DATA SHEET AAT2215 High Current Synchronous Step-Up Regulator with Programmable Current Limit General Description Features The AAT2215 SwitchReg™ is a high current, synchronous step-up converter with a programmable peak NMOS current limit. It is ideal to prevent the input current from overloading the system power in PC Card GSM/GPRS/3G and WiMax modem card applications. The AAT2215's internal compensation is optimized for the large bulk tantalum output capacitors needed to support the output voltage during large load pulses. • • • • • • The output voltage may be programmed from 3.0V to 5.5V by external resistor divider. Light load switching frequency modulation and low quiescent current maintain high efficiency performance for light load mode conditions. • • • • • • • • Two current limits are designed into the AAT2215. One is the low-side power MOSFET programmable peak current limit, which works when the device is in step-up regulation state. An external resistor is used to program the current limit from 600mA to 4.0A. The other is the highside current limit, which operates in a linear mode to limit inrush current to 750mA when the output charges up to the input voltage. The AAT2215 includes internal over-voltage protection and a system ready signal. 2.4V to VOUT + 0.25V Input Voltage Range Adjustable 3.0V to 5.5V Output Voltage Internal Compensation 600kHz Switching Frequency Programmable Peak NMOS Current Limit (0.6A to 4.0A) Synchronous P-Channel MOSFET ▪ True Load Disconnect in Shutdown ▪ Reverse Current Block When Enabled ▪ Start-Up Inrush Current Limit (0.75A) and Overload Current Limit (3A) Up to 95% Efficiency Active-Low Power Ready Indicator (RDY) Very Low 55μA No-Load Operating Current Less than 1μA Shutdown Current 6V Output Over-Voltage Protection (OVP) Thermal Shutdown Protection (TSHDN) Short Circuit Protection Low-Profile TDFN33-12 Package Applications • • • • • The AAT2215 is available in a Pb-free, 3mm x 3mm, 12-pin TDFN package (TDFN33-12) rated from -40°C to +85°C. Media Tablets PCI-Express Cards PCMCIA Cards Modems Wireless Data Cards Typical Application Figure L1 2.2μH VIN 2.4V to VOUT + 0.25V IN RRDY 100kΩ CIN 10μF VOUT 3.8V LX OUT AAT2215 RDY RFB1 536kΩ COUT 22μF FB ON OFF RFB2 100kΩ EN RSET 100kΩ AGND RSET PGND Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 1 DATA SHEET AAT2215 High Current Synchronous Step-Up Regulator with Programmable Current Limit Pin Descriptions Pin Name 1, 2 LX 3 EN 4 IN 5 RDY 6 AGND 7 FB 8 RSET 9, 10 11, 12 OUT PGND EP Exposed Pad Function Inductor switching node. LX is internally connected to the source of the internal low-side N-channel MOSFET (NMOS), and synchronous high-side P-channel MOSFET (PMOS). Externally connected to the switching side of the power inductor as shown in the Typical Application drawing. Enable input. A logic high enables the AAT2215 regulator. A logic low forces the AAT2215 into shutdown mode, placing the output into a high-impedance state (true load disconnect) and reducing the quiescent current to less than 1μA. Input supply. IN powers the analog control circuitry during start-up. Bypass IN to GND with a 10μF or greater ceramic capacitor. Power ready signal (active low). RDY is an open-drain, active-low output. RDY is pulled low when the feedback voltage exceeds 95% of the target voltage. Analog ground. AGND is internally connected to the analog ground of the control circuitry. Feedback input. FB senses the output voltage for regulation control. For adjustable output versions, connect a resistive divider network from the output to FB to GND to set the output voltage accordingly. The FB regulation threshold is 0.6V. Programmable current-limit control. Connect an external resistor between RSET and AGND to set the peak NMOS current-limit threshold. The current-limit threshold may be adjusted from 0.6A to 4.0A.9 Output of step-up regulator. OUT internally connects to the synchronous high-side P-channel MOSFET. Power ground. PGND is internally connected to the source of the low-side N-channel MOSFET. Substrate/thermal ground. The exposed pad is internally connected to the substrate of the controller, and provides the lowest thermal impedance between the regulator and the PCB. Connect the exposed pad directly to the ground plane to reduce thermal stress. Pin Configuration TDFN33-12 (Top View) LX LX EN IN RDY AGND 2 1 12 2 11 3 10 4 9 5 8 6 7 PGND PGND OUT OUT RSET FB Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 DATA SHEET AAT2215 High Current Synchronous Step-Up Regulator with Programmable Current Limit Absolute Maximum Ratings1 Symbol VIN VOUT, VLX VEN VFB VRDY VGND TJ TS TLEAD Description IN to PGND OUT, LX to PGND2 EN to AGND FB to AGND RDY to AGND AGND to PGND Junction Temperature Range Storage Temperature Range Maximum Soldering Temperature (at leads, 10 sec.) Value -0.3 to 6 -0.3 to 6 -0.3 to 6 -0.3 to 6 -0.3 to 6 -0.3 to 0.3 -40 to 150 -65 to 150 300 Units V °C Thermal Characteristics3 Symbol Description TDFN33-12 Thermal Impedance θJA Maximum Junction-to-Ambient Thermal Resistance PD Maximum Power Dissipation4 Value Units 50 2 °C/W W Value Units -40 to 85 2.4 to VOUT + 0.25 3.0 to 5.5 °C Operating Characteristics Symbol TA VIN VOUT Description Operating Ambient Temperature Range Input Voltage Range Output Voltage Range V 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. 2. The P-channel between LX and OUT that changes the substrate connection to control the body diode. This allows the high-side diode when the regulator is active, but allows the output to be isolated from the input during shutdown (true load disconnect). 3. Mounted on 1.6mm thick FR4 board. 4. Derate 25mW/°C above 25°C. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 3 DATA SHEET AAT2215 High Current Synchronous Step-Up Regulator with Programmable Current Limit Electrical Characteristics VIN = 3.3V, VOUT = 3.8V, AGND = PGND. TA = +25°C, unless otherwise noted. Symbol VIN VIN(MIN) VOUT VUVLO IQ ISHDN Description Input Voltage Range Minimum Start-Up Voltage Output Voltage Range Input Under-Voltage Lockout Supply Current with No Load Shutdown Current VFB FB Accuracy IFB FB Leakage Current ΔVOUT/IOUT Load Regulation ΔVOUT/VIN VOVP fOSC DMAX tON(MIN) RON(PMOS) RON(NMOS) ISTRT ILIM(PMOS) Line Regulation OUT Over-Voltage Protection Threshold Oscillator Frequency Maximum Duty Cycle Minimum On-Time High-Side P-Channel On-Resistance Low-Side N-Channel On-Resistance Input Start-Up PMOS Inrush Current Limit PMOS Linear Overload Current Limit ILIMPK Low-Side Peak Current Limit Threshold Enable, Power Ready and Start-Up Features VEN(H) Logic Input Threshold High for EN Logic Input Threshold Low for EN VEN(L) IEN EN Input Current VRDY Power Ready Threshold RRDY RDY On-Resistance Thermal TSD Over-Temperature Shutdown Threshold Over-Temperature Shutdown Hysteresis TSD(HYS) 4 Conditions Min Typ 2.4 2.3 VIN Rising, Hysteresis = 0.1V No Load Current; Not Switching EN = GND, VIN = 5.5V TA = 25°C, IOUT = 10mA TA = -40°C to 85°C, IOUT = 10mA VFB = 0 to 1.0V VIN = 3.3V, VOUT = 3.8V, 0 to 2.5A Load VIN = 2.4V to VOUT, IOUT = 10mA Hysteresis = 200mV VOUT + 0.5V < VIN, RLOAD = 1Ω VOUT = 0V RSET = 75kΩ, TA = 25°C RSET = 63.4kΩ, TA = 25°C RSET = 1000kΩ, TA = 25°C 3.0 1.9 0.588 0.582 -0.2 2.1 55 0.60 0.60 Max VOUT + 0.25 2.4 5.5 2.3 80 1 0.612 0618 +0.2 1 5.6 480 0.5 2.625 0.3 6.0 600 90 80 70 90 0.75 3.0 3.5 4.0 0.6 6.4 720 Temperature Rising 4.375 95 2700 150 15 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 μA V μA %/V V kHz % ns mΩ 0.4 +1.0 -1.0 V %/A 1.4 VEN = GND or 5.5V FB Rising, Hysteresis = 10% VFB = 0.62V, ISINK = 10μA Units A V μA % Ω °C DATA SHEET AAT2215 High Current Synchronous Step-Up Regulator with Programmable Current Limit No Load Quiescent Current vs Input Voltage No Load Quiescent Current vs Temperture (Close Loop,VOUT = 3.8V) (Close Loop,VIN = 3.3V, VOUT = 3.8V) 180 330 Quiescent Current (μA) Quiescent Current (μA) 360 300 270 240 210 180 25°C 150 85°C 120 -40°C 90 165 150 135 120 105 90 2.4 2.5 2.6 2.7 2.8 2.9 3 3.1 3.2 3.3 -40 -15 Input Voltage (V) No Load Quiescent Current vs Input Voltage 35 60 85 No Load Quiescent Current vs Temperature (Open Loop) (Open Loop, VIN = 3.3V) 50 50 48 46 44 42 25°C 40 85°C 38 -40°C Quiescent Current (μA) Quiescent Current (μA) 10 Temperature (°C) 36 48 46 44 42 40 38 36 2.4 2.5 2.6 2.7 2.8 2.9 3 3.1 3.2 3.3 -40 -15 Input Voltage (V) 10 35 60 85 Temperature (°C) Frequency vs Temperature Enable Threshold vs Input Voltage 1.2 1.1 620 1.0 600 VEN (V) Frequency (Khz) 640 580 560 0.9 0.8 540 VENH 0.7 520 VENL 500 0.6 -40 -15 10 35 Temperature (°C) 60 85 2.4 2.7 3 3.3 3.6 3.9 4.2 4.5 4.8 5.1 Input voltage (V) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 5 DATA SHEET AAT2215 High Current Synchronous Step-Up Regulator with Programmable Current Limit Enable Threshold vs Temperature Feedback Voltage vs Input Voltage 1.2 0.609 VENH 1.1 0.606 VENL 0.603 VFB (V) VEN (V) 1.0 0.9 0.8 0.600 0.597 0.7 0.594 0.6 -40 -15 10 35 60 0.591 85 2.4 2.7 3 3.3 Temperature (°C) 3.6 3.9 4.2 4.5 4.8 5.1 Input Voltage (V) Feedback Voltage vs Temperature Efficiency (L = 2.2μH, VOUT = 3.8V) 100 0.609 90 0.606 Efficiency (%) 80 VFB (V) 0.603 0.600 0.597 0.594 0.591 70 60 50 VIN = 2.4V 40 VIN = 2.7V 30 20 VIN = 3.0V 10 VIN = 3.3V 0 -40 -15 10 35 60 85 0.1 1.0 Temperature (°C) 10.0 100.0 Efficiency Load Regulation (L = 2.2μH, VOUT = 5.0V) (L = 2.2μH, VOUT = 5.0V) 0.9 VIN = 2.4V 90 0.7 Output Error (%) 80 Efficiency (%) 10000.0 Output Current (mA) 100 70 60 VIN = 2.4V 50 VIN = 2.7V 40 VIN = 3.0V 30 20 VIN = 3.3V 10 VIN = 4.2V VIN = 2.7V VIN = 3.0V 0.5 VIN = 3.3V 0.3 VIN = 4.2V 0.1 -0.1 0 0.1 1.0 10.0 100.0 Output Current (mA) 6 1000.0 1000.0 10000.0 -0.3 0.0 0.1 1.0 10.0 100.0 1000.0 Output Current (mA) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 10000.0 DATA SHEET AAT2215 High Current Synchronous Step-Up Regulator with Programmable Current Limit Load Regulation Line Regulation (L = 2.2μH, VOUT = 3.8V) (L = 2.2μH, VOUT = 3.8V) 0.6 0.5 VIN = 2.4V VIN = 3.0V 0.2 IOUT = 1mA 0.4 VIN = 2.7V Output Error (%) Output Error (%) 0.4 VIN = 3.3V 0.0 -0.2 -0.4 IOUT = 100mA 0.3 IOUT = 500mA 0.2 IOUT = 1000mA 0.1 IOUT = 1500mA 0.0 -0.1 -0.2 -0.3 -0.4 -0.6 0.0 0.1 1.0 10.0 100.0 1000.0 10000.0 -0.5 2.4 2.5 Output Current (mA) 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 Input Voltage (V) Soft Start Output Voltage Ripple (VOUT = 3.8V; VIN = 3.3V; IOUT = 0A) (VIN = 3.3V; VOUT = 3.8V; l = 2.2μH; IOUT = 0mA) VOUT (AC) (20mV/div) 0V VEN (1V/div) 0V VOUT (1V/div) 0V IL (0.5A/div) IIN 0A (0.5A/div) 0A Time (100μs/div) Time (400μs/div) Output Voltage Ripple Output Voltage Ripple (VIN = 3.3V; VOUT = 3.8V; L = 2.2μH; IOUT = 1A) (VIN = 3.3V; VOUT = 3.8V; L = 2.2μH; IOUT = 2.5A) VOUT (AC) (100mV/div) 0V 0V VOUT (AC) (20mV/div) IL (1.0A/div) IL (0.5A/div) 0A 0A Time (800ns/div) Time (800ns/div) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 7 DATA SHEET AAT2215 High Current Synchronous Step-Up Regulator with Programmable Current Limit Load Transient Load Transient (VOUT = 3.8V; VIN = 3.3V; IOUT = 100mA to 1.2A; L = 2.2μH; COUT = 22μF + 220μF) (VOUT = 3.8V; VIN = 3.3V; L = 2.2μH; IOUT = 100mA to 2.5A; COUT = 22μF + 220μF) VOUT (AC) 0V (500mV/div) VOUT (AC) 0V (200mV/div) 2.5A IOUT 0A (0.5A/div) IOUT 0A (1A/div) 100mA Time (400μs/div) 100mA Time (400μs/div) Line Transient Response (VIN = 2.7V to 3.3V; VOUT = 3.8V; L = 2.2μH; IOUT = 100mA; COUT= 22μF) VOUT (AC) 0V (100mV/div) 3.3V VIN (0.6V/div) 2.7V Time (400μs/div) 8 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 DATA SHEET AAT2215 High Current Synchronous Step-Up Regulator with Programmable Current Limit Functional Block Diagram OUT IN UVLO Over-Temperature Protection Internal Power Select Control Logic DH Reverse Current Block When Enabled True Load Disconnect PMOS Current Control Mode Control OVP EN NMOS Current Control RSET PMOS Comp OUT LX 6.0V RDY 0.6V NMOS DL PGND 0.575V Slope Compensation Error Amp. FB AGND Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 9 DATA SHEET AAT2215 High Current Synchronous Step-Up Regulator with Programmable Current Limit Functional Description The AAT2215 synchronous step-up converter is targeted for PC Card GSM/GPRS/3G and WiMax modem card applications. It includes a 0.75A start-up PMOS current limit to ensure fast, controlled power-up, a 3A overload PMOS current limit after startup, and a programmable peak NMOS step-up current limit up to 4A for continuous step-up operation within the PCMCIA specifications. The 600kHz switching frequency of the AAT2215 facilitates output filter component size reduction for improved power density and reduced overall footprint. It also provides greater bandwidth and improved transient response over other lower frequency step-up converters. The compensation and feedback is integrated with only three external components (CIN, COUT, L). Low RDS(ON) synchronous power switches provide high efficiency for heavy load conditions. Switching frequency modulation and low quiescent current maintains this high efficiency for light load mode condition. In addition to the improved efficiency, the synchronous step-up has the added performance advantage of true load disconnect during shutdown (<1μA shutdown current), reverse current blocking when enabled, inrush current limit, and short-circuit protection. PWM Control Scheme with Low-Noise Light-Load The AAT2215 is a fixed-frequency PWM peak current mode control step-up converter. For light load condition (70mA to 80mA and below), the converter stays in a variable frequency (Light Load) mode to reduce the dominant switching losses. In addition to Light Load operation, a zero current comparator blocks reverse current in the P-channel synchronous MOSFET, forcing DCM operation at light load. These controls, along with very low quiescent current, help to maintain high efficiency over the complete load range without increased output voltage ripple during light load conditions. Shutdown and True Load Disconnect A typical synchronous step-up (step-up) converter has a conduction path from the input to the output via the parasitic body diode of the P-channel MOSFET when the converter shuts down. The AAT2215 design a special power selection for the substrate to keep the parasitic body diode in off-state during shutdown and startup. This enables the AAT2215 to provide true load disconnect during shutdown and PMOS inrush current limit at startup. 10 During the initial PMOS linear mode start-up period, the start-up control circuitry is powered by the input supply pin. When the output voltage of the AAT2215 enters step-up mode (VIN ≈ VOUT), the step-up control circuitry draws power directly from the output supply to ensure sufficient voltage head-room. When EN is set to logic low, the step-up converter is forced into shutdown state with less than 1μA input current. Soft-start and PMOS Current Limit Protection Start-Up Inrush Current Protection When initially powering up, the load disconnect feature allows the output voltage to be less than the input voltage. In order to avoid large surge current when the regulator is enabled, the AAT2215 operates the synchronous P-channel MOSFET in a current-limited linear mode to softly charge the large output capacitor. This linear start-up feature effectively limits the input current to 0.75A until the output voltage exceeds the input voltage. After VOUT exceeds VIN, the regulator switches the body diode connection and begins step-up operation. Overload Current-Limit Protection Once start-up is completed, (RDY is pulled low), the AAT2215 increases the PMOS overload current-limit threshold to 3A. If the output is overloaded, causing VOUT to drop below VIN by 210mV, the regulator will switch back to a linear operating mode. This activates the 3A PMOS overload current protection and the AAT2215 will reverse the body-diode connection. This effectively limits the output current under such fault conditions. Combined with the thermal shutdown protection, the PMOS current-limit protects the regulator against overload and short-circuit fault conditions. The overload current limit is fixed at 3A, and short-circuit protection also adopts this 3A current limit; the 3A current limit is not changed with RSET value. Programmable Peak NMOS Current-Limit When the output voltage of the AAT2215 enters step-up mode (VIN < VOUT), the NMOS starts switching and the NMOS peak current-limit becomes active. During the inductor charge cycle, the low-side NMOS turns on and the AAT2215 monitors the current through the NMOS. If the current exceeds the current-limit threshold set by Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 DATA SHEET AAT2215 High Current Synchronous Step-Up Regulator with Programmable Current Limit the RSET resistor, the regulator immediately turns off the low-side NMOS. The regulator limits the instantaneous peak inductor/NMOS current, so the current-limit threshold must be set high enough to support the desired output current. Power Ready To indicate the output voltage is in regulation, an activelow open-drain output pin (RDY) pulls down when the feedback voltage is above 95% of the nominal regulation voltage level. RDY becomes a high-impedance output if the feedback voltage drops below 85% of the nominal regulation voltage level. Application Information RSET Selection for Programmable Current Limit The current limit of the internal low-side NMOS power switch is programmable from 0.6A to 4.0A by an external resistor connected from RSET to ground. When the inductor’s peak current reaches the current limit, the RDY indicator is pulled high. Table 1 gives standard 1% standard metal film resistor example values for the peak NMOS current-limit programming. Over-Voltage Protection The AAT2215’s over-voltage protection function prevents the output voltage from exceeding the fixed 6V (typ) over-voltage point, which would exceed the absolute maximum rating of the regulator. If OUT exceeds 6V, the regulator will stop switching until the output voltage drops below 5.8V (200mV hysteresis) and FB is below its regulation threshold. When the junction temperature exceeds the over-temperature threshold, the AAT2215 thermal protection circuitry shuts down the regulator. Thermal shutdown disables switching and PMOS current limit is functional to control the current flowing through to avoid any damage of the step-up converter. When the over-temperature fault condition is removed, the step-up recovers regulation automatically. ILIMIT (A) 63.4 75.0 82.0 100.0 118.0 150.0 180.0 300.0 432.0 1000.0 4 3.48 3.1 2.6 2.15 1.75 1.52 1.02 0.82 0.6 Table 1: Examples of 1% Standard Resistor Value of RSET 4.5 4 3.5 3 ILIMIT (A) Thermal Shutdown RSET (kΩ) 2.5 2 1.5 1 0.5 0 0 100 200 300 400 500 600 700 800 900 1000 Resistance (kΩ) Figure 1: ILIMIT vs RSET Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 11 DATA SHEET AAT2215 High Current Synchronous Step-Up Regulator with Programmable Current Limit Output Voltage Programming Input Capacitor The output voltage of the AAT2215 may be programmed from 3.0V to 5.5V with an external resistive voltage divider. Resistors R1 and R2 in Figure 1 program the output voltage as shown by the following equation: Select a low ESR ceramic capacitor with a value of at least 10μF as the input capacitor. Place the input capacitor as close to the IN and PGND pins as possible in order to minimize the stray resistance from the converter to the input power source. R1 = VOUT VREF - 1 · R2 where 0.6V is the feedback reference voltage (VREF). To limit the bias current required for the external feedback resistor string while maintaining good noise immunity, the suggested value for R2 is 100kΩ. Table 2 summarizes the resistor values with R2 set to 100kΩ for good noise immunity and 6μA increased load current and gives some 1% standard metal film resistor values for R1 at different output voltage settings. VOUT(V) R2 = 100kΩ R1 = (kΩ) 3 3.3 3.6 3.8 4.2 4.5 5 5.5 400 450 500 536 600 650 733 816 Table 2: Resistor Selection for Output Voltage Inductor Selection The AAT2215 is designed to operate with a 2.2μH inductor for all input/output voltage combinations. For high efficiency, choose a ferrite inductor with a high frequency core material to reduce core losses. The inductor should have low ESR (equivalent series resistance) to reduce the I2R losses, and must be able to handle the peak inductor current without saturating. To minimize radiated noise, use a shielded inductor. 12 Output Capacitor The output capacitor provides energy to the load when the high-side MOSFET is switched off. The output capacitance together with the boost switching frequency, duty cycle, and load current value determine the capacitive output voltage ripple when the boost operation is in the continuous PWM state. IOUT · D ∆VOUT = C OUT · fSW where D is the duty ratio of low-side MOSFET turn-on time divided by the switching period. It is calculated using the equation: D=1- VIN VOUT The output capacitor’s ESR increases the output ripple by IOUT · ESR. The total output ripple is: IOUT · D ∆VOUT = (IOUT · ESR) + C OUT · fSW So the minimum recommended output capacitor value may be determined by: 1 IOUT · D COUT ≥ ∆V · f OUT - (IOUT · ESR) SW Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 DATA SHEET AAT2215 High Current Synchronous Step-Up Regulator with Programmable Current Limit High Load Pulse Application Together with a large value output capacitor or supercap, the AAT2215 can support a higher load pulse in lower input current limited applications such as GSM burst mode in WCDMA, Edge, GPRS and TD-SCDMA applications. The large capacitance is determined by NMOS peak current limit, inductor current ripple, VIN, VOUT, load pulse high current level and elapsed time. The capacitor value can be calculated using the following three steps as follows: TON is 577μs for a 217Hz 12.5% duty cycle load pulse. Considering 20% capacitance tolerance, the minimum capacitance should be 220μF. Figure 2 shows the AAT2215 operating waveform under a 2.0A 577μs load pulse with 220μF tantalum capacitor as COUT, as well as a 22μF ceramic capacitor to closely filter the output voltage. Load Pulse Response 5.00 4.50 Output Voltage (0.5V/div) (top) V · I ·η IOUT_BOOST = IN LIM VOUT 4.00 3.50 2.50 Finally, derive the COUT at a certain load-on period TON: COUT = I COUT ∙ TON ∆VOUT To consider the real tantalum capacitor having 20% tolerance, the selected capacitance should be 20% higher than the calculated value. Example: A 2.0A, 217Hz 12.5% duty cycle load pulse is applied on 3.8V VOUT at 3.3V VIN. An input peak current limit of 2.4A and a VOUT drop of less than 450mV are required. Under these conditions, with 89% efficiency, the AAT2215's output current is I OUT _ BOOST = 3.3·2.4·89% = 1.86A 3.8 The maximum current necessary for the large capacitor value is: 2 ILOAD 1 0 Second, calculate the maximum current the large capacitor COUT should provide: I COUT = I LOAD _ PEAK - I OUT _ BOOST VOUT 3.00 Output Current (0.5A/div) (bottom) First calculate the AAT2215's load-on current from the expected ILIM. Assume the input current equals ILIM because the inductor current ripple is low enough when compared to the input current: Time (800μs/div) Figure 2: AAT2215 Operation Waveform When 2.0A 217Hz 577μs Load Pulse is Applied. Layout Guidance For best performance of the AAT2215, the following guidelines should be followed when designing the PCB layout: 1. Make the power trace as short and wide as possible, including the input/output power lines and switching node, etc. 2. Connect the analog and power grounds together with a single short line and connect all low current loop grounds to analog ground to decrease the power ground noise on the analog ground and achieve better load regulation. 3. For good power dissipation, connect the exposed pad under the package to the top and bottom ground planes by PCB pads. I COUT = 2.0 - 1.86 = 0.14A Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 13 DATA SHEET AAT2215 High Current Synchronous Step-Up Regulator with Programmable Current Limit Schematic and Layout R4 (opt) C4 (opt) LX U1 AAT2215 C1 10μF OUT OUT FB RSET AGND EP 6 PGND 0 VIN GND 12 11 10 R3 100k JP1 PGND VOUT 3.8V 9 C21 22μF 7 8 RDY VIN VIN PGND R1 536k RSET 100k 5 L1 2.2μH 1 LX 2 LX 4 VIN 3 EN VIN C22 220μF C3 (open) R2 100k AGND RDY Figure 3: AAT2215 Evaluation Board Schematic. Figure 4: AAT2215 Evaluation Board Top Side Layout. 14 Figure 5: AAT2215 Evaluation Board Bottom Side Layout. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 DATA SHEET AAT2215 High Current Synchronous Step-Up Regulator with Programmable Current Limit Part Number Inductance (μH) Max DC Current (A) DCR (mΩ) Size LxWxH (mm) Type CHRH103RNP-2R2NC CDRH103RNP-3R3NC 7440650033 LQH6PPN3R3N43 2.2 3.3 3.3 3.3 6.7 5.5 4.7 4.5 20 21 20 16 10x10x2.8 10x10x2.8 10x10x2.8 6x6x4.3 Shielded Shielded Shielded Shielded Table 3: Surface Mount Inductors. Part Number AAT2215IWP-0.6 RC0603FR-07536KL RC0603FR-07100KL RC0603FR-07100KL RC0603FR-07100KL GRM21BR61C106K GRM21BR60J226M TPSY227M006R0150 CDRH103RNP-2R2NC Description High Current Step-Up Converter with Adjustable Current Limit Res 536kΩ 1/10W 1% 0603 SMD Res 100kΩ 1/10W 1% 0603 SMD Res 100kΩ 1/10W 1% 0603 SMD Res 100kΩ 1/10W 1% 0603 SMD Cap Ceramic 10μF 0805 X5R 16V 10% Cap Ceramic 22μF 0805 X5R 6.3V 20% Cap Tan 220μF case 6.3V 20% Inductor 2.2μH 6.7A SMD Manufacturer Skyworks Yageo Murata AVX Sumida Table 4: AAT2215 Evaluation Board Bill of Materials. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 15 DATA SHEET AAT2215 High Current Synchronous Step-Up Regulator with Programmable Current Limit Ordering Information Package Marking1 Part Number (Tape and Reel)2 TDFN33-12 P5XYY AAT2215IWP -T1 Skyworks Green™ products are compliant with all applicable legislation and are halogen-free. For additional information, refer to Skyworks Definition of Green™, document number SQ04-0074. Package Information3 TDFN33-12 Index Area 0.40 ± 0.05 Detail "A" C0.3 0.45 ± 0.05 2.40 ± 0.05 3.00 ± 0.05 0.1 REF 3.00 ± 0.05 1.70 ± 0.05 Top View Bottom View 0.23 ± 0.05 Pin 1 Indicator (optional) 0.05 ± 0.05 0.23 ± 0.05 0.75 ± 0.05 Detail "A" Side View All dimensions in millimeters. 1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD. 3. The leadless package family, which includes QFN, TQFN, DFN, TDFN and STDFN, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing process. A solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder connection. 16 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 DATA SHEET AAT2215 High Current Synchronous Step-Up Regulator with Programmable Current Limit Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved. Information in this document is provided in connection with Skyworks Solutions, Inc. (“Skyworks”) products or services. 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Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 17