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AAT1150 1MHz 1A Step-Down DC/DC Converter General Description The AAT1150 SwitchRegTM is a member of AnalogicTech's Total Power Management ICTM (TPMICTM) product family. The step-down switching converter is ideal for applications where high efficiency, small size, and low ripple are critical. Able to deliver 1A with internal power MOSFETs, the current-mode controlled IC provides high efficiency using synchronous rectification. Fully internally compensated, the AAT1150 simplifies system design and lowers external parts count. The AAT1150 is available in an MSOP-8 package and is rated over the -40C to +85C temperature range. Features * * * * * * * * * * * * * * * * * SwitchRegTM VIN Range: 2.7V to 5.5V Up to 95% Efficiency 110m RDS(ON) MOSFET Switch <1.0A of Shutdown Current 1MHz Switching Frequency Fixed or Adjustable VOUT: 1.0V to 4.2V High Initial Accuracy: 1% 1.0A Peak Current Integrated Power Switches Synchronous Rectification Internally Compensated Current Mode Control Constant PWM Mode for Low Output Ripple Internal Soft Start Current Limit Protection Over-Temperature Protection MSOP-8 package -40C to +85C Temperature Range Applications * * * * * Cable/DSL Modems Computer Peripherals High Efficiency Conversion From 5V or 3.3V Supply Network Cards Set-Top Boxes Typical Application INPUT 10F VP FB AAT1150 4.1H LX ENABLE 100 VCC OUTPUT SGND 0.1F PGND 2x 22F 1150.2005.03.1.2 1 AAT1150 1MHz 1A Step-Down DC/DC Converter Pin Descriptions Pin # 1 2 3 4 5 6, 7 Symbol FB SGND EN VCC VP LX Function Feedback input pin. This pin must be connected to the converter's output. It is used to set the output of the converter to regulate to the desired value. Signal ground. Enable input pin. When connected high, the AAT1150 is in normal operation. When connected low, it is powered down. This pin should not be left floating. Power supply. It supplies power for the internal circuitry. Input supply voltage for converter power stage. Inductor connection pins. These pins should be connected to the output inductor. Internally, Pins 6 and 7 are connected to the drains of the P-channel switch and N-channel synchronous rectifier. Power ground return for the output stage. 8 PGND Pin Configuration MSOP-8 (Top View) FB SGND EN VCC 1 8 PGND LX LX VP 1 2 2 7 3 6 4 5 2 1150.2005.03.1.2 AAT1150 1MHz 1A Step-Down DC/DC Converter Absolute Maximum Ratings1 TA = 25C, unless otherwise noted. Symbol VCC, VP VLX VFB VEN TJ VESD Description VCC, VP to GND LX to GND FB to GND EN to GND Operating Junction Temperature Range ESD Rating2 - HBM Value 6 -0.3 to VP+0.3 -0.3 to VCC+0.3 -0.3 to 6 -40 to 150 3000 Units V V V V C V Thermal Characteristics Symbol JA PD Description Maximum Thermal Resistance (MSOP-8)3 Maximum Power Dissipation (MSOP-8, TA = 25C)3, 4 Value 150 667 Units C/W mW Recommended Operating Conditions Symbol T Description Ambient Temperature Range Rating -40 to +85 Units C 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. Human body model is a 100pF capacitor discharged through a 1.5K resistor into each pin. 3. Mounted on a demo board. 4. Derate 6.7mW/C above 25C. 1150.2005.03.1.2 3 AAT1150 1MHz 1A Step-Down DC/DC Converter Electrical Characteristics VIN = VCC = VP = 5V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = 25C. Symbol VIN VOUT Description Input Voltage Range Output Voltage Tolerance Conditions VIN = VOUT + 0.3 to 5.5V, IOUT = 0 to 1A VIN = 4.2V, ILOAD = 0 - 1A VIN = 2.7 to 5.5V VIN Rising VIN Falling No Load, VFB = 0 VEN = 0V, VIN = 5.5V TA = 25C TA = 25C TA = 25C VIN = 5V, VOUT = 3.3V, IOUT = 600mA VIN = 2.7 to 5.5V VIN = 2.7 to 5.5V VEN = 5.5V TA = 25C Min 2.7 -4.0 Typ Max 5.5 4.0 Units V % % %/V VOUT (VOUT*VIN) Load Regulation VOUT/VOUT Line Regulation VUVLO VUVLO(HYS) IQ ISHDN ILIM RDS(ON)H RDS(ON)L VEN(L) VEN(H) IEN FOSC TSD THYS Under-Voltage Lockout Under-Voltage Lockout Hysteresis Quiescent Supply Current Shutdown Current Current Limit High Side Switch On Resistance Low Side Switch On Resistance Efficiency Enable Low Voltage Enable High Voltage Enable Pin Leakage Current Oscillator Frequency Over-Temperature Shutdown Threshold Over-Temperature Shutdown Hysteresis 3.0 0.2 2.5 1.2 250 160 1.2 110 100 93 0.6 1.4 700 1000 140 15 1.0 1200 150 150 300 1.0 V mV A A A m m % V V A kHz C C 4 1150.2005.03.1.2 AAT1150 1MHz 1A Step-Down DC/DC Converter Typical Characteristics High Side RDS(ON) vs. Temperature 170 170 Low Side RDS(ON) vs. Temperature 150 3.6V RDS(ON) (m) 2.7V 150 RDS(ON) (m) 130 130 3.6V 2.7V 5.5V 4.2V 0 20 40 60 80 100 120 110 110 90 4.2V 5.5V 90 70 -20 0 20 40 60 80 100 120 70 -20 Temperature (C) Temperature (C) RDS(ON) vs. Input Voltage 130 1.2 Enable Threshold vs. Input Voltage 120 Enable Threshold (V) 1.1 High Side RDS(ON) (m) 110 VEN(H) 1 100 0.9 90 Low Side 0.8 VEN(L) 80 2.5 3 3.5 4 4.5 5 5.5 0.7 2.5 3 3.5 4 4.5 5 5.5 Input Voltage (V) Input Voltage (V) Oscillator Frequency Variation vs. Supply Voltage 3.5 2.5 Oscillator Frequency Variation vs. Temperature (VIN = 3.6V) 10 6 Variation (%) 1.5 0.5 -0.5 -1.5 2.5 3 3.5 4 4.5 5 5.5 Variation (%) 2 -2 -6 -10 -20 0 20 40 60 80 100 Supply Voltage (V) Temperature (C) 1150.2005.03.1.2 5 AAT1150 1MHz 1A Step-Down DC/DC Converter Typical Characteristics Output Voltage vs. Temperature (IOUT = 900mA; VOUT = 1.5V) Output Voltage Error (%) 1.0 Line Regulation (VOUT = 1.5V) 0.25 0.15 0.6 0.2 VIN = 2.7V Accuracy (%) IOUT = 1.0A 0.05 -0.05 -0.15 -0.25 -0.2 VIN = 3.6V IOUT = 0.4A -0.6 -1.0 -20 0 20 40 60 80 100 2.5 3 3.5 4 4.5 5 5.5 Temperature (C) Input Voltage (V) Load Regulation (VOUT = 1.5V; VIN = 3.6V) 0 -1 0 -1 Load Regulation (VOUT = 3.3V; VIN = 5.0V) VOUT Error (%) Error (%) -2 -3 -4 -2 -3 -4 -5 -5 0 150 300 450 600 750 900 0 150 300 450 600 750 900 1050 IOUT (mA) Output Current (mA) Efficiency vs. Input Voltage (VOUT = 1.5V) 100 Loop Gain and Phase vs. Output Capacitor (VIN = 3.6V; IOUT = 0.3A; CO = 22F) 40 225 180 135 90 45 0 2x 2x 3x 4x IO = 1A 90 32 24 16 Phase (degrees) Efficiency (%) Gain (dB) 4x Phase 3x 80 70 60 50 2.5 3 3.5 IO = 0.4A 8 0 -8 -16 -45 -90 -135 -180 -225 1000 -24 -32 -40 4 4.5 5 5.5 Gain 10 100 Input Voltage (V) Frequency (kHz) 6 1150.2005.03.1.2 AAT1150 1MHz 1A Step-Down DC/DC Converter Typical Characteristics No Load Input Current vs. Temperature (VCC = VP) 12 200 190 180 170 160 150 140 130 120 110 100 -20 -20 -5 10 25 40 55 70 85 -5 Non-Switching IQ vs. Temperature (FB = 0V; VP = VCC) Operating Current (A) VCC = 5.5V Input Current (mA) 10 8 6 4 2 0 VCC = 5.0V VCC = 5.5V VCC = 5.0V VCC = 4.2V VCC = 3.6V VCC = 2.7V 10 25 40 55 70 85 VCC = 4.2V VCC = 3.6V VCC = 2.7V Temperature (C) Temperature (C) Switching Waveform (VIN = 3.6V; VOUT = 1.5V; IOUT = 1.2A) Transient Response (VIN = 3.6V; VOUT = 1.5V; ILOAD = 0.25 to 1.2A) VOUT 50mV/div V(LX) 2V/div IL 500mA/div Inductor Current 500mA/div 500nsec/div 20s/div Output Ripple (VIN = 3.6V; VOUT = 1.5V; IOUT = 0A) Output Ripple (VIN = 3.6V; VOUT = 1.5V; IOUT = 1A) VOUT 5mV/div BW = 20MHz VOUT 5mV/div BW = 20MHz LX 2V/div LX 2V/div 500nsec/div 500nsec/div 1150.2005.03.1.2 7 AAT1150 1MHz 1A Step-Down DC/DC Converter Typical Characteristics Output Ripple (VIN = 5.0V; VOUT = 3.3V; IOUT = 0A) Output Ripple (VIN = 5.0V; VOUT = 3.3V; IOUT = 1A) VOUT 5mV/div BW = 20MHz VOUT 5mV/div BW = 20MHz LX 2V/div LX 2V/div 500nsec/div 500nsec/div Inrush Limit (VIN = 3.6V; VOUT = 1.5V; IL = 1A) Enable 2V/div VOUT 1V/div IL 0.5A/div 200sec/div 8 1150.2005.03.1.2 AAT1150 1MHz 1A Step-Down DC/DC Converter Functional Block Diagram VCC VP= 2.7V- 5.5V 1.0V REF FB OP. AMP CMP DH LOGIC LX 1M DL Temp. Sensing OSC SGND EN PGND Applications Information Control Loop The AAT1150 is a peak current mode buck converter. The inner wide bandwidth loop controls the peak current of the output inductor. The output inductor current is sensed through the P-channel MOSFET (high side) and is also used for short-circuit and overload protection. A fixed slope compensation signal is added to the sensed current to maintain stability. The loop appears as a voltageprogrammed current source in parallel with the output capacitor. The voltage error amplifier output programs the current loop for the necessary inductor current to force a constant output voltage for all load and line conditions. The feedback resistive divider is inter- nal, dividing the output voltage to the error amplifier reference voltage of 1.0V. The error amplifier does not have a large DC gain typical of most error amplifiers. This eliminates the need for external compensation components while still providing sufficient DC loop gain for load regulation. The crossover frequency and phase margin are set by the output capacitor value only. Soft Start/Enable Soft start increases the inductor current limit point in discrete steps when the input voltage or enable input is applied. It limits the current surge seen at the input and eliminates output voltage overshoot. The enable input, when pulled low, forces the AAT1150 into a low power, non-switching state. The total input current during shutdown is less than 1A. 1150.2005.03.1.2 9 AAT1150 1MHz 1A Step-Down DC/DC Converter Power and Signal Source Separate small signal ground and power supply pins isolate the internal control circuitry from the noise associated with the output MOSFET switching. The low pass filter R1 and C3 in schematic Figures 1 and 2 filters the noise associated with the power switching. Current Limit and Over-Temperature Protection For overload conditions, the peak input current is limited. Figure 3 displays the VI current limit characteristics. As load impedance decreases and the output voltage falls closer to zero, more power is dissipated internally, raising the device temperature. Thermal protection completely disables switching when internal dissipation becomes excessive, protecting the device from damage. The junction over-temperature threshold is 140C with 15C of hysteresis. 1.5V Efficiency vs. IOUT 2.7V-5.5V R1 100 R2 EN 100k C1 10F C3 0.1F SGND PGND LX L1 4.1H C2, C4 2x 22F AAT1150-1.5 VP VCC FB 80 V OUT 1.5V 1A 100 2.7V Efficiency (%) LX 60 4.2V 40 20 3.6V RTN C1 Murata 10F 6.3V X5R GRM42-6X 5R106K6.3 C2, C4 MuRata 22F 6.3V GRM21BR60J226ME39L 0805 X5R L1 Sumida CDRH5D18-4R 1H 0 10 100 1000 IOUT (mA) Figure 1: Lithium-Ion to 1.5V Converter. 3.3 Volt Efficiency vs. IOUT 3.5V-5.5V R1 100 AAT1150-3.3 VP VCC R2 EN C1 10F 100k C3 0.1F SGND PGND LX FB V OUT 3.3V 1A 100 90 80 VIN = 5.0V Efficiency (%) LX L1 4.1H 70 60 50 40 30 20 10 0 10 100 1000 C2, C4 2x 22F RTN C1 Murata 10F 6.3V X5R GRM42-6X 5R106K6.3 C2, C4 MuRata 22F 6.3V GRM21BR60J226ME39L X5R 0805 L1 Sumida CDRH5D18-4R 1H IOUT (mA) Figure 2: 5V Input to 3.3V Output Converter. 10 1150.2005.03.1.2 AAT1150 1MHz 1A Step-Down DC/DC Converter 3.5 3 2.5 VCC = VP = 5.0V VO = 3.3V Figure 2 Schematic VOUT (V) 2 1.5 1 0.5 0 0 0.5 1 1.5 2 2.5 VCC = VP = 3.6V VO = 1.5V Figure 1 Schematic IOUT (A) Figure 3: Current Limit Characteristic. Inductor The output inductor is selected to limit the ripple current to some predetermined value, typically 20% to 40% of the full load current at the maximum input voltage. 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. During overload and short-circuit conditions, the average current in the inductor can meet or exceed the ILIMIT point of the AAT1150 without affecting converter performance. Some inductors may have sufficient 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 a 1.0A load and the ripple set to 30% at the maximum input voltage, the maximum peak-topeak ripple current is 300mA. The inductance value required is 3.9H. V VOUT 1 - OUT IO k F VIN 1.5V 1.5V 11.0A 0.3 830kHz 4.2V The factor "k" is the fraction of full load selected for the ripple current at the maximum input voltage. The corresponding inductor RMS current is: IRMS = 2 I2 Io = 1.0A I+ o 12 I is the peak-to-peak ripple current which is fixed by the inductor selection above. For a peak-to-peak current of 30% of the full load current, the peak current at full load will be 115% of the full load. The 4.1H inductor selected from the Sumida CDRH5D18 series has a 57m DCR and a 1.95A DC current rating. At full load, the inductor DC loss is 57mW which amounts to a 3.8% loss in efficiency. Input Capacitor The primary function of the input capacitor is to provide a low impedance loop for the edges of pulsed current drawn by the AAT1150. A low ESR/ESL ceramic capacitor is 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 radiated and conducted EMI while facilitating optimum performance of the AAT1150. Ceramic X5R or X7R capacitors are ideal for this function. The size required will vary depending on the load, output voltage, and input voltage source impedance characteristics. A typical value is around 10F. The input capacitor RMS L= L= L = 3.9H 1150.2005.03.1.2 11 AAT1150 1MHz 1A Step-Down DC/DC Converter current varies with the input voltage and the output voltage. The equation for the RMS current in the input capacitor is: Adjustable Output For applications requiring an output other than the fixed outputs available, the 1V version can be programmed externally (see Figure 6). Resistors R3 and R4 force the output to regulate higher than 1V. R4 should be 100 times less than the internal 1m resistance of the FB pin. Once R4 is selected, R3 can be calculated. For a 1.25V output with R4 set to 10k, R3 is 2.55k. IRMS = IO VO VO 1VIN VIN The input capacitor RMS ripple current reaches a maximum when VIN is two times the output voltage where it is approximately one half of the load current. Losses associated with the input ceramic capacitor are typically minimal and are not an issue. Proper placement of the input capacitor can be seen in the reference design layout shown in Figures 4 and 5. R3 = (VO - 1) R4 = 0.25 10.0k = 2.55k Layout Considerations Figures 4 and 5 display the suggested PCB layout for the AAT1150. The most critical aspect of the layout is the placement of the input capacitor C1. For proper operation, C1 must be placed as closely as possible to the AAT1150. Output Capacitor Since there are no external compensation components, the output capacitor has a strong effect on loop stability. Larger output capacitance will reduce the crossover frequency with greater phase margin. For the 1.5V 1.0A design using the 4.1H inductor, two 22F capacitors provide a stable output. In addition to assisting stability, the output capacitor limits the output ripple and provides holdup during large load transitions. The output capacitor RMS ripple current is given by: VOUT (VIN - VOUT) L F VIN Thermal Calculations There are two types of losses associated with the AAT1150 output switching MOSFET: switching losses and conduction losses. Conduction losses are associated with the RDS(ON) characteristics of the output switching device. At full load, assuming continuous conduction mode (CCM), a simplified form of the total losses is: IRMS = 1 2 3 PLOSS = For a ceramic capacitor, the dissipation due to the RMS current of the capacitor is not a concern. Tantalum capacitors, with sufficiently low ESR to meet output voltage ripple requirements, also have an RMS current rating much greater than that actually seen in this application. IO2 (RDSON(H) VO + RDSON(L) (VIN - VO)) VIN + tsw F IO VIN + IQ VIN Once the total losses have been determined, the junction temperature can be derived from the JA for the MSOP-8 package. 12 1150.2005.03.1.2 AAT1150 1MHz 1A Step-Down DC/DC Converter Figure 4: AAT1150 Layout Top Layer. Figure 5: AAT1150 Layout Bottom Layer. VIN+ 3.3V R1 100 R2 C1 10F 100k C3 0.1F EN AAT1150-1.0 VP VCC EN LX FB R3 2.55k 1% V O + 1.25V 1A R4 10k 1% L1 2.7H SGND PGND LX C2, C4 2x 22F VC1 Murata 10F 6.3V X5R GRM42-6X 5R106K6.3 C2, C4 MuRata 22F 6.3V GRM21BR60J226ME39L X5R 0805 L1 Sumida CDRH4D28-2R7H Figure 6: 3.3V to 1.25V Converter (Adjustable Output). 1150.2005.03.1.2 13 AAT1150 1MHz 1A Step-Down DC/DC Converter Design Example Specifications IOUT = 1.0A IRIPPLE = 30% of Full Load at Max VIN VOUT = 1.5V VIN = 2.7V to 4.2V (3.6V nominal) Fs = 830kHz Maximum Input Capacitor Ripple IRMS = IO VO VO IO 1= = 0.5ARMS, VIN = 2 x VO VIN VIN 2 P = ESRCOUT IRMS2 = 5m 0.52 A = 1.25mW Inductor Selection L= V VOUT 1.5V 1.5V 1 - OUT = 1= 3.9H IO k F VIN 1.0A 0.3 830kHz 4.2V Select Sumida inductor CDRH5D18, 4.1H, 57m, 2.0mm height. I = 1.5V VO V 1.5V 1- O = 1= 280mA L F VIN 4.1H 830kHz 4.2V IPK = IOUT + I = 1.0A + 0.14A = 1.14A 2 P = IO2 DCR = 57mW Output Capacitor Dissipation IRMS = VOUT (VIN - VOUT) 1.5V (4.2V - 1.5V) 1 1 = = 82mARMS L F VIN 2 3 2 3 4.1H 830kHz 4.2V PESR = ESRCOUT IRMS2 = 5m 0.0822A = 33W 14 1150.2005.03.1.2 AAT1150 1MHz 1A Step-Down DC/DC Converter AAT1150 Dissipation P= IO2 (RDSON(H) VO + RDSON(L) (VIN -VO)) VIN + (tsw F IO + IQ) VIN = (0.14 1.5V + 0.145 (3.6V - 1.5V)) 3.6V + (20nsec 830kHz 1.0A + 0.3mA) 3.6V = 0.203W TJ(MAX) = TAMB + JA PLOSS = 85C + 150C/W 0.203W = 115C Table 1: Surface Mount Inductors. Manufacturer TaiyoYuden Toko Sumida Sumida MuRata MuRata Part Number NPO5DB4R7M A914BYW-3R5M-D52LC CDRH5D28-4R2 CDRH5D18-4R1 LQH55DN4R7M03 LQH66SN4R7M03 Value 4.7H 3.5H 4.2H 4.1H 4.7H 4.7H Max DC Current 1.4A 1.34A 2.2A 1.95A 2.7A 2.2A DCR 0.038 0.073 0.031 0.057 0.041 0.025 Size (mm) LxWxH Type 5.9 x 6.1 x 2.8 Shielded 5.0 x 5.0 x 2.0 Shielded 5.7 x 5.7 x 3.0 Shielded 5.7 x 5.7 x 2.0 Shielded 5.0 x 5.0 x 4.7 Non-Shielded 6.3 x 6.3 x 4.7 Shielded Table 2: Surface Mount Capacitors. Manufacturer MuRata MuRata MuRata MuRata Part Number GRM40 X5R 106K 6.3 GRM42-6 X5R 106K 6.3 GRM21BR60J226ME39L GRM21BR60J106ME39L Value 10F 10F 22F 10F Voltage 6.3V 6.3V 6.3V 6.3V Temp. Co. X5R X5R X5R X5R Case 0805 1206 0805 0805 1150.2005.03.1.2 15 AAT1150 1MHz 1A Step-Down DC/DC Converter Ordering Information Output Voltage 1.0V (Adj VOUT 1.0V) 1.5V 1.8V 2.5V 3.3V Package MSOP-8 MSOP-8 MSOP-8 MSOP-8 MSOP-8 Marking JZXYY HYXYY KAXYY KCXYY HZXYY Part Number (Tape and Reel) AAT1150IKS-1.0-T1 AAT1150IKS-1.5-T1 AAT1150IKS-1.8-T1 AAT1150IKS-2.5-T1 AAT1150IKS-3.3-T1 Package Information MSOP-8 4 4 1.95 BSC 3.00 0.10 4.90 0.10 0.60 0.20 PIN 1 0.254 BSC 0.95 REF 3.00 0.10 10 5 0.95 0.15 0.85 0.10 0.65 BSC 0.30 0.08 0.075 0.075 All dimensions in millimeters. 1. XYY = assembly and date code. 2. Sample stock is held on part numbers listed in bold. Contact local sales office for custom options. 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, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. AnalogicTech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with AnalogicTech's standard warranty. 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. Advanced Analogic Technologies, Inc. 830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737-4600 Fax (408) 737-4611 16 1150.2005.03.1.2 GAUGE PLANE 0.155 0.075 |
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