PRODUCT DATASHEET AAT1217 SwitchRegTM 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter General Description Features The AAT1217 is a high efficiency, synchronous, fixed frequency, step-up converter designed for single-cell or dual-cell alkaline, NiMH, or NiCd battery-powered 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. • • • • • • • • Light load mode operation and low quiescent current allow the AAT1217 to maintain high efficiency performance for light load conditions. With a 1.2A peak inductor current limit, the AAT1217 is capable of delivering 100mA to the load from a single AA cell, 400mA from dual AA cells, or up to 500mA from a single-cell lithiumion battery. 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 or 6-pin SOT23 package and is rated over the -40°C to +85°C ambient temperature range. • • • • • • • • • 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 500mA Output from a Single Li+ 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) CurrentMode Control Scheme with Internal Compensation 1.2MHz Fixed Switching Frequency 1.2A Current Limit Light Load Mode Operation 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 or SOT23-6 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 SW VIN 0.85V VIN C IN 4.7μF R3 1MΩ SW VIN 0.85V VOUT AAT1217-1.2 VIN R1 1.02M FB SHDN GND 1217.2008.03.1.3 VOUT 3.3V,100 mA C OUT 4.7μF C IN 4.7μF R2 604k www.analogictech.com R3 1MΩ VOUT 3.3V, 100 mA VOUT AAT1217-3.3 C OUT 4.7μF FB SHDN GND 1 PRODUCT DATASHEET AAT1217 SwitchRegTM 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter Pin Descriptions Pin # Symbol 1 2 SW GND 3 FB 4 5 6 SHDN VOUT VIN 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/SOT23-6 (Top View) 2 SW 1 6 VIN GND 2 5 VOUT FB 3 4 SHDN www.analogictech.com 1217.2008.03.1.3 PRODUCT DATASHEET AAT1217 SwitchRegTM 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter Absolute Maximum Ratings1 Symbol Description VIN VSW VFB, VSHDN VOUT TA TSTORAGE TLEAD TJ 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 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 V V V V °C °C °C °C Thermal Information3 Symbol Description θJA Maximum Thermal Resistance PD Maximum Power Dissipation Value TSOT23-6 SOT23-6 TSOT23-6 SOT23-6 190 150 526 667 Units °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. 1217.2008.03.1.3 www.analogictech.com 3 PRODUCT DATASHEET AAT1217 SwitchRegTM 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 Conditions Minimum Start-Up Voltage Minimum Operating Voltage Output Voltage Range IOUT = 1mA VSHDN = VIN Output Voltage Accuracy3 Reference Voltage ΔVOUT/ VOUT/ΔVIN Reference Voltage Line Regulation ΔVOUT/ VOUT/ΔIOUT Reference Voltage Load Regulation IQ ILNMOS ILPMOS RDS(ON)L RDS(ON)H ICL Δt(ICL) Quiescent Current (Shutdown) Quiescent Current (Active) NMOS Switch Leakage PMOS Switch Leakage NMOS Switch ON Resistance PMOS Switch ON Resistance 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 Measured on VOUT, VSHDN = VIN VSW = 5V VSW = 0V VOUT = 3.3V VOUT = 5V VOUT = 3.3V VOUT = 5V NMOS Current Limit Current Limit Delay to Output Min Typ Max 0.85 0.5 2.5 1 0.65 5.5 -4 +4 % 1.268 V 1.192 1.230 %/V 0.003 %/mA 0.004 750 0.01 300 0.1 0.1 0.35 0.30 0.60 0.55 1200 40 VFB = 1.15V, TA = -40°C to +85°C 80 85 FOSC Switching Frequency SHDN Input Low SHDN Input High SHDN Input Current TA = -40°C to +85°C 0.9 1.2 TSD Thermal Shutdown 1 500 5 5 Hysteresis 0.01 160 20 μA μA μA Ω Ω mA ns % 1.5 0.35 MHz 1 μA 1.00 VSHDN = 5.5V V 0.4 Maximum Duty Cycle ISHDN V 0.2 DMAX VSHDN Units V °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 www.analogictech.com 1217.2008.03.1.3 PRODUCT DATASHEET AAT1217 SwitchRegTM 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 VIN = 2.4V Efficiency (%) 80 90 70 VIN = 1.5V 60 50 VIN = 1.2V 40 30 40 30 10 100 VIN = 1.5V 50 20 10 VIN = 1.2V 60 10 1 0 0.1 1000 1 Output Current (mA) 1000 (VOUT = 5V; TA = 25° °C) 3.5 5.2 Output Voltage (V) Output Voltage (V) 100 Output Voltage vs. Output Current (VOUT = 3.3V; TA = 25° °C) 3.4 VIN = 2.4V VIN = 1.5V VIN = 1.2V 3.3 3.2 0 100 200 300 400 500 600 5.1 VIN = 1.2V VIN = 3.6V 4.9 4.8 0 100 200 300 400 500 600 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 Maximum Output Current (mA) 1.35 1.2 1.05 0.9 0.75 0.6 VIN = 2.4V VIN = 1.5V 5 Output Current (mA) Start-Up Voltage (V) 10 Output Current (mA) Output Voltage vs. Output Current 3.1 VIN = 2.4V 70 20 0 0.1 VIN = 3.6V 80 Efficiency (%) 90 0 20 40 60 80 100 120 140 160 180 200 Output Current (mA) 1217.2008.03.1.3 800 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) www.analogictech.com 5 PRODUCT DATASHEET AAT1217 SwitchRegTM 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter Typical Characteristics Output Voltage vs. Temperature No Load Input Current vs. Input Voltage 1000 3.35 900 3.34 800 Output Voltage (V) Input Current (µA) (VOUT = 3.3V; TA = 25°°C; No Load) 700 600 500 400 300 200 100 3.33 3.32 3.31 3.3 3.29 3.28 3.27 3.26 0 1 1.5 2 2.5 3 3.25 -50 0 25 50 75 100 Anti-Ringing Operation at SW Light Load Mode Operation (VIN = 2.4V; VOUT = 5V; IOUT = 20mA) (VIN = 1.8V; VOUT = 3.3V; IOUT = 5mA) VSW 2V/div -25 Temperature (°°C) Input Voltage (V) VSW 2V/div 0V 0V VOUT 50mV/div (AC) Time (400ns/div) Time (1ms/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 www.analogictech.com 1217.2008.03.1.3 PRODUCT DATASHEET AAT1217 SwitchRegTM 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter Functional Block Diagram + VIN VIN Start-Up Oscillator Slope Compensation L1 VOUT GOOD 2.3V – MUX SW VOUT VOUT Current Sense + CIN – COUT Antiringing Control To VIN Bandgap 1.23V + + R2 PWM Logic Comp EA FB R1 – – GND SHDN 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 1217.2008.03.1.3 Oscillator 1.2MHz rectifier is realized by a P-channel MOSFET (PMOS) with gate 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. www.analogictech.com 7 PRODUCT DATASHEET AAT1217 SwitchRegTM 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter Application Information 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. Light Load Mode Operation At very light load, the AAT1217 automatically switches into light load 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 antiringing 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. 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 R1(Ω) R2(Ω) 3.3V 5.0V 1.02M 1.02M 604k 332k Table 1: Resistor Selection for Output Voltage Setting. Fixed Output Voltage The 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: ΔIL IPEAK = IDC + 2 IDC = 8 www.analogictech.com IOUT · VOUT η · VIN ΔIL = VIN · D VOUT - VIN ; D= L · FSW VOUT ΔIL = VIN · (VOUT - VIN) L · FSW · VOUT 1217.2008.03.1.3 PRODUCT DATASHEET AAT1217 SwitchRegTM IPEAK = IPEAK IDC ΔIL IOUT VOUT VIN η D FSW L 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter IOUT · VOUT VIN · (VOUT - VIN) η · VIN + 2L · FSW · VOUT Peak Inductor Current DC Component (Average) of the Inductor Current Peak-Peak Inductor Ripple Current Output (Load) Current Output Voltage Input Voltage AAT1217 Efficiency (consult the performance graphs in the “Typical Characteristics” section of the data sheet) Steady-State Duty Cycle Switching Frequency 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. 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 Part Number Sumida CDH28D11/S Coiltronics SD3112 TDK VLF3012A Sumida CR43 Sumida CDRH4D28 Toko D53LC 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. L (μH) Max DCR (mΩ) Rated DC Current (A) 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 10 123 238 431 140 (typ) 246 (typ) 446 (typ) 100 190 410 71.2 108.7 182 31.3 72 128 45 90 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. 1217.2008.03.1.3 www.analogictech.com 9 PRODUCT DATASHEET AAT1217 SwitchRegTM 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter Output Capacitor Load Disconnect in Shutdown 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. 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). 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. External Diode Selection 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 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 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. 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. www.analogictech.com 1217.2008.03.1.3 PRODUCT DATASHEET AAT1217 SwitchRegTM 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter L1 4.7μH D1 MBR0520 1 VIN 0.85V SW 6 VIN VOUT 5 R4 510kΩ AAT1217 CIN 4.7μF 4 FB SHDN Q1 Si2305 DS 3 VOUT 3.3V,100mA R1 1.02MΩ COUT 4.7μF R2 604kΩ GND 2 R3 510kΩ Q2 2N3904 ON/OFF Control Figure 1: AAT1217 High Efficiency Load Disconnect Application Circuit. Figure 2: AAT1217 Evaluation Board Layout Example Top Layer. 1217.2008.03.1.3 Figure 3: AAT1217 Evaluation Board Layout Example Bottom Layer. www.analogictech.com 11 PRODUCT DATASHEET AAT1217 SwitchRegTM 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter Ordering Information Output Voltage1 Package Marking2 Part Number (Tape and Reel)3 Adj. Fixed 3.3V Fixed 5.0V Fixed 3.3V TSOT23-6 TSOT23-6 TSOT23-6 SOT23-6 VZMYY WAMYY WBMYY 3CXYY AAT1217ICA-1.2-T1 AAT1217ICA-3.3-T1 AAT1217ICA-5.0-T1 AAT1217IGU-3.3-T1 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/about/quality.aspx. Package Information TSOT23-6 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 1.00 +10° -0° 0.45 ± 0.15 0.000 + 0.100 - 0.000 Side View Detail "A" All dimensions in millimeters. 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 www.analogictech.com 1217.2008.03.1.3 PRODUCT DATASHEET AAT1217 SwitchRegTM 600mA, 1.2MHz, Micropower Synchronous Step-Up Converter SOT23-6 2.85 ± 0.15 1.90 BSC 2.80 ± 0.20 0.15 ± 0.07 4° ± 4° 1.10 ± 0.20 1.20 ± 0.25 0.075 ± 0.075 1.575 ± 0.125 0.95 BSC 10° ± 5° 0.40 ± 0.10 × 6 0.60 REF 0.45 ± 0.15 GAUGE PLANE 0.10 BSC All dimensions in millimeters. Advanced Analogic Technologies, Inc. 3230 Scott Boulevard, Santa Clara, CA 95054 Phone (408) 737-4600 Fax (408) 737-4611 © 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. 1217.2008.03.1.3 www.analogictech.com 13