DATA SHEET AAT1149: 3 MHz Fast Transient 400 mA Step-Down Converter Applications Description • Cellular phones The AAT1149 SwitchRegTM is a 3.0 MHz step-down converter with an input voltage range of 2.7 V to 5.5 V and output voltage as low as 1.0 V. It is optimized to react quickly to load variations and operate with a tiny 0603 inductor that is only 1 mm tall. • Digital cameras • Handheld instruments • Microprocessor/DSP core/IO power • PDAs and handheld computers • USB devices Features • Ultra-small 0603 inductor (height = 1 mm) • VIN range: 2.7 V to 5.5 V • VOUT adjustable from 1.0 V to VIN • Max output current: 400 mA • Up to 98% efficiency • 45 µA no-load quiescent current The AAT1149 output voltage is programmable using external feedback resistors. It can deliver 400 mA of load current while maintaining a low 45 µA no-load quiescent current. The 3.0 MHz switching frequency minimizes the size of external components while keeping switching losses low. The AAT1149 maintains high efficiency throughout the operating range, which is critical for portable applications. The AAT1149 is available in a Pb-free, space-saving 8-pin, 2.2 mm × 2.0 mm SC70JW package, and is rated over a −40 °C to +85 °C temperature range. A typical application circuit is shown in Figure 1. The pin configuration is shown in Figure 2. Signal pin assignments and functional pin descriptions are provided in Table 1. • 3.0 MHz switching frequency • 70 µs soft start • Fast load transient • Over-temperature protection • Current limit protection • 100% duty cycle low-dropout operation • Shutdown current: <1 µA • Temperature range: −40 °C to +85 °C • SC70JW (8-pin, 2.2 mm × 2 mm) package (MSL1, 260 °C per JEDEC-J-STD-020) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201987C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • July 1, 2013 1 PRELIMINARY DATA SHEET • AAT1149 3 MHZ FAST TRANSIENT 400 MA STEP-DOWN CONVERTER Figure 1. AAT1149 Typical Application Circuit Figure 2. AAT1149 8-Pin SC70JW (Top View) Table 1. AAT1149 Signal Descriptions Pin # Name Description 1 EN Enable pin. 2 FB Feedback input pin. This pin is connected to an external resistive divider for an adjustable output. 3 IN Input supply voltage for the converter. 4 LX 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 PGND Main power ground return pins. Connect to the output and input capacitor return. 7 PGND Main power ground return pins. Connect to the output and input capacitor return. 8 PGND Main power ground return pins. Connect to the output and input capacitor return. Electrical and Mechanical Specifications The absolute maximum ratings of the AAT1149 are provided in Table 2 and the electrical specifications are provided in Table 3. Typical performance characteristics of the AAT1149 are illustrated in Figures 3 through 28. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 2 July 1, 2013 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • 201987C PRELIMINARY DATA SHEET • AAT1149 3 MHZ FAST TRANSIENT 400 MA STEP-DOWN CONVERTER Table 2. AAT1149 Absolute Maximum Ratings (Note 1) Parameter Symbol Minimum Typical Maximum Units Input voltage to GND VIN 6.0 V LX to GND VLX −0.3 Vin + 0.3 V FB to GND VFB −0.3 Vin + 0.3 V EN to GND VEN −0.3 +6.0 V Operating junction temperature TJ −40 Maximum soldering temperature (at leads, 10 seconds) TLEAD 300 Maximum power dissipation (Note 2) PD 625 mW Thermal resistance θJA 160 °C/W +150 °C °C Note 1: Exposure to maximum rating conditions for extended periods may reduce device reliability. There is no damage to device with only one parameter set at the limit and all other parameters set at or below their nominal value. Exceeding any of the limits listed may result in permanent damage to the device. Note 2: Derate 6.25 mW/°C above 25 °C. CAUTION: Although this device is designed to be as robust as possible, Electrostatic Discharge (ESD) can damage this device. This device must be protected at all times from ESD. Static charges may easily produce potentials of several kilovolts on the human body or equipment, which can discharge without detection. Industry-standard ESD precautions should be used at all times. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201987C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • July 1, 2013 3 PRELIMINARY DATA SHEET • AAT1149 3 MHZ FAST TRANSIENT 400 MA STEP-DOWN CONVERTER Table 3. AAT1149 Electrical Specifications (Note 1) (VIN = 3.6 V, TA = −40 °C to 85 °C, Unless Otherwise Noted. Typical Values are at TA = 25 °C) Parameter Symbol Test Condition Min Typical Max Units Step-Down Converter Input voltage VIN 2.7 VIN rising UVLO threshold VUVLO Output voltage tolerance VOUT Adjustable output voltage range VOUT Hysteresis 5.5 V 2.7 V 100 mV VIN falling 1.8 IOUT = 0 to 400 mA, VIN = 2.7 V to 5.5 V −3.0 3.0 % V 1.0 VIN V 70 µA 1.0 µA Quiescent current IQ No load Shutdown current ISHDN VEN = GND 45 P-channel current limit ILIM High side switch On resistance RDS(ON)H 0.45 Ω Low side switch On resistance RDS(ON)L 0.40 Ω LX leakage current ILXLEAK VIN = 5.5 V, VLX = 0 to VIN, VIN = GND Line regulation ∆VLINEREG VIN = 2.7 V to 5.5 V Out threshold voltage accuracy VOUT 0.6 V output, no Load, TA = 25 °C 600 mA 1 0.1 591 600 µA %/V 609 mV 0.2 µA Out leakage current IOUT 0.6 V output Start-up time tS From enable to output regulation 70 µs Oscillator frequency fOSC TA = 25 °C 3.0 MHz Over-temperature shutdown threshold TSD 140 °C Over-temperature shutdown hysteresis THYS 15 °C EN Enable threshold low VEN(L) Enable threshold high VEN(H) Input low current IEN 0.6 V 1.0 µA 1.4 VIN = VOUT = 5.5 V −1.0 V Note 1: Performance is guaranteed only under the conditions listed in this Table. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 4 July 1, 2013 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • 201987C PRELIMINARY DATA SHEET • AAT1149 3 MHZ FAST TRANSIENT 400 MA STEP-DOWN CONVERTER Typical Performance Characteristics Figure 3. Efficiency vs Load Current (VOUT = 3 V, L = 3 µH) Figure 4. Load Regulation (VOUT = 3 V, L = 3 µH) Figure 5. Efficiency vs Load Current (VOUT = 1.8 V, L = 2.2 µH) Figure 6. Load Regulation (VOUT = 1.8 V, L = 2.2 µH) Figure 7. No Load Quiescent Current vs Input Voltage Figure 8. Switching Frequency vs Input Voltage Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201987C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • July 1, 2013 5 PRELIMINARY DATA SHEET • AAT1149 3 MHZ FAST TRANSIENT 400 MA STEP-DOWN CONVERTER Figure 9. Switching Frequency Variation vs Temperature Figure 10. Output Voltage Error vs Temperature (VIN = 3.6 V, VOUT = 1.8 V, IOUT = 400 mA) Figure 11. Line Regulation (VOUT = 3 V) Figure 12. Line Regulation (VOUT = 1.8 V) Figure 13. Line Regulation (VOUT = 1.1 V) Figure 14. Line Transient (VOUT = 1.8 V; 400 mA Load; No Feed Forward Capacitor) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 6 July 1, 2013 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • 201987C PRELIMINARY DATA SHEET • AAT1149 3 MHZ FAST TRANSIENT 400 MA STEP-DOWN CONVERTER Figure 15. Line Transient (VOUT = 1.8 V; No Feed Forward Capacitor) Figure 16. Line Transient (VOUT = 1.8 V; CFF = 100 pF) Figure 17. N-Channel RDS(ON) vs Input Voltage Figure 18. P-Channel RDS(ON) vs Input Voltage Figure 19. Load Transient (VOUT = 1.1 V; No Feed Forward Capacitor) Figure 20. Load Transient (Vout = 1.1 V; CFF = 100 pF) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201987C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • July 1, 2013 7 PRELIMINARY DATA SHEET • AAT1149 3 MHZ FAST TRANSIENT 400 MA STEP-DOWN CONVERTER Figure 21. Load Transient (VOUT = 1.8 V; No Feed Forward Capacitor) Figure 22. Load Transient (VOUT = 1.8 V; CFF = 100 pF) Figure 23. Load Transient (VOUT = 1.8 V; No Feed Forward Capacitor) Figure 24. Load Transient (VOUT = 1.8 V; CFF = 100 pF) Figure 25. Soft Start (VOUT = 1.8 V; No Feed Forward Capacitor) Figure 26. Soft Start (VOUT = 1.8 V; CFF = 100 pF) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 8 July 1, 2013 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • 201987C PRELIMINARY DATA SHEET • AAT1149 3 MHZ FAST TRANSIENT 400 MA STEP-DOWN CONVERTER Figure 27. Soft Start (VOUT = 3 V; No Feed-Forward Capacitor) Figure 28. Load Transient (VOUT = 1.1 V; No Feed-Forward Capacitor) Figure 29. AAT1149 Functional Block Diagram Functional Description The AAT1149 is a high performance 400 mA, 3.0 MHz monolithic step-down converter. It minimizes external component size, enabling the use of a tiny 0603 inductor that is only 1 mm tall, and optimizes efficiency over the complete load range. Apart from the small bypass input capacitor, only a small L-C filter is required at the output. Typically, a 1.8 µH inductor and a 4.7 µF ceramic capacitor are recommended (see Tables of values). A functional block diagram is provided in Figure 29. Only three external power components (CIN, COUT, and L) are required. Output voltage is programmed with external feedback resistors, ranging from 1.0 V to the input voltage. An additional feed-forward capacitor can also be added to the external feedback to provide improved transient response (see Figure 31). At dropout, the converter duty cycle increases to 100% and the output voltage tracks the input voltage minus the RDS(ON) drop of the P-channel high-side MOSFET. The input voltage range is 2.7 V to 5.5 V. The converter efficiency has been optimized for all load conditions, ranging from no load to 400 mA. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201987C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • July 1, 2013 9 PRELIMINARY DATA SHEET • AAT1149 3 MHZ FAST TRANSIENT 400 MA STEP-DOWN CONVERTER 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. Thermal protection completely disables switching when internal dissipation becomes excessive. The junction over-temperature threshold is 140 °C with 15 °C of hysteresis. Once an overtemperature or over-current fault condition is removed, the output voltage automatically recovers. Control Loop The AAT1149 is a peak current mode step-down converter. The current through the P-channel MOSFET (high side) is sensed for current loop control, as well as short circuit and overload protection. A fixed slope compensation signal is added to the sensed current to maintain stability for duty cycles greater than 50%. The peak current mode loop appears as a voltageprogrammed current source in parallel with the output capacitor. Under-Voltage Lockout 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 the adjustable output, the error amplifier reference is fixed at 0.6 V. The step-down converter uses peak current mode control with slope compensation to maintain stability for duty cycles greater than 50%. The output inductor value must be selected so the inductor current down slope meets the internal slope compensation requirements. Table 4 displays suggested inductor values for various output voltages. Internal bias of all circuits is controlled using the IN input. Under-Voltage Lockout (UVLO) guarantees sufficient VIN bias and proper operation of all internal circuitry before activation. Applications Information Inductor Selection Manufacturer’s specifications list both the inductor DC current rating, which is a thermal limitation, and the peak current rating, which is determined by the saturation characteristics. The inductor should not show any appreciable saturation under normal load conditions. Some inductors may meet the peak and average current ratings yet result in excessive losses due to a high Direct Current Resistance (DCR). Always consider the losses associated with the DCR and its effect on the total converter efficiency when selecting an inductor. Soft Start/Enable Soft start limits the current surge seen at the input and eliminates output voltage overshoot. When the EN pin is pulled low, it forces the AAT1149 into a low-power, non-switching state. The total input current during shutdown is less than 1 µA. Current Limit and Over-Temperature Protection For overload conditions, the peak input current is limited. 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. The 1.8 µH CDRH2D09 series inductor from Sumida has a 131 mΩ DCR and a 400 mA saturation current rating. At full load, the inductor DC loss is 21 mW which gives a 2.8% loss in efficiency for a 400 mA, 1.8 V output. Table 4. AAT1149 Suggested Inductor Values For Various Output Voltages Output Voltage (V) Typical Inductor Value (µH) 1.0 and 1.2 1.0 to 1.2 1.5 and 1.8 1.5 to 1.8 2.5 2.2 to 2.7 3.3 3.3 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 10 July 1, 2013 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • 201987C PRELIMINARY DATA SHEET • AAT1149 3 MHZ FAST TRANSIENT 400 MA STEP-DOWN CONVERTER Input Capacitor Select a 4.7 µF to 10 µF X7R or X5R ceramic capacitor for the input. To estimate the required input capacitor size, determine the acceptable input ripple level (VPP) and solve for C. The calculated value varies with input voltage and is a maximum when VIN is double the output voltage. C IN VOUT VOUT × 1 − VIN VIN = VPP − ESR × f S I OUT VOUT VOUT × 1 − VIN VIN C IN ( MIN ) = 1 = 4 for VIN = 2 × VOUT 1 VPP − ESR × 4 × f S I OUT Where fS is the switching frequency. Always examine the ceramic capacitor DC voltage coefficient characteristics when selecting the proper value. For example, the capacitance of a 10 µF, 6.3 V, X5R ceramic capacitor with 5.0 VDC applied is actually about 6 µF. The maximum input capacitor RMS current is: I RMS = I OUT V V × OUT × 1 − OUT V IN V IN The input capacitor RMS ripple current varies with the input and output voltage and always is less than or equal to half of the total DC load current. VOUT VOUT × 1 − VIN VIN 1 = D × (1 − D ) = 0.5 2 = 2 for VIN = 2 × VOUT I RMS（MAX） = I OUT 2 The term VOUT × 1 − VOUT appears in both the input voltage VIN VIN ripple and input capacitor RMS current equations and is a maximum when VOUT is twice VIN. This is why the input voltage ripple and the input capacitor RMS current ripple are a maximum at 50% duty cycle. The input capacitor provides a low impedance loop for the edges of pulsed current drawn by the AAT1149. Low Equivalent Series Resistance/Equivalent Series Inductance (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 AAT1149. 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 32. A laboratory test set-up typically consists of two long wires running from the bench power supply to the Evaluation Board input voltage pins. The inductance of these wires, along with the low ESR ceramic input capacitor, can create a high-Q network that may affect converter performance. This problem often becomes apparent in the form of excessive ringing in the output voltage during load transients. Errors in the loop phase and gain measurements can also result. Since the inductance of a short PCB trace feeding the input voltage is significantly lower than the power leads from the bench power supply, most applications do not exhibit this problem. In applications where the input power source lead inductance cannot be reduced to a level that does not affect the converter performance, a high ESR tantalum or aluminum electrolytic 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 provides holdup during large load transitions. A 4.7 µF to 10 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 (∆ILOAD) is dominated by the capacitance of the ceramic output capacitor. During a step increase in load current, the ceramic output capacitor alone supplies the load current until the loop responds. Within two or three switching cycles, the loop responds and the inductor current increases to match the load current demand. The relationship of the output voltage droop during the three switching cycles to the output capacitance can be estimated by: COUT = 3 × ∆I LOAD VDROOP × f S Once the average inductor current increases to the DC load level, the output voltage recovers. The above equation establishes a limit on the minimum value for the output capacitor with respect to load transients. The internal voltage loop compensation also limits the minimum output capacitor value to 4.7 µF. This is due to its effect on the loop crossover frequency (bandwidth), phase margin, and gain margin. Increased output capacitance reduces the crossover frequency with greater phase margin. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201987C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • July 1, 2013 11 PRELIMINARY DATA SHEET • AAT1149 3 MHZ FAST TRANSIENT 400 MA STEP-DOWN CONVERTER The maximum output capacitor RMS ripple current is given by: I RMS（MAX） = 1 2 3 × VOUT × (VIN ( MAX ) − VOUT ) L × f S × 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. Feedback Resistor Selection Resistors R1 and R2 in Figure 31 program the output to regulate at a voltage higher than 0.6 V. To limit the bias current required for the external feedback resistor string while maintaining good noise immunity, the minimum suggested value for R2 is 59 kΩ. Although a larger value can further reduce quiescent current, it also increases the impedance of the feedback node, making it more sensitive to external noise and interference. Table 5 summarizes the resistor values for various output voltages with R2 set to either 59 kΩ for good noise immunity or 121 kΩ for reduced no-load input current. V 1.5V R1 = OUT − 1 × R 2 = − 1 × 59 kΩ = 88.5kΩ V 0 . 6 V REF The AAT1149, combined with an external feed-forward capacitor (C3 in Figure 31), delivers enhanced transient response for extreme pulsed load applications. The addition of the feed-forward capacitor typically requires a larger output capacitor C1 for stability. devices. Switching losses are dominated by the gate charge of the power output switching devices. At full load, assuming Continuous Conduction Mode (CCM), a simplified form of the losses is given by: PTOTAL = 2 I OUT × (RDS ( ON ) H × VOUT + RDS ( ON ) L × [VIN − VOUT ]) + (t SW × f S × I OUT + I Q ) × VIN VIN IQ is the step-down converter quiescent current. The term tSW is used to estimate the full load step-down converter switching losses. For the condition where the step-down converter is in dropout at 100% duty cycle, the total device dissipation reduces to: 2 PTOTAL = I OUT × RDS ( ON ) H + I Q × VIN Since RDS(ON), quiescent current, and switching losses all vary with input voltage, the total losses should be investigated over the complete input voltage range. Given the total losses, the maximum junction temperature can be derived from the θJA for the SC70JW-8 package, which is 160 °C/W. TJ(MAX) = PTOTAL × θ JA + TA Layout The suggested PCB layout for the AAT1149 is shown in Figure 32. The following guidelines should be used to help ensure a proper layout. 1. The input capacitor (C2) should connect as closely as possible to IN (pin 3) and PGND (pins 6, 7, and 8). Table 5. Feedback Resistor Values VOUT (V) R1 (kΩ) (R2 = 59 kΩ) R1 (kΩ) (R2 = 121 kΩ) 1.00 39.2 80.6 1.10 49.9 100 1.20 59.0 121 1.30 68.1 140 1.40 78.7 162 1.50 88.7 182 1.80 118 243 1.85 124 255 2.00 137 280 2.50 187 383 3.30 267 549 Thermal Calculations There are three types of losses associated with the AAT1149 step-down converter: conduction losses, switching losses, and quiescent current losses. Conduction losses are associated with the RDS(ON) characteristics of the power output switching 2. C1 and L1 should be connected as closely as possible. The connection of L1 to the LX pin should be as short as possible. 3. The feedback trace or FB pin (pin 2) should be separate from any power trace and connect as closely as possible to the load point. Sensing along a high-current load trace degrades DC load regulation. If external feedback resistors are used, they should be placed as closely as possible to the FB pin (pin 2) to minimize the length of the high impedance feedback trace. 4. The resistance of the trace from the load return to PGND (pins 6, 7, and 8) should be kept to a minimum. This helps to minimize any error in DC regulation due to differences in the potential of the internal signal ground and the power ground. 5. A pad thickness of less than 1 mm is recommended to achieve higher stand-off. A high density, small footprint layout can be achieved using an inexpensive, miniature, nonshielded, high DCR inductor, as shown in Figure 30. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 12 July 1, 2013 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • 201987C PRELIMINARY DATA SHEET • AAT1149 3 MHZ FAST TRANSIENT 400 MA STEP-DOWN CONVERTER Evaluation Board Description The AAT1149 Evaluation Board schematic diagram is provided in Figure 31. The PCB layer details are shown in Figure 32. Figure 30. Minimum Evaluation Board Footprint Using 2.0 × 1.25 × 1.0 mm Inductor Figure 31. AAT1149 Evaluation Board Schematic Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201987C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • July 1, 2013 13 PRELIMINARY DATA SHEET • AAT1149 3 MHZ FAST TRANSIENT 400 MA STEP-DOWN CONVERTER Figure 32. AAT1149 Evaluation Board Layer Details Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 14 July 1, 2013 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • 201987C PRELIMINARY DATA SHEET • AAT1149 3 MHZ FAST TRANSIENT 400 MA STEP-DOWN CONVERTER Step-Down Converter Design Example Specifications VOUT = 1.8 V @ 400 mA, pulsed load ∆ILOAD = 300 mA VIN = 2.7 V to 4.2 V (3.6 V nominal) fS = 3.0 MHz TA = 85 °C 1.8 V Output Inductor L1 = 1 µs A × VOUT = 1 µs A × 1.8V = 1.8 µH For Taiyo Yuden inductor CBC2518T2R2M, 2.2 µH, DCR = 130 mΩ. ∆I L1 = V VOUT × 1 − OUT L1 × f S VIN I PKL1 = I OUT + ∆I L1 2 1.8V 1.8V = × 1 − = 156 mA 4.2V 2.2 µH × 3.0 MHz = 0.4V + 0.078 A = 0.478 A Where, IPKL1 is the peak current on L1. 2 × DCR = 0.4 A2 × 130 mΩ = 21mW PL1 = I OUT 1.8V Output Capacitor VDROOP = 0.1 V COUT == I RMS = 3 × ∆I LOAD 3 × 0.3 A = = 3.0 µH , use 4.7 µF VDROOP × f S 0.1V × 3.0 MHz 1 2 3 × VOUT × (VIN ( MAX ) − VOUT ) L1 × f S × VIN ( MAX ) = 1 2 3 × 1.8V × (4.2V − 1.8V ) = 45mArms 2.2 µH × 3.0 MHz × 4.2V 2 = 5mΩ × ( 45mA )2 = 10 µW PESR = ESR × I RMS Input Capacitor Input Ripple VPP = 25 mV C IN = I RMS = 1 V 4 × PP − ESR × f S I OUT = 1 25mV 4× − 5mΩ × 3.0 MHz 0.4A = 1.45 µF，use 2.2 µF I OUT = 0.2 Arms 2 2 P = ESR × I RMS = 5mΩ × ( 0.2 A )2 = 0.2mW AAT1149 Losses PTOTAL = = 2 I OUT × (RDS ( ON ) H × VOUT + RDS ( ON ) L × [VIN − VOUT ]) VIN + (t SW × f S × I OUT + I Q ) × VIN 0.4 2 × (0.725Ω × 1.8V + 0.7 Ω × [4.2V − 1.8V ]) + (5ns × 3 MHz × 0.4 A + 70 µA) × 4.2V = 140 mW 4.2V TJ(MAX) = PLOSS × θ JA + TA = (160°C / W ) × 140 mW + 85°C = 107°C Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201987C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • July 1, 2013 15 PRELIMINARY DATA SHEET • AAT1149 3 MHZ FAST TRANSIENT 400 MA STEP-DOWN CONVERTER Table 6 summarizes the feedback resistor values for various output voltages. Tables 7 and 8 list the typical surface mount inductors and surface mount capacitors. Table 6. Feedback Resistor Values VOUT (V) R1 (kΩ) (R2 = 59 kΩ) R1 (kΩ) (R2 = 121 kΩ) 1.0 39.2 80.6 1.0 1.2 59.0 121 1.2 1.5 88.7 182 1.5 1.8 118 243 1.8 2.5 187 383 2.2 3.3 267 549 3.3 L1 (µH) Table 7. Typical Surface Mount Inductors Manufacturer Part Number/Type Inductance (µH) Rated Current (mA) DCR (Ω) 1.0 520 180 0603 1.5 410 300 (height = 1 mm) 1.5 600 200 2.2 550 250 3.3 450 350 CBC2518 1.0 1000 80 Wire wound chip 2.2 890 130 1.2 590 97.5 1.5 520 110 1.8 480 131 2.5 440 150 3.0 400 195 1.0 485 300 LQH2MCN4R7M02 1.5 445 400 Unshielded 2.2 425 480 BRC1608 Taiyo Yuden BRL2012 CDRH2D09 Sumida Shielded Murata Coiltronics 3.3 375 600 1.2 720 75 SD3118 1.5 630 104 Shielded 2.2 510 116 3.3 430 139 Size (mm) L×W×H 0805 (height = 1 mm) 2.5×1.8×1.8 3.2×3.2×1.0 2.0×1.6×0.95 3.15×3.15×1.2 Table 8. Typical Surface Mount Capacitors Manufacturer Part Number Value (µF) Voltage (V) Temperature Coefficient Murata GRM219R61A475KE19 4.7 10 X5R 0805 Murata GRM21BR60J106KE19 10 6.3 X5R 0805 Murata GRM185R60J475M 4.7 6.3 X5R 0603 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 16 Case July 1, 2013 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • 201987C PRELIMINARY DATA SHEET • AAT1149 3 MHZ FAST TRANSIENT 400 MA STEP-DOWN CONVERTER Package Information Package dimensions and shown in Figure 33, and tape and reel dimensions are provided in Figure 34. Figure 33. AAT1149 8-pin SC70JW Package Dimensions Figure 34. AAT1149 Carrier Tape Dimensions Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201987C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • July 1, 2013 17 PRELIMINARY DATA SHEET • AAT1149 3 MHZ FAST TRANSIENT 400 MA STEP-DOWN CONVERTER Ordering Information Model Name AAT1149 Fast Transient Step-Down Converter Manufacturing Part Number (Note 1) AAT1149IJS-0.6-T1 Evaluation Board Part Number AAT1149IJS-0.6-EVB Note 1: Sample stock is generally held on the part number listed in BOLD. Copyright © 2012, 2013 Skyworks Solutions, Inc. All Rights Reserved. Information in this document is provided in connection with Skyworks Solutions, Inc. (“Skyworks”) products or services. These materials, including the information contained herein, are provided by Skyworks as a service to its customers and may be used for informational purposes only by the customer. Skyworks assumes no responsibility for errors or omissions in these materials or the information contained herein. Skyworks may change its documentation, products, services, specifications or product descriptions at any time, without notice. Skyworks makes no commitment to update the materials or information and shall have no responsibility whatsoever for conflicts, incompatibilities, or other difficulties arising from any future changes. No license, whether express, implied, by estoppel or otherwise, is granted to any intellectual property rights by this document. Skyworks assumes no liability for any materials, products or information provided hereunder, including the sale, distribution, reproduction or use of Skyworks products, information or materials, except as may be provided in Skyworks Terms and Conditions of Sale. 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Skyworks products are not intended for use in medical, lifesaving or life-sustaining applications, or other equipment in which the failure of the Skyworks products could lead to personal injury, death, physical or environmental damage. Skyworks customers using or selling Skyworks products for use in such applications do so at their own risk and agree to fully indemnify Skyworks for any damages resulting from such improper use or sale. Customers are responsible for their products and applications using Skyworks products, which may deviate from published specifications as a result of design defects, errors, or operation of products outside of published parameters or design specifications. Customers should include design and operating safeguards to minimize these and other risks. Skyworks assumes no liability for applications assistance, customer product design, or damage to any equipment resulting from the use of Skyworks products outside of stated published specifications or parameters. Skyworks, the Skyworks symbol, and “Breakthrough Simplicity” are trademarks or registered trademarks of Skyworks Solutions, Inc., in the United States and other countries. Third-party brands and names are for identification purposes only, and are the property of their respective owners. Additional information, including relevant terms and conditions, posted at www.skyworksinc.com, are incorporated by reference. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 18 July 1, 2013 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • 201987C