an A/D converter connected to the NTC pin. When NTC circuits are
active and the V
recommended to not leave the STCF04 in this status if battery drain must be minimized.

REF-EXT

is present, the typical current consumption is increased to 2 µA. It is

10.4 Monitoring mode

When the VDC voltage set by the FTR_REG is not 0, the comparator of the SuperCap
voltage is live. This comparator checks the voltage on the SuperCap continuously. If it is
higher than the V
voltage on the SuperCap is higher than V

30/43 Doc ID 022927 Rev 2

SUPMAX

threshold, then the READY pin is pulled low and stays low until the

SUPMAX

- 200 mV.

STCF04 Theory of operation

10.5 Idle mode

In this mode all internal blocks are turned ON. The DC-DC converter can be enabled by
setting the CHRG bit to 1. If it is enabled, the SuperCap is automatically charged. The NTC
circuit can be activated to monitor the temperature of the LED and I²C commands and
register settings are allowed to be executed immediately. The device enters this mode:

● from Monitoring when setting the PWR_ON bit

● from flash operation by resetting the FLASH pin or the FLASH_ON bit, or automatically

from flash operation when the time counter reaches zero

● from torch operation by resetting the TCH_ON bit.

The device automatically enters this mode also when an overload or an abnormal condition
has been detected during flash or torch operation (see

Ta bl e 1 7

).

10.6 AUX LED

The STCF04 is capable of driving an auxiliary LED. Its cathode is always connected to the
AUXLED pin, while its anode can be connected either to the V
to the V

pin is particularly advantageous in case of high AUXLED currents. The

OUT

maximum values of AUXLED currents are guaranteed only for anode voltages higher than

3.3 V, but V

may range from 2.7 V to 5.5 V, so in some cases it may not be possible to

BAT

use maximum currents.

BAT

or V

pin. Connecting it

OUT

10.7 Single or multiple flash using external (microprocessor) temporization

To avoid the I²C bus time latency, it is recommended to use the dedicated FLASH pin to
define the flash duration (hard-triggering). The FLASH_ON bit of CMD_REG should be set
before starting each flash operation, because it may have been reset automatically in the
previous flash operation.

The flash duration is determined by the pulse length that drives the FLASH pin. As soon as
the flash is activated, the system needs typically 0.3 ms to ramp up the output current on the
power LED. The internal time counter times out flash operation and keeps the LED
dissipated energy within safe limits in case of software deadlock; the FTIM register must be
set first.

Multiple flashes are possible by strobing the FLASH pin. The timeout counter cumulates
every flash ON-time until the defined timeout is reached unless it is reloaded by updating the
CMD_REG. The number of the flashes depends on V
discharged down to 4.2 V, the device goes automatically into Idle mode. After a flash
operation is timed out, the device automatically enters Idle mode by resetting the
FLASH_ON bit, and it also resets the F_RUN bit. The ATN pin is pulled down to inform the
microprocessor that the STAT_REG has been updated. Multiple flash is possible to trigger
as long as the READY pin is LOW.

, when the SuperCap is

FLED

Doc ID 022927 Rev 2 31/43

Theory of operation STCF04

10.8 External (microprocessor) temporization using the FLASH_ON bit

Even though it is possible, it is not recommended to use the FLASH_ON bit to start and stop
the flash operation, because of I²C bus latencies: this may result in inaccurate flash timing.
Nevertheless, if this operation mode is chosen, the FLASH pin must be kept HIGH (logic
level or wired to V
mode the time counter times out flash operation and keeps the energy dissipated by the
LED within safe limits in case of software deadlock.

), leaving the whole flash control to the I²C bus. Also in this operation

BAT

10.9 Single flash using internal temporization

Flash triggering can be obtained either by the FLASH pin (hard-triggering) or by I²C
commands (soft-triggering). The first solution is recommended for an accurate start time,
while the second is less accurate because of the I²C bus time latency. Stop time is defined
by the STCF04 internal temporization and its accuracy is determined by the internal
oscillator. For hard-triggering, it is necessary to set the FLASH_ON bit in advance. For soft­triggering, the FLASH pin must be kept High (logic level or wired to V
be started by setting the FTIM and the TRIG_EN through I²C (both are located in the CMD
REG). There is a delay time between the moment the flash is triggered and when it appears.
This delay is caused by the time necessary to charge up the output capacitor, which
depends on battery voltage. Once triggered, the flash operation is stopped when the time
counter reaches zero. As soon as the flash is finished, the F_RUN bit is reset, the ATN pin is
pulled down for 11 µs to inform the microprocessor that the STAT_REG has been updated
and the device goes back to Idle mode.

) and the flash can

BAT

10.10 Light sensor feature

This function works as an optional feature, which is able to optimize the length of the flash
according to the light conditions in the flashed area. It uses an external capacitor C
which is charged by a current coming from the external voltage reference, which is limited by
the light sensor (generally made by a phototransistor). Before the start of the flash
operation, the C
200 µs. During the flash operation the C
according to the light conditions in the flashed area. When the voltage level on the C
capacitor reaches the internal reference voltage, which is set by the light sensor register
(R4, LS_0~2), the STCF04 stops the operation of the flash and discharges the C
capacitor through an internal switch.

capacitor is discharged by the internal switch to the zero voltage during

INT

capacitor integrates the charging current

INT

INT

INT

INT

,

32/43 Doc ID 022927 Rev 2

STCF04 Typical performance characteristics

11 Typical performance characteristics

Figure 15. Flash current vs. input voltage

I

I

I

OUT

OUT

OUT

AM09307v1

= 1.2 A

= 4.8 A

= 8 A

8

7,5

7

6,5

6

5,5

5

4,5

[A]

4

OUT

3,5

I

3

2,5

2

1,5

1

0,5

0

2,25 2,5 2,75 33,25 3,5 3,75 4 4,25 4,5 4,75

[V]

V

IN

Figure 16. Torch current vs. input voltage

350
325
300

275
250
225
200
175

[mA]

150

OUT

I

125
100

75
50
25

0

2,25 2,5 2,75 33,25 3 ,5 3,75 4 4,25 4,5 4,75

AM09308v1

I

= 320 m A

OUT

I

= 160 mA

OUT

I

= 40 mA

OUT

[V]

V

IN

Doc ID 022927 Rev 2 33/43

Typical performance characteristics STCF04

Figure 17. Aux LED current vs. input voltage

I

I

OUT

OUT

AM09309v1

= 10 mA

= 100 mA

110
105
100

95
90

85
80

75
70
65
60

[mA]

55
50

OUT

I

45
40

35
30

25
20
15
10

5
0

2,25 2,5 2,75 33,25 3,5 3,75 4 4,25 4,5 4,75

V

[V]

IN

Figure 18. Charging efficiency vs. V

100

90

80

70

60

50

Eff. [%]

40

30

20

10

0

0123 456

voltage (VIN = 3.6 V)

OUT

[V]

V

OUT

AM09

310v1

34/43 Doc ID 022927 Rev 2

STCF04 Typical performance characteristics

Figure 19. Torch time - settings compared to real values

16

14

12

10

8

Time [s]

6

4

2

0

123 45

Step

AM09311v1

Time meas ured

Time set

Figure 20. Torch current - settings compared to real values

350

300

250

I

OUT

I

OUT

meas ured

set

AM09312v1

200

[mA]

150

OUT

I

100

50

0

02468 10 12 14

Step

Figure 21. Flash time - settings compared to real values

450

400

350

300

250

200

Time [ms]

150

100

50

0

0 5 10 15 20 25 30 35

Time meas ured

Time set

Step

AM09313v1

Doc ID 022927 Rev 2 35/43

Typical performance characteristics STCF04

Figure 22. Flash current - settings compared to real values

14

12

10

8

[A]

OUT

6

I

4

I

2

OUT

I

OUT

0

02468 10

Step

AM09314v1

meas ured

set

Figure 23. Aux LED time - settings compared to real values

1.6

1.4

1.2

Time meas ured

Time set

1

AM09315v1

0.8

Time [s]

0.6

0.4

0.2

0

051015

Step

Figure 24. Aux LED current- settings compared to real values

120

I

meas ured

100

80

[mA]

60

OUT

I

40

20

0

02468 10 12

OUT

I

set

OUT

Step

AM09

316v1

36/43 Doc ID 022927 Rev 2

STCF04 Typical performance characteristics

Figure 25. Operation in Flash mode - single flash pulse

Blue - SuperCap voltage; Green - LED current; Magenta - FLASH pin;

Figure 26. Operation in Flash mode - multiple flash pulses

Blue - SuperCap voltage; Green - LED current; Magenta - Battery current;

Doc ID 022927 Rev 2 37/43

Typical performance characteristics STCF04

Figure 27. Operation in Torch mode with TCHV_H bit = 0

Blue - SuperCap voltage; Green - LED current; Magenta - Battery current;

Figure 28. Operation in Torch mode with TCHV_H bit = 1

Blue - SuperCap voltage; Green - LED current; Magenta - Battery current.

38/43 Doc ID 022927 Rev 2

STCF04 Package mechanical data

12 Package mechanical data

In order to meet environmental requirements, ST offers these devices in different grades of
ECOPACK
specifications, grade definitions and product status are available at: www.st.com.
ECOPACK is an ST trademark.

®

packages, depending on their level of environmental compliance. ECOPACK

Doc ID 022927 Rev 2 39/43

Package mechanical data STCF04

TFBGA25 mechanical data

mm. mils.

Dim.

Min. Typ. Max. Min. Typ. Max.

A 1.0 1.1 1.16 39.4 43.3 45.7

A1 0.25 9.8

A2 0.78 0.86 30.7 33.9

b 0.25 0.300.35 9.8 11.8 13.8

D2.93.0 3.1 114.2 118.1 122.0

D1 2 78.8

E2.93.0 3.1 114.2 118.1 122.0

E1 2 78.8

e0.5 19.7

SE 0.25 9.8

40/43 Doc ID 022927 Rev 2

7539979/A

STCF04 Package mechanical data

Tape & reel TFBGA25 mechanical data

mm. inch.

Dim.

Min. Typ. Max. Min. Typ. Max.

A 330 12.992

C 12.8 13.2 0.504 0.519

D 20.2 0.795

N60 2.362

T 14.4 0.567

Ao 3.3 0.130

Bo 3.3 0.130

Ko 1.60 0.063

Po 3.9 4.1 0.153 0.161

P7.98.1 0.311 0.319

Doc ID 022927 Rev 2 41/43

Revision history STCF04

13 Revision history

Table 26. Document revision history

Date Revision Changes

14-Mar-2012 1 Initial release.

16-May-2012 2 Document status promoted from preliminary data to production data.

42/43 Doc ID 022927 Rev 2

STCF04

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Doc ID 022927 Rev 2 43/43