AAT1110

Fast Transient 800mA Step-Down Converter General Description The AAT1110 SwitchReg™ is a member of AnalogicTech's Total Power Management IC™ (TPMIC™) product family. It is a 1.4MHz stepdown converter with an input voltage range of 2.7V to 5.5V and output as low as 0.6V. Its low supply current, small size, and high switching frequency make the AAT1110 the ideal choice for portable applications. The AAT1110 is available in either a fixed version with internal feedback or a programmable version with external feedback resistors. It can deliver up to 800mA of load current while maintaining a low 27µA no load quiescent current. The 1.4MHz switching frequency minimizes the size of external components while keeping switching losses low. The AAT1110 feedback and control delivers excellent load regulation and transient response with a small output inductor and capacitor. The AAT1110 is designed to maintain high efficiency throughout the operating range and provides fast turn-on time. The AAT1110 is available in a space-saving 2.0x2.1mm SC70JW-8 package and is rated over the -40°C to +85°C temperature range. AAT1110 Features • • • • • • • • • • • • • SwitchReg™ VIN Range: 2.7V to 5.5V VOUT Fixed or Adjustable from 0.6V to VIN 27µA No Load Quiescent Current Output Current Up to 800mA 1.4MHz Switching Frequency 120µs Soft Start Fast Load Transient Over-Temperature Protection Current Limit Protection 100% Duty Cycle Low-Dropout Operation 0.6V Output From Enable to Output Regulation TA = 25°C 591 0.6 VIN = VOUT = 5.5V 1.4 -1.0 1.0 1. The AAT1110 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 1110.2006.04.1.0 Fast Transient 800mA Step-Down Converter Typical Characteristics Efficiency vs. Load (VOUT = 1.8V; L = 4.7µH) 100 1.0 AAT1110 DC Regulation (VOUT = 1.8V) VIN = 2.7V Output Error (%) 90 VIN = 4.2V 0.5 Efficiency (%) 80 70 60 50 0.1 1 VIN = 3.6V 0.0 VIN = 3.6V VIN = 4.2V -0.5 VIN = 2.7V -1.0 10 100 1000 0.1 1 10 100 1000 Output Current (mA) Output Current (mA) Efficiency vs. Load (VOUT = 2.5V; L = 6.8µH) 100 2.0 DC Regulation (VOUT = 2.5V) 1.5 VIN = 3.0V Output Error (%) 90 VIN = 5.0V VIN = 4.2V Efficiency (%) 1.0 0.5 0.0 -0.5 -1.0 -1.5 80 70 60 50 0.1 1 VIN = 4.2V VIN = 5.0V VIN = 3.6V VIN = 3.6V VIN = 3.0V -2.0 10 100 1000 0.1 1 10 100 1000 Output Current (mA) Output Current (mA) Efficiency vs. Load (VOUT = 3.3V; L = 6.8µH) 100 1.0 DC Regulation (VOUT = 3.3V; L = 6.8µH) VIN = 3.6V Output Error (%) 90 Efficiency (%) 0.5 80 VIN = 5.0V VIN = 4.2V VIN = 4.2V 0.0 70 60 50 0.1 1 10 100 1000 -0.5 VIN = 5.0V -1.0 0.1 1 10 100 1000 Output Current (mA) Output Current (mA) 1110.2006.04.1.0 5 Fast Transient 800mA Step-Down Converter Typical Characteristics Soft Start (VIN = 3.6V; VOUT = 1.8V; IOUT = 800mA) AAT1110 Line Regulation (VOUT = 1.8V) 1.8 1.6 Enable and Output Voltage (top) (V) 5.0 4.0 3.0 2.0 1.0 0.0 -1.0 -2.0 -3.0 -4.0 -5.0 0.40 0.30 Inductor Current (bottom) (A) Accuracy (%) 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 -0.2 0.20 0.10 0.00 -0.10 -0.20 -0.30 -0.40 2.5 3.0 3.5 IOUT = 400mA IOUT = 800mA IOUT = 1mA IOUT = 10mA 4.0 4.5 5.0 5.5 6.0 Time (100μs/div) Input Voltage (V) Output Voltage Error vs. Temperature (VIN = 3.6V; VO = 1.8V; IOUT = 400mA) 2.0 15.0 12.0 9.0 Switching Frequency vs. Temperature (VIN = 3.6V; VOUT = 1.8V) Output Error (%) Variation (%) 1.0 6.0 3.0 0.0 -3.0 -6.0 -9.0 -12.0 -15.0 -40 0.0 -1.0 -2.0 -40 -20 0 20 40 60 80 100 -20 0 20 40 60 80 100 Temperature (°C) Temperature (°C) Frequency vs. Input Voltage (IOUT = 800mA) 2.0 No Load Quiescent Current vs. Input Voltage 50 Frequency Variation (%) 1.0 0.0 -1.0 -2.0 -3.0 -4.0 2.7 Supply Current (μA) VOUT = 1.8V VOUT = 2.5V 45 40 35 30 25 20 15 10 85°C 25°C VOUT = 3.3V -40°C 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 3.1 3.5 3.9 4.3 4.7 5.1 5.5 Input Voltage (V) Input Voltage (V) 6 1110.2006.04.1.0 Fast Transient 800mA Step-Down Converter Typical Characteristics Load Transient Response (1mA to 600mA; VIN = 3.6V; VOUT = 1.8V; C1 = 10µF) 2.5 2.0 2.0 1.9 1.8 1.7 AAT1110 Load Transient Response (600mA to 800mA; VIN = 3.6V; VOUT = 1.8V; C1 = 10µF) Load and Inductor Current (500mA/div) (bottom) Load and Inductor Current (100mA/div) (bottom) Output Voltage (top) (V) 1.5 Output Voltage (top) (V) 0.8 0.7 0.6 0.5 0.4 0.5 0.0 -0.5 Time (50µs/div) Time (50µs/div) Load Transient Response (1mA to 600mA; VIN = 3.6V; VOUT = 1.8V; C1 = 10µF; CFF = 100pF) 2.2 2.0 2.0 1.9 1.8 1.7 Load Transient Response (600mA to 800mA; VIN = 3.6V; VOUT = 1.8V; C1 = 22µF) Load and Inductor Current (500mA/div) (bottom) Load and Inductor Current (100mA/div) (bottom) Output Voltage (top) (V) 1.8 1.6 Output Voltage (top) (V) 0.8 0.7 0.6 0.5 0.4 0.5 0.0 -0.5 Time (50µs/div) Time (50µs/div) Load Transient Response (1mA to 600mA; VIN = 3.6V; VOUT = 1.8V; C1 = 22µF; CFF = 100pF) 2.2 2.0 2.0 1.9 1.8 1.7 Load Transient Response (600mA to 800mA; VIN = 3.6V; VOUT = 1.8V; C1 = 10µF; CFF = 100pF) Load and Inductor Current (500mA/div) (bottom) Load and Inductor Current (100mA/div) (bottom) Output Voltage (top) (V) 1.8 Output Voltage (top) (V) 0.8 0.7 0.6 0.5 0.4 0.5 0.0 -0.5 Time (50µs/div) Time (50µs/div) 1110.2006.04.1.0 7 Fast Transient 800mA Step-Down Converter Typical Characteristics Line Response (VOUT = 1.8V @ 800mA) Output Voltage (AC coupled) (top) (mV) 1.86 1.84 1.82 1.80 1.78 1.76 1.74 1.72 1.70 1.68 1.66 7.6 7.1 6.6 20 10 0 -10 -20 -30 -40 -50 -60 AAT1110 Output Ripple (VIN = 3.6V; VOUT = 1.8V; IOUT = 800mA) 1.3 1.2 Inductor Current (bottom) (A) Output Voltage (top) (V) 6.1 5.6 5.1 4.6 4.1 3.6 3.1 2.6 1.1 1.0 0.9 0.8 0.7 0.6 0.5 Input Voltage (bottom) (V) Time (50µs/div) Time (500ns/div) Output Ripple (VIN = 3.6V; VOUT = 1.8V; IOUT = 1mA) P-Channel RDS(ON) vs. Input Voltage 0.30 0.25 Output Voltage (AC coupled) (top) (mV) 40 20 0 -20 -40 -60 -80 -100 -120 750 700 650 RDS(ON) (mΩ) 0.20 0.15 0.10 0.05 0.00 -0.05 -0.10 120°C 100°C Inductor Current (bottom) (A) 600 550 500 450 400 350 300 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 25°C 85°C Time (10µs/div) Input Voltage (V) N-Channel RDS(ON) vs. Input Voltage 750 700 650 120°C RDS(ON) (mΩ) 100°C 600 550 500 450 400 350 300 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 25°C 85°C Input Voltage (V) 8 1110.2006.04.1.0 Fast Transient 800mA Step-Down Converter Functional Block Diagram OUT VIN AAT1110 See note Err Amp . DH Voltage Reference Logic LX DL EN INPUT PGND AGND Note: For adjustable version, the internal feedback divider is omitted and the OUT pin is tied directly to the internal error amplifier. Functional Description The AAT1110 is a high performance 800mA 1.4MHz monolithic step-down converter. It has been designed with the goal of minimizing external component size and optimizing 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 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 (CIN, COUT, and L). The adjustable version can be programmed with external feedback to any voltage, ranging from 0.6V to the input voltage. An additional feed-forward capacitor 1110.2006.04.1.0 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 RDSON drop of the P-channel highside 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 800mA. 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. 9 Fast Transient 800mA Step-Down Converter AAT1110 1 2 3 Enable VIN C4 100pF 1 U1 AAT1110 R1 EN OUT VIN LX PGND PGND PGND AGND 8 7 6 5 2 3 4 VOUT =1.8V L1 118k 4.7μH C1 10μF R2 59k C3 n/a C2 4.7μF GND LX GND2 U1 AAT1110 SC70JW-8 L1 CDRH3D16-4R7 C2 4.7μF 10V 0805 X5R C1 10μF 6.3V 0805 X5R Figure 1: Enhanced Transient Response Schematic. Control Loop The AAT1110 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 voltage-programmed current 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 voltage is internally set to program the converter output voltage. For the adjustable output, the error amplifier reference is fixed at 0.6V. a low-power, non-switching state. The total input current during shutdown is less than 1µA. 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. 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 over-temperature or over-current fault conditions is removed, the output voltage automatically recovers. 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 AAT1110 into 10 Under-Voltage Lockout Internal bias of all circuits is controlled via the VIN input. Under-voltage lockout (UVLO) guarantees sufficient VIN bias and proper operation of all internal circuitry prior to activation. 1110.2006.04.1.0 Fast Transient 800mA Step-Down Converter Applications Information Inductor Selection 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. The internal slope compensation for the adjustable and low-voltage fixed versions of the AAT1110 is 0.24A/µsec. This equates to a slope compensation that is 75% of the inductor current down slope for a 1.5V output and 4.7µH inductor. 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 4.7µH CDRH3D16 series inductor selected from Sumida has a 105mΩ maximum DCR and a 900mA DC current rating. At full load, the inductor DC loss is 67mW which gives a 4.0% loss in efficiency for a 800mA, 2.5V output. AAT1110 Input Capacitor Select a 4.7µF to 22µF 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. 0.75 ⋅ VO 0.75 ⋅ 1.5V A m= = = 0.24 L 4.7μH μsec This is the internal slope compensation for the adjustable (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= = m μsec 0.75 ⋅ VO ≈ 3 A ⋅ VO A 0.24A μsec CIN = VO ⎛ V⎞ · 1- O VIN ⎝ VIN ⎠ ⎛ VPP ⎞ - ESR · FS ⎝ IO ⎠ =3 μsec ⋅ 2.5V = 7.5μH A VO ⎛ V⎞ 1 · 1 - O = for VIN = 2 × VO VIN ⎝ VIN ⎠ 4 In this case, a standard 6.8µH value is selected. For high-voltage fixed versions (≥2.5V), m = 0.48A/ µsec. Table 1 displays inductor values for the AAT1110 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 saturation characteristics. The inductor should not CIN(MIN) = 1 ⎛ VPP ⎞ - ESR · 4 · FS ⎝ IO ⎠ Always examine the ceramic capacitor DC voltage coefficient characteristics when selecting the proper value. For example, the capacitance of a 10µF, 6.3V, X5R ceramic capacitor with 5.0V DC applied is actually about 6µF. Configuration 0.6V Adjustable With External Feedback Fixed Output Output Voltage 1V, 1.2V 1.5V, 1.8V 2.5V, 3.3V 0.6V to 3.3V Table 1: Inductor Values. Inductor 2.2µH 4.7µH 6.8µH 4.7µH 1110.2006.04.1.0 11 Fast Transient 800mA Step-Down Converter The maximum input capacitor RMS current is: VO ⎛ V⎞ · 1- O VIN ⎝ VIN ⎠ AAT1110 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. IRMS = IO · 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 ⎛ V⎞ · 1- O = VIN ⎝ VIN ⎠ for VIN = 2 x VO D · (1 - D) = 0.52 = 1 2 Output Capacitor IO 2 IRMS(MAX) = The term VIN ⎝ VIN ⎠ appears in both the input voltage ripple and input capacitor RMS current equations and is a maximum when VO 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 AAT1110. 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 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 VO ⎛ V⎞ · 1- O The output capacitor limits the output ripple and provides holdup during large load transitions. A 4.7µF to 22µF X5R or X7R ceramic capacitor typically provides sufficient bulk capacitance to stabilize the output during large load transitions and has the ESR and ESL characteristics necessary for low output ripple. The output voltage droop due to a load transient is dominated by the capacitance of the ceramic output capacitor. During a step increase in load current, the ceramic 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: 3 · ΔILOAD VDROOP · FS COUT = 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 4.7µF. This is due to its effect on the loop crossover frequency (bandwidth), phase margin, and gain margin. Increased output capacitance will reduce the crossover frequency with greater phase margin. 12 1110.2006.04.1.0 Fast Transient 800mA Step-Down Converter AAT1110 Figure 2: AAT1110 Evaluation Board Top Side. Figure 3: Exploded View of Evaluation Board Top Side Layout. Figure 4: AAT1110 Evaluation Board Bottom Side. The maximum output capacitor RMS ripple current is given by: VOUT · (VIN(MAX) - VOUT) L · F · VIN(MAX) 2· 3 · 1 IRMS(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. the output to regulate at a voltage higher than 0.6V. To limit the bias current required for the external feedback resistor string while maintaining good noise immunity, the minimum suggested value for R2 is 59kΩ. Although a larger value will further reduce quiescent current, it will also increase the impedance of the feedback node, making it more sensitive to external noise and interference. Table 2 summarizes the resistor values for various output voltages with R2 set to either 59kΩ for good noise immunity or 221kΩ for reduced no load input current. ⎛ VOUT ⎞ ⎛ 1.5V ⎞ R1 = V -1 · R2 = 0.6V - 1 · 59kΩ = 88.5kΩ ⎝ REF ⎠ ⎝ ⎠ Adjustable Output Resistor Selection For applications requiring an adjustable output voltage, the 0.6V version can be externally programmed. Resistors R1 and R2 of Figure 5 program 1110.2006.04.1.0 13 Fast Transient 800mA Step-Down Converter The adjustable version of the AAT1110, combined with an external feedforward capacitor (C4 in Figure 1), delivers enhanced transient response for extreme pulsed load applications. The addition of the feedforward capacitor typically requires a larger output capacitor C1 for stability. R2 = 59kΩ VOUT (V) 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.8 1.85 2.0 2.5 3.3 AAT1110 Thermal Calculations There are three types of losses associated with the AAT1110 step-down converter: switching losses, conduction losses, and quiescent current losses. Conduction losses are associated with the RDS(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 conduction mode (CCM), a simplified form of the LDO losses is given by: IO2 · (RDSON(HS) · VO + RDSON(LS) · [VIN - VO]) VIN R2 = 221kΩ R1 75K 113K 150K 187K 221K 261K 301K 332K 442K 464K 523K 715K 1.00M R1 (kΩ) 19.6 29.4 39.2 49.9 59.0 68.1 78.7 88.7 118 124 137 187 267 PTOTAL = + (tsw · F · IO + IQ) · VIN IQ is the step-down converter quiescent current. The term tsw is used to estimate the full load stepdown converter switching losses. Table 2: Adjustable Resistor Values For Use With 0.6V Step-Down Converter. 1 2 3 VIN Enable 1 U1 AAT1110 EN OUT VIN LX PGND PGND PGND AGND 8 7 6 5 2 3 4 R1 118k VOUT C1 10μF L1 4.7μH R2 59k C2 4.7μF GND GND2 LX U1 AAT1110 SC70JW-8 L1 CDRH3D16-4R7 C1 10μF 10V 0805 X5R C2 4.7μF 10V 0805 X5R Figure 5: AAT1110 Adjustable Evaluation Board Schematic. 14 1110.2006.04.1.0 Fast Transient 800mA Step-Down Converter For the condition where the step-down converter is in dropout at 100% duty cycle, the total device dissipation reduces to: PTOTAL = IO2 · RDSON(HS) + IQ · VIN AAT1110 Layout The suggested PCB layout for the AAT1110 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 VIN (Pin 3) and PGND (Pins 6-8). 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 OUT 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 will degrade DC load regulation. 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 impedance 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. 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 · ΘJA + TAMB 1110.2006.04.1.0 15 Fast Transient 800mA Step-Down Converter Step-Down Converter Design Example Specifications VO VIN FS TAMB = 1.8V @ 600mA (adjustable using 0.6V version), Pulsed Load ΔILOAD = 300mA = 2.7V to 4.2V (3.6V nominal) = 1.4MHz = 85°C AAT1110 1.8V Output Inductor L1 = 3 μsec μsec ⋅ VO2 = 3 ⋅ 1.8V = 5.4μH A A (use 4.7µH; see Table 1) For Sumida inductor CDRH3D16, 4.7µH, DCR = 105mΩ. ⎛ VO V⎞ 1.8V 1.8V ⎞ ⎛ ⋅ 1- O = ⋅ ⎝1 = 156mA VIN ⎠ 4.7μH ⋅ 1.4MHz 4.2V ⎠ L1 ⋅ F ⎝ ΔIL1 = IPKL1 = IO + ΔIL1 = 0.6A + 0.068A = 0.668A 2 PL1 = IO2 ⋅ DCR = 0.6A2 ⋅ 105mΩ = 38mW 1.8V Output Capacitor VDROOP = 0.1V 3 · ΔILOAD 3 · 0.3A = = 6.4μF; use 10µF 0.1V · 1.4MHz VDROOP · FS 1 2· 3 · (VO) · (VIN(MAX) - VO) 1 1.8V · (4.2V - 1.8V) · = 45mArms = L1 · F · VIN(MAX) 2 · 3 4.7μH · 1.4MHz · 4.2V COUT = IRMS = Pesr = esr · IRMS2 = 5mΩ · (45mA)2 = 10μW 16 1110.2006.04.1.0 Fast Transient 800mA Step-Down Converter Input Capacitor Input Ripple VPP = 25mV AAT1110 CIN = ⎛ VPP ⎝ IO 1 1 = = 4.87μF; use 4.7μF ⎞ ⎛ 25mV ⎞ - 5mΩ · 4 · 1.4MHz - ESR · 4 · FS ⎠ ⎝ 0.6A ⎠ IRMS = IO = 0.3Arms 2 P = esr · IRMS2 = 5mΩ · (0.3A)2 = 0.45mW AAT1110 Losses IO2 · (RDSON(HS) · VO + RDSON(LS) · [VIN -VO]) VIN PTOTAL = + (tsw · F · IO + IQ) · VIN = 0.62 · (0.725Ω · 1.8V + 0.7Ω · [4.2V - 1.8V]) 4.2V + (5ns · 1.4MHz · 0.4A + 70μA) · 4.2V = 268mW TJ(MAX) = TAMB + ΘJA · PLOSS = 70°C + (160°C/W) · 268mW = 113°C 1110.2006.04.1.0 17 Fast Transient 800mA Step-Down Converter Adjustable Version (0.6V device) VOUT (V) 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.8 1.85 2.0 2.5 3.3 AAT1110 R2 = 59kΩ R1 (kΩ) 19.6 29.4 39.2 49.9 59.0 68.1 78.7 88.7 118 124 137 187 267 R2 = 221kΩ1 R1 (kΩ) 75.0 113 150 187 221 261 301 332 442 464 523 715 1000 L1 (µH) 2.2 2.2 2.2 2.2 2.2 2.2 4.7 4.7 4.7 4.7 6.8 6.8 6.8 Fixed Version VOUT (V) 0.6-3.3V R2, R4 Not Used R1 (kΩ) 0 L1 (µH) 4.7 Table 3: Evaluation Board Component Values. Manufacturer Sumida Sumida Sumida Coilcraft Coiltronics Coiltronics Coiltronics Part Number CDRH3D16-2R2 CDRH3D16-4R7 CDRH3D16-6R8 LPO3310-472 SD3118-4R7 SD3118-6R8 SDRC10-4R7 Inductance (µH) 2.2 4.7 6.8 4.7 4.7 6.8 4.7 Max DC Current (A) 1.20 0.90 0.73 0.80 0.98 0.82 1.30 DCR (Ω) 0.072 0.105 0.170 0.27 0.122 0.175 0.122 Size (mm) LxWxH 3.8x3.8x1.8 3.8x3.8x1.8 3.8x3.8x1.8 3.2x3.2x1.0 3.1x3.1x1.85 3.1x3.1x1.85 5.7x4.4x1.0 Type Shielded Shielded Shielded 1mm Shielded Shielded 1mm Shielded Table 4: Typical Surface Mount Inductors. Manufacturer MuRata MuRata MuRata Part Number GRM219R61A475KE19 GRM21BR60J106KE19 GRM21BR60J226ME39 Value 4.7µF 10µF 22µF Voltage 10V 6.3V 6.3V Temp. Co. X5R X5R X5R Case 0805 0805 0805 Table 5: Surface Mount Capacitors. 1. For reduced quiescent current, R2 and R4 = 221kΩ. 18 1110.2006.04.1.0 Fast Transient 800mA Step-Down Converter Ordering Information Output Voltage1 Adj. ≥ 0.6 AAT1110 Package SC70JW-8 Marking2 SRXYY Part Number (Tape and Reel)3 AAT1110IJS-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/pbfree. Package Information SC70JW-8 0.50 BSC 0.50 BSC 0.50 BSC 1.75 ± 0.10 0.225 ± 0.075 2.00 ± 0.20 2.20 ± 0.20 0.048REF 0.85 ± 0.15 1.10 MAX 0.15 ± 0.05 0.100 7° ± 3° 0.45 ± 0.10 2.10 ± 0.30 4° ± 4° All dimensions in millimeters. 1. Contact Sales for other voltage options. 2. XYY = assembly and date code. 3. Sample stock is generally held on part numbers listed in BOLD. © 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 1110.2006.04.1.0 0.05 ± 0.05 19