AAT1217 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter General Description The AAT1217 a high efficiency, synchronous, fixed frequency, step-up converter designed for singlecell or dual-cell alkaline, NiMH, or NiCd batterypowered applications. The high 1.2MHz switching frequency and completely integrated control circuitry minimize the total solution footprint area while maintaining excellent regulation, ripple, and transient response throughout the full load range. Pulse skipping mode operation and low quiescent current allow the AAT1217 to maintain high efficiency performance for light load and sleep mode conditions. With a 1.2A peak switch current limit, the AAT1217 is capable of delivering 100mA to the load from a single AA cell or up to 400mA from dual AA cells. The AAT1217 has a 0.85V start-up voltage with operation down to 0.5V. The AAT1217 is available in a Pb-free, space-saving low profile (1mm) 6-pin TSOT23 package and is rated over the -40°C to +85°C ambient temperature range. SwitchReg™ Features • • • • • • • • • • • • • • • • • VIN Operation Range: 0.5V to VOUT VOUT Range: 2.5V to 5.5V 100mA Output from a Single AA Cell Input 400mA Output from a Dual AA Cell Input High Efficiency: Up to 93% Efficiency Low Start-Up Voltage: 0.85V Typical Internal Synchronous Rectifier — VOUT ≤ 4.5V: No External Schottky Diode Fixed Frequency Pulse Width Modulation (PWM) Current-Mode Control Scheme with Internal Compensation 1.2MHz Fixed Switching Frequency 1.2A Current Limit Light Load Pulse Skipping Mode Operation Low 80µA No Load Input Current Over-Current Protection EMI Reduction Anti-Ringing Control Circuitry Low Shutdown Current: <1.0µA -40°C to +85°C Ambient Temperature Range Low Profile (1mm) TSOT23-6 Package Applications • • • • • • Cellular and Smart Phones Digital Still and Video Cameras Microprocessors and DSP Core Supplies MP3 Player Portable Instruments Wireless and DSL Modems Typical Application L1 4.7µH L1 4.7µH VIN: 0.85V C IN 4.7µF R3 1MΩ 1217.2007.07.1.0 VIN SW VOUT AAT1217-1.2 SHDN GND FB VOUT: 3.3V,100 mA R1 1.02MΩ R2 604kΩ C OUT 4.7µF VIN: 0.85V C IN 4.7µF R3 1MΩ VIN SW VOUT AAT1217-3.3 SHDN GND FB VOUT: 3.3V,100 mA C OUT 4.7µF 1 AAT1217 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter Pin Descriptions Pin # Symbol 2 3 GND FB 4 SHDN 5 6 VOUT VIN 1 SW Function Power Switch Pin. Ties to the drains of the PMOS synchronous rectifier and the NMOS switch. Ground Pin Feedback Input Pin. Connect FB to the center point of the external resistor divider. The feedback threshold voltage is 1.23V. Shutdown Signal Input. Logic high enables the IC. Logic low disables the IC. Shutdown current is <1µA. Power Output Pin. Tied to the source of the PMOS synchronous rectifier. Power Supply Input. Must be closely decoupled to GND, Pin 2, with a 4.7µF or greater ceramic capacitor. Pin Configuration TSOT23-6 (Top View) SW GND FB 2 1 6 2 5 3 4 VIN VOUT SHDN 1217.2007.07.1.0 AAT1217 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter Absolute Maximum Ratings1 Symbol VIN VSW VFB, VSHDN VOUT TA TSTORAGE TLEAD TJ Description Input Supply Voltage SW Voltage FB, SHDN Voltages VOUT Voltage Operating Ambient Temperature Range2 Storage Temperature Range Lead Temperature (Soldering, 10s) Operating Junction Temperature Range2 Thermal Information3 Symbol θJA PD Description Maximum Thermal Resistance Maximum Power Dissipation Value Units Value Units -0.3 to 6 -0.3 to 6 -0.3 to 6 -0.3 to 6 -40 to 85 -65 to 150 300 -40 to 150 190 526 V V V V °C °C °C °C °C/W mW 1. Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. 2. TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formula: TJ = TA + PD x θJA. 3. Mounted on an FR4 board. 1217.2007.07.1.0 3 AAT1217 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter Electrical Characteristics1 VIN = 1.2V, VOUT = 3.3V, TA = 25°C, unless otherwise noted. Symbol VIN VOUT VFB Description Minimum Start-Up Voltage Minimum Operating Voltage Output Voltage Range Output Voltage Accuracy3 Reference Voltage ∆VOUT/VOUT/ ∆VIN Reference Voltage Line Regulation ∆VOUT/VOUT/ ∆IOUT Reference Voltage Load Regulation IQ ILNMOS ILPMOS RDS(ON)L RDS(ON)H ICL ∆t(ICL) DMAX FOSC VSHDN ISHDN TSD Quiescent Current (Shutdown) Quiescent Current (Active) Quiescent Current (Active) NMOS Switch Leakage PMOS Switch Leakage NMOS Switch ON Resistance PMOS Switch ON Resistance NMOS Current Limit Current Limit Delay to Output Maximum Duty Cycle Switching Frequency SHDN Input Low SHDN Input High SHDN Input Current Thermal Shutdown Conditions IOUT = 1mA VSHDN = VIN IOUT = 10mA; TA = -40°C to +85°C TA = -40°C to +85°C VIN = 1.2V to 2.4V, IOUT = 10mA, VOUT = 3.3V VIN = 2.4V to 4.2V, IOUT = 10mA, VOUT = 5.0V VIN = 1.2V, IOUT = 10mA to 100mA VOUT = 3.3V VIN = 3.6V, IOUT = 10mA to 400mA VOUT = 5.0V VSHDN = 0 VIN = 1.8V, Current from input voltage source. VSHDN = VIN Measured on VOUT, VSHDN = VIN VSW = 5V VSW = 0V VOUT = 3.3V VOUT = 5V VOUT = 3.3V VOUT = 5V VFB = 1.15V, TA = -40°C to +85°C TA = -40°C to +85°C VSHDN = 5.5V Hysteresis Min 2.5 -4 1.192 Typ 0.85 0.5 1.230 0.2 Max 1 0.65 5.5 +4 1.268 0.003 750 80 0.9 1.00 1 300 0.1 0.1 0.35 0.30 0.60 0.55 1200 40 85 1.2 500 5 5 0.01 160 20 V % V %/mA 0.01 115 V %/V 0.4 0.004 Units µA µA µA Ω Ω 1.5 0.35 1 mA ns % MHz V µA °C 1. Specifications over the temperature range are guaranteed by design, characterization, and correlation with statistical process controls. 2. Not including the current into internal resistance divider. 3. For fixed 3.3V and 5.0V output voltage version. The adjustable output voltage is guaranteed by reference voltage accuracy. 4 1217.2007.07.1.0 AAT1217 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter Typical Characteristics Efficiency vs. Output Current Efficiency vs. Output Current (VOUT = 3.3V; TA = 25°°C) (VOUT = 5V; TA = 25° °C) 100 100 90 VIN = 3.6V 80 Efficiency (%) Efficiency (%) VIN = 2.4V 90 VIN = 2.4V 80 70 VIN = 1.5V 60 50 VIN = 1.2V 40 30 70 40 30 20 10 10 1 10 100 VIN = 1.5V 50 20 0 0.1 VIN = 1.2V 60 0 0.1 1000 1 Output Current (mA) 1000 Output Voltage vs. Output Current (VOUT = 3.3V; TA = 25°°C) (VOUT = 5V; TA = 25°°C) 3.5 5.2 Output Voltage (V) Output Voltage (V) 100 Output Current (mA) Output Voltage vs. Output Current 3.4 VIN = 2.4V VIN = 1.5V VIN = 1.2V 3.3 3.2 5.1 VIN = 1.2V VIN = 2.4V VIN = 1.5V 5 VIN = 3.6V 4.9 4.8 3.1 0 100 200 300 400 500 0 600 100 Output Current (mA) 200 300 400 500 600 Output Current (mA) Minimum Start-Up Voltage vs. Output Current Maximum Output Current vs. Input Voltage (VOUT = 3.3V; TA = 25° °C) (L = 4.7µH; TA = 25°°C) 1000 1.5 1.35 Maximum Output Current (mA) Start-Up Voltage (V) 10 1.2 1.05 0.9 0.75 0.6 0 20 40 60 80 100 120 140 Output Current (mA) 1217.2007.07.1.0 160 180 200 800 VOUT = 3.3V 600 VOUT = 5V 400 200 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Input Voltage (V) 5 AAT1217 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter Typical Characteristics No Load Input Current vs. Input Voltage Output Voltage vs. Temperature 150 3.35 140 3.34 Output Voltage (V) Input Current (µA) (VOUT = 3.3V; TA = 25°°C; No Load) 130 120 110 100 90 80 70 3.33 3.32 3.31 3.3 3.29 3.28 3.27 60 3.26 50 1.5 3.25 -50 1.8 2.1 2.4 2.7 3 -25 0 25 50 75 Temperature (°°C) Input Voltage (V) Pulse Skipping Mode Operation Anti-Ringing Operation at SW (VIN = 1.8V; VOUT = 3.3V; IOUT = 5mA) (VIN = 2.4V; VOUT = 5V; IOUT = 20mA) VSW 2V/div 100 VSW 2V/div 0V 0V VOUT 50mV/div (AC) Time (1ms/div) Time (400ns/div) Load Transient Response (VIN = 1.5V; VOUT = 3.3V; CFF = 100pF) IOUT 50mA/div 100mA 40mA 0A VOUT 100mV/div (AC) Time (100µs/div) 6 1217.2007.07.1.0 AAT1217 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter Functional Block Diagram VIN VIN L1 + – SW Slope Compensation MUX VOUT GOOD 2.3V – VOUT Current Sense CIN FB Antiringing Control To VIN Bandgap 1.23V + – + EA SHDN – Comp Shutdown Control Functional Description The AAT1217 is a synchronous step-up DC-DC converter. It utilizes internal MOSFET switches to achieve high efficiency over the full load current range. It operates at a fixed switching frequency of 1.2MHz, and uses the slope compensated current mode pulse width modulation (PWM) architecture. The device can operate with an input voltage below 1V; the typical start-up voltage is 0.85V. Synchronous Rectification The AAT1217 integrates a synchronous rectifier to improve efficiency as well as to eliminate the need for an external Schottky diode. The synchronous rectifier is used to reduce the conduction loss contributed by the forward voltage of an external Schottky diode. The synchronous rectifier is realized by a P-channel MOSFET (PMOS) with gate 1217.2007.07.1.0 + Start-Up Oscillator COUT VOUT R1 R2 PWM Logic GND Oscillator 1.2MHz control circuitry that incorporates relatively complicated timing concerns. An external Schottky diode is required when the output voltage is greater than 4.5V. Low Voltage Start-Up The AAT1217 can start-up with supply voltages down to 0.85V. During start-up, the internal low voltage start-up circuitry controls the internal NMOS switch. The AAT1217 leaves the start-up mode once VOUT exceeds 2.3V. An internal comparator (VOUT GOOD) monitors the output voltage and places the chip into normal operation once VOUT exceeds 2.3V. The AAT1217’s control circuitry is biased by VIN during start-up and biased by VOUT once VOUT exceeds VIN. When VOUT exceeds VIN, the AAT1217’s operation will be independent of VIN. 7 AAT1217 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter Current Mode Operation The AAT1217 is based on a slope compensated current mode PWM control topology. It operates at a fixed frequency of 1.2MHz. At the beginning of each clock cycle, the main switch (NMOS) is turned on and the inductor current starts to ramp. After the maximum duty cycle or the sense current signal equals the error amplifier (EA) output, the main switch is turned off and the synchronous switch (PMOS) is turned on. This control topology features cycle-by-cycle current limiting which can prevent the main switch from overstress and the external inductor from saturating. Pulse Skipping Mode Operation At very light load, the AAT1217 automatically switches into pulse skipping mode operation to improve efficiency. During this mode, the PWM control will skip some pulses to maintain regulation. If the load increases and the output voltage drops, the device will automatically switch back to normal PWM mode and maintain regulation. Anti-Ringing Control An anti-ringing circuitry is included to remove the high frequency ringing that appears on the SW pin when the inductor current goes to zero. In this case, a ringing on the SW pin is induced due to remaining energy stored in parasitic components of switch and inductor. The anti-ringing circuitry clamps the voltage internally to the battery voltage and therefore dampens this ringing. Device Shutdown When SHDN is set logic high, the AAT1217 is put into active mode operation. If SHDN is set logic low, the device is put into shutdown mode and consumes less than 1µA of current. After start-up, the internal circuitry is supplied by VOUT, however, if shutdown mode is enabled, the internal circuitry will be supplied by the input source again. 8 Application Information Adjustable Output Voltage An external resistor divider is used to set the output voltage. The output voltage of the switching regulator (VOUT) is determined by the following equation: R1 VOUT = 1.23V · 1 + R2 Table 1 lists the recommended resistor values for particular output voltage settings. VOUT 3.3V 5.0V Ω) R1(Ω 1.02M 1.02M Ω) R2(Ω 604k 332k Table 1: Resistor Selection for Output Voltage Setting. Fixed Output Voltage AAT1217 has two fixed output voltage options: 3.3V and 5V. An internal resistor divider is connected to the FB pin inside the package which eliminates the need for external feedback resistors. When designing with the fixed output voltage option, remember to leave the FB pin open; otherwise the output voltage will be affected. However, a feed-forward capacitor can still be added between the FB and VOUT pins to enhance the control loop performance. Inductor Selection The high switching frequency of 1.2MHz allows for small surface mount inductors. For most applications, the AAT1217 operates with inductors from 2.2µH to 10µH. Use the following equations to select the proper inductor value for a particular application condition: 1217.2007.07.1.0 AAT1217 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter ∆IL IPEAK = IDC + 2 IDC = IPEAK = IOUT · VOUT η · VIN ∆IL = VIN · D VOUT - VIN ; D= L · FSW VOUT ∆IL = VIN · (VOUT - VIN) L · FSW · VOUT VIN · (VOUT - VIN) IOUT · VOUT η · VIN + 2L · FSW · VOUT IPEAK Peak Inductor Current IDC DC Component (Average) of the Inductor Current ∆IL Peak-Peak Inductor Ripple Current IOUT Output (Load) Current VOUT Output Voltage VIN Input Voltage η AAT1217 Efficiency (consult the performance graphs in the “Typical Characteristics” section of the data sheet) D Steady-State Duty Cycle FSW Switching Frequency L Inductor Value For a given chosen inductor value and application conditions make sure the peak inductor current does not exceed the maximum current rating of the selected vendor’s inductor. For optimum load transient and efficiency, low DCR inductors should be selected. Table 2 lists some typical surface mount inductors that are suitable for typical AAT1217 applications. 1217.2007.07.1.0 Input Capacitor A surface mount 4.7µF or greater, X5R or X7R, ceramic capacitor is suggested for the input capacitor. The input capacitor provides a low impedance loop for the edges of pulsed current drawn by the AAT1217. Low ESR/ESL X7R and X5R ceramic capacitors are ideal for this function. To minimize stray inductance, the capacitor should be placed as close as possible to the IC. This keeps the high frequency content of the input current localized, minimizing EMI and input voltage ripple. Always examine the ceramic capacitor DC voltage coefficient characteristics to get the proper value. For example, the capacitance of a 10µF, 6.3V, X5R ceramic capacitor with 5.0V DC applied is actually about 6µF. 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 which can produce errors in loop phase and gain measurements. Since the inductance of a short printed circuit board (PCB) trace feeding the input voltage is significantly lower than the power leads from the bench power supply, most actual 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 input ceramic capacitor. The introduction of the high ESR capacitor dampens the high Q network and stabilizes the AAT1217. 9 AAT1217 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter Part Number Sumida CDH28D11/S Coiltronics SD3112 TDK VLF3012A Sumida CR43 Sumida CDRH4D28 Toko D53LC L (µH) 2.2 4.7 10 2.2 4.7 10 2.2 4.7 10 2.2 4.7 10 2.2 4.7 10 4.7 10 Output Capacitor Ω) Max DCR (mΩ 123 238 431 140 (typ) 246 (typ) 446 (typ) 100 190 410 71.2 108.7 182 31.3 72 128 45 90 In addition, the output voltage droop during 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 several switching cycles, the loop responds and the inductor current increases to match the load current demand. Larger output capacitor values help to reduce the voltage droop during large load current transients. An external Schottky diode is required when the output voltage is above 4.5V. The Schottky diode is optional for output voltages ≤ 4.5V, but can improve efficiency by about 2% to 3%. 10 1.15 0.75 0.53 1.12 0.8 0.55 1 0.74 0.49 1.75 1.15 1.04 2.04 1.32 1 1.87 1.33 Size WxLxH (mm) 3x3.3x1.2 3.1x3.1x1.2 2.8x2.6x1.2 4.3x4.8x3.5 5.0x5.0x3.0 5.0x5.0x3.0 Table 2. Typical Surface Mount Inductors. The output capacitor limits the output ripple and provides holdup during large load transitions. A 4.7µF to 10µF, X5R or X7R, ceramic capacitor is suggested for the output capacitor. Typically the recommended capacitor range provides sufficient bulk capacitance to stabilize the output voltage during large load transitions and has the ESR and ESL characteristics necessary for low output voltage ripple. External Diode Selection Rated DC Current (A) Load Disconnect in Shutdown In conventional synchronous step-up converters, a conduction path exists from input to output through the backgate (body diode) of the P-channel MOSFET during shutdown. Special application circuitry can disconnect the load from the battery during shutdown (see Figure 1). PCB Layout Guidance The AAT1217 typically operates at 1.2MHz. This is a considerably high frequency for DC-DC converters. PCB layout is important to guarantee satisfactory performance. It is recommended to make traces of the power loop, especially where the switching node is involved, as short and wide as possible. First of all, the inductor, input and output capacitor should be as close as possible to the device. Feedback and shutdown circuits should avoid the proximity of large AC signals involving the power inductor and switching node. The optional rectifier diode (D1 in Figure 1) can improve efficiency and alleviate the stress on the integrated MOSFETs. The diode should also be close to the inductor and the chip to form the shortest possible switching loop. While the two-layer PCB shown in Figures 2 and 3 is enough for most applications, large and integral multi-layer ground planes 1217.2007.07.1.0 AAT1217 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter Figure 1 is the schematic for a highly efficient load disconnect application circuit for the AAT1217. An example PCB layout for the AAT1217 is shown in Figures 2 and 3. are ideal for high power applications. Large areas of copper have lower resistance and help to dissipate heat. The converter's ground should join the system ground to which it supplies power at one point only. D1 MBR0520 L1 4.7µH 1 VIN 0.85V CIN 4.7µF 6 4 VIN SW AAT1217 SHDN VOUT FB GND 5 3 VOUT 3.3V,100mA Q1 Si2305 DS R4 510kΩ R1 1.02MΩ R2 604kΩ 2 ON/OFF Control R3 510kΩ COUT 4.7µF Q2 2N3904 Figure 1. AAT1217 High Efficiency Load Disconnect Application Circuit Figure 2. AAT1217 Evaluation Board Layout Example Top Layer 1217.2007.07.1.0 Figure 3. AAT1217 Evaluation Board Layout Example Bottom Layer 11 AAT1217 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter Ordering Information Output Voltage1 Package Adj. Fixed 3.3V Fixed 5.0V Marking2 TSOT23-6 TSOT23-6 TSOT23-6 Part Number (Tape and Reel)3 AAT1217ICA-1.2-T1 AAT1217ICA-3.3-T1 AAT1217ICA-5.0-T1 VZMYY WAMYY WBMYY All AnalogicTech products are offered in Pb-free packaging. The term “Pb-free” means semiconductor products that are in compliance with current RoHS standards, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. For more information, please visit our website at http://www.analogictech.com/pbfree. Package Information TSOT23-6 Part Dimensions 0.40 ± 0.10 0.95 BSC 0.127 BSC 1.60 BSC 2.80 BSC Detail "A" End View Top View 1.00 ± 0.10 0.25 BSC 2.90 BSC +10° -0° 0.45 ± 0.15 0.000 All dimensions in millimeters. 1.00 + 0.100 - 0.000 Side View Detail "A" 1. Please contact sales for other voltage options. 2. YY = Manufacturing Date Code. 3. Sample stock is generally held on part numbers listed in BOLD. 12 1217.2007.07.1.0 AAT1217 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter © Advanced Analogic Technologies, Inc. AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights, or other intellectual property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice. Except as provided in AnalogicTech’s terms and conditions of sale, AnalogicTech assumes no liability whatsoever, and AnalogicTech disclaims any express or implied warranty relating to the sale and/or use of AnalogicTech products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. In order to minimize risks associated with the customer’s applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed. AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated. All other brand and product names appearing in this document are registered trademarks or trademarks of their respective holders. Advanced Analogic Technologies, Inc. 830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737- 4600 Fax (408) 737- 4611 1217.2007.07.1.0 13