AAT2113A ANALOGICTECH | Alldatasheet
Document overview
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- PDF pages: 19
Technical content
Features
- 5mm x 5mm Total Solution Size
- 1.5A Maximum Output Current
- Tiny 0.47 μH Chip Inductor
- Excellent Transient Response
- Input Voltage: 2.7V to 5.5V
- Ultra-small, Low Profile 8-pin 2mm x 2mm FTDFN Package
- Fixed or Adjustable Output Voltage Options: ▪ Fixed Output Voltage: 1.2V ▪ Adjustable Output Voltage: 1.0V to 1.8V
- High Efficiency, Low Noise Architecture
- 3MHz Switching Frequency
- No External Compensation Required
- 55 μA No Load Quiescent Current
- 100% Duty Cycle Low-Dropout Operation
- Internal Soft Start
- Over-Temperature and Current Limit Protection
- <1 μA Shutdown Current
- -40°C to 85°C Temperature Range
Applications
- Cellular Phones
- Digital Cameras
- Hard Disk Drives
- MP3 Players
- PDAs and Handheld Computers
- Portable Media Players
- USB Devices
- Wireless Network Cards Typical Application Load Transient Response (VIN = 5V; VOUT = 1.2V; IOUT = 10% to 100%; COUT = 10µF, 6.3V, 0603) Time (20µs/div) 150mA 1.1V 1.15V 1.2V 1.25V 1.3V 1.5A 100mV 1.2V/1.5A 0.47µH L12.7V to 5.5V 4.7µF 6.3V 0603 1.0µF 6.3V 0402 10µF 6.3V 0603 VIN VOUT EN FB LX PGND VCC VP LX AGND FTDFN 22-8 AAT2113A
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET AAT2113A 3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET Pin Descriptions Pin # Symbol Function 1 PGND Main power ground return pin. Connect to the output and input capacitor return. 2 VP Input power supply tied to the source of the high side P-channel MOSFET. 3 VCC Power supply; supplies power for the internal circuitry. 4F B Feedback input pin. This pin is connected directly to the converter output for the 1.2V fi xed output version, or connected to an external resistor divider for the adjustable output version. 5 AGND Analog Ground. This pin is internally connected to the analog ground of the control circuitry. 6E N Enable pin. A logic low disables the converter and it consumes less than 1μA of current. When connected high, it resumes normal operation. 7, 8 LX Switching node. Connect the inductor to this pin. It is internally connected to the drain of both high and low side MOSFETs. Pin Configuration FTDFN22-8 (Top View) VCC FB PGND VP EN AGND LX LX
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET AAT2113A 3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET Absolute Maximum Ratings1 TA = 25°C unless otherwise noted. Symbol Description Value Units VCC, VP VP, VCC to GND 6.0 V VLX LX to GND -0.3 to VP + 0.3 V VFB FB to GND -0.3 to VP + 0.3 V EN EN to GND -0.3 to VCC + 0.3 V TJ Operating Junction Temperature Range -40 to 150 °C TLEAD Maximum Soldering Temperature (at leads, 10 sec.) 300 °C Thermal Characteristics Symbol Description Value Units ΘJA Maximum Thermal Resistance 70 °C/W PD Maximum Power Dissipation2, 3 1.4 W 1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at co nditions 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 14mW/°C above 25°C.
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET AAT2113A 3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET Electrical Characteristics1 VIN = 3.3V, TA = -40°C to 85°C unless otherwise noted. Typical values are at T A = 25°C. Symbol Description Conditions Min Typ Max Units VIN Input Voltage 2.7 3.3 5.5 V VOUT Output Voltage Range 1 1.2 1.8 V VUVLO UVLO Threshold VIN rising 2.4 V Hysteresis 180 mV V IN falling 1.6 V VOUT Output Voltage Tolerance IOUT = 0A to 1.5A, VIN = 3.3V, VOUT = 1.2V fi xed -3.0 +3.0 % IQ Quiescent Current No Load 55 90 μA ISHDN Shutdown Current EN = GND 1.0 μA ILIM Current Limit 23 A RDS(ON)H High Side Switch On-Resistance 140 m Ω RDS(ON)L Low Side Switch On-Resistance 100 m Ω ΔVLOADREG Load Regulation I LOAD = 0A to 1.5A 0.5 % ΔVLINEREG/ ΔVIN Line Regulation V IN = 3.3V to 4.0V 0.3 %/V VFB Feedback Threshold Voltage Accuracy (Adjustable Version) No load, TA = 25°C 0.0591 0.60 0.609 V ILXLEAK,R LX Reverse Leakage Current V IN unconnected, VLX = 5.5V, EN = GND 1.0 μA IFBLEAK FB Leakage Current V OUT = 1.2V 0.2 μA FOSC Internal Oscillator Frequency 2.6 3 3.4 MHz TS Start-up Time Enable to Output Regulation 60 μs TSD Over-Temperature Shutdown Threshold 140 °C THYS Over-Temperature Shutdown Hysteresis 25 °C EN Logic VIL EN Threshold Low 0.4 V VIH EN Threshold High 1.4 V ILEAK EN Leakage Current V EN = 5.5V -1.0 1.0 μA 1. The AAT2113A is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is ass ured by design, characterization, and cor- relation with statistical process controls.
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET Typical Characteristics Efficiency vs. Output Current (VOUT = 1.2V; L = 0.47µH) Output Current (mA) Efficiency (%) 0.1 1 10 100 1000 10000 100 VIN = 5.5V VIN = 5.0V VIN = 4.2V VIN = 3.6V VIN = 3.0V VIN = 2.7V Efficiency vs. Output Current (VOUT = 1.8V; L = 0.47µH) Output Current (mA) Efficiency (%) 0.1 1 10 100 1000 10000 100 VIN = 5.5V VIN = 5.0V VIN = 4.2V VIN = 3.6V VIN = 3.0V VIN = 2.7V Load Regulation (VOUT = 1.2V; L = 0.47µH) Output Current (mA) Load Regulation (%) 0.1 1 10 100 1000 10000 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 VIN = 5.5V VIN = 5.0V VIN = 4.2V VIN = 3.6V VIN = 3.0V VIN = 2.7V Load Regulation (VOUT = 1.8V; L = 0.47µH) Output Current (mA) Load Regulation (%) 0.1 1 10 100 1000 10000 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 VIN = 5.5V VIN = 5.0V VIN = 4.2V VIN = 3.6V VIN = 3.0V VIN = 2.7V Line Regulation (VOUT = 1.2V; L = 0.47µF) Input Voltage (V) Line Regulation (%) -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 IOUT = 1500mA IOUT = 1000mA IOUT = 500mA IOUT = 1mA Line Regulation (VOUT = 1.8V; L = 0.47µF) Input Voltage (V) Line Regulation (%) -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 IOUT = 1500mA IOUT = 1000mA IOUT = 500mA IOUT = 1mA
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET AAT2113A 3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET Typical Characteristics Output Voltage vs. Input Voltage (VOUT = 1.2V; IOUT = 1A) Input Voltage (V) Output Voltage (V) 1.15 1.16 1.17 1.18 1.19 1.20 1.21 1.22 1.23 1.24 1.25 T = 85°C T = 25°C T = -40°C Output Voltage vs. Input Voltage (VOUT = 1.8V; IOUT = 1A) Input Voltage (V) Output Voltage (V) 1.75 1.76 1.77 1.78 1.79 1.80 1.81 1.82 1.83 1.84 1.85 T = 85°C T = 25°C T = -40°C Output Voltage Error vs. Temperature (VOUT = 1.2V; VIN = 3.3V; IOUT = 1A) Temperature (°C) Output Voltage Error (%) -40 -20 0 20 40 60 80-30 -10 10 30 50 70 90 -1.5 -1.0 -0.5 0.0 0.5 1.0 Output Voltage Error vs. Temperature (VOUT = 1.8V; VIN = 3.3V; IOUT = 1A) Temperature (°C) Output Voltage Error (%) -40 -20 0 20 40 60 80-30 -10 10 30 50 70 90 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 Switching Frequency vs. Temperature (VOUT = 1.2V; IOUT = 1A) Temperature (°C) Switching Frequency (MHz) -40 -20 0 20 40 60 80-30 -10 10 30 50 70 90 2.84 2.86 2.88 2.90 2.92 2.94 2.96 2.98 3.00 3.02 3.04 Quiescent Current vs. Input Voltage (No Load) Input Voltage (V) Supply Current (µA) T = 85°C T = 25°C T = -40°C
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET AAT2113A 3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET Typical Characteristics Load Transient (VOUT = 1.2V; VIN = 3.3V; IOUT = 0A to 1.5A; COUT = 10µF) Time (20µs/div) Output Voltage (top) (50mV/div) Output Current (bottom) (500mA/div) 1.10 1.15 1.20 1.25 1.30 0.0 0.5 1.0 1.5 Load Transient (VOUT = 1.8V; VIN = 3.3V; IOUT = 0A to 1.5A; COUT = 10µF) Time (20µs/div) Output Voltage (top) (50mV/div) Output Current (bottom) (500mA/div) 1.70 1.75 1.80 1.85 1.90 -0.5 0.0 0.5 1.0 1.5 Load Transient (VOUT = 1.2V; VIN = 3.3V; IOUT = 75mA to 1350mA; COUT = 10µF) Time (20µs/div) Output Voltage (top) (50mV/div) Output Current (bottom) (500mA/div) 1.10 1.15 1.20 1.25 1.30 -0.5 0.0 0.5 1.0 1.5 Load Transient (VOUT = 1.8V; VIN = 3.3V; IOUT = 75mA to 1350mA; COUT = 10µF) Time (20µs/div) Output Voltage (top) (50mV/div) Output Current (bottom) (500mA/div) 1.70 1.75 1.80 1.85 1.90 0.0 0.5 1.0 1.5 Line Transient (VOUT = 1.2V; VIN = 3.3V to 3.6V; IOUT = 1A) Time (50µs/div) Input Voltage (top) (500mV/div) Output Voltage (bottom) (5mV/div) 3.0 3.5 4.0 1.190 1.195 1.200 1.205 1.210 Line Transient (VOUT = 1.8V; VIN = 3.3V to 3.6V; IOUT = 1A) Time (20µs/div) Input Voltage (top) (500mV/div) Output Voltage (bottom) (5mV/div) 3.0 3.5 4.0 1.795 1.800 1.805 1.810 1.815
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET AAT2113A 3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET Typical Characteristics Soft Start (VOUT = 1.2V; VIN = 3.3V; IOUT = 1A) Time (100µs/div) Enable Voltage (top) (1V/div) Output Voltage (middle) (1V/div) Inductor Current (bottom) (1A/div) Soft Start (VOUT = 1.8V; VIN = 3.3V; IOUT = 1A) Time (2ms/div) Enable Voltage (top) (1V/div) Output Voltage (middle) (1V/div) Inductor Current (bottom) (1A/div) Output Voltage Ripple (VOUT = 1.2V; VIN = 3.3V; IOUT = 1mA) Time (10µs/div) Output Voltage (top) (10mV/div) Inductor Current (bottom) (100mA/div) 1.19 1.20 1.21 -0.2 -0.1 0.1 0.2 0.3 Output Voltage Ripple (VOUT = 1.8V; VIN = 3.3V; IOUT = 1mA) Time (10µs/div) Output Voltage (top) (10mV/div) Inductor Current (bottom) (100mA/div) 1.79 1.80 1.81 -0.2 -0.1 0.1 0.2 0.3 Output Voltage Ripple (VOUT = 1.2V; VIN = 3.3V; IOUT = 1.5A) Time (200ns/div) Output Voltage (top) (20mV/div) Inductor Current (bottom) (500mA/div) 1.18 1.20 1.22 0.5 1.0 1.5 2.0 Output Voltage Ripple (VOUT = 1.8V; VIN = 3.3V; IOUT = 1.5A) Time (200ns/div) Output Voltage (top) (20mV/div) Inductor Current (bottom) (500mA/div) 1.78 1.80 1.82 1.0 1.5 2.0
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET Functional Description The AAT2113A SwitchReg is a 1.5A step-down converter with a typical input voltage of 3.3V and a fixed output voltage of 1.2V. The 3MHz switching frequency enables the use of small external components. The ultra-small, 2mm x 2mm footprint and high efficiency make the AAT2113A an ideal choice for portable applications. Typically, a 0.47μH inductor and a 10μF ceramic capaci- tor are recommended for a 1.2V output (see Figure 2 for recommended values). At dropout, the converter duty cycle increases to 100% and the output voltage tracks the input voltage minus the R DS(ON) drop of the P-channel high-side MOSFET (plus the DC drop of the external inductor). The device inte- grates extremely low R DS(ON) MOSFETs to achieve low dropout voltage during 100% duty cycle operation. The integrated low-loss MOSFET switches can provide excellent efficiency at heavy loads. Light load operation maintains high efficiency, low ripple and low spectral noise even at lower currents (typically <150mA). PWM mode operation maintains constant frequency and low output ripple at output loads greater than 200mA. In battery-powered applications, as V IN decreases, the converter dynamically adjusts the operating frequency prior to dropout to maintain the required duty cycle and provide accurate output regulation. Output regulation is maintained until the dropout voltage, or minimum input voltage, is reached. At 1.5A output load, dropout voltage headroom is approximately 200mV. The AAT2113A typically achieves better than ±0.5% output regulation across the input voltage and output load range. A current limit of 3.0A (typical) protects the IC and system components from short-circuit damage. Typical no load quiescent current is 55μA. Thermal protection completely disables switching when the maximum junction temperature is detected. The junction over-temperature threshold is 140°C with 15°C of hysteresis. Once an over-temperature or over-current fault condition is removed, the output voltage automati- cally recovers. Peak current mode control and optimized internal com- pensation provide high loop bandwidth and excellent response to input voltage and fast load transient events. Soft start eliminates output voltage overshoot when the enable or the input voltage is applied. Under-voltage lockout prevents spurious start-up events. Functional Block Diagram EN LX Err Amp Logic DH DL PGND VPFB AGND VREF = 0.6V Input Comp VCC AAT2113A-1.2V Only
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET Control Loop The AAT2113A is a peak current mode step-down con- verter. The current through the P-channel MOSFET (high side) is sensed for current loop control, as well as short- circuit and overload protection. A fixed slope compensa- tion signal is added to the sensed current to maintain stability for duty cycles greater than 50%. The peak cur- rent mode loop appears as a voltage-programmed cur- rent 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. The reference voltage is internally set to program the con- verter output voltage greater than or equal to 0.6V. Soft Start/Enable Soft start limits the current surge seen at the input and eliminates output voltage overshoot. The enable input, when pulled low, forces the AAT2113A into a low-power, non-switching state. The total input current during shut- down is less than 1μA. Current Limit and Over-Temperature Protection For overload conditions, the peak input current is limit- ed. To minimize power dissipation and stresses under current limit and short-circuit conditions, switching is terminated after entering current limit for a series of pulses. 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 140°C with 15°C of hys- teresis. 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 VCC input. Under-voltage lockout (UVLO) guarantees suffi- cient V IN bias and proper operation of all internal cir- cuitry prior to activation. Component Selection Inductor Selection The step-down converter uses peak current mode con- trol 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. For applications where the duty cycle is less than 50%, the inductor values can be chosen freely. 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 satura- tion 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. For low cost application and a sufficiently small footprint in a 5x5mm area, the LQM2HPNR47MG0 shielded chip inductor, which has 40mΩ DCR and 1.8A DC current rat- ing, is selected for 1.2V output. The inductors listed in Table 1 have been used with the AAT2113A. Manufacturer Part Number Value ( μH) DC Resistance ( Ω) Size (mm) Table 1: AAT2113A List of Inductors.
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET Input Capacitor Select a 4.7μF to 10μF X7R or X5R ceramic capacitor for the input. To estimate the required input capacitor size, determine the acceptable input ripple level (V PP) and solve for C. The calculated value varies with input volt- age and is a maximum when V IN is double the output voltage. VO VIN CIN = VO VIN VPP IO VO VIN VO VIN CIN(MIN) = 1 VPP IO Always examine the ceramic capacitor DC voltage coef- ficient characteristics when selecting the proper value. For example, the capacitance of a 10 μF, 6.3V, X5R ceramic capacitor with 3.5V DC applied is actually about 5μF. Some examples of DC bias voltage versus capaci- tance for different package sizes are shown in Figure 1. DC Bias Voltage (V) Capacitance (µF) Figure 1: 10μF Capacitor Value vs. DC Bias Voltage for Different Package Sizes. The maximum input capacitor RMS current is: IRMS = IO · · 1 - VO VIN VO 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. VIN VO VIN for VIN = 2 · VO IO RMS(MAX)I 2= The term VO VIN VO VIN appears in both the input voltage ripple and input capacitor RMS current equations and is a maximum when V O is twice V IN. 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 AAT2113A. 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. The proper placement of the input capacitor (C1) can be seen in the evaluation board layout in the Layout section of this datasheet (see Figure 3). A laboratory test set-up typically consists of two long wires running from the bench power supply to the eval- uation 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 dur- ing 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 induc- tance cannot be reduced to a level that does not affect the converter performance, a high ESR tantalum or alu- minum electrolytic should be placed in parallel with the low ESR/ESL bypass ceramic capacitor. This dampens the high Q network and stabilizes the system.
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET Output Capacitor The output capacitor limits the output ripple and pre- vents the output voltage droop during large load transi- tions. A 10 μF to 22 μF 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. 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 out- put 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 · ΔILOAD VDROOP · FS Once the average inductor current increases to the DC load level, the output voltage recovers. The above equa- tion 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 10 μF. This is due to its effect on the loop crossover frequency (bandwidth), phase margin, and gain margin. Increased output capac- itance will reduce the crossover frequency with greater phase margin. Feedback Resistor Selection Resistors R1 and R2 of Figure 5 program the output to regulate at a voltage higher than 0.6V for the AAT2113A adjustable version. To limit the bias current required for the external feedback resistor string while maintaining good noise immunity, the suggested value for R2 is 200kΩ. Table 1 summarizes the resistor values for vari- ous output voltages with R2 set to either 59kΩ or 200kΩ. Alternately, the feedback resistor may be calculated using the following equation: R1 = -1 · R2 = - 1 · 200kΩ = 400kΩ VOUT VREF 1.8V 0.6V The AAT2113A adjustable version, combined with an external feed forward capacitor (C2 in Figure 5), delivers enhanced transient response for extreme pulsed load applications. The suggested value for C2 is in the range of 22pF to 100pF. VOUT (V) R2 = 59kΩ R1 (kΩ) R2 = 200kΩ R1 (kΩ) 1.0 39.2 133 1.1 49.9 165 1.2 59 200 1.3 68.1 232 1.4 78.7 267 1.5 88.7 301 1.6 97.6 332 1.7 107 365 1.8 118 400 Table 2: Feedback Resistor Selection for Adjustable Output Voltage Version. Thermal Calculations There are three types of losses associated with the AAT2113A step-down converter: switching losses, con- duction losses, and quiescent current losses. Conduction losses are associated with the R DS(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 con- duction mode (CCM), a simplified form of the losses is given by: PTOTAL IO 2 · (RDS(ON)H · VO + RDS(ON)L · [VIN - VO]) VIN + (tsw · FS · IO + IQ) · VIN IQ is the step-down converter quiescent current. The term tSW is used to estimate the full load step-down con- verter switching losses. For the condition where the step-down converter is in dropout at 100% duty cycle, the total device dissipation reduces to: PTOTAL= IO 2 · RDS(ON)H + IQ · VIN
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET AAT2113A 3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET Since RDS(ON), quiescent current, and switching losses all vary with input voltage, the total losses should be inves- tigated over the complete input voltage range. Given the total losses, the maximum junction tempera- ture can be derived from the θ JA for the FTDFN22-8 package, which is 70°C/W. TJ(MAX) = PTOTAL · ΘJA + TAMB PCB Layout Considerations The suggested PCB layout for the AAT2113A is shown in Figures 3 and 4 (fixed version) or Figures 6 and 7 (adjust- able version). The following guidelines should be used to help ensure a proper layout: 1. The input capacitor (C1) should be connected as close as possible to VP and PGND. 2. The output capacitor and L1 should be connected as closely as possible. The connection of L1 to the LX pin should be as short as possible. 3. For the fixed version, the feedback trace or FB pin should be separated from any power trace and con- nected as closely as possible to the load point. Sensing along a high-current load trace will degrade DC load regulation. For the adjustable version, the trace connecting the FB pin to resistors R1 and R2 should be as short as possible by placing R1 and R2 immediately next to the AAT2113A. The sense trace connection from R1 to the output voltage should be separate from any power trace and connect as closely as possible to the load point. The external feed-forward capacitor C2 should be connected as close as possible in parallel with R1 for enhanced transient response. 4. The resistance of the trace from the load return to PGND should be kept to a minimum. This will help to minimize any error in DC regulation due to differ- ences in the potential of the internal signal ground and the power ground. 5. Connect unused signal pins to ground to avoid unwanted noise coupling.
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET AAT2113A 3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET AAT2113A Design Example Specifications VOUT = 1.2V @ 1.5A, Pulsed Load ΔILOAD = 1.5A VIN = 3.3V FS = 3MHz TAMB = 85°C in 8-pin 2x2mm DFN low profile package Output Inductor For Murata, 0.47μH LQM2HPNNR47MG0 shielded chip inductor has a 40m Ω DCR. VO VO 1.2V 1.2V ΔI = · 1 - = · 1 - = 542mAL1 · FS VIN 0.47μH · 3MHz 3.3V IPK = IOUT + ΔI = 1.5A + 0.271A = 1.8A2 PL1 = IOUT 2 · DCR = 1.5A2 · 40mΩ = 90mW Output Capacitor For VDROOP = 0.12V (10% Output Voltage) 3 · ΔILOAD VDROOP · FS 3 · 1.5A 0.12V · 3MHz COUT = = = 12.5μF; use 10μF For VDROOP = 0.06V (5% Output Voltage) 1.5μH · 3MHz · 5V 23 RMS(MAX)I L · FS · VIN(MAX) = · 3 · ΔILOAD VDROOP · FS 3 · 1.5A 0.06V · 3MHz COUT = = = 25μF; use 22μF
- = 58.5mArms VOUT · (VIN(MAX) - VOUT) = PRMS = ESR · IRMS 2 = 5mΩ · (58.5mA)2 = 17μW
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET AAT2113A 3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET Input Capacitor For Input Ripple VPP = 30mV CIN = = = 5.6μF; use 4.7μF1 - ESR · 4 · FS VPP IO - 5mΩ · 4 · 3MHz30mV 1.5A IOUT1 RMSI P = ESR · (IRMS)2 = 5mΩ · (0.75A)2 = 2.8mW 2== 0 . 7 5 A AAT2113A Losses All values assume 85°C ambient temperature and thermal resistance of 70°C/W in the 8-pin 2x2mm DFN low profile package. PTOTAL = IOUT 2 · RDS(ON)H + (tSW · FSW · IOUT + IQ) · VIN = 416mW = 1.5A2 · 152mΩ + (5ns · 3MHz · 1.5A + 50μA) · 3.3V TJ(MAX) = TAMB + ΘJA · PLOSS = 85°C + (70°C/W) · 416mW = 114°C
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET AAT2113A 3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET
Ordering Information
Output Voltage Package Marking 1 Part Number (Tape and Reel)2 1.2V FTDFN22-8 8BXYY AAT2113AIXS-1.2-T1 Adjustable (0.6V) FTDFN22-8 8AXYY AAT2113AIXS-0.6-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
2.000 ± 0.050 Index Area 2.000 ± 0.050 Top View 0.500 ± 0.050 Detail "A" 0.400 ± 0.050 Pin 1 Identification 0.000 + 0.100 - 0.000 Side View 0.230 ± 0.050 0.750 ± 0.050 Bottom View 0.450 ± 0.0500.250 ± 0.050 Detail "A" 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 c onnection.
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET AAT2113A 3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm PackageSwitchReg TM PRODUCT DATASHEET Advanced Analogic Technologies, Inc.
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