AAT1157 1MHz 1.2A Buck DC/DC Converter General Description Features The AAT1157 SwitchReg™ is a member of AnalogicTech's Total Power Management IC™ (TPMIC™) product family. The step-down switching converter is ideal for applications where fixed frequency and low ripple are required over the full range of load conditions. The 2.7V to 5.5V input voltage range makes the AAT1157 ideal for singlecell lithium-ion/polymer battery applications. Capable of up to 1.2A with internal MOSFETs, the current-mode controlled IC provides high efficiency over a wide operating range. Fully integrated compensation simplifies system design and lowers external parts count. The device operates at a fixed 1MHz switching frequency across all load conditions. • • • • • • • • • • • VIN Range: 2.7V to 5.5V Up to 95% Efficiency 110 mΩ RDS(ON) Internal Switches <1µA Shutdown Current 1MHz Buck Switching Frequency Fixed or Adjustable VOUT ≥ 0.8V Integrated Power Switches Current Mode Operation Internal Compensation Stable with Ceramic Capacitors Constant PWM Operation for Low Output Ripple Internal Soft Start Over-Temperature Protection Current Limit Protection 16-Pin QFN 3x3mm Package -40°C to +85°C Temperature Range • • • • • The AAT1157 is available in the Pb-free, 16-pin 3x3mm QFN package and is rated over the -40°C to +85°C temperature range. SwitchReg™ Applications • • • • • • • HDD MP3 Players Notebook Computers PDAs Point-of-Load Regulation Set Top Boxes Smart Phones Wireless Notebook Adapters Typical Application U1 AAT1157 3.3V 12 R1 100 C1 10µF 11 10 7 9 6 C2 0.1µF 8 5 1157.2005.11.1.4 VP FB VP LX VP LX EN VCC LX N/C N/C PGND N/C PGND SGND PGND 2.5V 4 R3 187k 15 14 13 L1 3.0µH 16 3 R4 59k C3-C4 2x 22µF 2 1 1 AAT1157 1MHz 1.2A Buck DC/DC Converter Pin Descriptions Pin # Symbol 1, 2, 3 PGND 4 FB 5 SGND Signal ground. Connect the return of all small signal components to this pin. (See board layout rules.) 7 EN Enable input pin. A logic high enables the converter; a logic low forces the AAT1157 into shutdown mode reducing the supply current to less than 1µA. The pin should not be left floating. 6, 8, 16 N/C Not internally connected. 9 VCC Bias supply. Supplies power for the internal circuitry. Connect to input power via low pass filter with decoupling to SGND. 10, 11, 12 VP Input supply voltage for the converter power stage. Must be closely decoupled to PGND. 13, 14, 15 LX Connect inductor to these pins. Switching node internally connected to the drain of both high- and low-side MOSFETs. EP Function Main power ground return pin. Connect to the output and input capacitor return. (See board layout rules.) Feedback input pin. This pin is connected to the converter output. It is used to set the output of the converter to regulate to the desired value via an internal resistive divider. For an adjustable output, an external resistive divider is connected to this pin. Exposed paddle (bottom); connect to PGND directly beneath package. Pin Configuration QFN33-16 (Top View) LX LX LX N/C 13 14 15 16 PGND PGND PGND FB 1 12 2 11 3 10 4 9 VP VP VP VCC 8 7 6 5 N/C EN N/C SGND 2 1157.2005.11.1.4 AAT1157 1MHz 1.2A Buck DC/DC Converter Absolute Maximum Ratings1 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 Units 6 -0.3 to VP + 0.3 -0.3 to VCC + 0.3 -0.3 to -6 -40 to150 3000 V V V V °C V Value Units 50 4.2 2.0 °C/W °C/W W Value Units -40 to 85 °C Thermal Characteristics Symbol θJA θJC PD Description 3 Maximum Thermal Resistance (QFN33-16) Maximum Thermal Resistance (QFN33-16) Maximum Power Dissipation (QFN33-16) (TA = 25°C)3, 4 Recommended Operating Conditions Symbol T Description Ambient Temperature Range 1. Stresses above those listed in Absolute Maximum Ratings may cause 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 100pF capacitor discharged through a 1.5kΩ resistor into each pin. 3. Mounted on a demo board (FR4, in still air). Exposed pad must be mounted to PCB. 4. Derate 20mW/°C above 25°C. 1157.2005.11.1.4 3 AAT1157 1MHz 1.2A Buck DC/DC Converter Electrical Characteristics1 VIN = VCC = VP = 5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = 25°C. Symbol VIN Description Input Voltage Range VOUT Output Voltage Tolerance ∆VOUT/VOUT ∆VOUT(VOUT*∆VIN) IQ ISHDN ILIM Load Regulation Line Regulation Quiescent Supply Current Shutdown Current Current Limit VUVLO VUVLO(HYS) VIL VIH IIL IIH RDS(ON)H RDS(ON)L FOSC TSD THYS Conditions Under-Voltage Lockout Under-Voltage Lockout Hysteresis Input Low Voltage Input High Voltage Input Low Current Input High Current High Side Switch On Resistance Low Side Switch On Resistance Oscillator Frequency Over-Temperature Shutdown Threshold Over-Temperature Shutdown Hysteresis VIN = VOUT + 0.2 to 5.5V, IOUT = 0 to 1.2A VIN = 4.2V, ILOAD = 0 to 1.2A VIN =2.7 to 5.5V No Load VEN = 0V, VIN = 5.5V TA = 25°C VIN Rising, VEN = VCC VIN Falling, VEN = VCC Min Typ Max Units 2.7 5.5 V -4 +4 % ±2.5 ±0.1 160 300 1.0 1.7 2.5 1.2 250 0.6 1.4 VIN = VFB = 5.5V VIN = VFB = 0V TA = 25°C TA = 25°C TA = 25°C 750 110 100 1000 1.0 1.0 150 150 1250 % %/V µA µA A V mV V V µA µA mΩ mΩ kHz 140 °C 15 °C 1. The AAT1157 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correlation with statistical process controls. 4 1157.2005.11.1.4 AAT1157 1MHz 1.2A Buck DC/DC Converter Typical Characteristics No Load Supply Current vs. Input Voltage DC Regulation (VOUT = 2.5V) 2.0 300 VIN = 3.6V 1.0 Output Error (%) Supply Current (µ µA) 85°C 250 200 25°C 150 -40°C 100 50 VIN = 3.3V -1.0 -2.0 -3.0 -4.0 0 2.5 3 3.5 4 4.5 5 1 5.5 10 100 10000 Output Current (mA) P-Channel RDSON vs. Input Voltage N-Channel RDSON vs. Input Voltage 200 180 180 100°C 160 120°C 160 RDSON (mΩ Ω) 140 120 100 85°C 80 25°C 60 100°C 120°C 140 120 100 80 85°C 60 40 40 20 20 0 2.5 25°C 0 3 3.5 4 4.5 5 5.5 2.5 3 3.5 4 4.5 5 Input Voltage (V) Input Voltage (V) Output Voltage vs. Temperature Frequency vs. Input Voltage (VIN = 3.6V; VOUT = 2.5V; IOUT = 1.0A) 5.5 (VOUT = 1.8V) 0.1 1.3 0 Frequency (MHz) Output Voltage Error (%) 1000 Input Voltage (V) 200 RDSON (mΩ Ω) VIN = 3.0V 0.0 -0.1 -0.2 -0.3 -0.4 -0.5 1.28 1.26 1.24 1.22 -0.6 -0.7 -40 -20 0 20 40 Temperature (°°C) 1157.2005.11.1.4 60 80 100 1.2 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 Input Voltage (V) 5 AAT1157 1MHz 1.2A Buck DC/DC Converter Output Ripple (VOUT = 2.5V; IOUT = 1.2A; VIN = 3.6V) 3.5 4.0 3.0 2.0 2.5 0.0 2.0 -2.0 1.5 -4.0 1.0 -6.0 0.5 -8.0 0.0 -10.0 -0.5 0.02 2 -0.01 -0.02 1.5 -0.03 1 -0.04 0.5 -0.05 -0.06 0 Time (500ns/div) Load Transient Response (400mA-1.2A; VIN = 3.3V; VOUT = 2.5V) 0.24 4.2 0.20 4.0 0.16 3.8 0.12 3.6 0.08 3.4 0.04 3.2 0.00 3.0 -0.04 2.8 -0.08 Time (25µ µs/div) 0.08 4.0 0.05 3.5 0.02 3.0 -0.01 2.5 -0.04 -0.07 2.0 1.5 1.2A -0.10 -0.13 1.0 400mA -0.16 Load Current (A) (bottom) 4.4 Output Voltage (AC Coupled) (V) (top) Line Transient (IOUT = 1.2A; VO = 2.5V) Output Voltage (AC coupled) (bottom) (V) Input Voltage (top) (V) 2.5 0 Time (250µ µs/div) 6 3 0.01 Inductor Current (bottom) (A) 6.0 Output Voltage (AC coupled) (top) (V) Soft Start (VOUT = 2.5V; IOUT = 1.2A; VIN = 3.6V) Inductor Current (bottom) (A) Enable and Output Voltage (top) (V) Typical Characteristics 0.5 0.0 Time (20µ µs/div) 1157.2005.11.1.4 AAT1157 1MHz 1.2A Buck DC/DC Converter Functional Block Diagram VCC VP = 2.7V to 5.5V 1.0V REF FB OP. AMP CMP DH LOGIC 1MΩ LX DL Temp. Sensing OSC SGND Applications Information Control Loop The AAT1157 is a peak current mode buck converter. The inner wide bandwidth loop controls the inductor peak current. The 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 for duty cycles greater than 50%. The loop appears as a voltage-programmed 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 external voltage feedback resistive divider divides the output voltage to the error amplifier reference voltage of 0.6V. The low-DC gain voltage error amplifier eliminates the need for external compensation components while providing sufficient DC loop gain for good load regulation. The voltage loop crossover frequency and phase margin are set by the output capacitor. Soft Start/Enable Soft start increases the inductor current limit point in discrete steps once the input voltage or enable 1157.2005.11.1.4 EN PGND input is applied. It limits the current surge seen at the input and eliminates output voltage overshoot. When pulled low, the enable input forces the AAT1157 into a non-switching shutdown state. The total input current during shutdown is less than 1µA. Power and Signal Source Separate small signal ground and power supply pins isolate the internal control circuitry from the noise associated with the output power MOSFET switching. The low-pass filter R1 and C2 shown in the Figure 1 schematic filters the input noise associated with the power switching. Current Limit and Over-Temperature Protection For overload conditions, the peak input current sensed through the high-side P-channel MOSFET is limited. Thermal protection completely disables switching when internal dissipation becomes excessive, protecting the device from damage. The junction over-temperature threshold is 140°C with 15°C of hysteresis. Once the over-temperature or over-current fault is removed, the AAT1157 automatically recovers. 7 AAT1157 1MHz 1.2A Buck DC/DC Converter LX Enable 12 R1 100 R2 C1 10µF 100K C2 0.1µF 11 10 7 9 6 8 5 GND VOUT+ U1 AAT1157 VIN+ VP FB VP LX VP LX EN LX VCC N/C N/C N/C PGND PGND SGND PGND 4 R3 15 14 13 L1 3.0µH 16 3 R4 59.0k C3-C4 2x 22µF 2 1 VOUT(V) 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.8 2.0 2.5 3.3 R3 (kΩ) 19.6 29.4 39.2 49.9 59.0 68.1 78.7 88.7 118 137 187 267 GND C1 Murata 10µF 6.3V X5R GRM42-6X5R106K6.3 C3,C4 MuRata 22µF 6.3V GRM21BR60J226ME39L X5R 0805 L1 Sumida CDRH5D28-3R0NC Figure 1: AAT1157 Evaluation Board Schematic Lithium-Ion to 2.5V Converter. Inductor Input Capacitor The output inductor should limit the ripple current to 330mA at the maximum input voltage. This matches the inductor current downslope with the fixed internal slope compensation. For a 2.5V output and the ripple set to a maximum input voltage of 4.2V, the inductance value required to limit the ripple current to 330mA is 3.0µH. From this calculated value, a standard value can be selected. The primary function of the input capacitor is to provide a low impedance loop for the edges of pulsed current drawn by the AAT1157. 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 AAT1157. 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. Values range from 1µF to 10µF. The input capacitor RMS current varies with the input voltage and the output voltage. The equation for the RMS current in the input capacitor is: 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 DCR. Always consider the losses associated with the DCR and its effect on the total converter efficiency when selecting an inductor. L= = ⎛ VOUT VOUT ⎞ ⋅1∆IPP ⋅ F ⎝ VIN(MAX)⎠ 2.5V ⎛ 2.5V ⎞ ⋅ 10.33A ⋅ 1MHz ⎝ 4.2V ⎠ = 3.07µH For a maximum ripple current of 330mA, the peak switch and inductor current at 1.2A is 1.365A. A standard value of 3.0µH can be used in this example. The 3.0µH Sumida series CDRH5D28 inductor has a 24mΩ maximum DCR and a 2.4A DC current rating. 8 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. The proper placement of the input capacitor can be seen in the evaluation board layout (C1 in Figure 2). 1157.2005.11.1.4 AAT1157 1MHz 1.2A Buck DC/DC Converter For an X7R or X5R ceramic capacitor, the ESR is very low and 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 well beyond that actually seen in this application. 3. The trace connecting the FB pin to resistors R3 and R4 should be as short as possible by placing R3 and R4 immediately next to the AAT1157. The sense trace connection R3 to the output voltage should be separate from any power trace and connect as closely as possible to the load point. Sensing along a high-current load trace will degrade DC load regulation. 4. The resistance of the trace from the load return to the PGND (Pins 1, 2, and 3) and SGND (Pin 5) 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. SGND (Pin 5) can also be used to remotely sense the output ground at the point of load to improve regulation. 5. A low pass filter (R1 and C2) provides a cleaner bias source for the AAT1157 active circuitry. C2 should be placed as closely as possible to SGND (Pin 5) and VCC (Pin 9). 6. For good heat transfer, four 15 mil vias spaced on a 26 mil grid connect the QFN central paddle to the bottom side ground plane, as shown in Figures 2 and 3. Layout Thermal Calculations Figures 2 and 3 display the suggested PCB layout for the AAT1157. The following guidelines should be used to help insure a proper layout. There are three types of losses associated with the AAT1157: MOSFET switching losses, conduction losses, and quiescent current losses. The conduction losses are due to the RDSON characteristics of the internal P- and N-channel MOSFET power devices. At full load, assuming continuous conduction mode (CCM), a simplified form of the total losses is given by: Output Capacitor Since there are no external compensation components, the output capacitor has a strong effect on loop stability. Larger output capacitance reduces the crossover frequency while increasing the phase margin. For the 2.5V 1.2A design using the 3.0µH inductor, a 40µF capacitor provides a stable output. Table 1 provides a list of suggested output capacitor values for various output voltages. In addition to assisting in stability, the output capacitor limits the output ripple and provides holdup during large load transitions. The output capacitor RMS ripple current is given by: IRMS = 1. 2. 1 2⋅ 3 ⋅ VOUT ⋅ (VIN - VOUT) L ⋅ F ⋅ VIN The input capacitor (C1) should connect as closely as possible to VP (Pins 10, 11, and 12) and PGND (Pins 1, 2, and 3). C3-C4 and L1 should be connected as closely as possible. The connection from L1 to the LX node should be as short as possible. Figure 2: Evaluation Board Top Side. 1157.2005.11.1.4 Figure 3: Evaluation Board Bottom Side. 9 AAT1157 1MHz 1.2A Buck DC/DC Converter P= 59kΩ. Values higher than this can cause stability problems, while lower values can degrade light load efficiency. For a 2.5V output with R4 set to 59kΩ, R3 is 187kΩ. IO2 ⋅ (RDSON(HS) ⋅ VO + RDSON(LS) ⋅ (VIN - VO)) VIN + (tsw ⋅ F ⋅ IO ⋅ VIN + IQ) ⋅ VIN ⎛ VO ⎞ ⎛ 2.5V ⎞ R3 = V -1 · R4 = 0.6V - 1 · 59kΩ = 187kΩ ⎝ REF ⎠ ⎝ ⎠ Where IQ is the AAT1157 quiescent current. Once the total losses have been determined, the junction temperature can be derived from the θJA for the QFN package. Close attention should be paid to the proper layout for the QFN package. Proper size and placement of thermal routing vias below the central paddle is necessary for good heat transfer to other PCB layers and their ground planes. The θJA for the QFN package with no connection to the central paddle is 50°C/W. The actual θJA will vary with the number and type of vias. The PCB board size, number of board layers, and ground plane characteristics also influence the θJA. A good thermal connection from the paddle to the PCB ground plane layers can significantly reduce θJA. Table 1: Suggested Component Values. Output Voltage (V) 0.8 1.0 1.2 1.5 1.8 2.5 3.3 L1 (µH) 1.5 1.5 2.2 2.2 3.0 3.0 2.2 - Output Capacitor (C3-C4) (µF) R3 for Ω R4 = 59kΩ Ω) (kΩ 3x 22 2x 22 2x 22 2x 22 2x 22 2x 22 22 19.6 39.2 59 88.7 118 187 267 2.6 3.3 3.3 4.7 4.7 4.7 4.7 TJ = P · ΘJA + TAMB Buck-Boost Output Adjustable Output Resistors R3 and R4, as shown in Figure 1, force the output to regulate higher than the 0.6V reference voltage level. The optimum value for R4 is VIN 2.7V to 5.5V Figure 4 shows how to configure the AAT1157 in a buck boost configuration with an external MOSFET and Schottky diode. The converter has a 3.3V 600mA output with an input voltage ranging from 2.7V to 5.5V. U1 AAT1157 R1 100 C1 22µF C2 0.1µF VO 3.3V/600mA R2 267k 12 VP OUT 4 11 VP LX 15 10 VP LX 14 7 EN LX 13 9 VCC N/C 16 6 N/C PGND 8 N/C PGND 5 SGND PGND 3 L1 3.0µH D1 MBRM120L Q1 Si2302ADS R3 59.0k C3,C4 2x 22µF 2 1 L1 Sumida CDRH5D28-3R0 C1 Murata 22µF 10V X7R 1210 GRM32ER71A226KE20L C3,C4 MuRata 22µF 6.3V X5R 0805 GRM21BR60J226ME39L Figure 4: AAT1157 Buck Boost Converter. 10 1157.2005.11.1.4 AAT1157 1MHz 1.2A Buck DC/DC Converter Design Example Specifications IOUT 1.2A IRIPPLE 330mA VOUT 2.5V VIN 3.0V to 4.2V FS 1MHz TAMB = 85°C Maximum Input Capacitor Ripple: IRMS = I O · VO ⎛ V ⎞ · 1 - O = 0.59Arms VIN ⎝ VIN ⎠ P = esr · IRMS2 = 5mΩ · 0.592 A = 1.7mW Inductor Selection: L= ⎛ V ⎞ VOUT 2.5V 2.5V⎞ ⎛ ⋅ 1 - OUT = ⋅ 1= 3.07µH ∆IPP ⋅ F ⎝ VIN ⎠ 0.33A ⋅ 1MHz ⎝ 4.2V⎠ Select Sumida inductor CDRH5D28 3.0µH. ∆I = ⎛ 2.5V⎞ VO ⎛ V ⎞ 2.5V ⋅ 1- O = ⋅ ⎝1= 340mA L ⋅ F ⎝ VIN ⎠ 3.0µH ⋅ 1MHz 4.2V⎠ IPK = IOUT + ∆I = 1.2A + 0.17A = 1.37A 2 P = IO2 ⋅ DCR = (1.2A)2 ⋅ 31mΩ = 45mW Output Capacitor Ripple Current: IRMS = (VOUT) · (VIN - VOUT) 1 2.5V · (4.2V - 2.5V) · = 97.4mArms = L · F · VIN 2 · 3 3.0µH · 1MHz · 4.2V 2· 3 1 · Pesr = esr · IRMS2 = 5mΩ · (97.4mA)2 = 47.4µW 1157.2005.11.1.4 11 AAT1157 1MHz 1.2A Buck DC/DC Converter AAT1157 Dissipation and Junction Temperature Estimate: PTOTAL = = IO2 · (RDSON(HS) · VO + RDSON(LS) · (VIN -VO)) VIN + (tsw · F · IO + IQ) · VIN 1.2A2 · (0.17Ω · 2.5V + 0.16Ω · (4.2V - 2.5V)) 4.2V + (20nsec · 1MHz · 1.2A + 275µA) · 4.2V = 341mW TJ(MAX) = TAMB + ΘJA · PTOTAL = 85°C + 50°C/W · 0.341W = 102°C Surface Mount Inductors Manufacturer Part Number Sumida Sumida Sumida TaiyoYuden Sumida Sumida Sumida Sumida Sumida Sumida MuRata MuRata CDRH5D28-2R6 CDRH5D28-3R0 CDRH5D28-4R2 NPO5DB4R7M CDRH4D28-2R2 CDRH4D28-2R7 CDRH4D28-3R3 CDRH5D18-4R1 CDRH3D16/HP-2R2 CDRH3D16/HP-3R3 LQH55DN4R7M03 LQH66SN4R7M03 Value (µH) Max DC Current (A) DCR Ω) (mΩ Size (mm) LxWxH Type 2.6 3.0 4.2 4.7 2.2 2.7 3.3 4.1 2.2 3.3 4.7 4.7 2.6 2.4 2.2 1.4 2.04 1.6 1.57 1.95 2.3 1.8 2.7 2.2 18 24 31 38 31 43 49 57 59 85 41 25 5.7x5.7x3.0 5.7x5.7x3.0 5.7x5.7x3.0 5.9x6.1x2.8 5.0x5.0x3.0 5.0x5.0x3.0 5.0x5.0x3.0 5.7x5.7x2.0 4.0x4.0x1.8 4.0x4.0x1.8 5.0x5.0x4.7 6.3x6.3x4.7 Shielded Shielded Shielded Shielded Shielded Shielded Shielded Shielded Shielded Shielded Non-Shielded Shielded Surface Mount Capacitors Manufacturer Part Number MuRata MuRata MuRata GRM21BR60J106ME01L GRM21BR60J226ME01L GRM31CR60J106KA01L 12 Value (µF) Voltage (V) Temp. Co. Case 10 22 10 6.3 6.3 6.3 X5R X5R X5R 0805 0805 1206 1157.2005.11.1.4 AAT1157 1MHz 1.2A Buck DC/DC Converter Ordering Information Output Voltage Package Marking1 Part Number (Tape and Reel)2 FB = 0.8V, Adjustable ≥ 0.8V QFN33-16 OEXYY AAT1157IVN-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/pbfree. Package Information QFN33-16 0.230 ± 0.05 Pin 1 Identification 1 1.55 ± 0.15 13 9 0.500 ± 0.05 Top View 0.025 ± 0.025 Bottom View 0.850 ± 0.05 3.000 ± 0.05 0.400 ± 0.05 Pin 1 Dot By Marking 3.000 ± 0.05 5 0.203 ± 0.0254 Side View All dimensions in millimeters. 1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD. 1157.2005.11.1.4 13 AAT1157 1MHz 1.2A Buck DC/DC Converter © Advanced Analogic Technologies, Inc. AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights, or other intellectual property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice. Customers are advised 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 14 1157.2005.11.1.4