DATA SHEET AAT1272 1.5A Step-Up Current Regulator for Flash LEDs General Description Features The AAT1272 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 • User-Programmable Safety Timer • Single Resistor Sets Flash and Movie Mode Current • Two Wire, I2C Compliant Serial Interface ▪ Fast, 400kHz Serial Transfer Rate ▪ 16 Level Movie-mode Current ▪ Flash/Movie-mode ▪ Current Output Channel Control ▪ 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 AAT1272 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 AAT1272 ideally suited for small battery-powered applications. An industry-standard I2C serial digital input is used to enable, disable and set the movie-mode current for each flash LED with up to 16 movie-mode settings. The AAT1272 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 user-programmed delay or as a safety feature. The maximum flash and movie-mode current is set by one external resistor; the ratio of Flash to Movie-mode current is set at approximately 7.3:1. One or two LEDs can be connected to the AAT1272; in the case of two LEDs the output current is matched between each diode. The AAT1272 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. Applications • • • • • Digital Still Cameras (DSCs) LED Photo Flash/Torch Mobile Handsets MP3 Players PDAs and Notebook PCs The AAT1272 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 202085A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 1 DATA SHEET AAT1272 1.5A Step-Up Current Regulator for Flash LEDs Typical Application L1 1μH SW IN High Current Flash LEDs OUT CIN 2.2μF VBAT COUT 2.2μF I2C Interface AAT1272 Flash Enable FLEN Enable EN FLOUTA SDA SDA SCL SCL FLOUTB CT CT RSET AGND PGND FLGND RSET 107kΩ Pin Descriptions Pin # Symbol 1 CT 2 EN 3 FLEN 4 AGND 5 IN 6 SW 7 PGND 8 OUT 9 10 SCL SDA 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 input. EN is an active HIGH asserted input. EN must be strobed low-to-high to enable the AAT1272 to accept I2C programming instructions. 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 AAT1272 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 AAT1272 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 AAT1272 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 AAT1272. Connect OUT to the anode(s) of the Flash LED(s). I2C interface serial control line. I2C interface serial data/address. Flash Output B. Connect cathode of Flash LEDB to FLOUTB. For a single flash LED, connect FLOUTB and 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 AAT1272 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 AAT1272’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 AAT1272. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202085A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 DATA SHEET AAT1272 1.5A Step-Up Current Regulator for Flash LEDs Pin Configuration TDFN33-14 (Top View) CT EN FLEN AGND IN SW PGND 1 14 2 13 3 4 12 EP 11 5 10 6 9 7 8 RSET FLOUTA FLGND FLOUTB SDA SCL 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 AAT1272 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 202085A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 3 DATA SHEET AAT1272 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 fOSC tDEFAULT TSD TSD(HYS) I2C Control – Switching Frequency Default ON Time Thermal Shutdown Threshold Thermal Shutdown Hysteresis SDA, SCL VIL Input Threshold Low VIH Input Threshold High II VOL fSCL tLOW tHIGH Input Current Output Logic Low (SDA) SCL Clock Frequency SCL Clock Low Period SCL Clock High Period tHD_STA Hold Time START Condition tSU_STA Setup Time for Repeat START tSU_DAT SDA Data Setup Time tHD_DAT SDA Data Hold Time tSU_STO Setup time for STOP Condition Bus Free Time between STOP and tBUF START Condition EN, FLEN Logic Control VEN(L), EN, FLEN Input Low Threshold VFLEN(L) VEN(H), EN, FLEN Input High Threshold VFLEN(H) tFLEN_OND FLEN ON Delay Time tFLEN_OFFD FLEN OFF Delay Time Min Typ 2.7 EN = FLEN = IN, Set FL Load = 1.5A EN = IN, FLEN = AGND EN = FLEN = GND RSET = 107k; FLOUTA + FLOUTB RSET = 107k , Movie Mode Current Set = 100%; FLOUTA + FLOUTB TA = 25˚C CT = 74nF 0.67 0.23 Max Units 5.5 5.5 1 V V 1 1.2 1.5 1.5 10 μA A % 206 mA 2.0 600 140 15 2.5 MHz ms °C °C 0.4 V 1.4 V -1.0 1.0 0.4 400 0.6 μA V kHz μs μs μs μs ns μs μs 1.3 μs IPULLUP = 3mA 0 1.3 0.6 0.6 0.6 100 0.9 0.4 1.4 EN = AGND EN = AGND mA V V 40 10 μs μs 1. The AAT1272 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 202085A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 DATA SHEET AAT1272 1.5A Step-Up Current Regulator for Flash LEDs I2C Interface Timing Details SDA TSU_DAT TLOW THD_STA TBUF SCL THD_STA THD_DAT THIGH TSU_STA TSU_STO Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202085A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 5 DATA SHEET AAT1272 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 5.1 5.5 Boost Switching Frequency vs. Input Voltage Shutdown Current vs. Input Voltage (VEN/SET = VFLEN = 0V) 3 0.03 Shutdown Current (µA) Switching Frequency (MHz) 4.7 Input Voltage (V) 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) 120 800 700 600 500 400 300 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) 1000 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) 4.3 Input Voltage (V) (Movie Mode; L = 1µH) 6 3.9 5.5 -40 -15 10 35 Temperature (°C) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202085A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 60 85 DATA SHEET AAT1272 1.5A Step-Up Current Regulator for Flash LEDs Typical Characteristics Movie Mode Output Ripple (IFLOUTX = 103mA/Channel; L = 1µH) (IFLOUTX = 103mA/ch; VIN = 3.6V; L = 1µH) LED Current Accuracy (%) Movie Mode LED Current Accuracy vs. Input Voltage 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 60 85 Temperature (°C) Time (200ns/div) Flash On Time Delay vs. Input Voltage 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) 35 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) 4.7 5.1 5.5 1000 800 600 400 200 0 0 20 40 60 80 100 120 140 CT Capacitor (nF) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202085A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 7 DATA SHEET AAT1272 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) SDA (5V/div) VOUT (2V/div) 0V 2V 0V 0V VSINK (500mV/div) VSINK (2V/div) 0V IFLOUTX (1A/div) IFLOUTX (100mA/div) 0A 0V 0A Time (50µs/div) Movie Mode Transition Characteristic Flash Timeout vs. Temperature (IFLOUTX = 102mA to 188mA/ch; COUT = 0.22µF; VIN = 3.6V; L = 1µH) (IFLOUTX = 750mA/ch; VIN = 3.6V; CT = 47nF) 0V 0V VSINK (2V/div) IFLOUTX (100mA/div) 500 Flash Timeout (ms) SDA (5V/div) VOUT (2V/div) 0V 450 400 350 300 250 200 0A -40 Time (100µs/div) 8 Time (100µs/div) -15 10 35 Temperature (°C) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202085A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 60 85 DATA SHEET AAT1272 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 85°C 25°C -40°C 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.4 2.7 3.1 3.5 3.9 4.3 Input Voltage (V) 4.7 5.1 5.5 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 Input Voltage (V) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202085A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 9 DATA SHEET AAT1272 1.5A Step-Up Current Regulator for Flash LEDs Functional Block Diagram IN SW OUT FLOUTA FLOUTB EN FLEN SCL Control SDA RSET CT AGND PGND FLGND Functional Description The AAT1272 is a boost converter with a current-regulated output designed to drive high current white LEDs used in camera flash applications. The maximum flash current is set by an external resistor, RSET, which sets the flash current and the maximum movie-mode current. The maximum movie-mode current is equal to the maximum programmed flash current minus the programmed flash-to-movie-mode ratio whose default value is 7.3. 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 AAT1272 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 10 I2C-compliant 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. The AAT1272 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. Movie Mode The movie mode current level, the flash safety timer, the output channel enable, and the flash-to-movie mode current ratio can be set using the AAT1272’s I2Ccompliant interface. The movie-mode current level can be adjusted in 16 steps using a logarithmic scale where Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202085A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 DATA SHEET AAT1272 1.5A Step-Up Current Regulator for Flash LEDs each code is 1dB below the previous code. The flash safety delay can be reduced from the maximum value programmed externally by CT in 16 linear steps. The flash current outputs FLOUTA and FLOUTB can be enabled or disabled individually or together. The flashto-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. Lastly, the EN pin must be toggled low-tohigh to enable the AAT1272 to accept I2C programming instructions. Over-Temperature Protection Thermal protection disables the AAT1272 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 voltage automatically recovers when the over-temperature fault condition is removed. Over-Voltage Protection (Open LED, Open Circuit) The AAT1272’s output voltage is limited by internal overvoltage protection circuitry, which prevents damage to the AAT1272 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. Auto-Disable Feature The AAT1272 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. Applications Information LED Selection The AAT1272 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 The LED current is controlled by the RSET resistor. For maximum accuracy, a 1% tolerance resistor is recommended. FLOUTA and FLOUTB can be programmed up to a maximum total flash current of 1.5A or up to 750mA per channel. FLOUTA and FLOUTB output current is matched across the programming range. A flash event is initiated by asserting the FLEN pin. A flash event is automatically terminated when FLEN is disabled or if the safety timer terminates before the FLEN pin is disabled. The maximum flash current in each FLOUTA and FLOUTB is set by the RSET resistor and can be calculated using the following equation: IFLOUTA = IFLOUTB = 81kΩ · A 81kΩ · A = = ~750mA per channel RSET 107kΩ To prevent excessive power dissipation during higher flash current operation, RSET values smaller than 107kΩ are not recommended. Movie Mode LED Current The maximum movie-mode current level is set by the maximum, programmed flash current reduced by the programmed flash-to-movie-mode ratio in which the default value is 7.3: IMOVIE-MODE[A/B] = IFLOUT[A/B](MAX) 750mA = = 103mA 7.3 7.3 To change the configuration or the settings, the AAT1272 can be programmed via the I2C interface. Triggering the FLEN low to high will enable a flash event with the maximum flash current set by the RSET resistor or with programmed flash current set via the I2C interface. Concurrently, the flash timer is also initiated. All data and register contents are cleared (reset to the default value) after each flash event. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202085A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 11 DATA SHEET AAT1272 1.5A Step-Up Current Regulator for Flash LEDs Flash Safety Timeout The AAT1272 includes a timer circuit that enables the flash current for a programmed period of time. 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 experiences hang-up or freeze. The flash safety timeout, T can be calculated by the following equation: T = 7.98s/μF · CT Where T is in seconds and CT is the capacitance of the timer capacitor in μF. For example, using a 47nF capacitor for CT sets the flash timeout to: Flash Safety Timeout = 7.98s/μF · 0.047μF = 375ms The relationship between the flash safety timeout and the capacitance of the timer capacitor is illustrated in Figure 1. Flash Timeout (ms) 1000 800 600 400 200 20 40 60 80 100 120 START and STOP conditions are always generated by the master. Prior to initiating a START, both the SDA and SCL pins are in idle mode (idle mode is when there is no activity on the bus and SDA and SCL are pulled high by the external pull-up resistors). A START condition occurs when the master strobes the SDA line low and after a short period strobes the SCL line low. A START condition acts as a signal to all ICs that transmission activity is about to occur on the I2C bus. A STOP condition, as shown in Figure 2, is when master releases the bus and SCL changes from low to high followed by SDA low-tohigh transition. The master does not issue an ACKNOWLEDGE and releases the SCL and SDA pins. I2C Address Bit Map 140 CT Capacitor (nF) Figure 1: Flash Safety Timeout vs. Timer Capacitor. I2C Serial Interface The AAT1272 is fully compliant with the industry-standard I2C interface. The I2C two-wire communications bus consists of SDA and SCL lines. SDA provides data, while SCL provides clock synchronization with speed up to 400kHz. SDA data transfers device address followed by a register address and data bits sequence. When using the I2C interface, EN is pulled high to enable the device or low to disable the device. The I2C serial interface 12 I2C START and STOP Conditions Figure 4 illustrates the address bit transfer. The 7-bit address is transferred with the Most Significant Bit (MSB) first and is valid when SCL is high. This is followed by the R/W bit in the Least Significant Bit (LSB) location. The R/W bit on the eighth bit determines the direction of the transfer (a '1' for read or a '0' for write). The AAT1272 is a write-only device and the R/W bit must be set low. The Acknowledge bit (ACK) is set to low by the AAT1272 to acknowledge receipt of the address. 1200 0 0 requires a master to initiate all the communications with target devices. The AAT1272 is a target device and only supports the write protocol. The AAT1272 is manufactured with a target device address of 0x37 (Hex). See Figure 2 for the I2C interface diagram. I2C Register Address/Data Bit Map Figure 5 illustrates the Register Address or the serial data bit transfer. The 8-bit data is always transferred most significant bit first and is valid when SCL is high. The Acknowledge bit (ACK) is set low by the AAT1272 to acknowledge receipt of the register address or the data. I2C Acknowledge Bit (ACK) The Acknowledge bit is the ninth bit of each transfer on the SDA line. It is used to send back a confirmation to the master that the data has been received properly by the target device. For each ACK to take place, the master must first release the SDA line, and then the target device will pull the SDA line low, as shown in Figures 1, 4, and 5. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202085A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 DATA SHEET AAT1272 1.5A Step-Up Current Regulator for Flash LEDs ack from slave start MSB Device Address LSB w ack ack from slave MSB Register Address LSB ack ack from slave MSB DATA LSB ack stop SCL SDA start AAT1272 Device Address = 37h w ack Register Address = 00h Data = 06h ack ack stop Figure 2: I2C Interface Diagram. STOP START SDA SDA SCL SCL Figure 3: I2C STOP and START Conditions. START: A High “1” to Low “0” Transition on the SDA Line While SCL is High “1” STOP: A Low “0” to High “1” Transition on the SDA Line While SCL is High “1” SCL 1 2 3 4 5 6 7 MSB SDA A6 8 9 LSB A5 A4 A3 A2 A1 A0 R/W ACK Device Address Figure 4: I2C Address Bit Map; 7-bit Slave Address (A6-A0), 1-bit Read/Write (R/W), 1-bit Acknowledge (ACK). SCL 1 2 3 4 5 6 7 MSB SDA D7 8 9 LSB D6 D5 D4 D3 D2 D1 D0 ACK Register Address / Data Figure 5: I2C Register Address and Data Bit Map; 8-bit Data (D7-D0), 1-bit Acknowledge (ACK). Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202085A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 13 DATA SHEET AAT1272 1.5A Step-Up Current Regulator for Flash LEDs Device Register Information To program the register through the I2C interface, the master needs to send the AAT1272’s device address, 0x37 (Hex), first, and then sends an 8-bit register address and 8-bit data. The AAT1272 has two registers, Register 0 and Register 1. If no instruction is written to the register, the default value is applied. Register 0 (REG0), Register Address: 00h Bits [7:4] Program the movie-mode current with 16 different percentage levels. Bits [3:0] Program the flash safety timeout with 16 different fractions from the hardware configuration, CT. MSB 7 LSB 6 5 4 3 2 1 0 Flash Safety Timeout 0000 = 16/16 (default) 0001 = 15/16 0010 = 14/16 0011 = 13/16 0100 = 12/16 0101 = 11/16 0110 = 10/16 0111 = 9/16 1000 = 8/16 1001 = 7/16 1010 = 6/16 1011 = 5/16 1100 = 4/16 1101 = 3/16 1110 = 2/16 1111 = 1/16 Movie Mode Current 0000 = 100% (default) 0001 = 89.1% 0010 = 79.4% 0011 = 70.8% 0100 = 63.1% 0101 = 56.2% 0110 = 50.1% 0111 = 44.7% 1000 = 39.8% 1001 = 35.5% 1010 = 31.6% 1011 = 28.2% 1100 = 25.1% 1101 = 22.4% 1110 = 20% 1111 = 0% Figure 6: AAT1272 Register 0 Programming. 14 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202085A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 DATA SHEET AAT1272 1.5A Step-Up Current Regulator for Flash LEDs Register 1 (REG1); Register Address: 01h Bits [5:4] Program the FLOUTA and FLOUTB with four ON/OFF configurations. Bits [3:0] Program the flash-to-movie mode ratio with 16 different fractions from the hardware configuration, RSET. MSB X LSB X 5 4 3 2 1 0 Flash-to-Movie Mode Ratio 0000 = 1/2 0001 = 1/3.8 0010 = 1/5.5 0011 = 1/7.3 (default) 0100 = 1/8.9 0101 = 1/10.5 0110 = 1/12.2 0111 = 1/13.8 1000 = 1/14.9 1001 = 1/16.5 1010 = 1/18 1011 = 1/19.6 1100 = 1/21.1 1101 = 1/22.6 1110 = 1/24 1111 = OFF 00 01 10 11 FLOUTA FLOUTB OFF OFF (default) OFF* ON ON OFF* ON ON *with 2-3mA standby current Figure 7: AAT1272 Register 1 Programming. Selecting the Boost Inductor The AAT1272 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. 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 *Denotes the default value. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202085A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 15 DATA SHEET AAT1272 1.5A Step-Up Current Regulator for Flash LEDs 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 AAT1272 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. PCB Layout Guidelines 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 AAT1272 1.5A step-up regulator is shown in Figures 4 and 5. The following PCB layout guidelines should be considered: 1. 2. 3. 4. 5. 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. Minimize the distance under the inductor between IN and switching pin SW; minimize the size of the PCB area connected to the SW pin. Maintain a ground plane and connect to the IC PGND pin(s) as well as the PGND connections of CIN and COUT. 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. 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. 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 Drum Drum Drum Drum Drum Core Core Core Core Core Table 6: Typical Suggested Surface Mount Inductors. Manufacturer Murata 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. 16 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202085A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 DATA SHEET AAT1272 1.5A Step-Up Current Regulator for Flash LEDs SCL VOUT SDA FLEN JP1 0 R2 JP2 0 10k VCC D1 Enable D2 U1 1 2 3 JP3 4 5 6 L1 1μH C1 2.2μF 7 CT EN FLEN AGND IN SW PGND 14 RSET FLA FLGND FLB SDA SCL OUT 13 12 11 10 9 8 AAT1272 TDFN33-14 C3 74nF R1 107k L1 C1, C2 C3 D1, D2 C2 2.2μF 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 8: AAT1272 Evaluation Board Schematic. DC - DC + VCC JP7 MCU JP8 0 R5 R6 R7 10K 10K 10K 1 Movie Mode Control Safety Timer A / B Control 0 0 0 2 SW 1 3 21 43 5 4 SW 2 VDD GP5 GP4 GP3 VSS GP0 GP1 GP2 R8 10 k C4 1μF U2 8 FLEN 7 6 5 R4 330 PIC12F675 0 R3 330 21 43 5 LED 1 RED 21 43 5 LED 2 GRN SW 3 SW4 JP4 R9 100k 21 43 5 R10 10k R11 10k SCL JP5 FLEN SDA JP6 SCL SDA Figure 9: AAT1272 Evaluation Board MCU Section Schematic. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202085A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 17 DATA SHEET AAT1272 1.5A Step-Up Current Regulator for Flash LEDs Figure 10: AAT1272 Evaluation Board Top Side Layout. Component Part Number U1 AAT1272IWO U2 SW1 – SW3 R1 R2, R9 R5 - R8, R10, R11 R3, R4 JP1, JP2, JP8 C1, C2 C3 C4 L1 D1-D2 LED1 LED2 JP3, JP4, JP5, JP6, JP7 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 11: AAT1272 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: AAT1272 Evaluation Board Bill of Materials. 18 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202085A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 DATA SHEET AAT1272 1.5A Step-Up Current Regulator for Flash LEDs Ordering Information Package Marking1 Part Number (Tape and Reel)2 TDFN33-14 ZNXYY AAT1272IWO-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. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202085A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 19 DATA SHEET AAT1272 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. Skyworks may change its documentation, products, services, specifications or product descriptions at any time, without notice. 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Additional information, including relevant terms and conditions, posted at www.skyworksinc.com, are incorporated by reference. 20 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202085A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012