STCF04
High power white LED SuperCap™ driver with I²C interface
Datasheet − production data
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
TFBGA25 (3 x 3 mm)
Applications
■
Cell phones and smartphones
■
Camera flashes/strobe
■
PDAs and digital still cameras
■
Controlled LED current in all modes
■
Soft and hard triggering of Flash, Torch and
Picture light modes
Description
■
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
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
September 2012
This is information on a product in full production.
Doc ID 022927 Rev 3
1/43
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
9
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
Description of the internal registers . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
9.1
2/43
Logic pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Commands (CMD_REG) 00(hex) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
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STCF04
10
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
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
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3/43
List of tables
STCF04
List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
Table 9.
Table 10.
Table 11.
Table 12.
Table 13.
Table 14.
Table 15.
Table 16.
Table 17.
Table 18.
Table 19.
Table 20.
Table 21.
Table 22.
Table 23.
Table 24.
Table 25.
Table 26.
4/43
Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Thermal data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
List of external components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
I²C address table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Interface protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
I²C register mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Command register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Flash register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Flash mode dimming registers settings (EXT_REG = 0) . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Flash time dimming register settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
AUX LED register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Auxiliary LED dimming table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Auxiliary LED timing table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Status register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Status register details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Feature register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Light sensor reference dimming register settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
DC-DC converter output voltages (VOUT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
DC-DC converter coil peak current limit values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Torch register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Torch mode dimming registers settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
The safety timeout for Torch mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Doc ID 022927 Rev 3
STCF04
List of figures
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
Figure 23.
Figure 24.
Figure 25.
Figure 26.
Figure 27.
Figure 28.
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Pin connection (top view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Behavior of the READY pin in different modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Data validity on the I²C bus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Timing diagram on I²C bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Bit transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Acknowledge on I²C bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Writing to a single register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Writing to multiple registers with incremental addressing . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Reading from a single register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Reading from multiple registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
State machine diagram of the STCF04 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Reset timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Flash current vs. input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Torch current vs. input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Aux LED current vs. input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Charging efficiency vs. VOUT voltage (VIN = 3.6 V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Torch time - settings compared to real values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Torch current - settings compared to real values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Flash time - settings compared to real values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Flash current - settings compared to real values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Aux LED time - settings compared to real values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Aux LED current- settings compared to real values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Operation in Flash mode - single flash pulse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Operation in Flash mode - multiple flash pulses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Operation in Torch mode with TCHV_H bit = 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Operation in Torch mode with TCHV_H bit = 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
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Description (continued)
1
STCF04
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 3
STCF04
Diagram
2
Diagram
Figure 1.
Block diagram
LSCON
VBAT
LSIN
PVBAT
VLX1
VLX2
VOUT
AUXLED
AUXLED
BOOST
CONVERTER
BUCK
CONVERTER
PREREG
& BIAS
SUPERCAP
BALANCING
&
SUPERCAP
VOLTAGE &
BALANCING
CONTROL
VOLTAGE
CONTROL
READY
FLASH
FLASH
TRIGGERING
TRIGGERING
&CURRENT
&CURRENT
LIMITITING
LIMITITING
TORCH
CONTROL
FLASH
LOGIC
MX
NTC_ON
TORCH
TORCH
DIMMING
DIMMING
OSCILLATOR & TIME
COUNTER
+
-
PGND
CURRENT
SENSING
NTC_W
REF4
PROTECTIONS &
DIAGNOSTICS
SCL
I²C
+
-
REF5
NTC_H
INTERF
ADD
ISENS
MX
NTC_ON
LED
FAIL
SDA
DRIVE
LED
ATN
RESET
VMID
REF
120 mV..1.2 V
ON - CHIP
TEMP
OVER CURRENT
PGND
AGND
Doc ID 022927 Rev 3
NTC
BIAS
RX
ENABLE/
1.8 V REF
NTC
7/43
Pin configuration
3
8/43
STCF04
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
RX
RX resistor connection
D1
VOUT
SuperCap connection
C1
VMID
SuperCap middle pin connection
E5
NTC
NTC resistor connection
A3
READY
SuperCap status flag pin
B3
SCL
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
A5
SDA
E3
AUXLED
Auxiliary red LED connection
B2
LSCON
Light sensor capacitor connection
D3
VBAT
Signal supply voltage
A2
LSIN
Light sensor input
C5
DRIVE
MOSFET driver output
C2, D2
PGND
Power ground + die back connection
I²C clock signal
Supply voltage
I²C data
Doc ID 022927 Rev 3
STCF04
Maximum ratings
4
Maximum ratings
Table 3.
Absolute maximum ratings
Symbol
Parameter
VBAT, PVBAT
VLX
VOUT
VDCDC
VMID
AUXLED
LED
Value
Unit
Signal supply voltage
- 0.3 to 6
V
Inductor connection
- 0.3 to 6
V
SuperCap connection
- 0.3 to 6
V
DC-DC converter output
- 0.3 to 6
V
SuperCap middle pin connection
- 0.3 to 6
V
AUXLED connection
- 0.3 to 6
V
LED connection
- 0.3 to 6
V
- 0.3 to VBAT + 0.3
V
- 0.3 to VBAT + 0.3
V
SCL, SDA, ATN, ADD,
READY, TORCH,
Logic pins
FLASH, RESET
PVBAT
Power supply voltage
DRIVE
External MOSFET drive
- 0.3 to 6
V
Light sensor input
- 0.3 to 6
V
LSCON
Light sensor capacitor connection
- 0.3 to 6
V
RX
Connection for reference resistor
- 0.3 to 3
V
Connection for LED temperature sensing
- 0.3 to 3
V
Flash regulator sensing connection
- 0.3 to 3
V
±2
kV
1
W
LSIN
NTC
ISENS
ESD
Human body model
PTOT
Continuous power dissipation (at TA=70 °C)
TOP
Operating junction temperature range
- 40 to 85
°C
Junction temperature
- 40 to 150
°C
Storage temperature range
- 65 to 150
°C
TJ
TSTG
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
RthJA
Parameter
Thermal resistance junction-ambient
(1)
Value
Unit
56
°C/W
1. This parameter corresponds to the PCB board, 8 layers with 1 inch² of cooling area.
Doc ID 022927 Rev 3
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 VOUT.
10/43
Doc ID 022927 Rev 3
STCF04
Application
Table 5.
List of external components
Component
Manufacturer
Part number
Value
Size
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
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
TFL
STMicroelectronics
STL8NH3LL
8 A / 12 mΩ
3.3 x 3.3 x 0.9 mm
RFL
Tyco
TL2BR01FTE
0R01
1206
10 µF / 6.3 V
0402
L
CSUP
TDK
(1)
TDK
RLIGHT*
Tyco
TFOTO*
Vishay
CINT
0402
TEMT6000
4 x 2 x 1 mm
AUXLED
Red LED
0603
CR
100 nF
0402
1. Optional components for the auxiliary light sensor feature.
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 3
11/43
Electrical characteristics
6
STCF04
Electrical characteristics
TA = 25 °C, VIN = 3.6 V connected to VBAT and PVBAT, CIN = 10 µF, CSUP = 1.6F/5 V L = 1 µH,
RX = 15 kΩ, VFLED = 4.2 V/10 A. Unless otherwise specified, typical values are at 25 °C.
Table 6.
Symbol
VIN
VPW_ON
RESET
IO
VISENS
IPEAK
Electrical characteristics
Parameter
Test conditions
Operating input supply
voltage
VIN rising
Output current
adjustment range
ITORCH
Torch mode VIN=2.7 V to 5.5 V
Auxiliary LED output
current adjustment
range IAUXLED
Idle mode, VI or VO=3.3 V to 5.5 V
Current sensing input
VIN=2.7 V to 5.5 V, ILED = 12 A
RFL = 10 mΩ
15
0
V
V
108
100
120
VIN=2.7 V to 5.5 V, IDC0=1
1.80
VIN=2.7 V to 5.5 V
VOUT tolerance
Percentage with respect to
programmed voltage
IMID
Active balancing output
ΔIO
132
mV
A
4.5
5.5
VFLED+
0.25
V
V
-5
+5
%
VIN=2.7 V to 5.5 V
-400
400
mA
Output current variation
Torch mode ILED = 300 mA
-10
10
%
Quiescent current in
Shutdown mode
VIN=2.7 to 5.5 V, NTC_ON=0
Quiescent current in
Shutdown mode
VIN=2.7 to 5.5 V, NTC_ON=1
2
Quiescent current in
Monitoring mode
NTC_ON=0, SuperCap monitoring=1
45
1
Quiescent current in Idle
NTC_ON, CHRG=0
mode
12/43
5.5
320
1.45
Regulated voltage
range optimized for
Torch mode
fs
Unit
2.3
VIN=2.7 V to 5.5 V, IDC0=0
VIN=2.7 V to 5.5 V
IQ
Max.
mA
Regulated voltage
range optimized for
Flash mode
VOUT
Typ.
2.5
Power-ON reset
threshold
Switch peak current limit
Min.
Switching frequency
VIN=2.7 V
Doc ID 022927 Rev 3
µA
1
1.8
mA
MHz
STCF04
Table 6.
Symbol
Electrical characteristics
Electrical characteristics (continued)
Parameter
Efficiency of the
converter
ν
Test conditions
Min.
VIN=3.7 V, VDC_0,1=1, IDC0=1
VIN=2.7 V to 4.2 V, IDC_0=1,
Efficiency in Torch mode TCHV_H=1 ITORCH=320 mA
operation
V =2.7 V to 4.2 V, IDC_0=1,
Unit
%
50
IN
SuperCap regulated
voltage hysteresis
Max.
85
70
TCHV_H=0 ITORCH=320 mA
VSUPHYST
Typ.
VSUPMAX=5.5 V, VSUPMIN=5.5 VVSUPHYST, TCHV_H=1 or
FLASH_ON=1
1.3
VSUPMAX=5.0 V, VSUPMIN=5.0 VVSUPHYST, TCHV_H=1 or
FLASH_ON=1
0.8
VSUPMAX=4.5 V, VSUPMIN=4.5 VVSUPHYST, TCHV_H=1 or
FLASH_ON=1
0.3
VSUPMAX=4.2 V, VSUPMIN=4.2 VVSUPHYST, TCHV_H=0
0.2
V
SuperCap voltage ready
PWR_ON=0, VDC_0 or/and VDC_1=1
hysteresis
0.2
V
OTP
Overtemperature
protection
VIN=5.5 V
140
C
OTHYST
Overtemperature
hysteresis
VIN=5.5 V
20
C
V_NTCW
NTC threshold warning
Idle mode, INTC=2 mA max.
0.56
V
V_NTCH
NTC threshold hot
Idle mode, INTC=2 mA max.
1.2
V
VMONIREADY
VOL
Output logic signal level
IATN, READY=+10 mA
low ATN, READY
IOZ
Output logic leakage
current ATN, READY
VIL
VATN, READY =3.3 V
Input logic signal level
SCL, SDA, TEST,
RESET, SCHRG,
FLASH, TORCH, ADD
VIN=2.7 V to 5.5 V
ILSCON
Input reset current
VIN=2.7 V to 5.5 V, VREF=1.6 V
VLSIN
Analog input signal
range
VIN=2.7 V to 5.5 V
VIH
MOSFET driver output
VDRIVE
TON
0.3
V
1
mA
0
0.4
1.4
3.0
V
0.1
10
mA
1.6
V
Source: IDRIVE = -8 mA
4.27
V
Sink: IDRIVE = +8 mA
1.05
V
Reference voltage
range
EXT_REG=1 (1)
LED current rise time
ILED=0 to ILED=max.
Flash triggered by external trig
Doc ID 022927 Rev 3
0.12
1.2
V
0.3
ms
13/43
Electrical characteristics
Table 6.
Symbol
Electrical characteristics (continued)
Parameter
TRESMIN
Minimum RESET time
TLSCAPRES
Reset time of the light
sensor capacitor
14/43
STCF04
Test conditions
VIN=2.7 V to 5.5 V
Doc ID 022927 Rev 3
Min.
Typ.
Max.
Unit
1
µs
200
µs
STCF04
7
Introduction
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 RFL resistor and it can be adjusted by I²C
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 VOUT,
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 VOUT =
VFLED + 0.25 V. This mode is optimized for maximum efficiency in Torch mode. The
SuperCap must be recharged after the end of Torch mode operation.
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 3
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 Table 7). This pin cannot be left
floating.
16/43
Doc ID 022927 Rev 3
STCF04
Table 7.
Detailed description
I²C address table
ADD pin
A7
A6
A5
A4
A3
A2
A1
A0
GND
0
1
1
0
0
0
0
R/W
VBAT
0
1
1
0
0
0
1
R/W
SDA
0
1
1
0
0
1
0
R/W
SCL
0
1
1
0
0
1
1
R/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 VDC register, otherwise the READY pin is HIGH when VSuperCap goes below VDC
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.
- FLASH:
The READY pin goes LOW as soon as the SuperCap voltage reaches the threshold voltage
set by the VDC register. It stays LOW until the SuperCap voltage decreases below 4.2 V and
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 3
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
CS11340
8.1.9
START and STOP conditions
Both data and clock lines remain HIGH when the bus is not busy. As shown in Figure 6, a
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.
Figure 6.
18/43
Timing diagram on I²C bus
Doc ID 022927 Rev 3
STCF04
8.1.10
Detailed description
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
AM11867v1
8.1.11
Acknowledge
The master (microprocessor) puts a resistive HIGH level on the SDA line during the
acknowledge clock pulse (see Figure 8). The peripheral (STCF04) that acknowledges must
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 VI supply is below 2.7 V.
Figure 8.
8.1.12
Acknowledge on I²C bus
Interface protocol
The interface protocol is composed of (Table 8):
- A START condition (START)
- A device address + R/W bit (read =1 / write =0)
- A register address byte
Doc ID 022927 Rev 3
19/43
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
7
6
5
4
3
2
S
T M
A S
R B
T
8.1.13
1
0
Register address
7
6
5
4
3
2
Data
1
L
A M
R
S
C S
W
B
K B
0
7
L
S
B
A M
C S
K B
6
5
4
3
2
1
0
L
S
B
A
C
K
S
T
O
P
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 8th bit is the R/W bit, which is 0 in this case. R/W = 1 means a reading
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 below.
Figure 9.
Writing to a single register
DEVICE
ADDRESS
7 bits
S M
T S
A B
R
T
8.1.14
W
R
I
T
E
AM11863v1
ADDRESS OF
REGISTER
DATA
L A M
S C S
B K B
L R A M
S / C S
B W K B
L A S
S C T
B K O
P
SDA LINE
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 Figure 10 below.
20/43
Doc ID 022927 Rev 3
STCF04
Detailed description
Figure 10. Writing to multiple registers with incremental addressing
DEVICE
ADDRESS
7 bits
S M
T S
A B
R
T
W
R
I
T
E
L R A
S / C
B W K
ADDRESS OF
REGISTER i
DATA i
L A
S C
B K
M
S
B
DATA i +1
L A
S C
B K
M
S
B
M
S
B
DATA i +2
L A
S C
B K
DATA i+2
L A M
S C S
B K B
L A M
S C S
B K B
M
S
B
DATA i +n
SDA LINE
8.1.15
L A
S C
B K
S
T
O
P
AM11864v1
Reading from a single register
The reading operation starts with a START bit followed by the 7-bit device address of the
STCF04. The 8th bit is the R/W bit, which is 0 in this case. The STCF04 confirms receipt of
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.
Figure 11. Reading from a single register
DEVICE
ADDRESS
7 bits
S M
T S
A B
R
T
W
R
I
T
E
L R A M
S / C S
B W K B
ADDRESS
OF
REGISTER
DEVICE
ADDRESS
7 bits
L A S
S C T
B K A
R
T
SDA LINE
8.1.16
R
E
A
D
R A
/ C
W K
DATA
L N S
S O T
O
B
A P
C
K
AM11865v1
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 3
21/43
Detailed description
STCF04
Figure 12. Reading from multiple registers
DEVICE
ADDRESS
7 bits
S M
T S
A B
R
T
W
R
I
T
E
L R A M
S / C S
B W K B
DEVICE
ADDRESS
7 bits
ADDRESS OF
REGISTER i
L A S
S C T
B K A
R
T
R
E
A
D
R A
/ C
W K
DATA i
DATA i +1
L A M
S C S
B K B
SDA LINE
22/43
Doc ID 022927 Rev 3
DATA i +2
L A M
S C S
B K B
DATA i+2
L A M
S C S
B K B
DATA i +n
L A M
S C S
B K B
L N S
S O T
B
O
A P
C
K
AM11866v1
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)
MSB
LSB
SUB ADD=00 PWR_ON FLASH_ON
Power-ON
RESET value
9.1.1
0
0
TCH_ON
NTC_ON
TCHV_H
CHRG
MONTR
N/A
0
0
0
0
0
0
PWR_ON
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.
9.1.2
FLASH_ON
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 3
23/43
Description of the internal registers
9.1.4
STCF04
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
CL_REG
(Write mode)
MSB
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
0
0
0
0
0
0
0
0
LSB
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.
Table 12.
Flash mode dimming registers settings (EXT_REG = 0)
F_DIM (hex)
0
1
2
3
4
5
6
7
DRIVE voltage
[mV]**
12
48
60
72
84
96
108
120
LED current [A]*
0.012 V /
RFL
0.048 V /
RFL
0.060 V /
RFL
0.072 V /
RFL
0.084 V /
RFL
0.096 V /
RFL
0.108 V /
RFL
0.120 V /
RFL
Example LED
current (A) for
RFL = 10 mΩ
1.2
4.8
6
7.2
8.4
9.6
10.8
12
Note:
24/43
RFL is the external sensing resistor, external MOS transistor connected, see Figure 3.
Doc ID 022927 Rev 3
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 Table 13). 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)
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
Flash length[ms]
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
90
FTIM_DIM(hex)
10
11
12
13
14
15
16
17
18
19
1A
1B
1C
1D
1E
1F
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)
MSB
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
0
0
0
0
0
0
0
0
LSB
AUXI_0~3: this 4-bit register defines the AUX LED current from 0 to 100 mA. See Table 15
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)
0
1
2
3
4
5
6
7
8
9
A
B
AUX LED current
[mA]
0
6
10
15
20
25
33
40
53
67
80
100
Doc ID 022927 Rev 3
25/43
Description of the internal registers
Table 16.
STCF04
Auxiliary LED timing table
AUXT (hex)
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
AUX LED
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
STAT_REG
(Read mode)
MSB
SUB ADD=03
N/A
F_RUN
FL_R
NTC_W
NTC_H
OT_F
FL_OVR
LTH
Power-ON, Shutdown
mode RESET value
0
0
0
0
0
0
0
0
LSB
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 RX exceeds VREF4 = 0.56 V. This threshold corresponds to a
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 RX exceeds VREF5 = 1.2 V. This threshold corresponds to an excess
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 3
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
NO
NO
YES
YES
YES
NO
NO
Forces Idle
mode when set
NO
NO
NO
YES
YES
NO
NO
Sets ATN LOW
when set
NO
YES
YES
YES
YES
YES
NO
Latched
1.
(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.
9.5
Feature (FTR_REG) 04(hex)
Table 19.
Feature register
LS_REG
(Write mode)
MSB
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
0
0
0
0
0
0
0
0
LSB
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)
0
1
2
3
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.
Note:
DC-DC converter output voltages (VOUT)
VDC_1
VDC_0
VOUT
0
0
4.5 V
0
1
5.0 V
1
0
5.5 V
See Section 10.4.
IDC_0: this bit defines the peak current limit value of the DC-DC converter.
Doc ID 022927 Rev 3
27/43
Description of the internal registers
Table 22.
STCF04
DC-DC converter coil peak current limit values
IDC_0
ICOIL (PEAK)
0
1.45 A
1
1.80 A
9.6
Torch register (TRCH_REG) 05(hex)
Table 23.
Torch register
VRID_REG
(Read mode)
SUB ADD=05
Power-ON, Shutdown
mode RESET value
MSB
LSB
TTRCH1 TTRCH0
0
TDIM_3
TDIM_2
TDIM_1
TDIM_0
N/A
N/A
0
0
0
0
0
0
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.
Table 24.
Torch mode dimming registers settings
TDIM (hex)
0
1
2
3
4
5
6
7
8
9
A
B
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.
28/43
The safety timeout for Torch mode
TTRCH1
TTRCH0
Torch time
0
0
Infinity
0
1
5s
1
0
10s
1
1
15s
Doc ID 022927 Rev 3
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
Battery plug-in
From any states
!PWR_ON || !RESET
Shutdown
!PWR_ON & NTC
!PWR_ON & MONTR
PWR_ON
!PWR_ON & !NTC
NTC
!PWR_ON || !MONTR
NTC
!NTC & PWR_ON
IDLE
AuxLed_ON
MaxTimeLed
!TCH_ON
Monitoring
Aux
LED
On
!CHRG
|| (READY
& !FLASH _ON &
!TCH_ON)
CHRG
|| FLASH_ON
|| TCH_ON
Status_Register
read
MaxTimeFlash
CHRG
FLASH_ON
& READY
FLASH_ON
& READY &
LS
LOCK
TCH_ON
& READY
&!TCHV_H
Torch
eff.
+
CHRG
+ NTC
TCH_ON
& READY
&TCHV_H
ALARM
From any states
Flash
+
CHRG
+ NTC
Flash
+
CHRG
+ NTC
+ LS
Torch
+
CHRG
+ NTC
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 3
29/43
Theory of operation
10.2
STCF04
Power-ON reset
This mode is initiated by applying a supply voltage above the VPW_ON RESET threshold
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 TRESMIN time (1 µs) at least to guarantee correct resetting of the device. When the
reset function driven by the RESET pin is not needed, the RESET pin must be connected to
the VBAT = VIN.
Figure 14. Reset timing
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 VREF-EXT is present, the typical current consumption is increased to 2 µA. It is
recommended to not leave the STCF04 in this status if battery drain must be minimized.
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 VSUPMAX threshold, then the READY pin is pulled low and stays low until the
voltage on the SuperCap is higher than VSUPMAX - 200 mV.
30/43
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STCF04
10.5
Theory of operation
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 Table 17).
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 VBAT or VOUT pin. Connecting it
to the VOUT pin is particularly advantageous in case of high AUXLED currents. The
maximum values of AUXLED currents are guaranteed only for anode voltages higher than
3.3 V, but VBAT may range from 2.7 V to 5.5 V, so in some cases it may not be possible to
use maximum currents.
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 VFLED, when the SuperCap is
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.
Doc ID 022927 Rev 3
31/43
Theory of operation
10.8
STCF04
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 VBAT), leaving the whole flash control to the I²C bus. Also in this operation
mode the time counter times out flash operation and keeps the energy dissipated by the
LED within safe limits in case of software deadlock.
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 VBAT) and the flash can
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.
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 CINT,
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 CINT capacitor is discharged by the internal switch to the zero voltage during
200 µs. During the flash operation the CINT capacitor integrates the charging current
according to the light conditions in the flashed area. When the voltage level on the CINT
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 CINT
capacitor through an internal switch.
32/43
Doc ID 022927 Rev 3
STCF04
Typical performance characteristics
I OUT [A]
Figure 15. Flash current vs. input voltage
8
7,5
7
6,5
6
5,5
5
4,5
4
3,5
3
2,5
2
1,5
1
0,5
0
2,25
AM09307v1
I OUT = 1.2 A
I OUT = 4.8 A
I OUT = 8 A
2,5
2,75
3
3,25
3,5
3,75
4
4,25
4,5
4,75
VIN [V]
Figure 16. Torch current vs. input voltage
I OUT [mA ]
11
Typical performance characteristics
AM09308v1
350
325
300
275
250
225
200
175
150
125
100
75
50
25
0
2,25
IOUT = 320 mA
IOUT = 160 mA
IOUT = 40 mA
2,5
2,75
3
3,25
3,5
3,75
4
4,25
4,5
4,75
VIN [V]
Doc ID 022927 Rev 3
33/43
Typical performance characteristics
STCF04
I OUT [mA ]
Figure 17. Aux LED current vs. input voltage
110
105
100
95
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
2,25
AM09309v1
I OUT = 10 mA
I OUT = 100 mA
2,5
2,75
3
3,25
3,5
3,75
4
4,25
4,5
4,75
VIN [V]
Figure 18. Charging efficiency vs. VOUT voltage (VIN = 3.6 V)
AM09310v1
100
90
80
70
Eff. [%]
60
50
40
30
20
10
0
0
1
2
3
VOUT [V]
34/43
Doc ID 022927 Rev 3
4
5
6
STCF04
Typical performance characteristics
Figure 19. Torch time - settings compared to real values
AM09311v1
16
14
Time [s]
12
10
8
6
Time measured
4
Time set
2
0
1
2
3
4
5
Step
Figure 20. Torch current - settings compared to real values
AM09312v1
350
I OUT measured
300
I OUT set
I OUT [mA]
250
200
150
100
50
0
0
2
4
6
8
10
12
14
Step
Figure 21. Flash time - settings compared to real values
AM09313v1
450
Time measured
400
Time set
350
Time [ms]
300
250
200
150
100
50
0
0
5
10
15
20
25
30
35
Step
Doc ID 022927 Rev 3
35/43
Typical performance characteristics
STCF04
Figure 22. Flash current - settings compared to real values
AM09314v1
14
12
I OUT [A]
10
8
6
4
I OUT measured
2
I OUT set
0
0
2
4
6
8
10
Step
Figure 23. Aux LED time - settings compared to real values
AM09315v1
1.6
Time measured
1.4
Time set
1.2
Time [s]
1
0.8
0.6
0.4
0.2
0
0
5
10
15
Step
Figure 24. Aux LED current- settings compared to real values
AM09316v1
120
I OUT measured
100
I OUT set
I OUT [mA]
80
60
40
20
0
0
2
4
6
Step
36/43
Doc ID 022927 Rev 3
8
10
12
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 3
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 3
STCF04
12
Package mechanical data
Package mechanical data
In order to meet environmental requirements, ST offers these devices in different grades of
ECOPACK® packages, depending on their level of environmental compliance. ECOPACK
specifications, grade definitions and product status are available at: www.st.com.
ECOPACK is an ST trademark.
Doc ID 022927 Rev 3
39/43
Package mechanical data
STCF04
TFBGA25 mechanical data
mm.
mils.
Dim.
A
Min.
Typ.
Max.
Min.
Typ.
Max.
1.0
1.1
1.16
39.4
43.3
45.7
A1
0.25
A2
0.78
b
0.25
D
2.9
D1
E
9.8
0.86
30.7
0.30
0.35
9.8
11.8
13.8
3.0
3.1
114.2
118.1
122.0
2
2.9
3.0
33.9
78.8
3.1
114.2
118.1
E1
2
78.8
e
0.5
19.7
SE
0.25
9.8
122.0
7539979/A
40/43
Doc ID 022927 Rev 3
STCF04
Package mechanical data
Tape & reel TFBGA25 mechanical data
mm.
inch.
Dim.
Min.
Typ.
A
Max.
Min.
Typ.
330
13.2
12.992
C
12.8
D
20.2
0.795
N
60
2.362
T
Max.
0.504
0.519
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
P
7.9
8.1
0.311
0.319
Doc ID 022927 Rev 3
41/43
Revision history
13
STCF04
Revision history
Table 26.
42/43
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.
13-Sep-2012
3
Modified: TFL value 12 mΩ Table 5 on page 11.
Doc ID 022927 Rev 3
STCF04
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