DATA SHEET AAT1142 800mA Voltage-Scaling Step-Down Converter General Description Features The AAT1142 SwitchReg is a dynamically programmable 2.2MHz step-down converter with an input voltage range of 2.7V to 5.5V and output from 0.6V to 2.0V. Its low supply current, high level of integration, and small footprint make the AAT1142 the ideal choice for microprocessor core power in systems such as smartphones. * VIN Range: 2.7V to 5.5V * VOUT Programmable Range: 0.6V to 2.0V * Dynamic Voltage Management: 50mV Output Resolution Fast, Stable Response * Serial Control Options: I2C Two-Wire Interface S2Cwire Single-Wire Interface * 800mA Output Current * Up to 93% Efficiency * Line, Load Regulation Less Than 0.5% * 2.2MHz Switching Frequency * Ultra-Small External Filter * Low 35A No Load Quiescent Current * 100% Duty Cycle Low Dropout Operation * Internal Soft Start * Over-Temperature Protection * Current Limit Protection * Multi-Function MODE/SYNC Pin: PFM/PWM for High Efficiency PWM Only for Low Noise Clock Input to Synchronize to System Clock * TDFN33-12 Package * Temperature Range: -40C to +85C The 2.2MHz switching frequency allows the use of a small external inductor and capacitors. Peak current mode control and internal compensation provide stable operation and fast voltage response without over/undershoot or ringing. The AAT1142 delivers up to 800mA of output current while consuming 35A of typical no load quiescent current. Dynamic Voltage Management is provided through I2C or Skyworks' S2CwireTM (Simple Serial ControlTM) single wire interface. The user can program the output from 0.6V to 2.0V in 50mV steps. The AAT1142 optimizes power efficiency throughout the load range via PWM/PFM mode. Pulling the MODE/SYNC pin high enables PWM Only mode, maintaining constant frequency and low noise across the operating range. Alternatively, the converter may be synchronized to an external clock input via the MODE/SYNC pin. Overtemperature and short-circuit protection safeguard the AAT1142 and system components from damage. Applications * * * * * * * The AAT1142 is available in a Pb-free, low-profile 3x3x0.8mm TDFN33-12 package. The device is rated over the -40C to +85C temperature range. Camcorders Cellular Phones and Smartphones Digital Still Cameras Handheld Instruments Microprocessor / DSP Core MP3, Portable Music, and Portable Media Players PDAs and Handheld Computers Typical Application VOUT: 0.6V to 2.0V 800mA Maximum VIN: 2.7V to 5.5V Efficiency vs. Load (VOUT = 1.8V) L1 PVIN, VIN 100 LX 2.2H AAT1142 FB C1 10F MODE/SYNC PGND SDA SCL I 2C S Cwire* AGND *Optional S2Cwire or I2C Input 80 70 VIN = 4.2V 60 VIN = 5.0V 50 PWM Only Mode 40 EN/SET 2 VIN = 3.6V VIN = 2.7V 90 Efficiency (%) C2 4.7F 30 0 1 10 100 1000 Output Current (mA) Skyworks Solutions, Inc. * Phone [781] 376-3000 * Fax [781] 376-3100 * sales@skyworksinc.com * www.skyworksinc.com 201931B * Skyworks Proprietary Information * Products and Product Information are Subject to Change Without Notice. * May 17, 2012 1 DATA SHEET AAT1142 800mA Voltage-Scaling Step-Down Converter Pin Descriptions Pin Number Symbol 12 LX 11 PGND 10 MODE/SYNC 9 8 SDA SCL 7 EN/SET 6 FB 4, 5 3 1 2 EP AGND VIN PVIN N/C Function Connect the output inductor to this pin. The switching node is internally connected to the drain of both high- and low-side MOSFETs. Main power ground return pin. Connect to the output and input capacitor return. Connect to ground for PFM/PWM mode and optimized efficiency throughout the load range. Connect to high for low noise PWM Only operation under all operating conditions. Connect to an external clock for synchronization (PWM Only). I2C control pin: Data input. I2C control pin: Clock input. I2C enable pin. Pull high to enable the AAT1142; pull low to disable the AAT1142. Also serves as S2Cwire input for programmable output voltages. Feedback input pin. This pin is connected directly to the converter output for programmable output. Ground connection pin. Input voltage for the converter. Input voltage for the power switches. Not connected. Exposed paddle (bottom); connect to ground as closely as possible to the device. Pin Configuration TDFN33-12 (Top View) PVIN N/C VIN AGND AGND FB 2 1 12 2 11 3 10 4 9 5 8 6 7 LX PGND MODE/SYNC SDA SCL EN/SET Skyworks Solutions, Inc. * Phone [781] 376-3000 * Fax [781] 376-3100 * sales@skyworksinc.com * www.skyworksinc.com 201931B * Skyworks Proprietary Information * Products and Product Information are Subject to Change Without Notice. * May 17, 2012 DATA SHEET AAT1142 800mA Voltage-Scaling Step-Down Converter Absolute Maximum Ratings1 Symbol Description VIN, PVIN VLX VFB VSDA/SCL Input Voltage and Input Power to GND LX to GND FB to GND SDA/SCL to GND VMODE/SYNC, VEN/SET TJ TLEAD Value 6.0 -0.3 to VIN + 0.3 -0.3 to VIN + 0.3 -0.3 to 6.0 Units V MODE/SYNC and EN/SET to GND -0.3 to 6.0 Operating Junction Temperature Range Maximum Soldering Temperature (at leads, 10 sec) -40 to 150 300 C Value Units 2.0 50 W C/W Thermal Information2 Symbol PD JA Description Maximum Power Dissipation3 Thermal Resistance 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. 3. Derate 20mW/C above 25C. Skyworks Solutions, Inc. * Phone [781] 376-3000 * Fax [781] 376-3100 * sales@skyworksinc.com * www.skyworksinc.com 201931B * Skyworks Proprietary Information * Products and Product Information are Subject to Change Without Notice. * May 17, 2012 3 DATA SHEET AAT1142 800mA Voltage-Scaling Step-Down Converter Electrical Characteristics1 L = 2.2H, CIN = COUT = 10F, VIN = 3.6V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = 25C. Symbol Description Conditions Step-Down Converter Input Voltage VIN UVLO Threshold VUVLO VOUT VOUT VSLEW IQ ISHDN ILIM RDS(ON)H RDS(ON)L ILXLEAK VOUT/ VOUT*VIN ROUT TS FOSC FSYNC TSD THYS EN/SET and VEN/SET(L) VEN/SET(H) TEN/SET(L) TEN/SET(H) TOFF TLATCH IEN/SET Output Voltage Tolerance VOUT Programmable Range Output Voltage Programming Slew Rate Quiescent Current Shutdown Current P-Channel Current Limit High Side Switch On Resistance Low Side Switch On Resistance LX Leakage Current Line Regulation Output Impedance Start-Up Time Oscillator Frequency SYNC Frequency Range Over-Temperature Shutdown Threshold Over-Temperature Shutdown Hysteresis MODE/SYNC Enable Threshold Low Enable Threshold High EN/SET Low Time EN/SET High Time EN/SET Timeout EN/SET Latch Timeout Input Low Current VMODE/SYNC(L) Enable Threshold Low VMODE/SYNC(H) Enable Threshold High IMODE/SYNC Input Low Current Min Typ 2.7 VIN Rising Hysteresis VIN Falling IOUT = 0mA to 800mA, VIN = 2.7V to 5.5V Max Units 5.5 2.7 V 250 2.0 -3.0 0.6 COUT = 10F No Load EN/SET = AGND = PGND 3.0 2.0 10 35 70 1.0 1.0 0.29 0.24 1 0.2 k s 100 2.2 1.0 3.0 140 15 VEN/SET < 0.6V VEN/SET > 1.4V VEN/SET < 0.6V VEN/SET > 1.4V VIN = VFB = 5.5V 50 -1.0 VIN * 0.7 -1.0 MHz C 0.6 1.4 0.3 A %/V 250 From Enable to Output Regulation A A VIN = 5.5V, VLX = 0V to VIN VIN = 2.7V to 5.5V mV V % V mV/s 75 75 500 500 1.0 VIN * 0.4 1.0 V s A V A 1. The AAT1142 is guaranteed to meet performance specifications over the -40C to +85C 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 * sales@skyworksinc.com * www.skyworksinc.com 201931B * Skyworks Proprietary Information * Products and Product Information are Subject to Change Without Notice. * May 17, 2012 DATA SHEET AAT1142 800mA Voltage-Scaling Step-Down Converter Characteristics of SDA and SCL Bus Lines Standard Mode Parameter Symbol SCL Clock Frequency Hold Time for START Condition; After this Period, the First Clock Pulse is Generated LOW Period of the SCL Clock HIGH Period of the SCL Clock Set-up Time for a Repeated START Condition Data in Hold Time Data in Set-Up Time Set-Up Time for STOP Condition Bus Free Time Between a STOP and START Condition Input Low Level Input High Level Min fSCL tHD;STA tLOW tHIGH tSU;STA tHD;DAT tSU;DAT tSU;STO tBUF VIL VIH Max Fast Mode Min 100 4.0 4.7 4.0 4.7 0 350 4.0 4.7 3.45 0.6 1.3 0.6 0.6 0 350 0.6 1.3 VIN* 0.3 VIN * 0.7 Max Units 400 kHz s 0.9 s s VIN * 0.3 VIN * 0.7 Skyworks Solutions, Inc. * Phone [781] 376-3000 * Fax [781] 376-3100 * sales@skyworksinc.com * www.skyworksinc.com 201931B * Skyworks Proprietary Information * Products and Product Information are Subject to Change Without Notice. * May 17, 2012 V 5 DATA SHEET AAT1142 800mA Voltage-Scaling Step-Down Converter Typical Characteristics Efficiency vs. Load DC Regulation (VOUT = 0.9V) (VOUT = 0.9V) 2.0 100 Efficiency (%) Output Accuracy (%) VIN = 3.6V VIN = 2.7V 90 VIN = 4.2V 80 70 60 50 40 PWM Only Mode VIN = 5.0V 30 20 0 1 10 100 1.0 VIN = 2.7V VIN = 4.2V -1.0 0 1 Output Accuracy (%) Efficiency (%) (VOUT = 1.0V) VIN = 4.2V 70 60 PWM Only Mode VIN = 5.0V 40 30 1.0 1 10 100 VIN = 2.7V VIN = 4.2V 1000 0 1 (VOUT = 1.2V) PWM Only Mode 60 50 VIN = 5.0V 30 20 0 1 10 Output Current (mA) 6 1000 2.0 Output Accuracy (%) Efficiency (%) DC Regulation (VOUT = 1.2V) 70 40 100 Efficiency vs. Load VIN = 4.2V 80 10 Output Current (mA) VIN = 3.6V VIN = 2.7V 90 VIN = 5.0V -1.0 Output Current (mA) 100 VIN = 3.6V 0.0 -2.0 20 0 1000 2.0 VIN = 3.6V VIN = 2.7V 50 100 DC Regulation (VOUT = 1.0V) 80 10 Output Current (mA) Efficiency vs. Load 90 VIN = 5.0V -2.0 1000 Output Current (mA) 100 VIN = 3.6V 0.0 100 1000 1.0 VIN = 2.7V VIN = 3.6V 0.0 VIN = 4.2V VIN = 5.0V -1.0 -2.0 0 1 10 100 Output Current (mA) Skyworks Solutions, Inc. * Phone [781] 376-3000 * Fax [781] 376-3100 * sales@skyworksinc.com * www.skyworksinc.com 201931B * Skyworks Proprietary Information * Products and Product Information are Subject to Change Without Notice. * May 17, 2012 1000 DATA SHEET AAT1142 800mA Voltage-Scaling Step-Down Converter Typical Characteristics Efficiency vs. Load DC Regulation (VOUT = 1.8V) (VOUT = 1.8V) 2.0 100 Efficiency (%) Output Accuracy (%) VIN = 3.6V VIN = 2.7V 90 80 70 VIN = 4.2V 60 VIN = 5.0V 50 PWM Only Mode 40 30 1.6 1.2 VIN = 5.0V 0.8 VIN = 4.2V 0.4 0.0 VIN = 2.7V -0.4 -0.8 VIN = 3.6V -1.2 -1.6 -2.0 0 1 10 100 1000 0 1 Output Current (mA) 100 1000 Output Current (mA) Soft Start Line Regulation (VIN = 3.6V; VOUT = 1.8V; IOUT = 800mA) (VOUT = 1.0V) 3.5 1.00 3.0 3 0.75 2.0 2.5 1.0 2 0.0 1.5 -1.0 1 -2.0 0.5 -3.0 0 -4.0 -0.5 Output Accuracy (%) 4.0 Inductor Current (bottom) (A) Output and Enable Voltage (top) (V) 10 0.50 IOUT = 650mA 0.25 0.00 -0.25 -0.50 -1.00 2.5 Time (50s/div) IOUT = 0mA IOUT = 100mA -0.75 3.0 3.5 4.0 4.5 5.0 5.5 Output Voltage Accuracy vs. Temperature Switching Frequency vs. Temperature (VIN = 3.6V; VOUT = 1.0V; IOUT = 400mA) (VIN = 3.6V; VOUT = 1.0V; IOUT = 400mA) 2.0 4.0 1.5 2.0 1.0 Variation (%) Accuracy (%) Input Voltage (V) 0.5 0.0 -0.5 -1.0 -2.0 -4.0 -6.0 -8.0 -1.5 -2.0 -40 0.0 -30 -20 -10 0 10 20 30 40 Temperature (C) 50 60 70 80 -10.0 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 Temperature (C) Skyworks Solutions, Inc. * Phone [781] 376-3000 * Fax [781] 376-3100 * sales@skyworksinc.com * www.skyworksinc.com 201931B * Skyworks Proprietary Information * Products and Product Information are Subject to Change Without Notice. * May 17, 2012 7 DATA SHEET AAT1142 800mA Voltage-Scaling Step-Down Converter Typical Characteristics P-Channel RDS(ON) vs. Input Voltage N-Channel RDS(ON) vs. Input Voltage 450 450 125C 400 100C RDS(ON)L (m ) RDS(ON)H (m ) 400 85C 350 300 25C 250 100C 2.5 3 3.5 4 4.5 5 5.5 6 6.5 85C 300 250 25C 200 200 150 2.5 Input Voltage (V) 3 3.5 4 4.5 5 5.5 6 6.5 Input Voltage (V) Load Transient Response (400mA to 800mA; VIN = 3.6V; VOUT = 1.0V) 2.6 2.4 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 -0.2 3.0 2.8 2.6 2.4 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 -0.1 -0.2 Time (50s/div) Load and Inductor Current (bottom) (200mA/div) 1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 Output Voltage (top) (V) Load Transient Response (10mA to 400mA; VIN = 3.6V; VOUT = 1.2V) Load and Inductor Current (bottom) (200mA/div) Output Voltage (top) (V) 125C 350 Time (50s/div) No Load Quiescent Current vs. Input Voltage Line Response (VOUT = 1.8V) (VOUT = 1.2V; IOUT = 650mA) 85C 45 25C 40 -40C 35 30 25 2.5 3.0 3.5 4.0 4.5 Input Voltage (V) 5.0 5.5 6.0 Output Voltage (top) (VAC) 50 20 8 0.2 6.0 0.1 5.5 0.0 5.0 -0.1 4.5 -0.2 4.0 -0.3 3.5 -0.4 3.0 55 Time (500s/div) Skyworks Solutions, Inc. * Phone [781] 376-3000 * Fax [781] 376-3100 * sales@skyworksinc.com * www.skyworksinc.com 201931B * Skyworks Proprietary Information * Products and Product Information are Subject to Change Without Notice. * May 17, 2012 Input Voltage (bottom) (V) Supply Current (A) 60 DATA SHEET AAT1142 800mA Voltage-Scaling Step-Down Converter Typical Characteristics Output Ripple Output Ripple (VIN = 4.2V; VOUT = 0.8V; No Load) (VIN = 4.2V; VOUT = 0.8V; IOUT = 650mA) Output Voltage (top) (V) 0.80 0.06 0.04 0.75 0.70 0.02 0.65 0.00 -0.02 0.60 0.82 0.80 0.81 0.78 0.80 0.76 0.79 0.74 0.78 0.72 0.77 0.70 0.76 0.68 0.75 0.66 0.74 0.64 0.73 0.62 0.72 Time (4s/div) Output Programming Step from 1.2V to 0.9V (VIN = 3.6V; ROUT = 1.85 ) (VIN = 3.6V; ROUT = 1.85 ) 1.30 0.90 1.20 0.85 1.20 0.85 1.10 0.80 1.10 0.80 1.00 0.75 1.00 0.75 0.90 0.70 0.90 0.70 0.80 0.65 0.80 0.65 0.70 0.60 0.70 0.60 0.60 0.55 0.60 0.55 0.50 0.50 0.50 0.50 0.40 0.45 0.40 0.45 0.30 0.40 0.30 0.40 Output Voltage (top) (V) 0.90 Output Current (bottom) (A) 1.30 Output Current (bottom) (A) Output Voltage (top) (V) 0.60 Time (200ns/div) Output Programming Step from 0.9V to 1.2V Time (50s/div) Inductor Current (bottom) (A) 0.08 Inductor Current (bottom) (A) 0.85 Output Voltage (top) (V) 0.10 0.90 Time (50s/div) Skyworks Solutions, Inc. * Phone [781] 376-3000 * Fax [781] 376-3100 * sales@skyworksinc.com * www.skyworksinc.com 201931B * Skyworks Proprietary Information * Products and Product Information are Subject to Change Without Notice. * May 17, 2012 9 DATA SHEET AAT1142 800mA Voltage-Scaling Step-Down Converter Functional Block Diagram VIN FB PVIN MODE/SYNC Voltage Reference Err. Amp. DH Logic EN/SET LX DL SDA SCL Control Logic PGND AGND Functional Description The AAT1142 is a high performance, 800mA step-down converter with an input voltage range from 2.7V to 5.5V. The AAT1142 uses Dynamic Voltage Management, which allows the system host to quickly set the output voltage through the integrated I2C or S2Cwire interface. Through this interface, the host can change the output voltage to track processor idle and active states, greatly extending battery life without degrading system performance. I2C provides an industry-standard, dual-line interface, while S2Cwire provides a single-line, high-speed serial interface. The 2.2MHz switching frequency allows the use of small external components. Only three external components 10 are needed to program the output from 0.6V to 2.0V. Typically, one 4.7F capacitor, one 10F capacitor, and one 2.2H inductor are required. The integrated low-loss MOSFET switches provide up to 93% efficiency. PFM operation maintains high efficiency under light load conditions (typically <50mA). Pulling the MODE/SYNC pin high allows optional PWM Only low noise mode. This maintains constant frequency and low output ripple across all load conditions. Alternatively, the IC can be synchronized to an external clock via the MODE/SYNC input. External synchronization can be maintained between 1MHz and 3MHz. At low input voltages, the converter dynamically adjusts the operating frequency prior to dropout to maintain the required duty cycle and provide accurate output regula- Skyworks Solutions, Inc. * Phone [781] 376-3000 * Fax [781] 376-3100 * sales@skyworksinc.com * www.skyworksinc.com 201931B * Skyworks Proprietary Information * Products and Product Information are Subject to Change Without Notice. * May 17, 2012 DATA SHEET AAT1142 800mA Voltage-Scaling Step-Down Converter tion. Output regulation is maintained until the dropout voltage, or minimum input voltage, is reached. The AAT1142 achieves better than 0.5% output regulation across the input voltage and output load range. Maximum continuous load is 800mA. A current limit of 1A (typical) protects the IC and system components from short-circuit damage. Typical no load quiescent current is 35A. Thermal protection completely disables switching when the maximum junction temperature is detected. The junction over-temperature threshold is 140C with 15C of hysteresis. Once an over-temperature or over-current fault condition is removed, the output voltage automatically recovers. Peak current mode control and optimized internal compensation provide high loop bandwidth and excellent response to input voltage and fast load transient events. The output voltage is stable across all operating conditions, ensuring fast transitions with no overshoot or ringing. Soft start eliminates output voltage overshoot when the enable or the input voltage is applied. Under-voltage lockout prevents spurious start-up events. Control Loop The AAT1142 is a peak current mode step-down converter. The current through the P-channel MOSFET (high side) is sensed for current loop control, as well as shortcircuit and overload protection. A fixed slope compensation signal is added to the sensed current to maintain stability for duty cycles greater than 50%. The peak current mode loop appears as a voltage-programmed current source in parallel with the output capacitor. The output of the voltage error amplifier programs the current mode loop for the necessary peak switch current to force a constant output voltage for all load and line conditions. Internal loop compensation terminates the transconductance voltage error amplifier output. Loop stability and fast transient response are maintained across the entire input and output voltage range with a small 2.2H output inductor and 10F output capacitor. Soft Start/Enable Soft start limits the current surge seen at the input and eliminates output voltage overshoot. When pulled low, the enable input forces the AAT1142 into a low-power, non-switching state. The total input current during shutdown is less than 1A. The turn-on time from EN to output regulation is 100s (typical). Alternatively, the EN/SET pin serves as the input for S2Cwire single line control. Details of S2Cwire operation and timing diagrams are provided in the Applications Information section of this datasheet. Current Limit and Over-Temperature Protection Switching is terminated after entering current limit for a series of pulses to minimize power dissipation and stresses under overload and short-circuit conditions. Switching is terminated for seven consecutive clock cycles after a current limit has been sensed for a series of four consecutive clock cycles. Thermal protection completely disables switching when internal dissipation becomes excessive. The junction over-temperature threshold is 140C with 15C of hysteresis. Once an over-temperature or over-current fault condition is removed, the output voltage automatically recovers. Under-Voltage Lockout Internal bias of all circuits is controlled via the VIN input. Under-voltage lockout (UVLO) guarantees sufficient VIN bias and proper operation of all internal circuitry prior to activation. Skyworks Solutions, Inc. * Phone [781] 376-3000 * Fax [781] 376-3100 * sales@skyworksinc.com * www.skyworksinc.com 201931B * Skyworks Proprietary Information * Products and Product Information are Subject to Change Without Notice. * May 17, 2012 11 DATA SHEET AAT1142 800mA Voltage-Scaling Step-Down Converter Applications Information I2C START and STOP Conditions The AAT1142 output voltage may be programmed from 0.6V to 2.0V through I2C or S2Cwire serial interface. When using I2C or S2Cwire, the output voltage can be programmed across the entire output voltage range or in increments as small as 50mV (see Figure 1). START and STOP conditions are initialized by the I2C bus master. The master determines the START (beginning) and STOP (end) of a transfer with the slave device. Prior to initiating a START or after STOP, both the SDA and SCL lines are in bus-free mode. Bus-free mode is when SDA and SCL are both in the high state (see Figure 2). The AAT1142 is compatible with the I2C interface, which is a widely used two-line serial interface. The I2C twowire communications bus consists of SDA and SCL lines. SDA provides data, while SCL provides clock input. SDA data consists of an address bit sequence followed by a data bit sequence. SDA data transfer is synchronized to SCL rising clock edges. When using the I2C interface, EN/SET is pulled high to enable the output or low to disable the output. To ensure a disable event, the EN/SET pulse width must be greater than the latch time (500s maximum). The I2C serial interface requires a master to initiate all the communications with slave devices. The I2C protocol is a bidirectional bus allowing both read and write actions to take place; while the AAT1142 is a slave device and only supports the write protocol. The AAT1142 is a receiver-only (or write-only) slave device and the Read/Write (R/W) bit is set low. The AAT1142 address is preset to 0x14 (Hex). I2C Address Bit Map Figure 3 illustrates the address bit map format. The 7-bit address is sent 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 determines the direction of the transfer (`1' for read, `0' for write). The AAT1142 is a write-only device and this bit must be set low when communicating with the AAT1142. The Acknowledge bit (ACK) is set to low by the AAT1142 slave to acknowledge receipt of the address. 2.5 Output Voltage Level (V) I2C Serial Interface 2.0 1.5 1.2 (default) 1.0 0.5 0.0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 32 I C/S Cwire Register 2 2 Figure 1: AAT1142 Graphical Output Voltage Programming Map. 12 Skyworks Solutions, Inc. * Phone [781] 376-3000 * Fax [781] 376-3100 * sales@skyworksinc.com * www.skyworksinc.com 201931B * Skyworks Proprietary Information * Products and Product Information are Subject to Change Without Notice. * May 17, 2012 DATA SHEET AAT1142 800mA Voltage-Scaling Step-Down Converter STOP START SDA SDA SCL SCL Figure 2: I2C Start and Stop 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 A5 A4 A3 A2 A1 A0 MSB SDA A6 8 9 LSB R/W ACK Slave Address Figure 3: I2C Address Bit Map; 7-bit Slave Address (A6-A0), 1-bit Read/Write (R/W), 1-bit Acknowledge (ACK). Skyworks Solutions, Inc. * Phone [781] 376-3000 * Fax [781] 376-3100 * sales@skyworksinc.com * www.skyworksinc.com 201931B * Skyworks Proprietary Information * Products and Product Information are Subject to Change Without Notice. * May 17, 2012 13 DATA SHEET AAT1142 800mA Voltage-Scaling Step-Down Converter I2C Data Bit Map I2C Software Protocol Figure 4 illustrates the data bit format. The 8-bit data is always sent with the most significant bit first and is valid when SCL is high. The ACK bit is set low by the AAT1142 slave device to acknowledge receipt of the data. An I2C master / slave data transfer, detailing the address and data bits, is shown in Figure 5. The programming sequence is as follows: 1. 2. 3. 4. 5. 6. I2C Acknowledge Bit The ACK bit is the ninth bit in the address and data byte. The master must first release the SDA line, and then the slave will pull the SDA line low. The AAT1142 sends a low bit to acknowledge receipt of each byte. This occurs during the ninth clock cycle of Address and Data transfers (see Figures 4 and 5). SCL 1 Send a start condition Send the I2C slave address with the R/W bit set low Wait for acknowledge within the clock cycle Send the data bits Wait for acknowledge within the clock cycle Send the stop condition I2C Output Voltage Programming The AAT1142 output voltage is programmed through the I2C interface according to Table 1. The data register encoded on the SCL and SDA lines determines the output voltage set-point after initial start-up. Upon powerup and prior to I2C programming, the default output voltage is set to 1.8V. 2 3 4 5 6 7 D6 D5 D4 D3 D2 D1 8 MSB SDA 9 LSB D7 D0 ACK Data Figure 4: I2C Data Bit Map; 8-bit Data (D7-D0), 1-bit Acknowledge (ACK). SCL 1 2 3 0 0 1 4 5 6 7 0 0 Slave Address Start 0 1 8 9 R/W ACK 0 0/1 1 2 3 4 0/1 0/1 0/1 0/1 5 6 7 8 0/1 0/1 0/1 0/1 Data 9 ACK Stop 0/1 7-bit address (0x14) Figure 5: I2C SCL, SDA Transfer Protocol Example; 7-bit Slave Address (A6-A0 = 0x14), 1-bit Read/Write (R/W = 0), 1-bit Acknowledge (ACK), 8-bit Data (D7-D0), 1-bit Acknowledge (ACK). 14 Skyworks Solutions, Inc. * Phone [781] 376-3000 * Fax [781] 376-3100 * sales@skyworksinc.com * www.skyworksinc.com 201931B * Skyworks Proprietary Information * Products and Product Information are Subject to Change Without Notice. * May 17, 2012 DATA SHEET AAT1142 800mA Voltage-Scaling Step-Down Converter Data Bits Data Register D7 D6 D5 D4 D3 D2 D1 D0 Output Voltage (V) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X 0 X X X X X X X X X X X X X X X X X X X X X X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 (default) 1.25 1.30 1.35 1.40 1.45 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 1.95 2.00 2.00 2.00 2.00 Table 1: AAT1142 I2C Output Voltage Programming Map (X = don't care). S2Cwire Serial Interface S2Cwire Serial Interface Timing Skyworks' S2Cwire serial interface is a proprietary highspeed single-wire interface. The S2Cwire interface records rising edges of the EN/SET input and decodes them into one of 32 registers which determines the output voltage, as shown in Table 2. Each state corresponds to an output voltage setting. The S2Cwire serial interface has flexible timing. Data can be clocked-in at speeds up to 1MHz. After data has been submitted, EN/SET is held high to latch the data for a period TLAT. The output is subsequently changed to the predetermined voltage. When EN/SET is set low for a time greater than TOFF, the AAT1142 is disabled. When disabled, the data register is reset to the default value. When using the S2Cwire interface, both I2C inputs should be tied to the ground return. This disables the I2C functionality. Skyworks Solutions, Inc. * Phone [781] 376-3000 * Fax [781] 376-3100 * sales@skyworksinc.com * www.skyworksinc.com 201931B * Skyworks Proprietary Information * Products and Product Information are Subject to Change Without Notice. * May 17, 2012 15 DATA SHEET AAT1142 800mA Voltage-Scaling Step-Down Converter S2Cwire Timing Diagram THI TLO TOFF T LAT EN/SET 1 2 n-1 n 64 0 Data Reg Rising Clock Edges/Data Register Output Voltage (V) Rising Clock Edges/Data Register Output Voltage (V) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 No change 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 (default) 1.25 1.30 1.35 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 1.40 1.45 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 1.95 2.00 2.00 2.00 2.00 Table 2: AAT1142 S2Cwire Output Voltage Programming Map. n 0 Manufacturer's specifications list both the inductor DC current rating, which is a thermal limitation, and the peak current rating, which is determined by the saturation characteristics. The inductor should not show any appreciable saturation under normal load conditions. Some inductors may meet the peak and average current ratings yet result in excessive losses due to a high DCR. Always consider the losses associated with the DCR and its effect on the total converter efficiency when selecting an inductor. The 2.2H CDRH2D14 series Sumida inductor has a 94m DCR and a 1.5A DC current rating. At full 800mA load, the inductor DC loss is 60mW which gives a 4.8% loss in efficiency for an 800mA, 1.0V output. Input Capacitor Select a 4.7F to 10F X7R or X5R ceramic capacitor for the input. To estimate the required input capacitor size, determine the acceptable input ripple level (VPP) and solve for C. The calculated value varies with input voltage and is a maximum when VIN is double the output voltage. Component Selection Inductor Selection The step-down converter uses peak current mode control with slope compensation to maintain stability for duty cycles greater than 50%. The output inductor value must be selected so the inductor current down slope meets the internal slope compensation requirements. The internal slope compensation for the programmable AAT1142 is 0.61A/s. This equates to a slope compensation that is 75% of the inductor current down slope for a 1.8V output and 2.2H inductor. 0.75 * VO 0.75 * 1.8V A m= = = 0.61 L 2.2H s 16 CIN = V VO * 1- O VIN VIN VPP - ESR * FS IO VO V 1 * 1 - O = for VIN = 2 * VO VIN VIN 4 CIN(MIN) = 1 VPP - ESR * 4 * FS IO Always examine the ceramic capacitor DC voltage coefficient characteristics when selecting the proper value. For example, the capacitance of a 10F, 6.3V, X5R ceramic Skyworks Solutions, Inc. * Phone [781] 376-3000 * Fax [781] 376-3100 * sales@skyworksinc.com * www.skyworksinc.com 201931B * Skyworks Proprietary Information * Products and Product Information are Subject to Change Without Notice. * May 17, 2012 DATA SHEET AAT1142 800mA Voltage-Scaling Step-Down Converter capacitor with 5.0V DC applied is actually about 6F. Output Capacitor The maximum input capacitor RMS current is: The output capacitor limits the output ripple and provides holdup during large load transitions. A 4.7F to 10F X5R or X7R ceramic capacitor typically provides sufficient bulk capacitance to stabilize the output during large load transitions and has the ESR and ESL characteristics necessary for low output ripple. A smaller capacitor may result in slightly increased no load output regulation and output ripple with input voltages above 5V. This should be verified under actual operating conditions. IRMS = IO * VO V * 1- O VIN VIN The input capacitor RMS ripple current varies with the input and output voltage and will always be less than or equal to half of the total DC load current. VO V * 1- O = VIN VIN D * (1 - D) = 0.52 = 1 2 for VIN = 2 * VO IRMS(MAX) = V IO 2 V The term VINO * 1 - VINO appears in both the input voltage ripple and input capacitor RMS current equations and is a maximum when VO is twice VIN. This is why the input voltage ripple and the input capacitor RMS current ripple are a maximum at 50% duty cycle. The input capacitor provides a low impedance loop for the edges of pulsed current drawn by the AAT1142. Low ESR/ESL X7R and X5R ceramic capacitors are ideal for this function. To minimize stray inductance, the capacitor should be placed as closely as possible to the IC. This keeps the high frequency content of the input current localized, minimizing EMI and input voltage ripple. A laboratory test set-up typically consists of two long wires running from the bench power supply to the evaluation board input voltage pins. The inductance of these wires, along with the low-ESR ceramic input capacitor, can create a high Q network that may affect converter performance. This problem often becomes apparent in the form of excessive ringing in the output voltage during load transients. Errors in the loop phase and gain measurements can also result. Since the inductance of a short PCB trace feeding the input voltage is significantly lower than the power leads from the bench power supply, most applications do not exhibit this problem. In applications where the input power source lead inductance cannot be reduced to a level that does not affect the converter performance, a high ESR tantalum or aluminum electrolytic capacitor should be placed in parallel with the low ESR, ESL bypass ceramic capacitor. This dampens the high Q network and stabilizes the system. The output voltage droop due to a load transient is dominated by the capacitance of the ceramic output capacitor. During a step increase in load current, the ceramic output capacitor alone supplies the load current until the loop responds. Within two or three switching cycles, the loop responds and the inductor current increases to match the load current demand. The relationship of the output voltage droop during the three switching cycles to the output capacitance can be estimated by: COUT = 3 * ILOAD VDROOP * FS Once the average inductor current increases to the DC load level, the output voltage recovers. The above equation establishes a limit on the minimum value for the output capacitor with respect to load transients. The internal voltage loop compensation also limits the minimum output capacitor value to 4.7F. This is due to its effect on the loop crossover frequency (bandwidth), phase margin, and gain margin. Increased output capacitance will reduce the crossover frequency with greater phase margin. Thermal Calculations There are three types of losses associated with the AAT1142 step-down converter: switching losses, conduction losses, and quiescent current losses. Conduction losses are associated with the RDS(ON) characteristics of the power output switching devices. Switching losses are dominated by the gate charge of the power output switching devices. At full load, assuming continuous conduction mode (CCM), a simplified form of the losses is given by: PTOTAL = IO2 * (RDS(ON)H * VO + RDS(ON)L * [VIN - VO]) VIN + (tsw * FS * IO + IQ) * VIN Skyworks Solutions, Inc. * Phone [781] 376-3000 * Fax [781] 376-3100 * sales@skyworksinc.com * www.skyworksinc.com 201931B * Skyworks Proprietary Information * Products and Product Information are Subject to Change Without Notice. * May 17, 2012 17 DATA SHEET AAT1142 800mA Voltage-Scaling Step-Down Converter IQ is the step-down converter quiescent current. The term tsw is used to estimate the full load step-down converter switching losses. For the condition where the step-down converter is in dropout at 100% duty cycle, the total device dissipation reduces to: Layout The suggested PCB layout for the AAT1142 is used to help ensure a proper layout. 1. 2. PTOTAL = IO2 * RDS(ON)H + IQ * VIN Since RDS(ON), quiescent current, and switching losses all vary with input voltage, the total losses should be investigated over the complete input voltage range. Given the total losses, the maximum junction temperature can be derived from the JA for the TDFN33-12 package which is 50C/W. 3. 4. TJ(MAX) = PTOTAL * JA + TAMB 5. 6. The input capacitor should connect as closely as possible to VIN and PGND. C1 and L1 should be connected as closely as possible. The connection of L1 to the LX pin should be as short as possible. The feedback pin should be separate from any power trace and connected close to the VOUT terminal. Sensing along a high-current load trace will degrade VOUT load regulation. The resistance of the trace from the GND terminal to PGND should be kept to a minimum. This will help to minimize any error in DC regulation due to differences in the potential of the internal signal ground and the power ground. Connect unused signal pins to ground to avoid unwanted noise coupling. When using S2Cwire, connect SDA and SCL to ground to disable I2C functionality. Connect the exposed paddle (EP) to the GND plane. Manufacturer Part Number Inductance (H) Max DC Current (A) DCR () Size (mm) LxWxH Type Sumida Sumida Taiyo Yuden Taiyo Yuden CDRH3D16-2R2 CDRH2D14-2R2 NR3010T2R2M CBC3225T2R2MR 2.2 2.2 2.2 2.2 1.20 1.50 1.10 1.13 0.072 0.094 0.095 0.080 3.8x3.8x1.8 3.2x3.2x1.55 3.0x3.0x1.0 3.2x2.5x2.5 Shielded Shielded Shielded Non-Shielded Table 3: Typical Surface Mount Inductors. Manufacturer Part Number Type Value Voltage Temp. Co. Case Murata Murata Murata Murata GRM188R60J106ME47D GRM21BR60J106KE19L GRM188R60J475KE19D GRM21BR61A475KA73L Ceramic Ceramic Ceramic Ceramic 10 10 4.7 4.7 6.3 10 6.3 10 X5R X5R X5R X5R 0603 0805 0603 0805 Table 4: Surface Mount Capacitors. 18 Skyworks Solutions, Inc. * Phone [781] 376-3000 * Fax [781] 376-3100 * sales@skyworksinc.com * www.skyworksinc.com 201931B * Skyworks Proprietary Information * Products and Product Information are Subject to Change Without Notice. * May 17, 2012 DATA SHEET AAT1142 800mA Voltage-Scaling Step-Down Converter Ordering Information Package Marking Part Number (Tape and Reel) TDFN33-12 AAT1142-1.2 Skyworks GreenTM products are compliant with all applicable legislation and are halogen-free. For additional information, refer to Skyworks Definition of GreenTM, document number SQ04-0074. Package Information TDFN33-121 Index Area 0.40 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. 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 * sales@skyworksinc.com * www.skyworksinc.com 201931B * Skyworks Proprietary Information * Products and Product Information are Subject to Change Without Notice. * May 17, 2012 19 DATA SHEET AAT1142 800mA Voltage-Scaling Step-Down Converter Copyright (c) 2012 Skyworks Solutions, Inc. All Rights Reserved. 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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 * sales@skyworksinc.com * www.skyworksinc.com 201931B * Skyworks Proprietary Information * Products and Product Information are Subject to Change Without Notice. * May 17, 2012