AAT1278IUP-T1

DATA SHEET AAT1278 1.5A Single Flash LED Driver General Description Features The AAT1278 is a high-efficiency, 1.5A high-current boost converter for LED photo flash applications. It maintains output current regulation by switching the internal high-side and low-side switch transistors, pulsewidth modulated at a fixed frequency of 2MHz. The high switching frequency allows the use of a small external inductor and output capacitor, making the AAT1278 ideally suited in all single cell, Li-ion-powered applications. • • • • • • • Skyworks' proprietary AS2Cwire™ (Advanced Simple Serial Control™) serial digital interface is used to enable, disable, configure, and program the operation of the AAT1278. Using the AS2Cwire interface, the movie-mode current level for each LED, and the flash-to-movie-mode current ratio can be programmed to one of 16 levels. The AAT1278 includes a separate Flash Enable input to initiate the flash operation and a Flash Inhibit pin which reduces the flash current to movie-mode levels during high battery demand. • • • • Input Voltage Range: 2.7V to 5.5V Single Channel Flash Output Up to 1.5A Regulated Output Current Up to 88% Efficiency 2MHz Switching Frequency Separate Flash Enable Single Resistor Sets Flash and Movie Mode Current ▪ AS2Cwire Single Wire Programming: • Movie Mode Current • Flash/Movie Mode Current Ratio True Load Disconnect Soft-Start and Input Current Limit Over-Voltage (Open LED, Open Circuit), Short Circuit, and Over-Temperature Protection -40°C to +85°C Temperature Range Applications • • • • • 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. The AAT1278 can drive one high current LED. LED Photo Flash / Torch Camera Enabled Mobile Devices Cellphones/Smartphones Digital Still Cameras (DSCs) Multimedia Mobile Phones The AAT1278 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 AAT1278 is available in a Pb-free, thermally-enhanced CSP-12 package and operates over the -40°C to 85°C temperature range. Typical Application L1 1μH VBAT = 2.7V to 5.5V SW IN OUT CIN 2.2μF COUT 2.2μF Flash LED AAT1278 Enable/Set Input EN/SET Flash Enable FLEN Flash Inhibit FLINH FL RSET RSET PGND AGND FLGND Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202088A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 1 DATA SHEET AAT1278 1.5A Single Flash LED Driver Pin Descriptions Pin # Symbol Description A1 EN/SET A2 FLEN Flash enable pin. A low-to-high transition on the FLEN pin initiates a flash pulse and a high-to-low transition on the FLEN pin terminates a flash pulse. A3 AGND Analog ground pin. Connect AGND to PGND, and FLGND at a single point as close to the AAT1278 as possible. A4 PGND Power ground. Connect PGND to the same single point as AGND located as close to the AAT1278 as possible. B1 RSET Flash current set pin. Connect a resistor from RSET to AGND to program the desired flash current for the current sink FL. B2 IN B3, B4 C1 SW FL C2 FLGND C3 FLINH C4 OUT Enable and Serial Control input. EN/SET is the AS2Cwire addressing and programming input to: a) adjust the movie-mode current level; b) select the Flash-to-Movie-mode ratio. Flash output boost converter power input. Connect IN to the input power source. Connect a 2.2μF or larger ceramic capacitor from IN to PGND and locate as close as possible to the AAT1278 package for optimum performance. Boost converter switching node. Connect a 1μH inductor between SW and IN. LED Flash current sink pin. Connect the cathode of Flash LED to FL. Flash ground pin. Connect FLGND to PGND, and AGND at a single point as close to the AAT1278 as possible. Flash inhibit pin. FLINH is an active HIGH control input with an internal 200k resistor to AGND. A low-to-high transition on the FLINH pin reduces FL sink current to the maximum (default) movie-mode current level. Power output of the boost converter. Connect a 2.2μF or larger ceramic capacitor from OUT to PGND as close as possible to the AAT1278. Connect OUT to the anode of the Flash LED. Pin Configuration CSP-12 (Top View) 4 3 2 1 2 PGND SW OUT A4 B4 C4 AGND SW FLINH A3 B3 C3 FLEN IN FLGND A2 B2 C2 ENSET RSET FL A1 B1 C1 A B C Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202088A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 DATA SHEET AAT1278 1.5A Single Flash LED Driver Absolute Maximum Ratings1 Symbol IN, OUT, SW EN/SET, FLEN, FLINH, RSET, FL TJ TS TLEAD Description Value Maximum Rating -0.3 to 6.0 Maximum Rating -0.3 to VIN + 0.3 Operating Junction Temperature Range Storage Temperature Range Maximum Soldering Temperature (at Leads, 10 sec) Units V -40 to 150 -65 to 150 300 °C Value Units 114 0.88 °C/W W Thermal Information2 Symbol JA PD Description Thermal Resistance Maximum Power Dissipation3 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. 2. Mounted on an FR4 board. 3. Derate 8.8mW/°C above 25°C ambient. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202088A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 3 DATA SHEET AAT1278 1.5A Single Flash LED Driver Electrical Characteristics VIN = 3.6V; CIN = COUT = 2.2μF; RSET = 107kΩ; L = 1μH. TA = -40oC to 85°C unless otherwise noted. Typical values are at TA = 25°C. Symbol Description Conditions Power Supply – Switching Flash Driver Input Voltage Range VIN VOUT(MAX) Maximum Output Voltage IIN(Q) Supply Current IIN(LIM) ISHDN(MAX) IFL IFL(ACC) Input Current Limit Input Shutdown Current Output Current, Flash Mode Flash Current Accuracy IMM(LOAD) Output Current, Movie Mode fOSC TSD Switching Frequency Over-Temperature Shutdown Threshold TSD(HYS) Over-Temperature Shutdown Hysteresis EN/SET, FLEN VEN/SET(H), EN/SET, FLEN Input High Threshold VFLEN(H) VEN/SET(L), EN/SET, FLEN Input Low Threshold VFLEN(L) IEN/SET, IFLEN EN/SET, FLEN Input Leakage Current VT(FLINH) FLINH Input Threshold Voltage RIN(FLINH) FLINH Input Resistance to AGND tEN/SET(LO) 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 Time tEN/SET(LAT) EN/SET Latch Timeout Time tFLEN(ON) FLEN On Delay Time tFLEN(OFF) FLEN Off Delay Time FLINH ON Delay Time tFLINH(ON) 4 Min Typ Max Units 5.5 5.5 V V mA 2.7 EN/SET = FLEN = IN, Set FL Load = 1.5A EN/SET = IN, FLEN = AGND VIN - VF = 1V EN/SET, FLEN = AGND RSET = 107kΩ RSET = 107kΩ RSET = 107kΩ, Movie mode current set to 100% TA = 25°C 1.4 0.23 2 1.5 ±10 A μA A % 206 mA 1.0 1.2 1.5 2.0 140 15 2.5 1.4 VEN/SET, VFLEN = IN V -1 0.4 V 1 μA V kΩ μs ns ½ VIN 200 0.3 75 50 75 500 500 EN/SET = AGND EN/SET = AGND MHz °C °C 40 10 15 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202088A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 μs DATA SHEET AAT1278 1.5A Single Flash LED Driver 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 204mA 104mA 52mA 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) 3.5 3.9 4.3 4.7 5.1 5.5 Input Voltage (V) Supply Current vs. Input Voltage Movie Mode LED Current vs. Temperature (VEN = VFLEN = 3.6V) (IFL = 206mA/Ch; VIN = 3.6V; L = 1µH) 225 1000 Output Current (mA) 900 Supply Current (µA) 3.9 800 700 600 500 400 300 85°C 25°C -40°C 200 100 0 2.7 3.1 3.5 3.9 4.3 Input Voltage (V) 4.7 5.1 5.5 220 215 210 205 200 195 190 185 -40 -15 10 35 60 85 Temperature (°C) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202088A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 5 DATA SHEET AAT1278 1.5A Single Flash LED Driver Typical Characteristics Movie Mode Current Accuracy vs Input Voltage Movie Mode Output Ripple (IFL= 206mA; L = 1µH) (IFL = 206mA; VIN = 3.6V; L = 1µH) Current Accuracy (%) 4 3 VOUT (AC Coupled) (50mV/div) 2 1 0 VINDUCTOR (2V/div) -1 0V -2 IINDUCTOR (100mA/div) -3 -4 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 vs. Temperature (IFL = 1.5A; VIN = 4V; L = 1µH) (IFL = 1.5A; VIN = 4.2V; L = 1µH) 1580 VINDUCTOR (2V/div) Output Current (mA) VOUT (AC Coupled) (50mV/div) 0V IINDUCTOR (50mA/div) 1560 1540 1520 1500 1480 1460 1440 1420 1.65A -40 -15 4 70 3.5 60 3 50 40 30 20 -40°C 25°C 85°C 10 0 4.3 Input Voltage (V) 6 TFLEN_OFFD (µs) TFLEN_OND (µs) 80 3.9 4.7 85 (IFL = 1.5A; COUT= 2.2µF; L = 1µH) (IFL = 1.5A; COUT = 2.2µF; L = 1µH) 3.5 60 Flash Mode Turn Off Time vs Input Voltage Flash On Time Delay vs. Input Voltage 3.1 35 Temperature (°C) Time (200ns/div) 2.7 10 5.1 2.5 2 1.5 1 -40C 25C 85C 0.5 5.5 0 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 • sales@skyworksinc.com • www.skyworksinc.com 202088A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 5.1 5.5 DATA SHEET AAT1278 1.5A Single Flash LED Driver Typical Characteristics Movie Mode Line Transient Flash Turn On Characteristic (IFL = 206mA; VIN = 4.2V to 3.6V) (IFL = 1.5A; VIN = 3.6V; COUT = 2.2µF; L = 1µH) 4.2V VIN (500mV/div) 3.6V IFL (AC Coupled) (50mA/div) VFLEN (2V/div) VOUT (2V/div) 0V 0V VFL (2V/div) 0V IFL (1A/div) 0A Time (50µs/div) Time (50µs/div) VFLEN (2V/div) VOUT (2V/div) Flash Turn Off Characteristic Movie Mode to Flash Turn On Characteristic (IFL = 1.5A; VIN = 3.6V; COUT = 2.2µF; L = 1µH) (IFL = 206mA to 1.5A; VIN = 3.6V; L = 1µH) VFLEN (2V/div) VOUT (2V/div) 0V 2V VFL (2V/div) 0V VFL (500mV/div) IFL (1A/div) 0A IFLOUTX (1A/div) 0V 2V 0V 0A Time (1µs/div) VEN/SET (5V/div) VOUT (2V/div) Time (50µs/div) Movie Mode Turn On Characteristic Movie Mode Transition Characteristic (IFL = 206mA; VIN = 3.6V; L = 1µH) (IFL = 206mA to 376mA; COUT = 0.22µF; VIN = 3.6V; L = 1µH) 0V VEN/SET (2V/div) VOUT (2V/div) 0V 0V VFL (500mV/div) IFL (200mA/div) 0V VFL (500mV/div) 0V IFL (200mA/div) 0V 0A 0A Time (100µs/div) Time (100µs/div) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202088A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 7 DATA SHEET AAT1278 1.5A Single Flash LED Driver 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 300 300 250 250 200 150 85°C 25°C -40°C 100 50 2.7 3.1 Input Voltage (V) TEN/SET(LAT) (µs) 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 85°C 25°C -40°C 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 • sales@skyworksinc.com • www.skyworksinc.com 202088A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 5.1 5.5 DATA SHEET AAT1278 1.5A Single Flash LED Driver Functional Block Diagram SW OUT (to Flash LED) FL IN EN/SET System Control Enable and AS2C Interface FLEN FLGND RSET FLINH AGND PGND Functional Description The AAT1278 is a boost converter with a current regulated output designed to drive high current white LED used in camera flash applications. The AAT1278 has a constant current sink channel to accurately regulate the current flow through a high current, high intensity white flash LED. The AAT1278 has two basic operating modes; a flash mode controlled by the FLEN pin and the movie/ torch light mode controlled through the AS2Cwire interface. Flash Mode A flash pulse may be initiated by pulling the FLEN input pin from a logic low-to-high state, which initiates a flash pulse. The maximum flash current in the AAT1278 is set by an external resistor, RSET, which sets the flash current and the maximum movie-mode current. 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 AAT1278 to revert the flash LED current to its maximum level, assuming that the FLEN pin is still active (high). Movie (Torch) Mode The movie / torch mode current level, and the flash to maximum movie mode current ratio are programmed by the AAT1278 AS2Cwire interface. The movie-mode current level can be adjusted to one of 16 steps using a logarithmic scale where each code level is 1dB below the previous code. The flash to maximum movie mode current ratio can be set from 2:1 to OFF with respect to the maximum programmed flash current as set by the RSET resistor. The manual FLEN signal has priority over movie-mode operation. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202088A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 9 DATA SHEET AAT1278 1.5A Single Flash LED Driver Movie mode operation is controlled entirely by the AS2Cwire interface via the EN/SET pin. The FLEN signal will override movie-mode AAT1278 operation when toggled to a logic high level. The part will not reenter movie mode when FLEN is brought low. To reenter movie mode after a flash event the part must be cycled off and back on to reset the movie mode and reprogrammed via the AS2Cwire interface to the desired movie mode operation. Shutdown and Output Disconnect (True Load Disconnect) A typical synchronous step-up (boost) converter has a conduction path from the input to the output via the body diode of the P-channel MOSFET. The AAT1278 design disconnects this body diode from the output and eliminates this conduction path. This enables the AAT1278 to provide true load disconnect during shutdown and inrush current limit at turn-on. Over-Voltage Protection (Open Flash LED, Open Circuit) The AAT1278 boost converter output is voltage limited by internal overvoltage protection circuitry to prevent damage to the device in the event an open LED or open circuit condition occurs. During an open circuit condition, the output voltage will rise to 5.5V (typical). The OVP circuit disables the boost converter to prevent the output voltage from rising above 5.5V. Once the open circuit condition is removed, normal boost operation will resume. Short Circuit Protection The AAT1278 is equipped with an auto-disable feature for the flash LED channel. After the IC is enabled and system start up commences, a test current of 2-3mA (typical) is forced through the sink channel. The channel will be disabled if the voltage of the SINK pin does not drop to a predetermined threshold. This feature is very convenient for disabling the current sink in the event the flash LED fails to a short circuit. This small test current is added to the set output current in both Flash and movie mode conditions. Over-Temperature Protection The AAT1278 has internal thermal protection circuitry to disable the device if the internal power dissipation exceeds a preset thermal limit. The junction over-temperature threshold is 140°C with 15°C of temperature hysteresis. During flash or movie-mode operation, if an environmen- 10 tal condition, flash current sink, or the boost converter causes the internal die temperature to rise above 140°C, the boost converter will be shut down. The boost converter output operation will automatically recover when the over-temperature fault condition is removed. Application Information Flash Mode LED Current Flash sink current can be programmed up to a maximum of 1.5A. The maximum flash current is set by the RSET resistor. For the desired flash current, the resistor value can be calculated using the following equation: RSET = 1A ∙ 162kΩ IFL(MAX) A flash event is initiated by asserting the FLEN pin. A flash event is automatically terminated when FLEN is deasserted. Any time that the FLINH pin is asserted, the default movie-mode current level will appear at FL channel. The default movie mode current level will be maintained on FL as long as the FLINH and FLEN pins are asserted. 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 Control of Movie Mode Operation In the AAT1278 control of the movie mode operation 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 internal data registers. Referring to Table 1:  Address 0 controls the movie mode (MM) current level as a percentage of the maximum movie mode current level.  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 a 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. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202088A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 DATA SHEET AAT1278 1.5A Single Flash LED Driver Address EN/SET Rising Edges 0 17 1 2 3 20 Function Default (No Programming) Movie Mode Current Not Used Not Used Flash/Movie Mode Current Ratio 100% 7.3:1 Table 1: AS2Cwire Serial Interface Addressing. 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 are 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, and Address 3 by 20 rising edges. Data is inclusively applied to any number of rising edges between 1 and 16. A typical write protocol is a burst of EN/SET rising edges which signify a particular address that is followed by a pause with EN/SET held high for the prescribed tLAT timeout period, then 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 AAT1278 has been disabled. When EN/SET is transitioned from high to low and held low longer than tOFF (500μs), the device enters a shutdown mode and draws less than 1uA from the input supply. All data and address are cleared (reset to 0) during shutdown. AS2Cwire addressing allows for control of the movie mode output current, 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 internal state machine will interpret instruction to program the output currents to the desired current level for moviemode operation. Movie Mode Current – Address 0 The AAT1278 movie mode current settings are controlled using the AS2Cwire interface. The default ratio between the flash current level and maximum movie mode current level is 7.3:1. For example, if an RSET value of 107kΩ is chosen, then the flash current is set to 1500mA. For movie mode operation, the maximum current available is then: IFL(MAX) 1500mA = = 206mA IMOVIE MODE = 7.3 7.3 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: AS2Cwire Serial Interface Timing Diagram. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202088A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 11 DATA SHEET AAT1278 1.5A Single Flash LED Driver Address 0 controls precise movie mode current levels. The movie mode current can be adjusted in a logarithmic fashion to one of 16 steps represented as a fraction of the maximum movie mode current in Table 2. On initial EN, the movie-mode output immediately supplies 100% of the set movie-mode current. Data Percentage of Maximum MM Current 1* 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 100% 89% 79% 71% 63% 56% 50% 45% 40% 36% 32% 28% 25% 22% 20% 0% Table 2: Address 0, Movie Mode (MM) Current Programming. 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 2:1 to OFF in 16 linear steps as shown in Table 3. The default value for Address 3 is Data = 4 and represents a flash to maximum movie mode current level of 7.3 to 1. The default maximum movie mode current can be calculated: IFL(MAX) IMOVIE MODE = 7.3 For example, if an RSET value of 107kΩ is chosen, then the flash current is set to 1500mA. For movie mode operation, the maximum current available is then: IMOVIE MODE = 1500mA = 206mA 7.3 The maximum movie mode current level can be calculated using the following equation: IMOVIE MODE = 162kΩ ∙ A 1 ∙ = Max Movie Mode Current RSET FL to MM Ratio Data Flash to Movie Mode Ratio 1 2 3 4* 5 6 7 8 9 10 11 12 13 14 15 16 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 24:1 OFF Table 3: Address 3, Flash/ Movie Mode Current Ratio. Shutdown Since the flash current sink is the only power returns for the flash LED loads, there is no leakage current to load if all the sink switches are disabled. When the EN/SET pin is held low for an amount of time greater than tOFF (500μs), the AAT1278 flash boost converter section enters shutdown mode and draws less than 1μA from the input power source. All data and address registers for the flash and/or movie mode are cleared (reset to 0) during shutdown. Selecting the Boost Inductor The AAT1278 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. * Denotes the default value. 12 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202088A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 DATA SHEET AAT1278 1.5A Single Flash LED Driver Selecting the Boost Capacitors In general, it is a good design practice to place a decoupling capacitor (input capacitor) between the IN and ground. 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 AAT1278 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 4). Typically, 6.3V or 10V rated capacitors are required for this flash LED boost output application. 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 de-rating can minimize this factor, but results may vary with package size 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 dur- ing 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 AAT1278 1.5A step-up regulator is shown in Figures 3 and 4. 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. 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 LED to maximize heatsinking capability. This may be necessary when using high current application and long flash duration application. Manufacturer Part Number Inductance (μH) Saturated Rated Current (A) DCR (mΩ) 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 2.69 2.5 48 45 44.8 48 60 Size (mm) LxWxH 4.0 3.8 5.2 4.0 4.1 x x x x x 4.0 3.8 5.2 4.0 4.1 x x x x x 1.2 1.2 1.0 1.2 1.2 Type shielded shielded shielded shielded shielded drum drum drum drum drum core core core core core Table 4: Typical Suggested Surface Mount Inductors. Manufacturer Part Number Capacitance (μF) Voltage Rating (V) Temp Co. Case Size Murata Murata Murata Murata Murata Murata GRM185R60J225KE26 GRM188R71A225KE15 GRM21BR70J225KA01 GRM21BR71A225KA01 GRM219R61A475KE19 GRM21BR71A106KE51 2.2 2.2 2.2 2.2 4.7 10 6.3 10 6.3 10 10 10 X5R X7R X7R X7R X5R X7R 0603 0603 0805 0805 0805 0805 Table 5: Typical Suggested Surface Mount Capacitors. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202088A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 13 DATA SHEET AAT1278 1.5A Single Flash LED Driver GND VIN R3 JP1 MCU R5 10K 2 4 Movie Mode Control Flash/Movie Mode Current Ratio 0 FLEN 0 R6 10K R7 10K U2 1 2 3 4 SW1 0 1 3 5 SW2 2 4 VDD GP5 GP4 GP3 VSS GP0 GP1 GP2 PIC12F675 1 3 5 8 7 6 5 FLINH 2 4 1 3 5 SW4 JP2 C3 1μF R10 100k R8 330 R9 330 R4 100k (opt) VOUT LED1 RED LED2 GRN SW3 2 4 0 10k D1 1 3 5 U1 JP3 EN/SET A3 A1 C1 A2 R2 100K B2 A4 C4 NA C1 2.2μF AGND EN/SET FL FLEN IN PGND RSET FLGND B1 C2 FLINHIBIT SW SW OUT C3 B3 B4 C4 L1 1μH AAT1278 CSP-12 R1 133k Figure 2: AAT1278 Evaluation Board Schematic. Figure 3: AAT1278 Evaluation Board Top Side Layout. 14 Figure 4: AAT1278 Evaluation Board Bottom Side Layout. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202088A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 C2 2.2μF DATA SHEET AAT1278 1.5A Single Flash LED Driver Component Part Number U1 AAT1278IUP U2 SW1-SW4 R1 R2,R4,R10 R3,R5,R6,R7 R8.R9 JP1, JP2, JP3 C1,C2 C3 L1 D1 LED1 LED2 PIC12F675 PTS645TL50 Chip Resistor Chip Resistor Chip Resistor Chip Resistor PRPN401PAEN GRM188R71A225KE15 GRM216R61A105KA01 SD3812-1R0-R FCW401Z 0805KRCT 0805KGCT Description 1.5A Step-Up Current Regulator for Flash LED;CSP-12 Package 8-bit CMOS,FLASH-based uC; 8-pin SOIC package Switch Tact, SPST, 5mm 133kΩ,1%,1/16W; 0402 100kΩ, 1%, 1/10W; 0603 10kΩ, 1%, 1/10W; 0603 330Ω, 1%, 1/10W; 0603 Conn. Header, 2mm zip 2.2uF, 10V, X7R, 0603 1uF, 10V, X5R, 0805 Drum Core, 1uH, 2.69A, 48mΩ White Flash LED Red LED; 0805 Green LED; 0805 Manufacturer Skyworks Microchip ITT Industries Vishay Vishay Vishay Vishay Sullins Electronics MuRata MuRata Cooper Bussmann Seoul Semiconductor HB HB Table 6: AAT1278 Evaluation Board Bill of Materials. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202088A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 15 DATA SHEET AAT1278 1.5A Single Flash LED Driver Ordering Information Package Marking1 Part Number(Tape and Reel)2 CSP-12 U3YW AAT1278IUP-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 CSP-12 E1 0.610 0.220 0.355 0.035 2.035 1.495 0.695 0.245 0.380 0.070 2.070 1.530 1.500 BSC 1.000 BSC 0.250 BSC N/A 0.780 0.270 0.405 0.105 2.105 1.565 b X Y X1 Y1 N 0.500 BSC 0.285 0.300 0.300 - 0.310 0.100 0.200 12 Balls + + + 4 + + + 3 + + + 2 + + + 1 C B E A A (Bottom View) 0.335 - A3 (Side View) Y1 NxØb U 3 LINE_1 Y W LINE_2 X1 e A2 A1 All dimensions in millimeters. Y (Side View) 1/2 D A A1 A2 A3 D E D1 E1 SD SE e D Max X Nominal D1 Min SD Symbol ENSET 1/2 E Ø 0.2 (Ref.) PIN A1 Indication (Top View) 1. YW = Year and Week code. 2. Sample stock is generally held on part numbers listed in BOLD. 16 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202088A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 DATA SHEET AAT1278 1.5A Single Flash LED Driver Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved. 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Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202088A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 21, 2012 17