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This is information on a product in full production.

September 2012 Doc ID 16757 Rev 3 1/26

STCF07

High power buck-boost white LED driver

Datasheet − production data

Features

■ Buck-boost DC-DC converter

■ Drives one power LED up to 1 A in flash mode

■ Drives one power LED up to 800 mA in

continuous mode

■ 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

– High current mode: up to 1 A

– Low current mode: from 20 mA

■ Adjustable current in both modes

■ Peak inductor limited to 2.3 A (typ.)

■ LED disconnected from the battery in

shutdown mode

■ NTC LED temperature protection

■ Overvoltage protection: 5.3 V

■ Short-circuit protection

■ Overtemperature protection

■ ULVLO function

■ 1 µA max shutdown current

■ QFN16 (4 x 4 x 1 mm) 16 leads

Applications

■ Camera flash for mobile phones

■ Power supply for high power LEDs

Description

The STCF07 is a dedicated, size-optimized

solution for driving a power LED. The device is a

buck-boost converter which guarantees proper

LED current control over all possible battery

voltage and LED forward voltage conditions. The

output current control ensures good current

regulation over the forward voltage spread

characteristics of high-brightness LEDs. The

device includes various functions to protect the

chip and the power LEDs. These include soft-start

control as well as detection and protection of chip

overtemperature and shorted LEDs. An optional

external NTC is supported to protect the LEDs

against overheating. It is possible to separately

program the current intensity in HIGH and LOW

mode using the SEL pin. The device is housed in

a 16-lead QFN16 (4 x 4 mm) package with a

height less than 1 mm.

QFN16 (4 x 4 mm)

Table 1. Device summary

Order code Package Packaging

STCF07PNR QFN16 (4 x 4 mm) Tape and reel

www.st.com

Summary of content (26 pages)

PAGE 1
STCF07 High power buck-boost white LED driver Datasheet − production data Features ■ Buck-boost DC-DC converter ■ Drives one power LED up to 1 A in flash mode ■ Drives one power LED up to 800 mA in continuous mode ■ LED temperature protection ■ Output current control ■ 1.8 MHz (typ.
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Contents STCF07 Contents 1 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 Electrical characteristics . . . . . . . .
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STCF07 Contents 10 Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 11 External component selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 11.1 Input and output capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 11.2 Inductor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 11.3 LED selection . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Block diagram STCF07 1 Block diagram Figure 1.
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STCF07 Pin configuration 2 Pin configuration Figure 2. STCF07 pin connections (top view) Table 2.
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Maximum ratings STCF07 3 Maximum ratings Table 3. Absolute maximum ratings Symbol Parameter Value Unit VBAT Signal supply voltage -0.3 to 6 V PVBAT Power supply voltage -0.3 to 6 V VLX1A, VLX1B Inductor connection 1 -0.3 to VI+0.3 V VLX2 Inductor connection 2 -0.3 to VI+0.3 V VOUT Output voltage -0.3 to 6 V Feedback and sense voltage -0.3 to 3 V Connection for reference resistor -0.3 to 3 V Current selection -0.3 to VI+0.3 V Enable -0.3 to VI+0.3 V Diagnostic -0.
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STCF07 Application information 4 Application information Figure 3. Application schematic diagram L VIN VLX1 VLX1 VLX2 VOUT PVBAT LED VBAT CIN FB1 COUT ENABLE CSEL RLC FB2 FAULT GND PGND RX FB2S NTC RHC NTC RX Optional components Note: Represents a typical application schematic for an output current of 800 mA (max) in continuous mode operation. For pulse/flash mode operation it is possible to increase the maximum output current up to 1 A. If the battery voltage is higher than 3.
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Electrical characteristics 5 STCF07 Electrical characteristics TA = 25 °C, VI = 3.6 V, 2 x CI = 10 µF, CO = 1 µF, L = 2.2 µH, RHC = 0.22 Ω, RLC = 1.8 Ω, RX = 15 kΩ Table 6. Symbol Electrical characteristics Parameter VI Input voltage supply UVLO Undervoltage lockout VPW_ONRESET Power ON reset threshold IO Test conditions Min. Typ. 2.7 Max. Unit 5.5 V VI = 2.7 V 2.2 V VI rising 2.3 V Output current - high current CSEL = VI; VI = 2.7 V to 5.5 V; level RHC = 0.16 Ω, POUT = 3.
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STCF07 Table 6. Symbol Electrical characteristics Electrical characteristics (continued) Parameter Min. Typ. Max. Unit 0.5 V Low level voltage ISINK = 5 mA 0.
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Introduction 6 STCF07 Introduction The STCF07 is a buck-boost converter designed to power and control the current of a power white LED. The device operates at a constant switching frequency of 1.8 MHz (typ). It provides an output voltage from 2.5 V up to 5.3 V, from a 2.7 V to 5.5 V supply voltage. This supply range allows the device to operate from a single-cell Lithium-Ion battery. The current is adjustable up to 1 A for an input voltage ranging from 2.7 V to 5.5 V and maximum output power up to 3.4 W.
PAGE 11
STCF07 Logic pin description 7 Logic pin description 7.1 CSEL pin This input pin allows the setting of two different levels of current. When the voltage on this pin is low, the internal multiplexer switches the feedback to the FB1 pin, which is the dedicated feedback pin for low current operation. When the voltage on the CSEL pin is high, the internal multiplexer switches the feedback to the FB2s pin, and enables the shorting transistor connected between the FB1 and FB2 pins.
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Detailed description STCF07 8 Detailed description 8.1 Buck-boost converter The regulation of the PWM controller is done by sensing the current of the LED through RLC or RLC + RHC, depending on the CSEL voltage. Depending of the forward voltage of the flash LED, the device can automatically change between buck (step-down) and boost (stepup) mode: 8.
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STCF07 Figure 4. Detailed description Startup: LED current rise time ENABLE IOUT ILED TON < 2 ms 8.6 STCF07 protection features 8.6.1 Peak current and short-circuit protection When the peak inductor current exceeds the maximum switch peak current limit of 2.3 A, the PWM controller turns off and is enabled at the next oscillation period. 8.6.
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Detailed description Figure 5. STCF07 Typical LED temperature sensing application with the NTC resistor RNTC = 100 k NTC Vref = 1.8 V VREF = 1.2 V RX = 15 k 8.6.5 Undervoltage lockout function If the device is ON and the battery voltage is as low as 2.2 V, the device goes into a FAULT state and the FAULT pin is put to LOW. To restart the device, the ENABLE pin must be reset LOW and HIGH.
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STCF07 PCB design 9 PCB design 9.1 PCB design rules The STCF07 is a powerful switched device, so the PCB must be designed following the rules for designing switched supplies. It is recommended to use at least a two-layer PCB. The power wiring must be as short and wide as possible, due to the high current. All external components should be placed close to the STCF07. High-energy switched loops should be as small as possible to reduce EMI.
PAGE 16
PCB design STCF07 9.2 PCB design of the demonstration board Figure 6. Top layer Figure 7.
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STCF07 Figure 8.
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PCB design STCF07 9.3 Schematic of the demonstration board Figure 9.
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STCF07 Typical performance characteristics Typical performance characteristics 10 Figure 10. IOUT 80 mA vs. VIN Figure 11. IOUT 800 mA vs. VIN 95.000 950.000 90.000 900.000 Output Current [mA] 1000.000 Output Current [mA] 100.000 85.000 80.000 75.000 70.000 25 °C 65.000 - 40 °C 60.000 800.000 750.000 700.000 25 °C 650.000 - 40 °C 600.000 85°C 55.000 50.000 2.50 850.000 85 °C 550.000 3.00 3.50 4.00 4.50 5.00 5.50 500.000 2.50 3.00 Input Voltage [V] 5.00 5.50 Figure 13.
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External component selection STCF07 11 External component selection 11.1 Input and output capacitor selection For input and output capacitors it is recommended to use ceramic capacitors with low ESR. For good device stability when supplied by a low input voltage of 2.7 V at maximum ratings, it is recommended to use 10 µF / 6.3 V as a minimum value for the input capacitor, and 4.7 µF / 6.3 V as a minimum value for the output capacitor. Note: See recommended components in Table 5 on page 7. 11.
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STCF07 11.5 External component selection RLC selection RLC resistor value can be calculated with the following equations: RLC = (160 mV - ILC * RHC) / ILC and PRLC = RLC * ILC2 where PRLC is the dissipated power on the RLC resistor. It is recommended to use a thin metal film resistor with a 1% or 5% tolerance. 11.6 NTC and RX resistor selection The NTC resistor for sensing LED temperature and the RX resistor create a voltage divider. The output of this divider is compared with the 1.
PAGE 22
Package mechanical data 12 STCF07 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.
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STCF07 Package mechanical data QFN16 (4 x 4) mechanical data mm. inch. Dim. Min. Typ. Max. Min. Typ. Max. 0.80 0.90 1.00 31.5 35.4 39.4 A1 0.02 0.05 0.8 2.0 A2 0.65 1.00 25.6 39.4 A3 0.20 A 7.9 b 0.18 0.25 0.30 7.1 9.8 11.8 D 3.85 4.00 4.15 151.6 157.5 163.4 D2 2.10 2.60 82.7 E 3.85 4.15 151.6 E2 2.10 2.60 82.7 e L ddd 4.00 0.50 0.30 0.40 102.4 157.5 163.4 102.4 19.7 0.50 0.08 11.8 15.7 19.7 3.
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Package mechanical data STCF07 Tape & reel QFNxx/DFNxx (4x4) mechanical data mm. inch. Dim. Min. Typ. A Min. Typ. 330 C 12.8 D 20.2 N 99 13.2 Max. 12.992 0.504 0.519 0.795 101 T 24/26 Max. 3.898 3.976 14.4 0.567 Ao 4.35 0.171 Bo 4.35 0.171 Ko 1.1 0.043 Po 4 0.157 P 8 0.
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STCF07 Revision history 13 Revision history Table 7. Document revision history Date Revision Changes 18-Nov-2009 1 First release. 12-Apr-2011 2 Updated Table 5 on page 7. 10-Sep-2012 3 Modified: Chapter 8.6.4 on page 13.
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STCF07 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.