DATA SHEET AAT1271 1.5A Step-Up Current Regulator for Flash LEDs General Description Features The AAT1271 is a high-efficiency, high-current boost converter capable of 1.5A typical output current. It is an ideal power solution for LED photo flash applications in all single cell Li-ion powered products. • VIN Range: 2.7V to 5.5V • Dual Channel Output • Up to 1.5A Regulated Output Current (750mA per channel) • Up to 85% Efficiency with Small Inductor (1μH) • 2 MHz Switching Frequency • Separate Flash Enable • Separate Flash Inhibit • User-Programmable Safety Timer • Single Resistor Sets Flash and Movie Mode Current • AS2Cwire Single Wire Programming: ▪ Movie Mode Current ▪ Flash/Movie Mode Current Ratio ▪ Movie Mode Output Configuration ▪ Flash Safety Timer • True Load Disconnect • Input Current Limit • Over-Voltage (Open LED, Open Circuit), Short Circuit, and Over-Temperature Protection • Shutdown Current < 1.0μA • 14-pin TDFN 3x3 mm Package • -40°C to +85°C Temperature Range The AAT1271 maintains output current regulation by switching the internal high-side and low-side switch transistors. The transistor switches are pulse-width modulated at a fixed frequency of 2MHz. The high switching frequency allows the use of a small inductor and output capacitor, making the AAT1271 ideally suited for small battery-powered applications. Skyworks' proprietary AS2Cwire™ (Advanced Simple Serial Control™) serial digital interface is used to enable, disable, configure, and program the operation of the AAT1271. Using the AS2Cwire interface, the movie-mode current level for each LED, the safety timer delay, and the flash-to-movie-mode current ratio can be programmed to one of 16 levels. In addition, the single-wire serial protocol sets output channel control. The AAT1271 also includes a separate Flash Enable input to initiate both the flash operation and the default timer which can be used either to terminate a flash event at the end of a userprogrammed delay or as a safety feature. Also included is a Flash Inhibit pin which reduces the flash current to movie-mode levels during high battery demand. The maximum flash and movie-mode current is set by one external resistor where the ratio of Flash to Moviemode current is set at approximately 7.3:1. One or two LEDs can be connected to the AAT1271, where in the case of two LEDs the output current is matched between each diode. Applications • • • • • Camcorder Video Light (Torch Light) Cellphones/Smartphones Digital Still Cameras (DSCs) LED Photo Flash/Torch Mobile Handsets The AAT1271 contains a thermal management system to protect the device in the event of an output short-circuit condition. Built-in circuitry prevents excessive inrush current during start-up. The shutdown feature reduces quiescent current to less than 1.0μA. The AAT1271 is available in a Pb-free, thermally-enhanced 14-pin 3x3mm TDFN package. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202084A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 20, 2012 1 DATA SHEET AAT1271 1.5A Step-Up Current Regulator for Flash LEDs Typical Application L1 1μH High Current Flash LEDs SW IN OUT CIN 2.2μF VBAT AAT1271 Movie-mode Enable and Set Flash Enable Flash Inhibit COUT 2.2μF EN/SET FLOUTA FLEN FLOUTB FLINH CT RSET GND AGND PGND FLGND CT RSET 107kΩ Pin Descriptions Pin # Symbol 1 CT 2 EN/SET 3 FLEN 4 AGND 5 IN 6 SW 7 PGND 8 OUT 9 GND 10 FLINH 11 FLOUTB 12 FLGND 13 FLOUTA 14 RSET EP 2 Function Flash timer control input. Connect a capacitor between CT and AGND to set maximum duration of the flash pulse. To disable the flash timer, connect CT to AGND. Enable and Serial Control input. EN/SET is the AS2Cwire addressing and programming input to: a) adjust the movie-mode current level; b) program the flash timer based on CT; c) select the Flash-to-Movie-mode ratio; and d) select FLOUTA and FLOUTB’s output configuration. Flash enable pin. A low-to-high transition on the FLEN pin initiates a flash pulse and starts the flash timer. Analog ground pin. Connect AGND to PGND, GND, and FLGND at a single point as close to the AAT1271 as possible. Power input. Connect IN to the input power supply voltage. Connect a 2.2μF or larger ceramic capacitor from IN to PGND as close as possible to the AAT1271 Boost converter switching node. Connect a 1μH inductor between SW and IN. Power ground pin. Connect PGND to AGND, GND, and FLGND at a single point as close to the AAT1271 as possible. Power output of the boost converter. Connect a 2.2μF or larger ceramic capacitor from OUT to PGND as close as possible to the AAT1271. Connect OUT to the anode(s) of the Flash LED(s). Ground pin. Connect GND to PGND, AGND, and FLGND at a single point as close to the AAT1271 as possible. Flash inhibit pin. FLINH is an active HIGH control input with an internal 200kΩ resistor to AGND. A low-tohigh transition on the FLINH pin reduces FLOUTA and FLOUTB output currents to the maximum (default) movie-mode current level for the duration of FLINH. Strobing the FLINH pin low to high does not reset the flash timer. Flash Output B. Connect cathode of Flash LEDB to FLOUTB. For a single flash LED, connect FLOUTB & FLOUTA together. For two flash LEDs, each output will conduct 50% of the total flash output current. Flash ground pin. Connect FLGND to PGND, GND, and AGND at a single point as close to the AAT1271 as possible Flash Output A. Connect cathode of Flash LEDA to FLOUTA. For a single flash LED, connect FLOUTA and FLOUTB together. For two flash LEDs, each output will conduct 50% of the total flash output current. Flash current setting input. A 107kΩ resistor from RSET to AGND sets the maximum flash current available at FLOUTA and FLOUTB to 1.5A. Each FLOUTA and FLOUTB channel will conduct 50% of the maximum programmed current. The AAT1271’s flash-to-movie-mode ratio is fixed at 7.3:1. Exposed paddle (bottom); Connect EP to PGND as close as possible to the AAT1271. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202084A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 20, 2012 DATA SHEET AAT1271 1.5A Step-Up Current Regulator for Flash LEDs Pin Configuration TDFN33-14 (Top View) CT EN/SET FLEN AGND IN SW PGND 1 14 2 13 3 4 12 EP 11 5 10 6 9 7 8 RSET FLOUTA FLGND FLOUTB FLINH GND OUT Absolute Maximum Ratings1 (TA = 25°C unless otherwise noted.) Symbol IN, SW, OUT RSET, EN/SET, FLEN, FLINH, CT, FLOUTA, FLOUTB TJ Ts TLEAD Description Value Units Maximum Rating -0.3 to 6.0 V Maximum Rating VIN + 0.3 V -40 to 150 -65 to 150 300 C C C Value Units 50 2 C/W W Operating Temperature Range Storage Temperature Range Maximum Soldering Temperature (at leads, 10 sec) Recommended Operating Conditions Symbol θJA PD Description Thermal Resistance Maximum Power Dissipation 1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time. The AAT1271 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correlation with statistical process controls. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202084A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 20, 2012 3 DATA SHEET AAT1271 1.5A Step-Up Current Regulator for Flash LEDs Electrical Characteristics1 VIN = 3.6V; CIN = 2.2μF; COUT = 2.2μF; L = 1μH; RSET = 107kΩ; TA = -40°C to 85°C, unless otherwise noted. Typical values are TA = 25°C. Symbol Description Conditions Power Supply Input Voltage Range VIN VOUT(MAX) Maximum Output Voltage IIN(Q) Supply Current ISHDN(MAX) IFL(TOTAL) IFL(MATCH) VIN Shutdown Current Total Output Current, Flash Mode FLOUTA and FLOUTB Current Matching IMM(LOAD) Total Output Current, Movie Mode IFL fOSC FLOUTA/FLOUTB Current Accuracy Switching Frequency Default ON Time tDEFAULT TSD Thermal Shutdown Threshold TSD(HYS) Thermal Shutdown Hysteresis EN/SET/ FLEN/ FLINH Logic Control VEN/SET(L), EN/SET, FLEN Input Low Threshold VFLEN(L) VEN/SET(H), EN/SET, FLEN Input High Threshold VFLEN(H) IEN/SET, IFLEN EN/SET or FLEN Input Leakage Current VT(FLINH) FLINH Input Threshold Voltage RIN(FLINH) FLINH Input Resistance to AGND tEN/SET(LOW) EN/SET Serial Interface Low Time tEN/SET(HI_ MIN) Minimum EN/SET high Time tEN/SET(HI_ MAX) Maximum EN/SET High Time tEN/SET(OFF) EN/SET Off Timeout tEN/SET(LAT) EN/SET Latch Timeout tFLEN_ON FLEN ON Delay Time tFLEN_OFF FLEN OFF Delay Time tFLINH_ON FLINH ON Delay Time FLINH OFF Delay Time tFLINH_OFF Min Typ 2.7 EN/SET = FLEN = IN, Set FL Load = 1.5A EN/SET = IN, FLEN = AGND EN/SET = FLEN = FLINH = GND RSET = 107k; FLOUTA + FLOUTB RSET = 107k , Movie Mode Current Set = 100%; FLOUTA + FLOUTB FLOUTA + FLOUTB = 1.2A TA = 25˚C CT = 74nF 0.67 0.23 Max Units 5.5 5.5 1 V V 1 1.2 -10 1.5 1.5 10 μA A % 206 mA 2.0 600 140 15 10 2.5 % MHz ms °C °C 0.4 V 1.4 FLEN/VEN/SET = VIN = 5V V -1 1 ½VIN 200 0.3 75 50 75 500 500 EN/SET = GND EN/SET = GND mA 40 10 93 5 μA V kΩ μs ns μs μs μs μs μs μs μs 1. The AAT1271 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correlation with statistical process controls. 4 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202084A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 20, 2012 DATA SHEET AAT1271 1.5A Step-Up Current Regulator for Flash LEDs Typical Characteristics Flash Mode Efficiency vs. Input Voltage 90 100 320mA, VF = 2.91V 540mA, VF = 3.00V 700mA, VF = 3.04V 900mA, VF = 3.04V 1500mA, VF = 3.15V 1200mA, VF = 3.27V 80 102mA/ch 52mA/ch 26mA/ch 85 Efficiency (%) 90 Efficiency (%) Movie Mode Efficiency vs. Input Voltage 70 60 50 80 75 70 65 60 55 40 2.7 3.1 3.5 3.9 4.3 4.7 5.1 50 2.7 5.5 3.1 3.5 4.7 5.1 5.5 Input Voltage (V) Boost Switching Frequency vs. Input Voltage Shutdown Current vs. Input Voltage (VEN/SET = VFLEN = 0V) 3 0.03 Shutdown Current (µA) Switching Frequency (MHz) 4.3 Input Voltage (V) (Movie Mode; L = 1µH) 2.5 2 1.5 1 85°C 25°C -40°C 0.5 0.025 0.02 0.015 0.01 0.005 25°C -40°C 0 0 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 2.7 3.1 Input Voltage (V) 900 115 Output Current (mA) 1000 800 700 600 500 400 300 85°C 25°C -40°C 200 100 3.9 4.3 Input Voltage (V) 4.7 5.1 5.5 4.7 5.1 110 105 100 95 90 FLOUTA FLOUTB 85 80 0 3.5 4.3 (IFLOUTX = 103mA/Ch; VIN = 3.6V; L = 1µH) 120 3.1 3.9 Movie Mode Current vs. Temperature (VEN = VFLEN = 3.6V) 2.7 3.5 Input Voltage (V) Supply Current vs. Input Voltage Supply Current (µA) 3.9 5.5 -40 -15 10 35 60 85 Temperature (°C) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202084A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 20, 2012 5 DATA SHEET AAT1271 1.5A Step-Up Current Regulator for Flash LEDs Typical Characteristics Movie Mode LED Current Accuracy vs. Input Voltage Movie Mode Output Ripple (IFLOUTX = 103mA/Channel; L = 1µH) (IFLOUTX = 103mA/ch; VIN = 3.6V; L = 1µH) Output Current (mA) 10 8 VOUT (AC Coupled) (50mV/div) 6 4 2 0 VINDUCTOR (2V/div) -2 0V -4 -6 IINDUCTOR (100mA/div) FLOUTA FLOUTB -8 -10 2.7 3.1 3.5 3.9 4.3 4.7 5.1 100mA 5.5 Input Voltage (V) Time (500ns/div) Flash Mode Output Ripple Flash LED Current Matching vs. Temperature (IFLOUTX = 750mA/ch; VIN = 4V; L = 1µH) (IFLOUTX = 750mA/Ch; VIN = 4.2V; L = 1µH) 800 790 VINDUCTOR (2V/div) Output Current (mA) VOUT (AC Coupled) (50mV/div) 0V IINDUCTOR (50mA/div) 780 770 760 750 740 730 720 FLOUTA FLOUTB 710 700 -40 1.65A -15 10 Flash On Time Delay vs. Input Voltage 85 Flash Timeout Delay vs. CT Capacitor (IFLOUTX = 750mA/ch; COUT = 2.2µF; L = 1µH) (IFLOUTX = 750mA/ch; VIN = 3.6V) 80 1200 Flash Timeout (ms) 70 TFLEN_OND (µs) 60 Temperature (°C) Time (200ns/div) 60 50 40 30 20 -40°C 25°C 85°C 10 0 2.7 3.1 3.5 3.9 4.3 Input Voltage (V) 6 35 4.7 5.1 5.5 1000 800 600 400 200 0 0 20 40 60 80 100 CT Capacitor (nF) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202084A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 20, 2012 120 140 DATA SHEET AAT1271 1.5A Step-Up Current Regulator for Flash LEDs Typical Characteristics Movie Mode Line Transient Flash Turn On Characteristic (IFLOUTX = 103mA/ch; VIN = 4.2V to 3.6V) (IFLOUTX = 750mA/ch; VIN = 3.6V; L = 1µH) 4.2V VIN (500mV/div) 3.6V IFLOUTx (AC Coupled) (50mA/div) VFLEN (5V/div) VOUT (2V/div) 0V 0V VSINK (2V/div) 0V IFLOUTX (1A/div) 0V Time (50µs/div) Time (50µs/div) Movie Mode to Flash Turn On Characteristic Movie Mode Turn On Characteristic (IFLOUTX = 103mA to 750mA/ch; VIN = 3.6V; L = 1µH) (IFLOUTX = 103mA/ch; VIN = 3.6V; L = 1µH) VFLEN (2V/div) VOUT (2V/div) VEN/SET (5V/div) VOUT (2V/div) 0V 2V 0V 0V VSINK (500mV/div) VSINK (500mV/div) 0V IFLOUTX (1A/div) IFLOUTX (100mA/div) 0A 0V 0A Time (50µs/div) Time (100µs/div) Movie Mode Transition Characteristic Flash Timeout vs. Temperature (IFLOUTX = 103mA to 188mA/ch; COUT = 0.22µF; VIN = 3.6V; L = 1µH) (IFLOUTX = 750mA/ch; VIN = 3.6V; CT = 47nF) 0V 0V VSINK (500mV/div) IFLOUTX (100mA/div) 500 Flash Timeout (ms) VEN/SET (2V/div) VOUT (2V/div) 0V 450 400 350 300 250 200 0A -40 Time (100µs/div) -15 10 35 60 85 Temperature (°C) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202084A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 20, 2012 7 DATA SHEET AAT1271 1.5A Step-Up Current Regulator for Flash LEDs Typical Characteristics EN, FLEN Low Threshold Voltage vs. Input Voltage 1.4 1.4 1.3 1.3 VEN/SET(L), VFLEN(L) (V) VEN/SET(H), VFLEN(H) (V) EN, FLEN High Threshold Voltage vs. Input Voltage 1.2 1.1 1.0 0.9 0.8 0.7 85°C 25°C -40°C 0.6 0.5 0.9 0.8 0.7 0.6 0.4 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 2.7 3.5 3.9 4.3 4.7 5.1 5.5 Input Voltage (V) EN/SET Off Timeout vs. Input Voltage EN/SET Latch Timeout vs. Input Voltage 300 250 85°C 25°C -40°C TEN/SET(LAT) (µs) 250 200 150 85°C 25°C -40°C 100 50 2.7 3.1 Input Voltage (V) 300 TEN/SET(OFF) (µs) 1.1 1.0 0.5 0.4 3.1 3.5 3.9 4.3 Input Voltage (V) 8 85°C 25°C -40°C 1.2 4.7 5.1 200 150 100 5.5 50 2.7 3.1 3.5 3.9 4.3 4.7 Input Voltage (V) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202084A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 20, 2012 5.1 5.5 DATA SHEET AAT1271 1.5A Step-Up Current Regulator for Flash LEDs Functional Block Diagram IN SW OUT FLOUTA FLOUTB EN/SET Control FLEN FLINH 200kΩ RSET CT Functional Description The AAT1271 is a boost converter with a current regulated output designed to drive high current white LEDs used in camera flash applications. The AAT1271 has two channels to accurately regulate the current flow through two separate white LEDs. There are two basic modes of operation in the AAT1271; a Flash mode controlled by the FLEN pin and the movie mode controlled through the AS2Cwire interface. Flash Mode A flash pulse is initiated by strobing the FLEN input pin low-to-high, which initiates a flash pulse and also starts the internal timer. The maximum flash current in the AAT1271 is set by an external resistor, RSET, which sets the flash current and the maximum movie-mode current reduced by a factor of 2. The flash timer will terminate the flash current regardless of the status of the FLEN pin. This can be either used as a simple flash timing pulse or can be used as a safety timer in the event of a control logic malfunction to prevent the LED from over-heating. The maximum flash time is determined by an external timing capacitor connected to the CT pin. The flash duration can be set from 50ms up to a maximum of 1s. The AS2Cwire interface allows further adjustment of the flash timer duration. This allows the flash timer duration to be reduced in 16 linear steps from the maximum time set by the timing capacitor. If the safety timer is not needed in the application, it can be disabled by connecting the CT pin directly to AGND. AGND PGND FLGND GND The AAT1271 has two LED current sources which share the output current equally. For a single white LED application, the two current sources can be connected together to apply full output current into the LED. In two LED applications, each diode can be connected to its corresponding current source (FLOUTA or FLOUTB) and the output current will be shared. In applications where only one LED is connected to either FLOUTA or FLOUTB, the unused current sink must be directly connected to OUT, thereby disabling that channel. In mobile GSM systems where the phone remains in constant contact with the base station by regular communication, a FLINH pin is provided to prevent both the camera flash and PA transmission pulses from occurring simultaneously. This avoids potential dips to the Li-ion battery voltage below the system’s undervoltage lockout threshold (UVLO). During a flash event, strobing the FLINH pin low-to-high reduces the LED current to the default movie-mode current level for the duration of FLINH. Strobing FLINH high-to-low instructs the AAT1271 to revert the flash LED current to its maximum level, assuming that the FLEN pin is still active (HIGH) and the flash timer has not expired. Movie Mode The movie mode current level, channel enable, and the flash to maximum movie mode current ratio are set using the AAT1271’s AS2Cwire interface at the EN/SET pin. The movie-mode current level can be adjusted in 16 steps using a logarithmic scale where each code is 1dB below the previous code. Channel current outputs (FLOUTA and FLOUTB) in movie-mode can be enabled or Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202084A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 20, 2012 9 DATA SHEET AAT1271 1.5A Step-Up Current Regulator for Flash LEDs disabled individually or together. Lastly, the flash to maximum movie mode current ratio can be set from 1:2 to 1:30 with respect to the maximum programmed flash current. The FLEN signal takes priority over movie-mode operation. voltage automatically recovers when the over-temperature fault condition is removed. Movie mode operation is controlled entirely by the AS2Cwire interface via the EN/SET pin. Address 2 controls the movie mode on and off functions. Using this register either or both of the LED channels can be turned on to the current values set in Address registers 0 and 3. The movie mode is not operational when the FLEN pin is high and the part is in flash mode operation. If the AAT1271 is in movie mode (FLEN=low) and the FLEN is strobed high the movie mode state will end and the part will operate in the flash mode. The part will not reenter movie mode when ENFL is brought low. To reenter movie mode after a flash event the part must be turned off and the AS2Cwire interface must be reprogrammed to the desired movie mode level. The AAT1271’s output voltage is limited by internal overvoltage protection circuitry, which prevents damage to the AAT1271 from open LED or open circuit conditions. During an open circuit, the output voltage rises and reaches 5.5V (typical), and the OVP circuit disables the switching, preventing the output voltage from rising higher. Once the open circuit condition is removed, switching will resume. The controller will return to normal operation and maintain an average output voltage. Over-Voltage Protection (Open LED, Open Circuit) Auto-Disable Feature The AAT1271 is equipped with an auto-disable feature for each LED channel. After the IC is enabled and started up, a test current of 2-3mA (typical) is forced through each sink channel. The channel will be disabled if the voltage of that particular SINK pin does not drop to a certain threshold. This feature is very convenient for disabling an unused channel or during an LED fail-short event. This small test current should be added to the set output current in both Flash and MM conditions. Over-Temperature Protection Thermal protection disables the AAT1271 when internal power dissipation becomes excessive, as it disables both MOSFETs. The junction over-temperature threshold is 140°C with 15°C of temperature hysteresis. The output Timing Diagram FLASH FLASH FLASH FLASH FLASH FLASH TIMES OUT tDLY(CT) MOVIE MODE NO FLASH LED CURRENT t DLY(CT) NO FLASH FLASH TIMES OUT SET BY CT FLASH LOWERED TO DEFAULT MOVIE-MODE DURING FLINH DATA TO MOVIE-MODE LEVEL EN/SET FLASH ENABLE FLASH INHIBIT No AS2C address programming shown. 10 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202084A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 20, 2012 DATA SHEET AAT1271 1.5A Step-Up Current Regulator for Flash LEDs Applications Information AS2Cwire Control of Movie Mode Operation and Flash Safety Timer LED Selection In the AAT1271 control of the movie mode operation and flash timer is managed by the Advanced Simple Serial Control (AS2Cwire) interface. AS2Cwire relies on the number of rising edges of the EN/SET pin to address and load the AAT1271’s registers. As shown in Table 1, Address 0 controls the Movie Current level as a percentage of the maximum movie mode current level. Address 1 controls the safety timer duration as a percentage of the maximum value set by an external timing capacitor. Address 2 enables the two LED channels independently during movie mode. Finally, Address 3 sets the maximum possible current for movie mode operation. The maximum movie mode current is set as a fraction of the flash current with peak value of 1/2 and default value of 1/7.3. The last column in Table 1 shows the default values for each of the address registers. The AAT1271 is specifically designed to drive white flash LEDs (typical forward voltage of 2.5V to 4.0V). Since the FLOUTA and FLOUTB input current sinks are matched with low voltage dependence; the LED-to-LED brightness will be matched regardless of the individual LED forward voltage (VF) levels. Flash Mode LED Current FLOUTA and FLOUTB can be programmed up to a maximum total flash current of 1.5A or up to 750mA per channel. The output currents in FLOUTA and FLOUTB are equal. The maximum flash current in each FLOUTA and FLOUTB is set by the RSET resistor. For the desired flash current in each output, the resistor value can be calculated using the following equation: 81kΩ × A 81kΩ × A = = 750mA per channel IFLOUTA = IFLOUTB = RSET 107kΩ A flash event is initiated by asserting the FLEN pin. A flash event is automatically terminated when FLEN is deasserted or if the safety timer terminates before the FLEN pin is de-asserted. Any time that the FLINH pin is asserted, the default movie-mode current level will appear at both FLOUTA and FLOUTB. The default moviemode current level will be maintained on FLOUTA and FLOUTB as long as the FLINH and FLEN pins are asserted, and the safety timer continues to run. In addition to setting the flash current via RSET, the flash current can be changed after FLEN is asserted by programming the movie mode current register with 16 different steps. AS2Cwire Serial Interface AS2Cwire latches data or address after the EN/SET pin has been held high for longer than tLAT (500μs). Address or data is differentiated by the number of EN/SET rising edges. Since the data registers are 4 bits each, the differentiating number of pulses is 24 or 16, so that Address 0 is signified by 17 rising edges, Address 1 by 18 rising edges and Address 2 by 19 rising edges and Address 3 by 20 rising edges. Data is applied to any number of rising edges between 1 and 16, inclusive. A typical write protocol is a burst of EN/SET rising edges, signifying a particular address, followed by a pause with EN/SET held high for the prescribed tLAT timeout period, a burst of rising edges signifying data, and a tLAT timeout for the data registers. Once an address is set, then multiple writes to the corresponding data register are allowed. Address 0 is the default address on the first rising edge after the AAT1271 has been disabled. Address EN/SET Rising Edges Function Default (No programming) 0 1 2 3 17 18 19 20 Movie Mode Current Flash Safety Timer Movie Mode Output Configuration Flash/Movie Mode Current Ratio 100% 16/16 FLOUTA and FLOUTB OFF 1/7.3 Table 1: AS2Cwire Serial Interface Addressing. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202084A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 20, 2012 11 DATA SHEET AAT1271 1.5A Step-Up Current Regulator for Flash LEDs When EN/SET is strobed low and held low longer than tOFF (500μs), the AAT1271 enters shutdown mode and draws less than 1uA from VIN. All data and address are cleared (reset to 0) during shutdown. The AS2Cwire addressing allows the control of the moviemode output current, the safety timer delay, independent control of the FLOUTA and FLOUTB current sinks, and the ratio of movie-mode current to flash current. If there are no programmed write instructions applied to the EN/SET pin prior to the assertion of the FLEN pin and the device is enabled, then all registers will be loaded with their default values shown in Table 1. In the event that the number of rising edges applied at the EN/SET pin is less than 17, the AAT1271’s state machine will interpret instruction to program the output currents to the desired current level for movie-mode operation. movie mode operation, the maximum current available at either FLOUTA or FLOUTB is then: IMOVIE MODE[A/B] = IFLOUT[A/B]MAX 750mA = = 103mA 7.3 7.3 Address 0 controls precise movie mode current levels. The FLOUTA/FLOUTB movie-mode current can be adjusted in logarithmic fashion to one of 16 steps represented as a fraction of the maximum movie mode current in Table 2. To adjust the movie-mode current the user must first access Address 0 before writing the data to set the MM Current value. Data Percentage of Maximum MM Current 1* 100% 2 89% 3 79% 4 71% 5 63% 6 56% 7 50% 8 45% 9 40% 10 36% 11 32% 12 28% 13 25% 14 22% 15 20% 16 0% Movie Mode Current – Address 0 The AAT1271 movie mode current settings are controlled using the AS2Cwire interface. Movie Mode current has a maximum value of 50% of the flash current with 240 possible current levels. The maximum movie mode current is set by Address register 3 (discussed below). The default ratio between the flash current level and maximum movie mode current level is 1:7.3. The corresponding FLOUTA/FLOUTB maximum movie mode current can be calculated: I IMOVIE MODE[A/B] = FLOUT[A/B]MAX 7.3 For example, if an RSET value of 107kΩ is chosen, then the FLOUTA/FLOUTB flash current is set to 750mA. For Table 2: Address 0, Movie Mode Current Programming. Address Data T HI T LO TLAT TLAT EN/SET 1 Address Data Reg 1 2 16 17 1 0 2... n ≤ 16 1 0 n Figure 1: AS2CwireTM Serial Interface Timing. * Denotes the default value. 12 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202084A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 20, 2012 DATA SHEET AAT1271 1.5A Step-Up Current Regulator for Flash LEDs Flash/Safety Timer – Address 1 A timer function that enables the flash current sinks for a programmed amount of time is incorporated in the AAT1271. The on-time is programmed by loading the Timing Register at Address 1 with a value from 1 to 16 and by choosing a value for the external timing capacitor, CT (see Table 3). When data is latched into Address 1, the data will be used at the next occurrence of an asserted FLEN, it will then revert back to the default value of Data 1, or 16/16. This feature eliminates the need for an external, housekeeping baseband controller to contain a safety delay routine. It also serves as a protection feature to minimize thermal issues with the Flash LEDs in the event an external controller’s flash software routine experience hang-up or freeze. If no write instruction is applied to Address 1, then the safety timer will default to the maximum delay programmed externally at CT. The Flash Time T can be calculated by the following equation: T = 7.98s/μF · CT (μF) Data Ratio of MM Timeout 1* 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 16/16 15/16 14/16 13/16 12/16 11/16 10/16 9/16 8/16 7/16 6/16 5/16 4/16 3/16 2/16 1/16 Table 3: Address 1, Flash Safety Timer Programming; Maximum Value Programmed by CT. Output Enable Control – Address 2 Where T is in seconds and CT is in μF. For example, using a 47nF capacitor at CT sets the flash timeout to: Flash Timeout = 7.98s/μF · 47nF = 375ms The relationship between the flash safety timeout and the capacitance of the timer capacitor is illustrated in Figure 2. In the case where two LEDs are used, each output can be enabled or disabled independently in movie mode as shown in Table 4. To enable or disable either or both FLOUTA and FLOUTB, a write instruction to Address 2 is applied to the AAT1271’s EN/SET pin. If no write instruction is applied, the default value for Address 2 is FLOUTA, FLOUTB = OFF. During a flash event, both FLOUTA and FLOUTB will be enabled regardless of the movie-mode setting. Flash Timeout (ms) 1200 Selection 1000 800 600 400 FLOUTA FLOUTB 1* 2 3 4 OFF OFF** ON ON OFF ON OFF** ON Table 4: Address 2, Movie Mode Output Configuration. 200 0 0 Data 20 40 60 80 100 120 140 CT Capacitor (nF) Figure 2: Flash Safety Timeout vs. Timer Capacitor. * Denotes the default value. ** A small current will flow due to the start-up test current. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202084A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 20, 2012 13 DATA SHEET AAT1271 1.5A Step-Up Current Regulator for Flash LEDs Flash to Maximum Movie Mode Current Ratio – Address 3 The maximum movie-mode current is a fixed ratio of the flash current controlled by Address 3. The ratio may be varied from 1:2 to OFF in 16 linear steps as shown in Table 5. The default value for Address 3 is Data=4 and represents a flash to maximum movie mode current level of 1 to 7.3. Data FL to MM Ratio 1 2 3 4* 5 6 7 8 9 10 11 12 13 14 15 16 1/2 1/3.8 1/5.5 1/7.3 1/8.9 1/10.5 1/12.2 1/13.8 1/14.9 1/16.5 1/18 1/19.6 1/21.1 1/22.6 1/24 OFF IMOVIE MODE[A/B] = IFLOUT[A/B]MAX 750mA = = 103mA 7.3 7.3 The maximum movie mode current level can be calculated using the following equation: IMOVIEMODE[A/B] = 81kΩ × A 1 = = Max Movie Mode Current RSET FL to MM Ratio Shutdown Since the sink switches are the only power returns for all loads, there is no leakage current to load if all the sink switches are disabled. When EN/SET pin is held low for an amount of time greater than tOFF (500μs), the AAT1271 enters shutdown mode and draws less than 1μA from VIN. All data and address registers are cleared (reset to 0) during shutdown. Selecting the Boost Inductor Table 5: Address 3, Flash/Movie Mode Current Ratio. The default maximum movie mode current can be calculated: IMOVIE MODE[A/B] = For example, if an RSET value of 107kΩ is chosen, then the FLOUTA/FLOUTB flash current is set to 750mA. For movie mode operation, the maximum current available at either FLOUTA or FLOUTB is then: IFLOUT[A/B]MAX 7.3 The AAT1271 controller utilizes PWM control and the switching frequency is fixed. To maintain 2MHz maximum switching frequency and stable operation, a 1μH inductor is recommended. Manufacturer’s specifications list both the inductor DC current rating, which is a thermal limitation, and peak inductor current rating, which is determined by the saturation characteristics. Measurements at full load and high ambient temperature should be performed to ensure that the inductor does not saturate or exhibit excessive temperature rise. Manufacturer Part Number Inductance (μH) Saturated Rated Current (A) DCR (mΩ) Size (mm) LxWxH Cooper Bussmann Cooper Bussmann Cooper Bussmann Sumida Coilcraft SD3812-1R0-R SDH3812-1R0-R SD10-1R0-R CDH38D11/S LPS4012-102NLC 1 1 1 1 1 2.69 3 2.25 2.8 2.5 48 45 44.8 48.8 60 4.0x4.0x1.2 3.8x3.8x1.2 5.2x5.2x1.0 4.0x4.0x1.2 4.1x4.1x1.2 Type Shielded Shielded Shielded Shielded Shielded Table 6: Typical Suggested Surface Mount Inductors. *Denotes the default value. 14 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202084A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 20, 2012 Drum Drum Drum Drum Drum Core Core Core Core Core DATA SHEET AAT1271 1.5A Step-Up Current Regulator for Flash LEDs The inductor (L) is selected to avoid saturation at minimum input voltage and maximum output load conditions. Worst-case peak current occurs at minimum input voltage (maximum duty cycle) and maximum load. Bench measurements are recommended to confirm actual IPEAK and to ensure that the inductor does not saturate at maximum LED current and minimum input supply voltage. The RMS current flowing through the boost inductor is equal to the DC plus AC ripple components. Under worst case RMS conditions, the current waveform is critically continuous. The resulting RMS calculation yields worst case inductor loss. The RMS current value should be compared against the inductor manufacturer’s temperature rise, or thermal derating guidelines: IRMS = IPEAK 3 For a given inductor type, smaller inductor size leads to an increase in DCR winding resistance and, in most cases, increased thermal impedance. Winding resistance degrades boost converter efficiency and increases the inductor’s operating temperature: PLOSS(INDUCTOR) = I2RMS · DCR Manufacturer Murata Selecting the Boost Capacitors In general, it is good design practice to place a decoupling capacitor (input capacitor) between the IN and GND pins. An input capacitor in the range of 2.2μF to 10μF is recommended. A larger input capacitor in this application may be required for stability, transient response, and/or ripple performance. The high output ripple inherent in the boost converter necessitates the use of low impedance output filtering. Multi-layer ceramic (MLC) capacitors provide small size and adequate capacitance, low parasitic equivalent series resistance (ESR) and equivalent series inductance (ESL), and are well suited for use with the AAT1271 boost regulator. MLC capacitors of type X7R or X5R are recommended to ensure good capacitance stability over the full operating temperature range. The output capacitor is selected to maintain the output load without significant voltage droop (∆VOUT) during the power switch ON interval. A 2.2μF ceramic output capacitor is recommended (see Table 7). Typically, 6.3V or 10V rated capacitors are required for this flash LED boost output. Ceramic capacitors selected as small as 0603 are available which meet these requirements. MLC capacitors exhibit significant capacitance reduction with applied voltage. Output ripple measurements should confirm that output voltage droop and operating stability are within acceptable limits. Voltage derating can minimize this factor, but results may vary with package size and among specific manufacturers. To maintain stable operation at full load, the output capacitor should be selected to maintain ∆VOUT between 100mV and 200mV. The boost converter input current flows during both ON and OFF switching intervals. The input ripple current is less than the output ripple and, as a result, less input capacitance is required. Part Number Capacitance (μF) Voltage Rating (V) Temp Co. Case Size GRM185R60J225KE26 GRM188R71A225KE15 GRM21BR70J225KA01 GRM21BR71A225KA01 GRM219R61A475KE19 2.2 2.2 2.2 2.2 4.7 6.3 10 6.3 10 10 X5R X7R X7R X7R X5R 0603 0603 0805 0805 0805 GRM21BR71A106KE51 10 10 X7R 0805 Table 7: Typical Suggested Surface Mount Capacitors. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202084A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 20, 2012 15 DATA SHEET AAT1271 1.5A Step-Up Current Regulator for Flash LEDs PCB Layout Guidelines 2. Minimize the distance under the inductor between IN and switching pin SW; minimize the size of the PCB area connected to the SW pin. 3. Maintain a ground plane and connect to the IC PGND pin(s) as well as the PGND connections of CIN and COUT. 4. Consider additional PCB exposed area for the flash LEDs to maximize heatsinking capability. This may be necessary when using high current application and long flash duration application. 5. Connect the exposed paddle (bottom of the die) to either PGND or GND. Connect AGND, FLGND to GND as close as possible to the package. Boost converter performance can be adversely affected by poor layout. Possible impact includes high input and output voltage ripple, poor EMI performance, and reduced operating efficiency. Every attempt should be made to optimize the layout in order to minimize parasitic PCB effects (stray resistance, capacitance, and inductance) and EMI coupling from the high frequency SW node. A suggested PCB layout for the AAT1271 1.5A step-up regulator is shown in Figures 4 and 5. The following PCB layout guidelines should be considered: 1. Minimize the distance from capacitor CIN and COUT’s negative terminals to the PGND pins. This is especially true with output capacitor COUT, which conducts high ripple current from the output to the PGND pins. DC- DC+ JP6 MCU R5 10K R6 10K R7 10K 1 2 3 4 SW1 Movie Mode Control 0 2 4 U2 1 3 5 SW2 Safety Timer 0 2 4 0 2 4 VSS GP 0 GP 1 GP 2 PIC12F675C3 1 3 5 8 7 6 5 R10 0 10k C4 1μF FLINH FLEN R9 330 LED2 GRN SW3 A/B Control VDD GP5 GP4 GP3 JP7 0 R8 330 LED 1 RED 0 2 4 SW4 2 4 1 3 5 JP3 SW5 JP4 VOUT JP1 0 R4 100k ( opt) R3 100k 1 3 5 1 3 5 D1 U1 JP5 EN /SET R2 100K L1 C1 2.2μF 1μH C3 74 nF 1 2 3 4 5 6 7 CT EN/SET FLEN AGND IN SW PGND RSET FLA FLGND FLB FLINH GND OUT R1 107k Cooper Bussmann SD3812-1R0-R, 1μH, 2.69A, 48mΩ Murata GRM188R71A225KE15 2.2μF, 0603, X7R, 10V Murata GRM155R71A743KA01, 74nF, 0402, X7R, 10V Lumiled LXCL-PWF4 or equivalent Figure 3: AAT1271 Evaluation Board Schematic. 16 D2 14 13 12 11 10 9 8 AAT1271 TDFN33-14 L1 C1, C2 C3 D1, D2 JP2 0 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202084A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 20, 2012 C2 2.2μF DATA SHEET AAT1271 1.5A Step-Up Current Regulator for Flash LEDs Figure 4: AAT1271 Evaluation Board Top Side Layout. Component Part Number U1 AAT1271IWO U2 SW1 – SW3 R1 R2, R3, R4 R5, R8 R6, R7 JP1, JP2, JP7 C1, C2 C3 C4 L1 D1-D2 LED1 LED2 JP3, JP4, JP5, JP6 PIC12F675 PTS645TL50 Chip Resistor Chip Resistor Chip Resistor Chip Resistor Chip Resistor GRM188R71A225KE15 GRM155R71A743KA01 GRM216R61A105KA01 SD3812-1R0-R LXCL-PWF4 CMD15-21SRC/TR8 CMD15-21VGC/TR8 PRPN401PAEN Figure 5: AAT1271 Evaluation Board Bottom Side Layout. Description 1.5A Step-Up Current Regulator for Flash LEDs; TDFN33-14 package 8-bit CMOS, FLASH-based μC; 8-pin PDIP package Switch, SPST, 5mm 107kΩ, 1%, 1/4W; 0402 100kΩ, 1%, 1/4W; 0603 10kΩ, 5%, 1/4W; 0603 330Ω, 5%, 1/4W; 0603 0Ω, 5% 2.2μF, 10V, X7R, 0603 74nF, 10V, X7R, 0402 1μF, 10V, X5R, 0805 Drum Core, 1μH, 2.69A, 48mΩ White Flash LED Red LED; 1206 Green LED; 1206 Conn. Header, 2mm zip Manufacturer Skyworks Microchip ITT Industries Vishay Vishay Vishay Vishay Vishay Murata Murata Murata Cooper Bussmann Lumileds, Philips Chicago Miniature Lamp Chicago Miniature Lamp Sullins Electronics Table 8: AAT1271 Evaluation Board Bill of Materials. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202084A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 20, 2012 17 DATA SHEET AAT1271 1.5A Step-Up Current Regulator for Flash LEDs Ordering Information Package Marking1 Part Number (Tape and Reel)2 TDFN33-14 ZUXYY AAT1271IWO-T1 Skyworks Green™ products are compliant with all applicable legislation and are halogen-free. For additional information, refer to Skyworks Definition of Green™, document number SQ04-0074. Package Information TDFN33-143 Detail "A" 3.000 ± 0.050 2.500 ± 0.050 Index Area 3.000 ± 0.050 1.650 ± 0.050 Top View Bottom View + 0.100 - 0.000 Pin 1 Indicator (Optional) 0.180 ± 0.050 Side View 0.400 BSC 0.000 0.203 REF 0.750 ± 0.050 0.425 ± 0.050 Detail "A" All dimensions in millimeters. 1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD. 3. The leadless package family, which includes QFN, TQFN, DFN, TDFN, and STDFN, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing process. A solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder connection. 18 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202084A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 20, 2012 DATA SHEET AAT1271 1.5A Step-Up Current Regulator for Flash LEDs Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved. Information in this document is provided in connection with Skyworks Solutions, Inc. (“Skyworks”) products or services. These materials, including the information contained herein, are provided by Skyworks as a service to its customers and may be used for informational purposes only by the customer. Skyworks assumes no responsibility for errors or omissions in these materials or the information contained herein. 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