AAT1130

AAT1130 ANALOGICTECH | Alldatasheet

Document overview

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• PDF pages: 19

Technical content

Features

• 2.5MHz Switching Frequency
• Input Voltage Range: 2.7V to 5.5V
• Output Voltage Range: 0.6V to 1.8V
• High 92% Peak Efficiency (V IN = 3.6V, VOUT = 1.8V)
• Low 60 μA Quiescent Current
• 500mA Maximum Continuous Output Current
• Fast Transient Response with Small LC Output Filter Components
• Fixed and Adjustable Output Voltage Options
• Internal Soft-Start
• Anti-Ringing Switch to Reduce EMI During Discontinuous Conduction Mode Operation
• Over-Temperature Protection
• Valley Current Limit Protection
• Available in SC70JW-10
• -40°C to 85°C Temperature Range

Applications

• Microprocessor/DSP Core and I/O
• Mobile Phones
• PDAs and Handheld Computers
• Digital Cameras
• Portable Music Players
• Handheld Games
• Handheld Instruments Typical Application LXVCC/VP PGND VOUT CIN COUT = 4.7μF L = 1μH Output:1.2V, 500mA maxInput: 2.7V to 5.5V EN GND AAT1130-12 (SC70JW)

2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET AAT1130 2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET Pin Descriptions Adj. Fixed Symbol Function 1 n/a FB Output voltage feedback input. FB senses the output voltage through a resistor voltage divider circuit. Connect the voltage divider from the output voltage to FB. The feedback threshold is 0.6V. (Adjustable output voltage versions only) 2 2 VOUT Output voltage feedback input. VOUT senses the output voltage. Connect VOUT to the output voltage node to regulate the output voltage. 3 3 VCC Input supply voltage. Connect VCC to the input supply voltage. 44 V P Power input supply voltage. Connect VP to the VCC pin, and to the input supply voltage. Bypass VP to PGND with a 2.2μF or greater capacitor.

55 L X

Switching node. Connect the LC fi lter between LX and the load. LX is internally connected to the drain of the p-channel MOSFET switch and n-channel MOSFET synchronous rectifi er. 6 1 EN Enable input. Active logic high. n/a 6 PGND Power ground. Connect PGND to GND at a single point as close to the AAT1130 as possible. 7, 8, 9, 10 7, 8, 9, 10 GND Ground. For fi xed version, connect GND to PGND at a single point as close to the AAT1130-xx as possible. Pin Configuration SC70JW-10 (Top View) Adjustable Output Fixed Output Voltage Version Voltage Version FB VOUT VCC VP LX GND GND GND GND EN EN VOUT VCC VP LX GND GND GND GND PGND

2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET AAT1130 2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET Absolute Maximum Ratings1 Symbol Description Value Units VVCC, VVP VCC, VP to GND 6.0 V VLX LX Voltage to PGND -0.3 to V VCC\\VVP +0.3 V VFB FB Voltage to GND -0.3 to V VCC\\VVP +0.3 V VEN EN Voltage to GND -0.3 to V VCC\\VVP +0.3 V VPGND PGND Voltage to GND -0.3 to 0.3 V TJ Operating Junction Temperature Range -40 to 150 °C TLEAD Maximum Soldering Temperature (at leads, 10 sec) 300 °C Thermal Information Symbol Description Value Units PD Maximum Power Dissipation 625 mW θJA Thermal Resistance2 160 °C/W 1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at c onditions other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time. 2. Mounted on a FR4 board.

2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET AAT1130 2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET Electrical Characteristics1 Symbol Description Conditions Min Typ Max Units VIN Input Voltage 2.7 5.5 V VOUT Output Voltage Range 0.6 1.8 V VUVLO UVLO Threshold VIN rising 2.65 V Hysteresis 100 mV IQ Quiescent Current Not Switching 60 90 μA ISHDN Shutdown Current EN = AGND = PGND 1.0 μA VOUT_TOL (fi xed output version) Output Voltage Tolerance V IN = 2.7V to 5.5V, 0 to 500mA Load -4 4 % VFB_ACC Feedback Voltage Accuracy T A = 25°C, No Load 0.59 0.6 0.61 V ILIM Valley Current Limit 550 650 mA RDS(ON)H High Side Switch On-Resistance 0.35 Ω RDS(ON)L Low Side Switch On-Resistance 0.25 Ω fON Switch On-Time V IN = 3.6V, VOUT = 1.2V 120 ns tOFF(MIN) Minimum Off-Time 75 ns ILXLEAK LX Leakage Current V IN = 5.5, VLX = 0 to VIN 1 μA IFBLEAK FB Leakage Current V FB = 5.5V, VEN = 0V, Adj Only 0.2 μA tS Startup Time From EN Asserted to Output Regulation 150 μs fS Switching Frequency V OUT = 1.2V, 500mA Load 2.5 MHz TSD Over-Temperature Shutdown Threshold 140 °C THYS Over-Temperature Shutdown Hysteresis 15 °C VEN(L) Enable Threshold Low 0.6 V VEN(H) Enable Threshold High 1.4 V IEN Enable Pin Current V IN = VFB =5.5V -1.0 1.0 μA 1. The AAT1130 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assu red by design, characterization, and correla- tion with statistical process controls.

2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET AAT1130 2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET Typical Characteristics Efficiency vs. Load Current (VOUT = 1V) Load Current (A) Efficiency (%) 100 0.0001 0.001 0.01 0.1 1 VIN = 2.7V VIN = 3.6V VIN = 4.2V VIN = 5V VIN = 5.5V Output Voltage Error vs. Load Current (VOUT = 1V) Load Current (A) Output Voltage Error (%) -2.5 -1.5 -0.5 0.5 1.5 0.0001 0.001 0.01 0.1 1 VIN = 2.7V VIN = 3.6V VIN = 4.2V VIN = 5V VIN = 5.5V Line Regulation (VOUT = 1V) Input Voltage (V) Output Voltage Error (%) -0.75 -0.5 -0.25 0.25 0.5 0.75 IOUT = 1mA IOUT = 10mA IOUT = 100mA IOUT = 300mA IOUT = 500mA Efficiency vs. Load Current (VOUT = 1.8V) Load Current (A) Efficiency (%) 0.0001 0.001 0.01 0.1 1 100 VIN = 2.7V VIN = 3.6V VIN = 4.2V VIN = 5V VIN = 5.5V Output Voltage Error vs. Load Current (VOUT = 1.8V) Load Current (A) Output Voltage Error (%) 0.0001 0.001 0.01 0.1 1 -2.5 -1.5 -0.5 0.5 VIN = 2.7V VIN = 3.6V VIN = 4.2V VIN = 5V VIN = 5.5V Line Regulation (VOUT = 1.8V) Input Voltage (V) -0.75 -0.5 -0.25 0.25 0.5 0.75 IOUT = 1mA IOUT = 10mA IOUT = 100mA IOUT = 300mA

2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET AAT1130 2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET Typical Characteristics Supply Current vs. Supply Voltage (Switching) Supply Voltage (V)) Supply Current (µA) 100 Switching Frequency vs. Input Voltage (VOUT = 1V; CIN = COUT = 2.2µF; L = 1µH) Input Voltage (V) Switching Frequency (MHz) 2.25 2.5 2.75 3.25 3.5 3.75 On-Time vs. Input Voltage (VOUT = 1V; CIN = COUT = 2.2µF; L = 1µH)) Input Voltage (V) On-Time (ns) 100 150 200 250 Switching Frequency vs. Input Voltage (VOUT = 1.8V; CIN = COUT = 2.2µF; L = 1.5µH)) Input Voltage (V) Switching Frequency (MHz) 1.25 1.5 1.75 2.25 2.5 2.75 On-Time vs. Input Voltage (VOUT = 1.8V; CIN = COUT = 2.2µF; L = 1.5µH)) Input Voltage (V) On-Time (ns) 100 150 200 250 300 350 400 Switching Frequency Variation vs. Load Current Load Current (mA) Switching Frequency Variation (%) 200 250 300 350 400 450 500 550 600 -20 -15 -10 20 VIN = 2.7V VIN = 3.3V VIN = 3.6V VIN = 4.2V VIN = 5V VIN = 5.5V

2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET AAT1130 2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET Typical Characteristics Supply Current vs. Temperature Temperature (V) Supply Current (µA) -40 -15 10 35 60 85 100 Output Voltage Error vs. Temperature Temperature (°C) Output Voltage Error (%) -0.5 -0.4 -0.3 -0.2 -0.1 0.1 0.2 -40 -15 10 35 60 85 RDS(ON) vs. Temperature Temperature (°C) RDS(ON) (mΩ) -40 -15 10 35 60 85 100 150 200 250 300 350 400 450 PMOS NMOS Efficiency vs. Load Current (VOUT = 1.8V Fixed) Load Current (A) Efficiency (%) 0.0001 0.001 0.01 0.1 1 100 VIN = 2.7V VIN = 3.6V VIN = 4.2V VIN = 5V VIN = 5.5V Output Voltage Error vs. Load Current (VOUT = 1.8V Fixed) Load Current (A) Output Voltage Error (%) 0.0001 0.001 0.01 0.1 1 -1.5 -0.5 0.5 1.5 VIN = 2.7V VIN = 3.6V VIN = 4.2V VIN = 5V VIN = 5.5V Line Regulation (VOUT = 1.8V Fixed) Input Voltage (V) Output Voltage Error (%) -0.75 -0.5 -0.25 0.25 0.5 0.75 IOUT = 1mA IOUT = 10mA IOUT = 100mA IOUT = 300mA

2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET AAT1130 2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET Typical Characteristics Switching Frequency vs. Output Voltage (IOUT = 500mA) Output Voltage (V) Switching Frequency (MHz) 1.25 1.75 2.25 2.75 3.25 3.75 Load Transient (VOUT = 1.8V Fixed; VIN = 3.6V; COUT = 4.7µF; L = 1.5µH) Time (5µs/div) Output Voltage (top) (V) Output Current (bottom) (A) 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 10mA 500mA Load Transient (VOUT = 1.8V Fixed; VIN = 3.6V; COUT = 4.7µF; L = 1.5µH) Time (5µs/div) Output Voltage (top) (V) Output Current (bottom) (A) 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 100mA 300mA Load Transient (VOUT = 1.8V; VIN = 3.6V; COUT = 4.7µF; CFF = 100pF; L = 1.5µH) Time (5µs/div) Output Voltage (top) (V) Output Current (bottom) (A) 1.75 1.80 1.85 1.90 1.55 1.55 1.60 1.65 1.70 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 100mA 300mA Load Transient (VOUT = 1.8V; VIN = 3.6V; COUT = 4.7µF; L = 1.5µH) Time (5µs/div) Output Voltage (top) (V) Output Current (bottom) (A) 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 100mA 300mA Load Transient (VOUT = 1.8V; VIN = 3.6V; COUT = 4.7µF; CFF = 100pF; L = 1.5µH) Time (5µs/div) Output Voltage (top) (V) Output Current (bottom) (A) 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 10mA 500mA

2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET AAT1130 2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET Typical Characteristics Load Transient (VOUT = 1.8V; VIN = 3.6V; COUT = 4.7µF; L = 1.5µH) Time (5µs/div) Output Voltage (top) (V) Output Current (bottom) (A) 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 10mA 500mA Load Transient (VOUT = 1.5V; VIN = 3.6V; COUT = 4.7µF; CFF = 100pF; L = 1.5µH) Time (5µs/div) Output Voltage (top) (V) Output Current (bottom) (A) 1.20 1.25 1.30 1.35 1.40 1.45 1.50 1.55 1.60 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 10mA 500mA Load Transient (VOUT = 1.5V; VIN = 3.6V; COUT = 4.7µF; L = 1.5µH) Time (5µs/div) Output Voltage (top) (V) Output Current (bottom) (A) 1.20 1.25 1.30 1.35 1.40 1.45 1.50 1.55 1.60 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 10mA 500mA Load Transient (VOUT = 1.5V; VIN = 3.6V; COUT = 4.7µF; CFF = 100pF; L = 1.5µH) Time (5µs/div) Output Voltage (top) (V) Output Current (bottom) (A) 1.20 1.25 1.30 1.35 1.40 1.45 1.50 1.55 1.60 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 100mA 300mA Load Transient (VOUT = 1.5V; VIN = 3.6V; COUT = 4.7µF; L = 1.5µH) Time (5µs/div) Output Voltage (top) (V) Output Current (bottom) (A) 1.20 1.25 1.30 1.35 1.40 1.45 1.50 1.55 1.60 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 300mA 100mA Load Transient (VOUT = 1V; VIN = 3.6V; COUT = 4.7µF; CFF = 100pF; L = 1µH) Time (5µs/div) Output Voltage (top) (V) Output Current (bottom) (A) 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 100mA 400mA

2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET AAT1130 2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET Typical Characteristics Load Transient (VOUT = 1V; VIN = 3.6V; COUT = 4.7µF; L = 1µH) Time (5µs/div) Output Voltage (top) (V) Output Current (bottom) (A) 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 100mA 400mA Load Transient (VOUT = 1V; VIN = 3.6V; COUT = 4.7µF; CFF = 100pF; L = 1µH) Time (5µs/div) Output Voltage (top) (V) Output Current (bottom) (A) 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 10mA 500mA Load Transient (VOUT = 1V; VIN = 3.6V; COUT = 4.7µF; L = 1µH) Time (5µs/div) Output Voltage (top) (V) Output Current (bottom) (A) 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 10mA 500mA Soft-Start (VOUT = 1.8V Fixed; VIN = 3.6V; COUT = 4.7µF; L = 1.5µH) Time (100µs/div) Enable Voltage (top) (V) Output Voltage (middle) (V) Output Current (bottom) (A) 200mA 0mA (100mA/Div) 1.8V (1V/Div) 3.6V(2V/Div) Line Transient (VOUT = 1.8V Fixed; COUT = 4.7µF; L = 1.5µH) Time (10µs/div) Output Voltage (top) (V) Output Voltage (bottom) (V) 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 2.6 3.1 3.6 4.1 4.6 5.1 5.6 6.1 6.6

2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET Functional Description The AAT1130 is a high performance 500mA 2.5MHz (maximum switching frequency during steady-state operation) monolithic step-down converter. It minimizes external component size, enabling the use of a tiny 0603 inductor that is only 1mm 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 μH inductor and a 4.7 μF ceramic capacitor are recommended for <1.2V output voltage applications (see table of values). Only three external power components (C IN, COUT, and L) are required, for fixed output voltage options. Output voltage is programmed with external feedback resistors, ranging from 0.6V to 1.8V. An additional feed-forward capacitor can also be added to the external feedback to provide improved transient response (see Figure 1). 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 500mA. The internal error comparator and incorporated compen- sation provide excellent transient response, load, and line regulation. Soft-start eliminates any output voltage over- shoot when the enable or the input voltage is applied. Control Loop The AAT1130 uses a current-mode control scheme that allows it to operate at very high switching frequencies. The current-mode control scheme operates with a fixed on-time for a given input voltage. The on-time varies inversely proportional to the input voltage and propor- tional to the output voltage giving the regulator a fixed switching frequency when in steady-state. This allows the use of very small external inductor and capacitor. The small size coupled with the low quiescent current and automatic transition to variable switching frequency mode makes it ideal for small battery operated applica- tions. Light Load Operation The AAT1130 monitors the synchronous rectifier current and when the current drops to zero, it turns off the syn- chronous rectifier to emulate an actual rectifier. This allows the regulator to operate in discontinuous conduc- Functional Block Diagram Shoot Through Protection Error Comparator Current Limit Comparator EN Current Sense Amplifier Soft-Start Control and FET Driver Logic Circuitry VOUT FB [Adj Only] VCC VP VREF VILIM PGND [Fixed Only] GND LX

2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET tion mode. In this mode the on-time remains the same as it is in continuous conduction mode, and therefore the inductor ripple current remains the same in both modes. But reduced load current requires more time for the out- put capacitor to discharge to the regulation voltage reducing the switching frequency. This has the added benefit of reducing the switching transition losses improving efficiency at light loads. Stability The AAT1130 requires no additional compensation com- ponents to guarantee stability. The only requirement for stability is to choose the appropriate output capacitor. Current-mode control simplifies compensation by con- trolling the inductor current to regulate the output volt- age. This approximates a single pole response in the loop gain even though a complex pole pair exists due to the LC filter. Therefore the crossover frequency is approximated as the DC loop gain multiplied by the single pole. The AAT1130 DC loop gain is a function of the 60mΩ current sense resistor and is determined by the equation: ALOOP(DC) = · VOUT 0.6V RLOAD 60mΩ And the dominant pole frequency is: fP = 2π · RLOAD · COUT Therefore the crossover frequency is: fC = ALOOP(DC) · fP VOUT 2π · 0.6V · 60mΩ · COUT The only requirement for stability is that the crossover frequency be much less than the 2.5MHz switching fre- quency. The crossover frequency can be as high as 1/2 of the switching frequency, or 1.25MHz. Therefore calcu- late the output capacitor by the equation: COUT > VOUT 2π · 0.6V · 60mΩ · 1.25MHz Example: Given that VOUT = 1.2V, then COUT > 4.24μF, therefore a 4.7μF capacitor is suitable. Due to the unique control method, the “inside” current control loop does not have the inherent instability that plagues most fixed frequency current-mode DC-DC reg- ulators. Soft-Start When the AAT1130 is enabled, it enters soft-start mode. In this mode, the output voltage slowly rises over 150μs allowing the output capacitor to charge without drawing excessive input current. This feature prevents over- stressing the battery or other input power source. Current Limit The AAT1130 includes a cycle-by-cycle current limit to prevent damage to itself and external circuitry. The cur- rent limit is a valley current limit using the n-channel synchronous rectifier to measure the current. If the syn- chronous rectifier current is above the valley current limit, the AAT1130 holds the synchronous rectifier on until the current is below the limit. This allows the AAT1130 to control the current in current limit even with a hard shorted output. Anti-Ringing Switch The AAT1130 includes an anti-ringing switch that dissi- pates any energy left in the inductor when the current is approximately zero. The anti-ringing switch turns on when both the p-channel switch and n-channel synchro- nous rectifier are off and the inductor current is approx- imately zero. The switch shorts the LX and VOUT nodes together, effectively shorting the inductor. The low on- resistance of the anti-ringing switch dissipates any energy left in the inductor preventing ringing at light loads. When either the switch or synchronous rectifier are on, the anti-ringing switch remains off. Over-Temperature The AAT1130 includes thermal protection that automati- cally turns off the regulator when the die temperature exceeds a safe level. The thermal protection turns on at a die temperature of 140°C and has a 15°C hysteresis.

2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET Applications Information Inductor Selection The step-down converter uses valley current mode con- trol with slope compensation to maintain stability for duty cycles greater than 50%. The output inductor value must be selected so the inductor current down slope meets the internal slope compensation requirements. Table 1 displays suggested inductor values for various output voltages. Manufacturer’s specifications list both the inductor DC current rating, which is a thermal limitation, and the peak current rating, which is determined by the satura- tion characteristics. The inductor should not show any appreciable saturation under normal load conditions. Some inductors may meet the peak and average current ratings yet result in excessive losses due to a high DCR. Always consider the losses associated with the DCR and its effect on the total converter efficiency when selecting an inductor. See Table 3 for suggested inductor values and vendors. Confi guration Output Voltage Inductor Value Adjustable and Fixed Output Voltage 1V, 1.2V, 1.3V 1.0 μH to 1.5μH 1.5V, 1.8V 1.5 μH to 2.2μH Table 1: Inductor Values for Specific Output Voltages. Input Capacitor Select a 4.7μF to 10μF X7R or X5R ceramic capacitor for the input. Always examine the ceramic capacitor DC voltage coefficient characteristics when selecting the proper value. For example, the capacitance of a 10 μF, 6.3V, X5R ceramic capacitor with 5.0V DC applied is actually about 6μF. The input capacitor provides a low impedance loop for the edges of pulsed current drawn by the AAT1130. Low ESR/ESL X7R and X5R ceramic capacitors are ideal for this function. To minimize stray inductance, the capaci- tor 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 (C1) can be seen in the evaluation board layouts in Figures 4, 5, 6, and 7. A laboratory test set-up typically consists of two long wires running from the bench power supply to the evalu- ation board input voltage pins. The inductance of these wires, along with the low-ESR ceramic input capacitor, can create a high Q network that may affect converter performance. This problem often becomes apparent in the form of excessive ringing in the output voltage dur- ing load transients. Errors in the loop phase and gain measurements can also result. Since the inductance of a short PCB trace feeding the input voltage is significantly lower than the power leads from the bench power supply, most applications do not exhibit this problem. In applications where the input power source lead 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 ceram- ic. This dampens the high Q network and stabilizes the system. Output Capacitor The output capacitor limits the output ripple and pro- vides holdup during large load transitions. A 4.7 μF to 10μF X5R or X7R ceramic capacitor typically provides sufficient bulk capacitance to stabilize the output during large load transitions and has the ESR and ESL charac- teristics necessary for low output ripple. The internal voltage loop compensation also limits the minimum output capacitor value to 4.7μF. This is due to its effect on the loop crossover frequency (bandwidth), phase margin, and gain margin. Increased output capac- itance will reduce the crossover frequency with greater phase margin. FB CFF Figure 1: AAT1130 External Resistor Output Voltage Programming.

2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET Feedback Resistor Selection Resistors R1 and R2 of Figure 4 program 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 volt- ages with R2 set to either 59kΩ for good noise immunity or 221kΩ for reduced no load input current. R1 = -1 · R2 = - 1 · 59kΩ = 88.5kΩ VOUT VFB 1.5V 0.6V The AAT1130, combined with an external feedforward capacitor (C3 in Figure 4), delivers enhanced transient response for extreme pulsed load applications. The addi- tion of the feedforward capacitor typically requires a larger output capacitor C1 for stability. VOUT (V) R2 = 59kΩ R1 (kΩ) R2 = 221kΩ R1 (kΩ) 0.9 29.4 113 1 39.2 150 1.1 49.9 187 1.2 59.0 221 1.3 68.1 261 1.4 78.7 301 1.5 88.7 332 1.8 118 442 Table 2: Feedback Resistor Values. Thermal Calculations There are three types of losses associated with the AAT1130 step-down converter: switching losses, conduc- tion losses, and quiescent current losses. Conduction losses are associated with the R DS(ON) characteristics of the power output switching devices. Switching losses are dominated by the gate charge of the power output switching devices. At full load, assuming continuous con- duction mode (CCM), a simplified form of the losses is given by: PTOTAL IO 2 · (RDS(ON)H · VO + RDS(ON)L · [VIN - VO]) VIN + (tsw · FS · IO + IQ) · VIN IQ is the step-down converter quiescent current. The term tsw is used to estimate the full load step-down con- verter switching losses. For the condition where the step-down converter is in dropout at 100% duty cycle, the total device dissipation reduces to: PTOTAL = IO 2 · RDS(ON)H + IQ · VIN Since RDS(ON), quiescent current, and switching losses all vary with input voltage, the total losses should be inves- tigated over the complete input voltage range. Given the total losses, the maximum junction temperature can be derived from the θ JA for the SC70JW-10 package which is 160°C/W. TJ(MAX) = PTOTAL · ΘJA + TAMB Layout The suggested PCB layout for the AAT1130 is shown in Figures 1, 2, and 3. The following guidelines should be used to help ensure a proper layout: 1. The input capacitor (C1) should connect as closely as possible to VCC/VP (pins 3 and 4) and PGND/GND (pins 7-10 for adjustable output voltage and pins 6-10 for fixed output voltage). 2. C1 and L1 should be connected as closely as possi- ble. The connection of L1 to the LX (pin 5) should be as short as possible. 3. The feedback trace or FB (pin 1 for adjustable 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. If external feedback resistors are used, they should be placed as closely as possible to the FB (pin 1 for adjustable output voltage) to mini- mize the length of the high impedance feedback trace. 4. The resistance of the trace from the load return to the PGND/GND (pins 7-10 for adjustable output volt- age and pins 6-10 for fixed output voltage) 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.

2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET AAT1130 2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET Manufacturer Part Number/Type Inductance (μH) Rated Current (mA) DCR (mΩ) (typ) Size (mm) LxWxH Murata LQM2HP_G0 1 1600 55 2.5x2x11.5 1500 70 2.2 1300 80 LQH32P_N0 1 2050 45 3.2x2.5x1.61.5 1750 57 2.2 1600 76 TDK VLF3010A 1.5 1200 68 2.8x2.6x12.2 1000 100 VLF3010S 1 1700 41 3.0x2.8x12.2 1100 77 Table 3: Suggested Inductor Components. Manufacturer Part Number Value Voltage Temp. Co. Case AVX 0603ZD225K 2.2 μF 10 X5R 0603 TDK C1608X5R1C225K 2.2 μF1 6 X5R 0603C1608X5R1A475K 4.7 μF1 0 C2012X5R1A106K 10 μF 10 0805 C3216X5R1A226K 22 μF 10 1206 Murata GRM188R61A225K 2.2 μF1 0 X5R 0603 GRM219R61A106K 10 μF 10 0805 GRM31CR71A226K 22 μF 10 X7R 1206 Taiyo Yuden LMK107BJ475KA 4.7 μF 10 X5R 0603 Table 4: Suggested Capacitor Components.

2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET AAT1130 2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET

Ordering Information

Output Voltage Package Marking 1 Part Number (Tape and Reel)2 Adjustable SC70JW-10 2VXXY AAT1130IJQ-0.6 1.8V SC70JW-10 2UXXY AAT1130IJQ-1.8 All AnalogicTech products are offered in Pb-free packaging. The term “Pb-free” means semiconductor products that are in compliance with current RoHS standards, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. For more information, please visit our website at http://www.analogictech.com/about/quality.aspx. 1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD.

2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET AAT1130 2.5MHz 500mA Step-Down DC/DC ConverterSwitchReg TM PRODUCT DATASHEET Advanced Analogic Technologies, Inc.

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Phone (408) 737-4600 Fax (408) 737-4611 © Advanced Analogic Technologies, Inc. AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech pr oduct. 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 specifi cations or to discontinue any product or service without notice. Except as provided in AnalogicTech’s terms and conditions of sale, AnalogicTech assumes no liability whatsoever, and AnalogicTech disclaims any express or implied warranty relating to the sale and/or use of AnalogicTech products including liability or warranties relating to fi tness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. In order to minimize risks associated with the customer’s applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to support this warranty. Specifi c testing of all parameters of each device is not necessarily performed. AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated. All other brand and product names appearing in this document are registered trademarks or trademarks of their respective holders.

Package Information

0.45 ± 0.10 0.05 ± 0.05 2.10 ± 0.30 4° ± 4° 0.15 ± 0.05 2.00 ± 0.20 7° ± 3° 0.85 ± 0.15

1.10 MAX

0.100 0.225 ± 0.075 1.75 ± 0.10 2.20 ± 0.20

0.40 BSC

All dimensions in millimeters.