DATA SHEET AAT3172 High Current LED Flash Driver Charge Pump General Description Features The AAT3172 is a high output current, high efficiency, low noise, low profile charge pump DC/DC converter, ideal for multi-function LED photo-flash applications where solution cost, size, and efficiency are critical. • • • • • • • • • • • • • • The dual charge pump in the AAT3172 is capable of delivering 600mA output current. Two current-controlled paths are available for users of dual flash LEDs that prefer current matching. Each LED channel can be easily programmed in 32 steps with a single GPIO output through the AS2Cwire™ (Advanced Simple Serial Control™) interface. This allows smooth transitions and flexible adjustment of brightness in flash or other lighting modes. The tri-mode (1X/1.5X/2X) operation of the internal charge pump offers excellent power efficiency for both flash and movie modes. Combined with a low external parts count (two 1μF flying capacitors and one small bypass capacitor at VIN and OUT), the AAT3172 is ideally suited for small, battery-powered applications. VIN Range: 2.7V to 5.5V 600mA Output Current Tri-Mode 1X/1.5X/2X in Current Mode Voltage Mode Operation: 1.5X, 100mA Dual Regulated Current Sinks Current Match Between Current Sinks 32 Current Steps Set by AS2Cwire 1μF Input, Output, and Flying Capacitors <1.0μA of Shutdown Small Application Circuit No Inductors Automatic Soft Start 12-Pin TDFN 3x3mm Package -40°C to +85°C Temperature Range Applications • • • • The AAT3172 has a thermal management system to protect the device in the event of a short-circuit condition at the output pin. Built-in soft-start circuitry prevents excessive inrush current during start-up. The shutdown feature disconnects the load from VIN and reduces quiescent current to less than 1.0μA. Camera Phones Digital Still Cameras (DSCs) PDAs and Notebook PCs Smart Phones The AAT3172 is available in the Pb-free, thermallyenhanced, 12-pin 3x3mm TDFN package. Typical Application C1 1μF C1+ 2.7V to 5.5V C2 1μF C1- C2+ VIN C IN 4.7μF C2VOUT C OUT 2.2μF AAT3172 Flash LED 1 Flash LED 2 F1 EN/SET EN/SET GND F2 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202099A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012 1 DATA SHEET AAT3172 High Current LED Flash Driver Charge Pump Pin Descriptions Pin # Symbol 1, 12 2 3 4 5 6 7 8 9 10 11 EP VIN C1+ C1GND F1 F2 EN/SET N/C C2C2+ VOUT Function Input power supply pin. Requires 4.7μF bypass capacitor to ground. Flying capacitor C1 positive terminal. Connect a 1.0μF capacitor between C1+ and C1-. Flying capacitor C1 negative terminal. Ground connection. Current sink input #1. Current sink input #2. AS2Cwire serial interface control pin. No connection. Flying capacitor C2 negative terminal. Flying capacitor C2 positive terminal. Connect a 1μF capacitor between C2+ and C2-. Charge pump output. Requires 2.2μF capacitor connected between this pin and ground. Exposed paddle (bottom); connect to GND directly beneath package. Pin Configuration TDFN33-12 (Top View) VIN C1+ C1GND F1 F2 2 1 12 2 11 3 10 4 9 5 8 6 7 VIN VOUT C2+ C2N/C EN/SET Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202099A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012 DATA SHEET AAT3172 High Current LED Flash Driver Charge Pump Absolute Maximum Ratings1 TA = 25°C, unless otherwise noted. Symbol VIN VEN Description Input Voltage EN to GND Voltage Maximum EN to Input Voltage Maximum DC Output Current Operating Junction Temperature Range Storage Temperature Range Maximum Soldering Temperature (at leads, 10 sec) VEN(MAX) IOUT TJ TS TLEAD Value Units -0.3 to 6.0 -0.3 to 6.0 VIN + 0.3 700 -40 to 150 -65 to 150 300 V V V mA °C °C °C Value Units 50 2.0 °C/W W Thermal Information2 Symbol JA PD Description Maximum 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. 2. Mounted on an FR4 board. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202099A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012 3 DATA SHEET AAT3172 High Current LED Flash Driver Charge Pump Electrical Characteristics1 CIN = 4.7μF, COUT = 2.2μF, C1 = C2 = 1.0μF; TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C, VIN = 3.6V. Symbol Description Conditions Power Supply Input Voltage Range VIN VOUT(MAX) Maximum Output Voltage ICC Operating Current ISHDN(MAX) IOUT(MAX)2 I(D-Match) I(D-Match) IDX FCLK VREG TSS EN/SET VIL VIH TEN/SET LO TEN/SET HI MIN TEN/SET HI MAX TOFF TLAT Input Current VIN Pin Shutdown Current Maximum Output Current Current Matching Between Outputs; High Current Current Matching Between Outputs; Low Current Output Current Accuracy Clock Frequency Voltage Mode Regulation Soft-Start Time Enable Threshold Low Enable Threshold High EN/SET Low Time Minimum EN/SET High Time Maximum EN/SET High Time EN/SET Off Timeout EN/SET Latch Timeout EN/SET Input Leakage Min Typ 2.7 ON/OFF Standby Mode, Code Address = 4, Data = 2 1X, No Load Current 3.0 VIN 5.5, 1.5X Mode, No Load Current 3.0 VIN 5.5, 2X Mode, No Load Current EN = 0 VF = 3.6V VIN = 3.6V, TA = 25°C, 428mA; Code Address = 3, Data = 2; Code Address = 0, Data = 4 VIN = 3.6V, TA = 25°C, 100mA; Code Address = 3, Data =1; Code Address = 0, Data = 1 TA = 25°C, Code 1, HI Scale EN/SET Code Address = 6, Data = 2 VIN = 2.7V VIN = 5.5V 5.5 10 300 2.0 3.0 Units 5.5 V V μA 4.0 6.0 1.0 mA 600 μA mA 8 % 8 % 270 4.1 Max 330 1 4.5 200 4.9 0.4 1.4 0.3 60 50 -1 60 500 500 1 mA MHz V μs V V μs ns μs μs μs μA 1. The AAT3172 is guaranteed to meet performance specifications from 0°C to 70°C. Specification over the -40°C to +85°C operating temperature range is assured by design, characterization, and correlation with statistical process controls. 2. Mounted on an FR4 board. 4 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202099A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012 DATA SHEET AAT3172 High Current LED Flash Driver Charge Pump Typical Characteristics VIN = 3.6V, CIN = 4.7μF, COUT = 2.2μF, C1 = C2 = 1μF, TA = 25°C, unless otherwise noted. Efficiency vs. Supply Voltage Turn-On to 1X Mode (VIN = 4.2V; 50mA/ch Load) 100 Efficiency (%) 90 EN (2V/div) 50mA/ch VF = 2.8V 80 70 152mA/ch VF = 3.0V 60 50 95mA/ch VF = 2.9V 40 VOUT (2V/div) VSINK (1V/div) IIN (200mA/div) 30 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 200μ μs/div Supply Voltage (V) Turn-On to 1.5X Mode Turn-On to 1X Mode (VIN = 3.2V; 50mA/ch Load) (VIN = 4.2V; 300mA/ch Load) EN (2V/div) EN (2V/div) VOUT (2V/div) VSINK (1V/div) VOUT (2V/div) VSINK (1V/div) IIN (200mA/div) IIN (500mA/div) 200μ μs/div 500μ μs/div Turn-On to 2X Mode Turn-Off from 1.5X Mode (VIN = 3.2V; 300mA/ch Load) (VIN = 3.2V; 50mA/ch Load) EN (2V/div) EN (2V/div) VOUT (2V/div) VSINK (1V/div) VF (1V/div) IIN (500mA/div) IIN (200mA/div) 500μ μs/div 200μ μs/div Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202099A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012 5 DATA SHEET AAT3172 High Current LED Flash Driver Charge Pump Typical Characteristics VIN = 3.6V, CIN = 4.7μF, COUT = 2.2μF, C1 = C2 = 1μF, TA = 25°C, unless otherwise noted. Load Characteristic Load Characteristic (VIN = 3.0V; 1.5X Mode; 50mA/ch Load) (VIN = 3.6V; 1.5X Mode; 152mA/ch Load) VIN (100mV/div) VIN (100mV/div) VOUT (200mV/div) VOUT (200mV/div) VSINK (200mV/div) VSINK (200mV/div) 2µs/div 2µs/div Load Characteristic Voltage Mode Load Regulation (VIN = 2.8V; 2X Mode; 152mA/ch Load) 4.8 Output Voltage (V) VIN (100mV/div) VOUT (200mV/div) VSINK (200mV/div) 4.7 VIN = 4.2V 4.6 4.5 4.4 VIN = 3.7V 4.3 VIN = 3.3V 4.2 4.1 0 15 2µs/div 30 45 60 75 90 105 120 135 150 Load Current (mA) Voltage Mode Line Regulation Voltage Mode Load Response (VIN = 3.7V) Output Voltage (V) 4.8 4.7 IOUT = 10mA 4.6 4.51V VOUT (100mV/div) 4.5 4.4 100mA IOUT = 120mA 4.3 IOUT (100mA/div) IOUT = 80mA 4.2 IOUT = 30mA 10mA 4.1 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 Input Voltage (V) 6 3.9 4.0 4.1 4.2 5ms/div Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202099A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012 DATA SHEET AAT3172 High Current LED Flash Driver Charge Pump Typical Characteristics VIN = 3.6V, CIN = 4.7μF, COUT = 2.2μF, C1 = C2 = 1μF, TA = 25°C, unless otherwise noted. Voltage Mode Load Response Voltage Mode Line Response (VIN = 3.3V) (100mA Load) 4.50V VOUT (100mV/div) 4.0V VIN (500mV/div) 100mA IOUT (100mA/div) 3.6V 10mA VOUT (200mV/div) 4.5V 5ms/div 1ms/div TLAT vs. VIN TOFF vs. VIN 160 180 -40°C TLAT (µs) 120 25°C 140 100 85°C 80 60 40 85°C 100 80 60 0 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 Input Voltage (V) Input Voltage (V) VIH vs. VIN Over-Temperature VIL vs. VIN Over-Temperature 1.0 1.0 -40°C 0.9 -40°C 0.8 0.7 25°C 85°C 0.5 VIL (V) 0.8 VIH (V) -40°C 20 0 0.6 120 40 20 0.9 25°C 160 TOFF (µs) 140 0.7 0.6 25°C 85°C 0.5 0.4 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 Input Voltage (V) 0.4 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 Input Voltage (V) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202099A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012 7 DATA SHEET AAT3172 High Current LED Flash Driver Charge Pump Functional Block Diagram C1+ C1- C2+ C2- VIN Charge Pump Section 1 Charge Pump Section 2 OUT 1MHz Oscillator Soft Start Control F1 EN/SET System Control; AS 2Cwire F2 GND Functional Description The AAT3172 is a high efficiency, low noise, dual stage tri-mode 1X/1.5X/2X charge pump device intended for photo-flash LED applications. The AAT3172 requires only four external components: two 1.0μF ceramic capacitors for the charge pump flying capacitors, one 4.7μF ceramic capacitor for CIN, and one 2.2μF ceramic capacitor for COUT. The charge pump is designed to deliver load currents up to 600mA. The dual stage charge pump section contains soft-start circuitry to prevent excessive in-rush current during start-up. System efficiency is maximized with a tri-mode, dual stage charge pump topology. The internal clock oscillator, which operates at 1MHz, allows the use of small external components. 8 The tri-mode charge pump architecture optimizes power conversion efficiency. Depending upon the combination of load current, input voltage, and nominal LED forward voltage, the charge pump will operate in a 1X, 1.5X, or 2X mode to generate the output voltage required to power the load for a programmed constant current setting. This results in significant power savings over voltage doubling architectures, especially when the LEDs are continuously operated at lower current levels in movie viewing or flashlight modes. Constant Current Channels The AAT3172 contains two programmable constant current sinks for integrated flash circuit control. Efficiency is optimized with the low dropout characteristic of the current sinks. The low dropout performance extends the Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202099A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012 DATA SHEET AAT3172 High Current LED Flash Driver Charge Pump battery operating range for 1X and 1.5X modes, improving efficiency and extending battery life. Each constant current sink is programmable through the AS2Cwire serial interface. Independent current settings can be used for a multistage flash LED control. This feature allows users to conveniently drive separate dual flash LEDs directly while achieving good brightness matching. Also, F1 and F2 can be connected together for single output configuration. Modes of Operation In addition to the data registers that set the current levels for the two current sinks, the AAT3172 has three mode registers. Register 3 is the HI/LO mode register. It sets the maximum per channel current level to either 300mA or 50mA. Each channel can be set independently so one channel can be for flash while the other can be in a low constant current mode. Register 4 is the ON/OFF register. When set with Data = 1, both current sources are enabled (default); when set with Data = 2, both current sources are disabled. When Register 4 is set to OFF, the device is in standby mode with significantly reduced quiescent current. The AAT3172 also includes a regulated output voltage mode setting. By setting Register 6 with Data = 2 for voltage mode, the charge pump delivers a regulated 4.5V output that continuously operates in 1.5X mode. It is suitable for driving loads of up to 100mA. The voltage mode may be used to drive LEDs with ballast resistors. Driving either F1 or F2 in current mode will override the voltage mode state until F1 and F2 are set back to zero current by either data or mode register. Setting Register 5 with Data = 1 will reset the mode back to current mode and the charge pump output voltage will regulate appropriately. AS2Cwire Serial Interface The AAT3172 utilizes the AS2Cwire serial interface to enable/disable the charge pump, set the operating mode, and adjust the output current level of each constant current sink. Each current sink can be independently programmed with sixteen current levels (see table below). AS2Cwire incorporates addressing to program the operating modes and current level settings. Constant Current Sink Nominal Programming Levels Data 300mA HI Scale ISINK (mA/ch) 50mA LO Scale ISINK (mA/ch) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 300 267 238 214 190 167 152 133 119 105 95 86 76 67 62 0 50 44 40 36 32 28 25 22 20 17 16 14 13 11 10 0 AS2Cwire relies on the number of rising edges of the EN/ SET pin to address and load the registers. AS2Cwire latches data or address after the EN/SET pin has been held high for time TLAT. 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 so forth. Data is set to any number of rising edges between 1 and including 16. 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 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 that address are allowed where only data is issued. When EN/SET is held low for an amount of time greater than TOFF, the AAT3172 enters into shutdown mode and draws less than 1μA from the supply. Address 0 is the default address on the first rising edge after the AAT3172 has been disabled. After shutdown, if only data is issued with the first rising edge (i.e., 1 - 16 edges, no address given), both current sinks will be programmed since the default will be Address 0. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202099A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012 9 DATA SHEET AAT3172 High Current LED Flash Driver Charge Pump AS2Cwire Serial Interface Addressing Address EN/SET Rising Edges Data Register 0 1 2 3 4 5 6 17 18 19 20 21 22 23 F1 and F2 Current Scale F1 Current Scale F2 Current Scale HI/LO ON/OFF Reserved Voltage/Current Mode ON/OFF Register (Address 4) Data MODE 1 2 ON OFF Voltage Register (Address 6) Data MODE 1 2 Current Voltage Thermal Protection HI/LO Scale Register (Address 3) Data F1 F2 1 2 3 4 LO HI LO HI LO HI HI LO The AAT3172 has a thermal protection circuit that will shut down the charge pump if the die temperature rises above the thermal limit, as is the case during a short circuit of the OUT pin. AS2Cwire Serial Interface Timing Address Data T HI T LO TLAT TLAT EN/SET 1 Address 10 2 17 18 1 0 2... n <= 16 1 Data Reg 1 0 Data Reg 2 0 n-1 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202099A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012 DATA SHEET AAT3172 High Current LED Flash Driver Charge Pump Applications Information Further, a single burst of data edges can be used to change from one setting to another for the last address. The address register is not reset after each write; therefore, submitting address edges is only required when changing the address. AS2Cwire Programming Generally, programming the AAT3172 is achieved by submitting bursts of address and data edges to the EN/ SET pin. However, in some cases multiple bursts of address and data are needed to enable a particular operating mode. In other cases, only a single burst of data edges is required. Additional Applications The constant voltage mode feature of the AAT3172 allows the user to combine the flash feature with additional applications. Additional applications such as auxiliary lighting and status LEDs can be added while eliminating the need for an additional power supply, which is normally required. Since the constant voltage mode can supply a regulated output at up to 100mA load, it is capable of driving five LEDs at 20mA each. It is suitable for keypad lighting, status lighting, and other applications where a 4.5V power supply could be used. To enable both flash channels to a current setting on the LO scale, the user submits a single burst of address and data edges. To enable both flash channels to a current setting on the HI scale, the user must submit a burst of address and data edges to program the current setting level, and then submit a second burst of address and data edges to program the HI/LO scale register to the HI scale. When enabling constant voltage mode, the LED channels F1 and F2 are automatically disabled so current does not flow through the flash LED during constant voltage mode. Because of this, very little programming is required. The user just addresses the voltage mode register and programs it to voltage mode. Shortcuts can also be used. If the device is in shutdown, both flash channels can be enabled to a setting on the LO scale by just giving a single burst of data edges. The address edges are not needed because all registers are reset during shutdown and address 0 is the default. C1 1μF C1+ 2.7V to 5.5V C1- C2+ VIN CIN 4.7μF EN/SET C2 1μF C2VOUT COUT 2.2μF AAT 3172 Flash LED F1 EN/SET F2 GND AUX_EN Figure 1: Flash Plus Auxiliary Lighting. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202099A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012 11 DATA SHEET AAT3172 High Current LED Flash Driver Charge Pump C1 1μF C1+ 2.7V to 5.5V C2 1μF C1- C2+ VIN CIN 4.7μF C2VOUT F1 EN/SET EN/SET C OUT 2.2μF AAT 3172 Flash LED STAT1 STAT2 F2 GND Figure 2: Flash Plus Status Lighting. LED Selection The AAT3172 is designed to drive high-intensity white LEDs. It is particularly suitable for LEDs with an operating forward-voltage in the range of 4.2V to 1.5V. The charge pump device can also drive other loads that have similar characteristics to white LEDs. For various load types, the AAT3172 provides a high-current, programmable ideal constant current source. Device Power Efficiency The AAT3172 power conversion efficiency depends on the charge pump mode. By definition, device efficiency is expressed as the output power delivered to the LED divided by the total input power consumed. η= POUT PIN When the input voltage is sufficiently greater than the LED forward voltage, the device optimizes efficiency by operating in 1X mode. In 1X mode, the device is working as a bypass switch and passing the input supply directly to the output. The power conversion efficiency can be approximated by: η= VF · ILED VF ≈ VIN · IIN VIN Due to the very low 1X mode quiescent current, the input current nearly equals the current delivered to the 12 LED. Further, the low-impedance bypass switch introduces negligible voltage drop from input to output. The AAT3172 further maintains optimized performance and efficiency by detecting when the input voltage is not sufficient to sustain LED current. The device automatically switches to 1.5X mode when the input voltage drops too low in relation to the LED forward voltage. In 1.5X mode, the output voltage can be boosted to 3/2 the input voltage. The 3/2 conversion ratio introduces a corresponding 1/2 increase in input current. For ideal conversion, the 1.5X mode efficiency is given by: η= VF VF · ILED = VIN · 1.5IIN 1.5 · VIN Similarly, when the input falls further, such that 1.5X mode can no longer sustain LED current, the device will automatically switch to 2X mode. In 2X mode, the output voltage can be boosted to twice the input voltage. The doubling conversion ratio introduces a corresponding doubling of the input current. For ideal conversion, the 2X mode efficiency is given by: η= VF VF · ILED = VIN · 2IIN 2 · VIN Capacitor Selection Careful selection of the four external capacitors (CIN, C1, C2, and COUT) is important because they will affect turn-on Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202099A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012 DATA SHEET AAT3172 High Current LED Flash Driver Charge Pump time, output ripple, and transient performance. Optimum performance will be obtained when low equivalent series resistance (ESR) (<100m) ceramic capacitors are used. A value of 1μF for the flying capacitors is a good starting point when choosing capacitors. If the LED current sinks are only programmed for light current levels, then the capacitor size may be decreased. Ceramic composition capacitors are highly recommended over all other types of capacitors for use with the AAT3172. Ceramic capacitors offer many advantages over their tantalum and aluminum electrolytic counterparts. A ceramic capacitor typically has very low ESR, is lowest cost, has a smaller PCB footprint, and is nonpolarized. Low ESR ceramic capacitors help maximize charge pump transient response. Equivalent Series Resistance ESR is an important characteristic to consider when selecting a capacitor. ESR is a resistance internal to a capacitor that is caused by the leads, internal connections, size or area, material composition, and ambient temperature. Capacitor ESR is typically measured in milliohms for ceramic capacitors and can range to more than several ohms for tantalum or aluminum electrolytic capacitors. Ceramic Capacitor Materials Ceramic capacitors less than 0.1μF are typically made from NPO or C0G materials. NPO and C0G materials typically have tight tolerance and are stable over temperature. Large capacitor values are typically composed of X7R, X5R, Z5U, or Y5V dielectric materials. Large ceramic capacitors are often available in lower-cost dielectrics, but capacitors greater than 4.7μF are not typically required for AAT3172 applications. Figure 3 illustrates an example of an adequate PCB layout. The bottom of the package features an exposed metal paddle. The exposed paddle acts, thermally, to transfer heat from the chip and, electrically, as a ground connection. The junction-to-ambient thermal resistance (JA) for the package can be significantly reduced by following a couple of important PCB design guidelines. The PCB area directly underneath the package should be plated so that the exposed paddle can be mated to the top layer PCB copper during the re-flow process. This area should also be connected to the top layer ground pour when available. Further, multiple copper plated thru-holes should be used to electrically and thermally connect the top surface paddle area to additional ground plane(s) and/or the bottom layer ground pour. The chip ground is internally connected to both the paddle and the GND pin. The GND pin conducts large currents and it is important to minimize any differences in potential that can result between the GND pin and exposed paddle. It is good practice to connect the GND pin to the exposed paddle area using a trace as shown in Figure 3. The flying capacitors C1 and C2 should be connected close to the chip. Trace length should be kept short to minimize path resistance and potential coupling. The input and output capacitors should also be placed as close to the chip as possible. Capacitor area is another contributor to ESR. Capacitors that are physically large will have a lower ESR when compared to an equivalent material, smaller capacitor. These larger devices can improve circuit transient response when compared to an equal value capacitor in a smaller package size. PCB Layout To achieve adequate electrical and thermal performance, careful attention must be given to the PCB layout. In the worst-case operating condition, the chip must dissipate considerable power at full load. Adequate heat-sinking must be achieved to ensure intended operation. Figure 3: Example PCB Layout. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202099A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012 13 DATA SHEET AAT3172 High Current LED Flash Driver Charge Pump Ordering Information Package Marking1 Part Number (Tape and Reel)2 TDFN33-12 QLXYY AAT3172IWP-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 Information3 TDFN33-12 Index Area 0.43 ± 0.05 0.1 REF C0.3 0.45 ± 0.05 2.40 ± 0.05 3.00 ± 0.05 Detail "A" 3.00 ± 0.05 1.70 ± 0.05 Top View Bottom View 0.23 ± 0.05 Pin 1 Indicator (optional) 0.05 ± 0.05 0.23 ± 0.05 0.75 ± 0.05 Detail "A" Side View 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. 14 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202099A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012 DATA SHEET AAT3172 High Current LED Flash Driver Charge Pump 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. Skyworks makes no commitment to update the materials or information and shall have no responsibility whatsoever for conflicts, incompatibilities, or other difficulties arising from any future changes. No license, whether express, implied, by estoppel or otherwise, is granted to any intellectual property rights by this document. Skyworks assumes no liability for any materials, products or information provided hereunder, including the sale, distribution, reproduction or use of Skyworks products, information or materials, except as may be provided in Skyworks Terms and Conditions of Sale. THE MATERIALS, PRODUCTS AND INFORMATION ARE PROVIDED “AS IS” WITHOUT WARRANTY OF ANY KIND, WHETHER EXPRESS, IMPLIED, STATUTORY, OR OTHERWISE, INCLUDING FITNESS FOR A PARTICULAR PURPOSE OR USE, MERCHANTABILITY, PERFORMANCE, QUALITY OR NON-INFRINGEMENT OF ANY INTELLECTUAL PROPERTY RIGHT; ALL SUCH WARRANTIES ARE HEREBY EXPRESSLY DISCLAIMED. SKYWORKS DOES NOT WARRANT THE ACCURACY OR COMPLETENESS OF THE INFORMATION, TEXT, GRAPHICS OR OTHER ITEMS CONTAINED WITHIN THESE MATERIALS. SKYWORKS SHALL NOT BE LIABLE FOR ANY DAMAGES, INCLUDING BUT NOT LIMITED TO ANY SPECIAL, INDIRECT, INCIDENTAL, STATUTORY, OR CONSEQUENTIAL DAMAGES, INCLUDING WITHOUT LIMITATION, LOST REVENUES OR LOST PROFITS THAT MAY RESULT FROM THE USE OF THE MATERIALS OR INFORMATION, WHETHER OR NOT THE RECIPIENT OF MATERIALS HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. Skyworks products are not intended for use in medical, lifesaving or life-sustaining applications, or other equipment in which the failure of the Skyworks products could lead to personal injury, death, physical or environmental damage. Skyworks customers using or selling Skyworks products for use in such applications do so at their own risk and agree to fully indemnify Skyworks for any damages resulting from such improper use or sale. Customers are responsible for their products and applications using Skyworks products, which may deviate from published specifications as a result of design defects, errors, or operation of products outside of published parameters or design specifications. Customers should include design and operating safeguards to minimize these and other risks. Skyworks assumes no liability for applications assistance, customer product design, or damage to any equipment resulting from the use of Skyworks products outside of stated published specifications or parameters. Skyworks, the Skyworks symbol, and “Breakthrough Simplicity” are trademarks or registered trademarks of Skyworks Solutions, Inc., in the United States and other countries. Third-party brands and names are for identification purposes only, and are the property of their respective owners. Additional information, including relevant terms and conditions, posted at www.skyworksinc.com, are incorporated by reference. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202099A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012 15