STCF02
High power white led driver
General features
Buck-boost DC/DC Converter Drives one power white led: up to 600mA between 2.7 to 4.5V Led temperature protection Output current control 1.8 MHz (typ) fixed frequency PWM Synchronous rectification High efficiency across the total input voltage range Operational modes: - Shutdown mode - Shutdown mode with NTC - Flash mode up to 600 mA - Medium flash mode - Torch mode: up to 250 mA Adjustable current in all three modes LED disconnected from the battery in shutdown mode Programmable safety shutdown in flash mode LED short and open circuit protection Overvoltage protection < 1A Shutdown current QFN20 4mm x 4 mm package
QFN20 (4mm x 4mm)
Description
The STCF02 is a high efficiency power supply solution to drive a single flash LED in camera phone, PDAs and other hand-held devices. It is a buck-boost converter that guarantees a proper LED current control over the battery voltage (particularly in the case, when the output voltage is lower than the input voltage); the output current control ensures a good current regulation over the forward voltage spread characteristics of the Flash LED. Three logic input signals can select 5 modes of operation: Shutdown mode (quiescent current less than 1A typ), Shutdown mode with NTC active, Torch mode (drives the LED up to 250mA), Flash mode (up to 600mA), and Medium flash mode (reduces the flash current). This highly efficient converter is able to accept input current from the battery (lower than 1.5A), while limiting the peak inductor current to 2.3A (typ). Other features include Soft start control, thermal shutdown, short circuit protection, overvoltage protection, and LED temperature protection. An alternative to LED temperature protection is that a safety flash time-out feature can be implemented instead. This device is available in a QFN20, 4mm x 4mm, no-lead package (height is less than 1mm).
Appl ication s
Cell phone and smart phones Camera flashes/strobes PDAS and digital still cameras
Order code
Part number STCF02PNR Package QFN20 (4x4 mm) Packaging 4500 parts per reel
February 2007
Rev. 6
1/19
www.st.com
19
Contents
STCF02
Contents
1 2 3 4 5 6 Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pin connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Detailed operating description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 6.10 6.11 6.12 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Buck-Boost converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Flash mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Medium flash mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Torch mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Shutdown mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Soft start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 LED Failure Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Overvoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Thermal shutdown protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Sensing of LED temperature by NTC resistor . . . . . . . . . . . . . . . . . . . . . . . . 14 Safety shutdown in flash mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
7 8
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2/19
STCF02
Application
1
Figure 1.
Application
Application circuit
Table 1.
Symbol RFLASH RTORCH R MF CI CO L NTC CCOMP RX C1
External components
Parameter Sensing flash current resistor - thick film type (0805) Sensing torch current resistor - thick film type (0603) Setting resistor for middle flash mode - thick film type (0402) Two Input filtering capacitor TDK C1608X5R0J106MT - Ceramic type (0603) 6.3V Output capacitance - Ceramic type 0603 6.3V INDUCTANCE TDKVLF5014A-4R7 DCR Negative thermistor - NCP18WF104J03RB - Thick film type Compensation capacitor - 0402 Reference resistor - 0402 Ceramic Capacitor Min. Typ. 0.27 6.2 8200 10 4.7 4.7 0.12 100 100 15 47 820 2x10 Max. Unit F F H k pF k pF
Note:
- The external components proposal should be considered as a design reference guide. The performances mentioned in the electrical characteristics table are not guaranteed for all the possible electrical parameters of the components included in this list. On the other hand the operation of STCF02 is not limited with the use of the external components listed above. - The CCOMP is optional and may be used if the error amplifier bandwidth (which by default is set to 2 KHz) has to be decreased because of an unstable driver function. Unstable operation could be caused by using different values of inductor and output capacitor then recommended.
3/19
Pin connections
STCF02
2
Figure 2.
Pin connections
Pin configuration (bottom view)
Table 2.
Pln N 1 2 3 4 5 6 7 8, 10 9 11 12 13 14 15 16 17 4/19
Pin description
Symbol VLX2 RX VO NTC FB1 RTBY FB2 GND COM1 COM2 VBAT PVBAT VLX1A VLX1B EN3 EN2 Name and function Inductor connection Note External coil is connected between this pin and VLX1. It should be placed as close as possible to the device in order to minimize resistance which cause losses. Rx resistor is connected between this pin and ground to set LED over Rx Resistor connection temperature threshold. Output voltage Anode of the LED is connected to this pin. This pin is used for the LED temperature sensing using an external NTC Resistor connection NTC resistor. Feedback pin for torch This pin is used for current sensing in Torch mode Cathode of the mode Flash LED and RTorch resistor are connected to this pin. This pin is used to short-circuit the RTORCH during FLASH and RTORCH Bypass MIDDLE FLASH MODE. This pin is used to sense the voltage across RFLASH. It must be Feedback pin for flash directly connected to the non-grounded terminal of RFLASH. mode Signal ground Compensation connection Compensation connection Supply voltage Power supply voltage Inductor connection This is the signal ground pin related to digital and analog signals and must be connected as close as possible to the sensing resistor. Optional external compensation should be connected to these pins. Optional external compensation should be connected to these pins. Supply pin of the device. Power supply pin of the device. External coil is connected between these pins and VLX2. They should be placed as close as possible to the device in order to minimize resistance which causes losses. It is mandatory to connect VLX1A and VLX1B together. Digital input that allows selection of the operational modes of the device (refer to truth table). Digital input that allows selection of the operational modes of the device (refer to truth table).
Enable Pin 3 Enable Pin 2
STCF02
Pln N 18 19 20 Exppad Symbol PGND RMFL EN1 PGND Name and function Power ground Middle flash resistor connection Enable Pin 1 Power ground Note
Pin connections
Power ground pin for power analog circuit. To be connected to the PCB ground plane. This pin is used for the current setting in Middle Flash Mode RMF resistor is connected to this pin. Digital input that allow selecting the operational modes of the device (refer to truth table). To be connected to the PCB Ground Plane for optimal electrical and thermal performance.
Figure 3.
Block diagram
5/19
Maximum ratings
STCF02
3
Table 3.
Maximum ratings
Absolute maximum ratings
Parameter Signal supply voltage Power supply voltage Enable input Output voltage Inductor connection 2 Feedback for torch current Feedback for flash current MOS Switch connection Connection for reference resistor Connection for setting resistor for middle flash LED temperature sensing connection Compensation connection Ambient operating temperature (1) Storage temperature range ESD rating Value -0.3 to 6 -0.3 to 6 -0.3 to 6 -0.3 to 6 -0.3 to VI + 0.3 -0.3 to VO + 0.3 -0.3 to 3 -0.3 to 3 -0.3 to 3 -0.3 to 3 -0.3 to 6 -0.3 to 6 -0.3 to 3 -40 to + 85 -65 to + 150 2 Unit V V V V V V V V V V V V V C C KV
Symbol VBAT PVBAT EN1,2,3 VO VLX2 FB1 FB2 RTBY RX RMFL NTC COM1,COM2 TOP TSTG VESD
VLX1A-VLX1B Inductor connection 1
1. STCF02 is guaranteed to meet specification from 0C to 70C specifications over the -40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process control.
Table 4.
Symbol RthJA
Thermal data
Parameter Thermal resistance junction-ambient (*) Value 59 Unit C/W
(*) Typical Application on a two layer board.
6/19
STCF02
Characteristics
4
Table 5.
Symbol VI ICC VUVLO
Characteristics
Electrical characteristics (All typical values are referred to TA = 25C, VI = 3.6V)
Parameter Input Operating Voltage Torch mode Medium flash mode Flash mode VI rising VI falling Flash mode for VI = 2.7V to 4.5V RFLASH_MIN=1.6 to RFLASH_MAX=0.27 Medium flash mode for VI = 2.7V to 4.5V RMFLASH_MIN=1.1k to RMFLASH_MAX=500k Torch mode VI = 2.7V to 4.5V RTORCH+RFLASH=6.4 to RTORCH+RFLASH=0.64 Flash and medium flash mode (1) Torch mode Flash Mode EN1=EN2=EN3=0 EN1=EN2=0 EN3=X (NTC ON) VI = 2.7V Application Circuit Figure 2 VI = 3.2 V to 4.2V, IO=600mA Application Circuit Figure 2 VI = 3.2 V to 4.2V, IO=25mA VI = 2.7V, IO=600mA VI = 4.2V No load VI = 2.7V to 4.5V (Note: 1) VI = 2.7V to 4.5V (Note: 1) VI = 4V, INTC = 2mA max EN1=EN2=0, EN3=X Disable Low VIL Enable High VIH PIN (IO=600mA) to PIN (IO=100mA) (Note: 1) EN1=EN2=0 to EN1=0 & EN2=1 or EN1=EN2=1 (Note 1) 1.4 1 30 2 5.2 140 20 1.192 0.3 1 0.4 2.5 150 Test Conditions Min. 2.7 616 590 555 5.1 5.1 100 Typ. 686 688 660 Max. 5.5 757 733 728 5 .3 5 .3 600 Unit V A
Under voltage lockout threshold Output Current Adjustment Range, IFLASH Output Current Adjustment Range, IMFLASH Output Current Adjustment Range, ITORCH
V
IO
25% IFLASH
IFLASH
mA
25 10 5 160 1 3 1.8 85 75 1.23
250 % % V mV A MHz % % A V C C V V A V A s ms
IO VO FB1,2 IQ f e1
Output current variation Regulated voltage range Feedback Voltage Quiescent Current in Stand By Frequency
5.1 170
78 72
Efficiency e2 IPK OVP OTP OTHYST Inductor peak current Over voltage protection Over temperature protection Over temperature hysteresis
NTC Voltage Reference NTCHYST Hysteresis NTCLEAK Voltage Reference leakage EN1, EN2, Logic signals level EN3 I_ENx TFL/TR TON Enable input current Transition time from PIN (Flash) to PIN (Torch) (see Figure 11) Led current rise time ILED = 0 to ILED = max (see Figure 13)
1. Not include tolerance of sensing resistor
Note: 1 Guaranteed by design
7/19
Characteristics
STCF02
Table 6.
EN1 0 1 0 1 1 1
Truth table selection mode
EN2 0 0 1 1 0 1 EN3 X 1 X 1 0 0 ILED 0 0 ITORCH=160mV/ (RTORCH+RFLASH) IMFLASH = f (IFLASH,RMFLASH) IFLASH = 160mV/RFLASH ILED_MAX (mA) 0 0 250 500 600 Mode Shutdown Shutdown Torch Medium Flash Flash NTC OFF ON ON ON ON
8/19
STCF02
Typical characteristics
5
Figure 4.
Typical characteristics
IIN vs VIN in torch mode Figure 5. IO vs VIN in torch mode 25 mA
Figure 6.
IO vs VIN in flash mode 600 mA
Figure 7.
VFB1 vs temp in torch mode
Figure 8.
Efficiency vs IO in torch mode
Figure 9.
Start-up to torch mode 25 mA at VBATT = 3.6V
9/19
Typical characteristics
STCF02
Figure 10. Start-up to flash mode 600 mA at VBATT = 3.6V
10/19
STCF02
Detailed operating description
6
6.1
Detailed operating description
Introduction
The STCF02 is a buck-boost converter, dedicated to power and control the current of a Power White Led in a camera cell Phone. The device operates at a constant switching frequency of 1.8MHz typ. It provides an output voltage down to 2.5V and up to 5.1 V, from a single cell 2.7 V to 5.5 V lithium-ion battery. The flash current is adjustable from 100mA to 600mA for the input voltage range from 2.7V to 4.5V. Torch current is adjustable from 25mA to 250mA. The device also includes a medium flash mode with the current set between the 25% of flash current and flash current. The device contains a pin for connection of NTC which senses the temperature of the LED.
6.2
Buck-Boost converter
Regulation of the PWM controller is made by sensing the current of the led through the RFLASH resistor (see Figure 2). Depending on the forward voltage of the Flash LED, the device can automatically change the operation mode between buck (step down) and boost (step up) mode. Three case can occur: Boost region (VO > VBAT): this configuration is used in most cases, as the output voltage (VO = VfLED + ILED x RFLASH) is higher than VBAT; Buck region (VO < VBAT); Buck / Boost region (VO ~ VI).
6.3
Flash mode
To select Flash mode the Enable pins have to be connected as follows: EN1=1, EN2=1, EN3=0. The STCF02 operates continuously to supply maximum current to the flash LED (up to 600 mA). The flash current can be adjusted by the RFLASH resistor. The control loop uses the FB2 pin to sense the voltage across RFLASH. The flash current is then programmed at: IFLASH= 160mV / RFLASH. For a flash current programmed at 600mA, the sensing resistor is equal to 0.27 . During this operation mode the MOS Switch between FB1 and RTBY pins is closed. If the EN3 is forced to High during Flash mode operation, the current is reduced to that of Torch mode. Such reduction of input power during transition from Flash to Torch mode is achieved within less than 30s. The NTC divider for measuring LED temperature is active.
11/19
Detailed operating description
STCF02
Figure 11. Reducing power during the EN3
6.4
Medium flash mode
To select this operating mode the Enable pins have to be connected as follows: EN1=1, EN2=0, EN3=0 In medium flash mode the current is set between the Torch and the flash mode levels and can be adjusted by connecting a resistor between the RMFL pin and the ground: The medium flash current is then programmed using the following equation: IMF=10-5/RFL · [3000+(13000·RMF/13000+RMF)]. (See Figure 12).
12/19
STCF02
Detailed operating description
Figure 12. Middle Flash Current (as a percentage of flash current) vs RMF
6.5
Torch mode
To select this operating mode the Enable pins have to be connected to any one of the follow states: EN1 = 0, EN2 = 1, EN3 = x EN1 = 1, EN2 = 1, EN3 = 1. The STCF02 can continuously provide a torch current adjustable between 25mA and 250mA. The torch current adjustment is made by resistor RTORCH (Figure 2). The control loop uses the FB1 pin to sense the voltage across RFLASH+RTORCH. The torch current is then programmed using the following equation: ITORCH=160mV/(RFLASH+RTORCH). If the programmed Flash current is 600mA (RFLASH = 0.27) and a 250mA Torch current is needed, the RTORCH resistance is equal to 0.37 . During Torch operation mode the MOS Switch between FB1 and RTBY pins is opened. The NTC divider for measuring LED temperature is active.
6.6
Shutdown mode
When the device is not used, two shutdown modes are available. They can be selected by the enable pins: EN1=0, EN2=0, EN3=X With this combination the NTC divider for measuring of LED temperature is not active. The quiescent current is less than 1A. EN=1, EN2=0, EN3=1 This combination of enable pins provides shutdown modes with an active NTC divider for sensing LED temperature. This Mode is useful for measuring the temperature before starting both TORCH and FLASH MODE operations.
13/19
Detailed operating description
STCF02
6.7
Soft start
To avoid spikes the battery during start-up sequence, a soft start function has been implemented. This soft start is achieved by progressively increasing the feedback voltage reference. In the worst case scenario the start up time as defined below (IO = IMAX) will not exceed 6ms. Figure 13. Start up - LED current rise time
6.8
LED Failure Protection
The device is self protected when the LED fails as a result of a short or open circuit. Such performances are tested using a standard mobile phone Lithium battery with internal resistance 170m typ.
6.9
Overvoltage protection
The device includes a power switch protection that stops the operation of the PWM controller when the voltage at the pin VO exceeds the OVP threshold.
6.10
Thermal shutdown protection
Internal thermal shutdown protection will switch off the device when the junction temperature exceeds 140C typical. The hysteresis comparator allows for the automatic restart of the PWM controller, when the temperature is reduced by 20C.
6.11
Sensing of LED temperature by NTC resistor
The device is able to switch off the power circuit, if high temperature on the LED is detected (see Figure 14).
14/19
STCF02
Detailed operating description
6.12
Safety shutdown in flash mode
To avoid LED burning during flash mode, which could be brought on by a micro-controller fault, a simple programmable RC circuit is possible to shutdown the device after a selected time through the RX Pin (see Figure 15). Figure 14. Typical application of LED temperature sensing by NTC resistor
Figure 15. Typical Application of Safety Shutdown
EN1 EN2 0 0 1 1 0 1 0 1
Mode All OFF Torch Mid-Flash Full-Flash
TimeOut N/A NO YES YES
15/19
Package mechanical data
STCF02
7
Package mechanical data
In order to meet environmental requirements, ST offers these devices in ECOPACK packages. These packages have a Lead-free second level interconnect. The category of second level interconnect is marked on the package and on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an ST trademark. ECOPACK specifications are available at: www.st.com.
16/19
STCF02
Package mechanical data
QFN20 (4x4) MECHANICAL DATA
mm. DIM. MIN. A A1 A2 A3 b D D2 E E2 e L ddd 0.18 3.875 0.75 3.875 0.75 0.45 0.35 0.8 TYP 0.9 0.02 0.65 0.25 0.23 4.00 1.7 4.00 1.7 0.50 0.55 0.30 4.125 2.25 4.125 2.25 0.55 0.75 0.08 7.1 152.6 29.5 152.6 29.5 17.7 13.8 M AX. 1.00 0.05 1.00 MIN. 31.5 TYP. 35.4 0.8 25.6 9.8 9.1 157.5 66.9 157.5 66.9 19.7 21.7 11.8 162.4 88.6 162.4 88.6 21.7 25.9 3.1 M AX . 39.4 2.0 39.4 mils
7169619-D
17/19
Revision history
STCF02
8
Table 7.
Date
Revision history
Revision history
Revision 1 2 3 4 5 6 First release. Document updating. The table 5 has been updated and add typical characteristics. Mistake on table 5 figure reference TFL/TR parameter. Text updates. Mistake value of IO test condition RMFLASH_MAX = 500 ==> 500k on Table 5. Changes
10-Nov-2005 19-Dec-2005 29-Jun-2006 27-Jul-2006 18-Oct-2006 09-Feb-2007
18/19
STCF02
Please Read Carefully:
Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries ("ST") reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST's terms and conditions of sale. Purchasers are solely responsible for the choice, selection and use of the ST products and services described herein, and ST assumes no liability whatsoever relating to the choice, selection or use of the ST products and services described herein. No license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted under this document. If any part of this document refers to any third party products or services it shall not be deemed a license grant by ST for the use of such third party products or services, or any intellectual property contained therein or considered as a warranty covering the use in any manner whatsoever of such third party products or services or any intellectual property contained therein.
UNLESS OTHERWISE SET FORTH IN ST'S TERMS AND CONDITIONS OF SALE ST DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY WITH RESPECT TO THE USE AND/OR SALE OF ST PRODUCTS INCLUDING WITHOUT LIMITATION IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION), OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER INTELLECTUAL PROPERTY RIGHT. UNLESS EXPRESSLY APPROVED IN WRITING BY AN AUTHORIZED ST REPRESENTATIVE, ST PRODUCTS ARE NOT RECOMMENDED, AUTHORIZED OR WARRANTED FOR USE IN MILITARY, AIR CRAFT, SPACE, LIFE SAVING, OR LIFE SUSTAINING APPLICATIONS, NOR IN PRODUCTS OR SYSTEMS WHERE FAILURE OR MALFUNCTION MAY RESULT IN PERSONAL INJURY, DEATH, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE. ST PRODUCTS WHICH ARE NOT SPECIFIED AS "AUTOMOTIVE GRADE" MAY ONLY BE USED IN AUTOMOTIVE APPLICATIONS AT USER'S OWN RISK.
Resale of ST products with provisions different from the statements and/or technical features set forth in this document shall immediately void any warranty granted by ST for the ST product or service described herein and shall not create or extend in any manner whatsoever, any liability of ST.
ST and the ST logo are trademarks or registered trademarks of ST in various countries. Information in this document supersedes and replaces all information previously supplied. The ST logo is a registered trademark of STMicroelectronics. All other names are the property of their respective owners.
2007 STMicroelectronics - All rights reserved STMicroelectronics group of companies Australia - Belgium - Brazil - Canada - China - Czech Republic - Finland - France - Germany - Hong Kong - India - Israel - Italy - Japan Malaysia - Malta - Morocco - Singapore - Spain - Sweden - Switzerland - United Kingdom - United States of America www.st.com
19/19
|
