AAT2146_08 ANALOGICTECH | Alldatasheet

Document overview

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Technical content

Features

  • V IN Range: 2.7V to 5.5V
  • Low Noise Light Load Mode
  • Low Ripple PWM Mode
  • V OUT Fixed or Adjustable from 0.6V to V IN
  • 37 μA No Load Quiescent Current
  • Up to 98% Efficiency
  • 600mA Max Output Current
  • 2MHz Switching Frequency
  • 150 μs Soft Start
  • Fast Load Transient
  • Over-Temperature Protection
  • Current Limit Protection
  • 100% Duty Cycle Low-Dropout Operation
  • <1μA Shutdown Current
  • SC70JW-8 Package
  • Temperature Range: -40°C to +85°C

Applications

  • Cellular Phones
  • Digital Cameras
  • Handheld Instruments
  • Microprocessor / DSP Core / IO Power
  • PDAs and Handheld Computers
  • USB Devices Typical Application (Fixed Output Voltage) 4.7µH 4.7µF 2.2µF EN OUT VIN LX AGND PGND PGND PGND AAT2146 VIN VO

Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET AAT2146 Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET Pin Descriptions Pin # Symbol Function 1 EN Enable pin. 2 OUT Feedback input pin. This pin is connected either directly to the converter output or to an external resistive divider for an adjustable output. 3 VIN Input supply voltage for the converter. 4L X Switching node. Connect the inductor to this pin. It is internally connected to the drain of both high- and low-side MOSFETs. 5 AGND Non-power signal ground pin. 6, 7, 8 PGND Main power ground return pins. Connect to the output and input capacitor return. Pin Configuration SC70JW-8 (Top View) OUT VIN LX PGND PGND PGND AGND EN 1

Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET AAT2146 Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET Absolute Maximum Ratings1 Symbol Description Value Units VIN Input Voltage GND 6.0 V VLX LX to GND -0.3 to VIN + 0.3 V VOUT OUT to GND -0.3 to VIN + 0.3 V VEN EN to GND -0.3 to VIN + 0.3 V TJ Operating Junction Temperature Range -40 to 150 °C TLEAD Maximum Soldering Temperature (at leads, 10 sec) 300 °C Thermal Information Symbol Description Value Units PD Maximum Power Dissipation2, 3 625 mW θJA Thermal Resistance2 160 °C/W 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 6.25mW/°C above 25°C.

Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET AAT2146 Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET Electrical Characteristics1 TA = -40°C to +85°C, unless otherwise noted. Typical values are T A = 25°C, VIN = 3.6V. Symbol Description Conditions Min Typ Max Units Step-Down Converter VIN Input Voltage 2.7 5.5 V VIN Rising 2.7 V VUVLO UVLO Threshold Hysteresis 100 mV VIN Falling 1.8 V VOUT Output Voltage Tolerance IOUT = 0mA to 600mA, VIN = 2.7V to 5.5V -3.0 +3.0 % VOUT Output Voltage Range 0.6 VIN V IQ Quiescent Current No Load, 0.6V Adjustable Version 37 70 μA ISHDN Shutdown Current EN = AGND = PGND 1.0 μA ILIM P-Channel Current Limit 800 mA RDS(ON)H High Side Switch On Resistance 0.35 Ω RDS(ON)L Low Side Switch On Resistance 0.30 Ω ΔVLinereg Line Regulation VIN = 2.7V to 5.5V; IOUT = 600mA 0.1 %/V VOUT Out Threshold Voltage Accuracy 0.6V Output, No Load; TA = 25°C 591 600 609 mV IOUT Out Leakage Current 0.6V Output 0.2 μA ROUT Out Impedance >0.6V Output 250 kΩ TS Start-Up Time From Enable to Output Regulation 150 μs FOSC Oscillator Frequency TA = 25°C 0.9 2.0 2.6 MHz TSD Over-Temperature Shutdown Threshold 140 °C THYS Over-Temperature Shutdown Hysteresis 15 °C EN VEN(L) Enable Threshold Low 0.6 V VEN(H) Enable Threshold High 1.4 V IEN Input Low Current VIN = VOUT = 5.5V -1.0 1.0 μA 1. The AAT2146 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assu red by design, characterization, and correla- tion with statistical process controls.

Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET AAT2146 Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET Typical Characteristics Efficiency vs. Output Current (VOUT = 1.8V) Output Current (mA) Efficiency (%) 100 0.1 1 10 100 1000 VIN = 2.7V VIN = 3.6V VIN = 4.2V Load Regulation (VOUT = 1.8V) Output Current (mA) Output Error (%) -0.8 -0.6 -0.4 -0.2 0.2 0.4 0.6 0.8 0.1 1 10 100 1000 VIN = 2.7V VIN = 3.6V VIN = 4.2V Efficiency vs. Output Current (VOUT = 2.5V) Output Current (mA) Efficiency (%) 100 0.1 1 10 100 1000 VIN = 3V VIN = 3.6V VIN = 4.2V VIN = 5V Load Regulation (VOUT = 2.5V) Output Current (mA) Output Error (%) -0.8 -0.6 -0.4 -0.2 0.2 0.4 0.6 0.8 0.1 1 10 100 1000 VIN = 3V VIN = 3.6V VIN = 4.2V VIN = 5V Efficiency vs. Output Current (VOUT = 3.3V) Output Current (mA) Efficiency (%) 100 0.1 1 10 100 1000 VIN = 3.6V VIN = 4.2V VIN = 5V Load Regulation (VOUT = 3.3V) Output Current (mA) Output Error (%) -0.8 -0.6 -0.4 -0.2 0.2 0.4 0.6 0.8 0.1 1 10 100 1000 VIN = 3.6V VIN = 4.2V VIN = 5V

Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET AAT2146 Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET Typical Characteristics Line Regulation (VOUT = 1.8V) Input Voltage (V) Accuracy (%) -0.5 -0.4 -0.3 -0.2 -0.1 0.1 0.2 0.3 0.4 0.5 1mA 400mA 600mA Switching Frequency vs. Temperature (VOUT = 1.8V; IOUT = 1A) Input Voltage (V) Switching Frequency (MHz)1.92 1.94 1.96 1.98 2.02 2.04 2.06 2.08 -40 -15 10 35 60 85 Frequency Variation vs. Input Voltage Input Voltage (V) Frequency Variation (%) VOUT = 1.8V VOUT = 3V Output Voltage Error vs. Temperature (VIN = 3.6V; VO = 1.8V, IOUT = 400mA) Temperature (°C) Output Voltage Error (%) -2.0 -1.0 0.0 1.0 2.0 -40 -20 0 20 40 60 80 10 No Load Quiescent Current vs. Input Voltage Input Voltage (V) Supply Current (µA) 85°C 25C -40°C P-Channel RDS(ON) vs. Input Voltage Input Voltage (V) RDS(ON) (mΩΩ) 200 250 300 350 400 450 500 550 2.5 3 3.5 4 4.5 5 5.5 6 120°C 100°C 85°C 25°C

Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET AAT2146 Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET Typical Characteristics N-Channel RDS(ON) vs. Input Voltage Input Voltage (V) RDS(ON) (mΩΩ) 200 250 300 350 400 450 500 550 2.5 3 3.5 4 4.5 5 5.5 6 120°C 100°C 85°C 25°C Load Transient (VIN = 3.6V; VOUT = 1.8V; COUT = 10µF; CFF = 100pF) Time (50µs/div) Output Voltage (top) (V) Output and Inductor Current (100mA/div) 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 300mA 1mA 300mA 1mA Load Transient (VIN = 3.6V; VOUT = 1.8V; COUT = 4.7µF; CFF = 0pF) Time (50µs/div) Output Voltage (top) (V) Output and Inductor Current (100mA/div) 1.5 1.55 1.6 1.65 1.7 1.75 1.8 1.85 400mA 300mA 400mA 300mA Load Transient (VIN = 3.6V; VOUT = 1.8V; COUT = 10µF; CFF = 0pF) Time (50µs/div) Output Voltage (top) (V) Output and Inductor Current (100mA/div) 1.5 1.55 1.6 1.65 1.7 1.75 1.8 1.85 400mA 400mA 300mA 300mA Load Transient (VIN = 3.6V; VOUT = 1.8V; COUT = 10µF; CFF = 100pF) Time (50µs/div) Output Voltage (top) (V) Output and Inductor Current (100mA/div) 1.5 1.55 1.6 1.65 1.7 1.75 1.8 1.85 400mA 300mA 400mA 300mA Line Transient (VOUT = 1.8V; VIN = 3.6V to 4.2V; IOUT = 400mA; CFF = 0pF) Time (50µs/div) Input Voltage (top) (V) Output Voltage (bottom) (V) 0.6 1.2 1.8 2.4 3.6 4.2 4.8 1.76 1.78 1.8 1.82 1.84 1.86 1.88 1.9 1.92

Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET AAT2146 Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET Typical Characteristics Output Ripple (VOUT = 1.8V; VIN = 3.6V; IOUT = 1mA; CFF = 0pF) Time (10µs/div) Output Voltage (top) (V) Inductor Current (bottom) (A) -0.06 -0.05 -0.04 -0.03 -0.02 -0.01 0.01 0.02 -0.05 0.05 0.1 0.15 0.2 0.25 0.3 0.35 Output Ripple (VOUT = 1.8V; VIN = 3.6V; IOUT = 400mA; CFF = 0pF) Time (200ns/div) Output Voltage (top) (V) Inductor Current (bottom) (A) -0.06 -0.05 -0.04 -0.03 -0.02 -0.01 0.01 0.02 -0.2 0.2 0.4 0.6 0.8 1.2 1.4 Soft Start (VIN = 3.6V; VOUT = 1.8V; IOUT = 400mA) Time (100µs/div) Enable Voltage (top) (V) Output Voltage (middle) (V) Input Current (bottom) (A) -0.5 0.5

Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET Functional Description The AAT2146 is a high performance 600mA 2MHz mono- lithic step-down converter. It has been designed with the goal of minimizing external component size and optimiz- ing efficiency over the complete load range, and pro- duces reduced ripple and spectral noise. Apart from the small bypass input capacitor, only a small L-C filter is required at the output. Typically, a 4.7μH inductor and a 4.7μF ceramic capacitor are recommended (see table of values). The fixed output version requires only three external power components (C IN, COUT, and L). The adjustable ver- sion can be programmed with external feedback to any voltage, ranging from 0.6V to the input voltage. An addi- tional feed-forward capacitor can also be added to the external feedback to provide improved transient response (see Figure 1). At dropout, the converter duty cycle increases to 100% and the output voltage tracks the input voltage minus the R DSON drop of the P-channel high-side MOSFET. The input voltage range is 2.7V to 5.5V. The converter efficiency has been optimized for all load conditions, ranging from no load to 600mA. The internal error amplifier and compensation provides excellent transient response, load, and line regulation. Soft start eliminates any output voltage overshoot when the enable or the input voltage is applied. Functional Block Diagram EN LX Err .Amp Logic DH DL PGND VINOUT AGND Voltage Reference INPUT See note Note: For adjustable version, the internal feedback divider is omitted and the OUT pin is tied directly to the internal error amplifier.

Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET Control Loop The AAT2146 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. For fixed voltage versions, the error amplifier reference volt- age is internally set to program the converter output voltage. For the adjustable output, the error amplifier reference is fixed at 0.6V. 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 AAT2146 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 conditions 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 V IN bias and proper operation of all internal circuitry prior to activation. L1 CDRH3D16-4R7 4.7µH 10µF 4.7µF U1 AAT2146 SC70JW-8 C1 10µF 10V 0805 X5R C2 4.7µF 10V 0805 X5R CFF 100pF 0402 X5R VOUT GND VIN CFF Enable LX EN1 OUT2 VIN3 LX4 AGND 5 PGND 6 PGND 7 PGND 8 AAT2146 GND2 118k 59k Figure 1: Enhanced Transient Response Schematic.

Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET Applications Information 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. The internal slope compensation for the adjustable and low-voltage fixed versions of the AAT2146 is 0.24A/ μs. This equates to a slope compensation that is 75% of the inductor current down slope for a 1.5V output and 4.7μH inductor. 0.75 ⋅ VO m = = = 0.24 L 0.75 ⋅ 1.5V 4.7µH A µs This is the internal slope compensation for the adjust- able (0.6V) version or low-voltage fixed versions. When externally programming the 0.6V version to 2.5V, the calculated inductance is 7.5μH. 0.75 ⋅ VO L = = ≈ 3 ⋅ VO = 3 ⋅ 2.5V = 7.5µH m 0.75 ⋅ VO 0.24A µs A µs A A µs In this case, a standard 6.8μH value is selected. For high-voltage fixed versions ( ≥2.5V), m = 0.48A/ μs. Table 1 displays inductor values for the AAT2146 fixed and adjustable options. 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. The 4.7 μH CDRH3D16 series inductor selected from Sumida has a 105mΩ DCR and a 900mA DC current rat- ing. At full load, the inductor DC loss is 17mW which gives a 2.8% loss in efficiency for a 400mA, 1.5V out- put. Input Capacitor Select a 2.2μF 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 5.0V DC applied is actually about 6μF. Confi guration Output Voltage Inductor 0.6V Adjustable With External Feedback 1V, 1.2V 2.2μH 1.5V, 1.8V 4.7μH 2.5V, 3.3V 6.8μH Fixed Output 0.6V to 3.3V 4.7μH Table 1: Inductor Values. The maximum input capacitor RMS current is: 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. VO VIN VO VIN

Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET for VIN = 2 · VO IO RMS(MAX)I 2= The term VO VIN VO VIN appears in both the input voltage rip- ple 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 AAT2146. 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 (C2) can be seen in the evaluation board layout in Figure 2. A laboratory test set-up typically consists of two long wires running from the bench power supply to the evalu- ation 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. This dampens the high Q network and stabilizes the system. Output Capacitor The output capacitor limits the output ripple and pro- vides holdup during large load transitions. A 4.7 μF to 10μF X5R or X7R ceramic capacitor typically provides sufficient bulk capacitance to stabilize the output during large load transitions and has the ESR and ESL charac- teristics 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 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 rela- tionship of the output voltage droop during the three switching cycles to the output capacitance can be esti- mated 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 4.7μF. 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. The maximum output capacitor RMS ripple current is given by: VOUT · (VIN(MAX) - VOUT) RMS(MAX)I L · F · VIN(MAX) Dissipation due to the RMS current in the ceramic output capacitor ESR is typically minimal, resulting in less than a few degrees rise in hot-spot temperature.

Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET VOUT (V) R2 = 59kΩ R2 = 221kΩ R1 (kΩ)R 1 0.8 19.6 75K 0.9 29.4 113K 1.0 39.2 150K 1.1 49.9 187K 1.2 59.0 221K 1.3 68.1 261K 1.4 78.7 301K 1.5 88.7 332K 1.8 118 442K 1.85 124 464K 2.0 137 523K 2.5 187 715K 3.3 267 1.00M Table 2: Adjustable Resistor Values For Use With 0.6V Step-Down Converter. Thermal Calculations There are three types of losses associated with the AAT2146 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 · (RDSON(HS) · VO + RDSON(LS) · [VIN - VO]) VIN + (tsw · F · 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 · RDSON(HS) + IQ · VIN 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 SC70JW-8 pack- age which is 160°C/W. TJ(MAX) = PTOTAL · ΘJA + TAMB L1 CDRH3D16-4R7 4.7μH 10μF 4.7μF U1 AAT2146 SC70JW-8 C2 4.7μF 10V 0805 X5R VOUT =1.8V GND VIN Enable LX EN OUT VIN LX AGND PGND PGND PGND AAT2146 GND2 118k 59k C1 10μF 6.3V 0805 X5R 100pF n/a Figure 5: AAT2146 Adjustable Evaluation Board Schematic.

Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET AAT2146 Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET Layout The suggested PCB layout for the AAT2146 is shown in Figures 2, 3, and 4. The following guidelines should be used to help ensure a proper layout. 1. The input capacitor (C2) should connect as closely as possible to V IN (Pin 3) and PGND (Pins 6-8). 2. C1 and L1 should be connected as closely as possi- ble. The connection of L1 to the LX pin should be as short as possible. 3. The feedback trace or OUT pin (Pin 2) should be separate from any power trace and connect as close- ly as possible to the load point. Sensing along a high-current load trace will degrade DC load regula- tion. If external feedback resistors are used, they should be placed as closely as possible to the OUT pin (Pin 2) to minimize the length of the high imped- ance feedback trace. 4. The resistance of the trace from the load return to the PGND (Pins 6-8) 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. A high density, small footprint layout can be achieved using an inexpensive, miniature, non-shielded, high DCR inductor. An evaluation board is available with this induc- tor and is shown in Figure 6. The total solution footprint area is 40mm Figure 6: Minimum Footprint Evaluation Board Using 2.0mm x 1.6mm x 0.95mm Inductor.

Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET AAT2146 Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET Step-Down Converter Design Example Specifications VO = 1.8V @ 400mA (adjustable using 0.6V version), Pulsed Load ΔILOAD = 300mA VIN = 2.7V to 4.2V (3.6V nominal) FS = 2MHz TAMB = 85°C 1.8V Output Inductor L1 = 3 ⋅ VO2 = 3 ⋅ 1.8V = 5.4µHµs A µs A (use 4.7μH; see Table 1) For Sumida inductor CDRH3D16, 4.7μH, DCR = 105mΩ. IPKL1 = IO + ΔIL1 = 0.4A + 0.055A = 0.455A2 PL1 = IO 2 ⋅ DCR = 0.4A2 ⋅ 105mΩ = 17mW 1.8V Output Capacitor VDROOP = 0.1V 4.7µH · 2.0MHz · 4.2V 23 RMSI L1 · F · VIN(MAX) = · 3 · ΔILOAD VDROOP · FS 3 · 0.3A 0.1V · 2.0MHz COUT = = = 4.5µF; use 4.7µF

  • = 32mArms (VO) · (VIN(MAX) - VO) = Pesr = esr · IRMS 2 = 5mΩ · (32mA)2 = 6µW Input Capacitor Input Ripple VPP = 25mV CIN = = = 2.17µF; use 2.2µF1 VPP IO 25mV 0.4A IO RMSI P = esr · IRMS 2= = 0.2Arms

Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET AAT2146 Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET AAT2146 Losses PTOTAL + (tsw · F · IO + IQ) · VIN IO 2 · (RDSON(HS) · VO + RDSON(LS) · [VIN -VO]) VIN + (5ns · 2.0MHz · 0.4A + 70µA) · 4.2V = 131mW 4.2V TJ(MAX) = TAMB + ΘJA · PLOSS = 85°C + (160°C/W) · 131mW = 105.9°C

Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET AAT2146 Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET Adjustable Version (0.6V device) VOUT (V) R2 = 59kΩ R1 (kΩ) R2 = 221kΩ1 R1 (kΩ) L1 (μH) 0.8 19.6 75.0 2.2 0.9 29.4 113 2.2 1.0 39.2 150 2.2 1.1 49.9 187 2.2 1.2 59.0 221 2.2 1.3 68.1 261 2.2 1.4 78.7 301 4.7 1.5 88.7 332 4.7 1.8 118 442 4.7 1.85 124 464 4.7 2.0 137 523 6.8 2.5 187 715 6.8 3.3 267 1000 6.8 Fixed Version VOUT (V) R2, R4 Not Used R1 (kΩ) L1 (μH) 0.6-3.3V 0 4.7 Table 3: Evaluation Board Component Values. Manufacturer Part Number Inductance ( μH) Max DC Current (A) DCR ( Ω) Size (mm) LxWxH Type Sumida Coiltronics Table 4: Typical Surface Mount Inductors. Manufacturer Part Number Value Voltage Temp. Co. Case Murata GRM219R61A475KE19 4.7 μF 10V X5R 0805 Murata GRM21BR60J106KE19 10μF 6.3V X5R 0805 Murata GRM21BR60J226ME39 22μF 6.3V X5R 0805 Table 5: Surface Mount Capacitors. 1. For reduced quiescent current, R2 and R4 = 221k Ω.

Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET AAT2146 Low Noise, Fast Transient 600mA Step-Down ConverterSwitchReg TM PRODUCT DATASHEET Advanced Analogic Technologies, Inc.

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Output Voltage1 Package Marking2 Part Number (Tape and Reel)3 Adj ≥ 0.6 SC70JW-8 YXXYY AAT2146IJS-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

0.225 ± 0.075 0.45 ± 0.10 0.05 ± 0.05 2.10 ± 0.30 2.00 ± 0.20 7° ± 3° 4° ± 4° 0.15 ± 0.05

1.10 MAX

0.100 2.20 ± 0.20 0.048REF 0.50 BSC 0.50 BSC 0.50 BSC All dimensions in millimeters. 1. Contact Sales for other voltage options. 2. XYY = assembly and date code. 3. Sample stock is typically held on part numbers listed in BOLD.