DATA SHEET AAT2114A 2.5A Low-Noise, Fast Transient 3MHz Step-Down Regulator General Description Features The AAT2114A SwitchReg™ step-down converter delivers up to 2.5A to support the adjustable 1.0V to VIN output from the 2.7V to 5.5V input source. The 3MHz switching frequency allows a high-bandwidth design that minimizes the external LC component requirements. • 2.5A Maximum Output Current • 3MHz Switching Frequency ▪ Stable With 20μF Output Capacitor • 2.7V to 5.5V Input Voltage Range • Adjustable 1.0V to VIN Output Voltage • Up to 95% Efficiency • Excellent Current-Mode Transient Response • Low-Noise Light-Load Architecture • 70μA No Load Quiescent Current • No External Compensation Required • Internal Soft Start • Over-Temperature and Current-Limit Protection • <1μA Shutdown Current • -40°C to +85°C Temperature Range • 16-Pin, 3mm x 3mm QFN Package The AAT2114A high-frequency converter consumes only 70μA no-load quiescent current. The internally compensated, high-frequency, current-mode control scheme provides excellent transient response, minimal output ripple, and reduced spectral noise. Additionally, the AAT2114A provides tight output accuracy across the entire load and input voltage operating ranges. The regulator maintains high efficiency by integrating the high-side and low-side MOSFETs and designing the gate drivers to minimize dead-time switching losses. The regulator also reduces the switching frequency under light load conditions, minimizing power loss over the entire load range. Applications • • • • For system fault protection, the AAT2114A includes overtemperature and short-circuit current-limit protection to safeguard the AAT2114A and system components from overload conditions. Cellular Phones Digital Cameras MP3/Portable Media Players Wireless Cards The compact 3mm x 3mm QFN package footprint, minimal LC requirements, and high efficiency make the AAT2114A an ideal choice for low-power portable applications operating from a Li-ion/polymer battery. Typical Application Load Transient Response Output Voltage (top) (V) 1.4 1.3 1.2 190mV 1.1 3 2 1 0 Output Current (bottom) (A) (250mA to 2.5A; VIN = 3.6V; VOUT = 1.2V; COUT = 2x10µF; CFF = 100pF) VIN 2.7V-5.5V 9 10,11,12 CIN 10μF 6V 0603 VCC VP LX 13,14,15 16 N/C RFBH 59kΩ AAT2114A 1, 2, 3 PGND FB 4 6 ON N/C 7 8 RFBL 59kΩ CFF 100pF COUT 2x10μF 6V 0603 5 EN OFF VOUT 1.2V, 2.5A L1 0.47μH N/C SGND GND EP Time (50µs/div) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202004C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013 1 DATA SHEET AAT2114A 2.5A Low-Noise, Fast Transient 3MHz Step-Down Regulator Pin Descriptions Pin # Name 1, 2, 3 PGND 4 FB 5 SGND 6, 8, 16 N/C 7 EN 9 VCC 10, 11, 12 VP 13, 14, 15 LX EP GND Function Power Ground. PGND is internally connected to the source of the low-side N-channel MOSFET. Connect to the input capacitor and output capacitor return. Feedback Input. FB senses the output voltage for regulation control. Connect a resistive divider network from the output to FB to SGND to set the output voltage accordingly. The adjustable FB regulation threshold is 0.6V. Signal/Analog Ground. SGND is internally connected to the analog ground of the control circuitry. Connect the return of the feedback components to this ground. Not Internally Connected. This pin is not internally connected and may be either left open or shorted to an adjacent pin. Enable Input. A logic high enables the AAT2114A regulator. A logic low forces the AAT2114A into shutdown mode, placing the output into a high-impedance state and reducing the quiescent current to less than 1μA. Do NOT leave EN floating. Bias Input Supply. VCC supplies power to the analog and logic signal control circuitry of the AAT2114A. Input Power Supply. Connect VP to the input power source. Bypass VP to PGND with a 10μF or greater ceramic capacitor. VP internally connects to the source of the high-side P-channel MOSFET and MOSFET drivers as shown in the Functional Block Diagram. Inductor Switching Node. LX is internally connected to the source of the high-side P-Channel MOSFET and the drain of the low-side N-channel MOSFET. Externally connected to the power inductor as shown in the Typical Application Circuit. Thermal/Substrate Ground. GND is internally connected to the substrate of the controller and serves as the lowest thermal impedance path. Connect directly to the system ground plane to keep the thermal impedance low. Pin Configuration QFN33-16 (Top View) LX LX LX N/C 13 14 15 16 PGND PGND PGND FB 1 12 2 11 EP 3 10 4 9 VP VP VP VCC 8 7 6 5 N/C EN N/C SGND 2 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202004C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013 DATA SHEET AAT2114A 2.5A Low-Noise, Fast Transient 3MHz Step-Down Regulator Absolute Maximum Ratings1 Symbol VP VCC VLX VEN VFB VGND TJ TLEAD TA Description VP to PGND VCC to SGND LX to PGND EN to SGND FB to SGND SGND to GND, PGND to GND Operating Junction Temperature Range Maximum Soldering Temperature (at leads, 10 sec.) Ambient Temperature Range Value Units -0.3 to +6 -0.3 to +6 -0.3 to (VP + 0.3) -0.3 to (VCC + 0.3) -0.3 to (VCC + 0.3) -0.3 to +0.3 -40 to +150 300 -40 to +85 V V V V V V C C C Value Units 43 2.3 C/W W Thermal Characteristics Symbol Description QFN33-16 Thermal Impedance2 θJA Maximum Junction-to-Ambient Thermal Resistance PD Maximum Power Dissipation3 1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time. 2. Mounted on a FR4 demo board in still air. The exposed pad must be mounted to the PCB. 3. Derate 23mW/°C above 25°C. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202004C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013 3 DATA SHEET AAT2114A 2.5A Low-Noise, Fast Transient 3MHz Step-Down Regulator Electrical Characteristics1 Typical Application Circuit: CIN = 10μF, COUT = 2x 10μF, L = 0.47μH. VP = 3.6V, VCC = EN = VP, SGND = PGND = GND. TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C. Symbol Description Conditions VIN VOUT Input Voltage Range Output Voltage Range VP, VCC VUVLO Input Under-Voltage Lockout IQ ISHDN VFB IFB ΔVOUT/IOUT ΔVOUT/VIN ILIMPK RDS(ON)HI RDS(ON)LO fOSC tSS TSHDN VEN IEN No Load Supply Current Shutdown Current FB Regulation Threshold FB Leakage Current Load Regulation2 Line Regulation High-Side P-Channel MOSFET Current Limit High-Side P-Channel MOSFET On-Resistance Low-Side N-Channel MOSFET On-Resistance Internal Oscillator Frequency Soft-Start Period Over-Temperature Shutdown Threshold EN Input Logic Threshold EN Input Current VCC Rising Hysteresis No Load Current; Not Switching EN = GND, VP = 5.5V, LX = GND No Load, TA = +25°C, VIN = 5V VFB = 1.0V 0.25 to 2.5A Load VIN = 2.7V to 5.5V Min Typ 2.7 1.0 0.1 70 591 600 5 1 0.5 Max Units 5.5 VIN 2.7 V V V V μA μA mV nA % %/V A mΩ mΩ MHz μs °C V μA 140 1 609 200 2 3 VIN = 3.3V 2.2 Hysteresis = 15°C VIN = VEN = 0V or 5.5V 120 100 3.0 60 140 0.4 -1.0 3.8 1.4 +1.0 1. The AAT2114A 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. 2. Guaranteed by design. 4 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202004C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013 DATA SHEET AAT2114A 2.5A Low-Noise, Fast Transient 3MHz Step-Down Regulator Typical Characteristics Efficiency vs. Load Load Regulation (VOUT = 3.3V; L = 1.5µH) (VOUT = 3.3V; L = 1.5µH) 100 Efficiency (%) 80 70 60 50 40 VIN = 4.2V VIN = 5.0V VIN = 5.5V 30 20 0.1 1 10 100 1000 Output Voltage Error (%) 3.0 90 2.0 1.0 0.0 -1.0 -3.0 0.1 10000 VIN = 4.2V VIN = 5.0V VIN = 5.5V -2.0 1 Output Current (mA) Load Regulation (VOUT = 2.5V; L = 1µH) (VOUT = 2.5V; L = 1µH) 70 60 50 VIN = 3.6V VIN = 4.2V VIN = 5.0V VIN = 5.5V 40 1 10 100 1000 Output Voltage Error (%) Efficiency (%) 80 30 10000 2.0 1.0 0.0 -1.0 -3.0 0.1 10000 VIN = 3.6V VIN = 4.2V VIN = 5.0V VIN = 5.5V -2.0 1 Output Current (mA) 10 100 1000 Efficiency vs. Load Load Regulation (VOUT = 1.8V; L = 0.86µH) (VOUT = 1.8V; L = 0.86µH) 80 70 60 VIN = 2.7V VIN = 3.6V VIN = 4.2V VIN = 5.0V VIN = 5.5V 40 30 1 10 100 Output Current (mA) 1000 10000 Output Voltage Error (%) 3.0 90 50 10000 Output Current (mA) 100 Efficiency (%) 1000 3.0 90 20 0.1 100 Efficiency vs. Load 100 20 0.1 10 Output Current (mA) VIN = 2.7V VIN = 3.6V VIN = 4.2V VIN = 5.0V VIN = 5.5V 2.0 1.0 0.0 -1.0 -2.0 -3.0 0.1 1 10 100 1000 10000 Output Current (mA) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202004C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013 5 DATA SHEET AAT2114A 2.5A Low-Noise, Fast Transient 3MHz Step-Down Regulator Typical Characteristics Efficiency vs. Load Load Regulation (VOUT = 1.2V; L = 0.47µH) (VOUT = 1.2V; L = 0.47µH) 100 Output Voltage Error (%) 3.0 Efficiency (%) 90 80 70 60 VIN = 2.7V VIN = 3.6V VIN = 4.2V VIN = 5.0V VIN = 5.5V 50 40 30 20 0.1 1 10 100 1000 10000 VIN = 2.7V VIN = 3.6V VIN = 4.2V VIN = 5.0V VIN = 5.5V 2.0 1.0 0.0 -1.0 -2.0 0.1 1 Output Current (mA) Line Regulation (VOUT = 1.2V; L = 0.47µH) 1.0 0.5 IOUT = 0.10mA IOUT = 1mA IOUT = 10mA IOUT = 0.1A IOUT = 0.5A IOUT = 1.25A IOUT = 2A IOUT = 2.5A 0.0 -0.5 -1.0 -1.5 -2.0 3.0 3.5 4.0 4.5 5.0 Output Voltage Error (%) 2.0 2.5 IOUT = 0.10mA IOUT = 1mA IOUT = 10mA IOUT = 0.1A 1.5 1.0 0.0 -1.0 -1.5 -2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Input Voltage (V) Output Voltage Error vs. Temperature (VIN = 4.2V; VOUT = 3.3V) (VIN = 3.6V; VOUT = 2.5V) 3.0 3.0 IOUT = 0.10mA IOUT = 1mA IOUT = 10mA IOUT = 0.1A IOUT = 0.5A IOUT = 1.25A IOUT = 2A IOUT = 2.5A Output Voltage Error (%) Output Voltage Error (%) IOUT = 0.5A IOUT = 1.25A IOUT = 2A IOUT = 2.5A -0.5 5.5 Output Voltage Error vs. Temperature 1.0 0.0 -1.0 -2.0 -25 0 25 50 Temperature (°C) 6 10000 0.5 Input Voltage (V) -3.0 -50 1000 Line Regulation 1.5 2.0 100 (VOUT = 1.8V; L = 0.86µH) 2.0 Output Voltage Error (%) 10 Output Current (mA) 75 100 IOUT = 0.10mA IOUT = 1mA IOUT = 10mA IOUT = 0.1A 2.0 IOUT = 0.5A IOUT = 1.25A IOUT = 2A IOUT = 2.5A 1.0 0.0 -1.0 -2.0 -3.0 -50 -25 0 25 50 Temperature (°C) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202004C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013 75 100 DATA SHEET AAT2114A 2.5A Low-Noise, Fast Transient 3MHz Step-Down Regulator Typical Characteristics Output Voltage Error vs. Temperature Output Voltage Error vs. Temperature (VIN = 3.6V; VOUT = 1.8V) (VIN = 3.6V; VOUT = 1.2V) 3.0 IOUT = 0.10mA IOUT = 1mA IOUT = 10mA IOUT = 0.1A 2.0 IOUT = 0.5A IOUT = 1.25A IOUT = 2A IOUT = 2.5A Output Voltage Error (%) Output Voltage Error (%) 3.0 1.0 0.0 -1.0 -2.0 -3.0 -50 -25 0 25 50 75 100 IOUT = 0.10mA IOUT = 1mA IOUT = 10mA IOUT = 0.1A 2.0 1.0 0.0 -1.0 -2.0 -3.0 -50 Temperature (°C) -25 0 25 50 75 100 Temperature (°C) Load Transient Response Load Transient Response (250mA to 2.5A; VIN = 5.0V; VOUT = 3.3V; COUT = 2x10µF; C5 = 100pF) (250mA to 2.5A; VIN = 3.6V; VOUT = 2.5V; COUT = 2x10µF; C5 = 100pF) 2.9 3.5 2.7 3.1 3 2 2.5 2.3 3 2 1 1 Output Current (bottom) (A) 3.3 Output Voltage (top) (V) 3.7 Output Current (bottom) (A) Output Voltage (top) (V) IOUT = 0.5A IOUT = 1.25A IOUT = 2A IOUT = 2.5A 0 0 Time (50µs/div) Load Transient Response Load Transient Response (250mA to 2.5A; VIN = 3.6V; VOUT = 1.8V; COUT = 2x10µF; C5 = 100pF) (250mA to 2.5A; VIN = 3.6V; VOUT = 1.2V; COUT = 2x10µF; C5 = 100pF) 1.4 1.9 1.3 1.7 3 2 1 1.2 1.1 3 2 1 0 0 Time (50µs/div) Output Current (bottom) (A) 1.8 Output Voltage (top) (V) 2.0 Output Current (bottom) (A) Output Voltage (top) (V) Time (50µs/div) Time (50µs/div) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202004C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013 7 DATA SHEET AAT2114A 2.5A Low-Noise, Fast Transient 3MHz Step-Down Regulator Line Transient Response Line Transient Response (VIN = 3.6V to 4.2V; VOUT = 2.5V; IOUT = 2.5A; COUT = 2x10µF; C5 = 100pF) (VIN = 3.6V to 4.2V; VOUT = 1.8V; IOUT = 2.5A; COUT = 2x10µF; C5 = 100pF) 4.8 4.2 4.2 3.0 2.52 2.50 3.6 3.0 1.82 1.80 2.48 1.78 2.46 1.76 Time (20µs/div) Time (20µs/div) Output Ripple Output Ripple (VIN = 3.6V; VOUT = 1.2V; IOUT = 10mA) (VIN = 3.6V; VOUT = 1.2V; IOUT = 2.5A) 1.24 1.24 0.6 0.4 0.2 1.20 1.18 3.0 2.5 2.0 0.0 1.5 Time (10µs/div) Time (200ns/div) Enable Soft Start 4 3 2 1 3 0 2 1 Inductor Current (bottom) (A) Enable Voltage (top) (V) Output Voltage (middle) (V) (VIN = 3.6V; VOUT = 1.2V; IOUT = 2.5A) 0 Time (20µs/div) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202004C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013 Inductor Current (bottom) (A) 1.18 Output Voltage (top) (V) 1.22 1.20 Inductor Current (bottom) (A) Output Voltage (top) (V) 1.22 8 Output Voltage (bottom) (V) 3.6 Input Voltage (top) (V) 4.8 Output Voltage (bottom) (V) Input Voltage (top) (V) Typical Characteristics DATA SHEET AAT2114A 2.5A Low-Noise, Fast Transient 3MHz Step-Down Regulator Typical Characteristics Switching Frequency vs. Input Voltage Switching Frequency vs. Temperature (VOUT = 1.2V; IOUT = 2.5A) (VIN = 3.6V; IOUT = 2.5A; VOUT = 1.2A) Switching Frequency (MHz) Frequency Variation (%) 10 8 6 4 2 0 -2 -4 -6 -8 -10 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 3.30 3.20 3.10 3.00 2.90 2.80 2.70 -40 -20 0 Input Voltage (V) 20 40 60 80 100 Temperature (°C) Input Current vs. Input Voltage Enable Threshold vs. Input Voltage 100 1.2 90 1.1 VIH and VIL (V) Input Current (µA) (VEN = VIN; VOUT = 1.2V; Closed Loop Switching) 80 70 60 50 85°C 25°C -40°C 40 30 2.5 3 3.5 4 4.5 Input Voltage (V) 5 5.5 1.0 0.9 0.8 EN Rising EN Falling 0.7 0.6 6 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 Input Voltage (V) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202004C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013 9 DATA SHEET AAT2114A 2.5A Low-Noise, Fast Transient 3MHz Step-Down Regulator Functional Block Diagram VCC VP Slope Compensation FB SGND VP 0.6V REF OSC PGND Temperature Sensing EN Functional Description The AAT2114A is a high performance 2.5A monolithic step-down converter operating at a 3MHz switching frequency. It minimizes external component size, optimizes efficiency over the complete load range, and produces reduced ripple and spectral noise. Apart from the small bypass input capacitor, only a small L-C filter is required at the output. Typically, a 0.47μH inductor and a 22μF ceramic capacitor are recommended for a 1.2V output (see table of recommended values). Light load operation maintains high efficiency, low ripple and low spectral noise even at lower currents (typically <150mA). The current limit of 4A (typical) protects the IC and system components from short-circuit damage. Typical no load quiescent current is 70μA. Thermal protection completely disables switching when the maximum junction temperature is detected. The junction over-temperature threshold is 140°C with 15°C of hysteresis. Once an over-temperature or over-current fault condition is removed, the output voltage automatically recovers. Peak current mode control and optimized internal compensation provide high loop bandwidth and excellent response to input voltage and fast load transient events. Soft start eliminates output voltage overshoot when the 10 Control Logic LX enable or the input voltage is applied. Under-voltage lockout prevents spurious start-up events. Control Loop The AAT2114A 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 determines the transconductance voltage error amplifier output. The 0.6V reference voltage is internally set to program the converter output voltage greater than or equal to 1.0V. 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 AAT2114A into a low-power, non-switching state. The total input current during shutdown is less than 1μA. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202004C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013 DATA SHEET AAT2114A 2.5A Low-Noise, Fast Transient 3MHz Step-Down Regulator Current Limit and Over-Temperature Protection appreciable saturation under normal load conditions. For overload conditions, the peak input current is limited. The on-time is terminated after a current limit has been sensed. 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. Under-Voltage Lockout 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. Input Capacitor Select a 10μF 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 CIN. The calculated value varies with input voltage and is a maximum when VIN is double the output voltage. Internal bias of all circuits is controlled via the VCC input. Under-voltage lockout (UVLO) guarantees sufficient VIN bias and proper operation of all internal circuitry prior to activation. CIN(MIN) = Component Selection VPP - ESR · FSW IO D= 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 inductor value can be calculated by: L1 = D · (1 - D) 0.47 · VOUT 1.2 For low cost application and a sufficiently small footprint, the TDK VLS252012T-R47N2R1 shielded chip inductor, which has 47mΩ DCR, is selected for 1.2V output (see Table 1). VO VIN The peak ripple voltage occurs when VIN = 2x VO (50% duty cycle), resulting in a minimum output capacitance recommendation: 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. The maximum input capacitor RMS current is: IRMS = IO · 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 IRMS = IO · D · (1 - D) VO V · 1- O VIN VIN VOUT (V) Inductor Selection 1.2 1.8 2.5 3.3 TDK, VLS252012T-R47N2R1, 0.47μH, ISAT = 3.7A, DCR = 47mΩ Sumida, CDRH38D16R/HP, 0.9μH, ISAT = 2.66A, DCR = 20mΩ TDK, VLS252012T-1R0N1R7, 1.0μH, ISAT = 2.7A, DCR = 88mΩ TDK, VLF5014AT-1R5M1R7, 1.5μH, ISAT = 2.9, DCR = 51mΩ Table 1: Inductor Selection. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202004C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013 11 DATA SHEET AAT2114A 2.5A Low-Noise, Fast Transient 3MHz Step-Down Regulator 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. IRMS(MAX) = IO 2 occurs when VIN = 2 · VO. The calculated value varies with the input voltage and is at a maximum when VIN is twice the output voltage VOUT. The input capacitor provides a low impedance loop for the edges of pulsed current drawn by the AAT2114A. 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 can be seen in the evaluation board layout shown 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 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 capacitor. This dampens the high Q network and stabilizes the system. Output Capacitor The output capacitor limits the output ripple and maintains the output voltage during large load transitions. A 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. 12 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: COUT = 3 · ΔIO VDROOP · FSW 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 20μF. 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. Adjustable Feedback Network The output voltage on the AAT2114A is programmed with external resistors R3 and R4. To limit the bias current required for the external feedback resistor string while maintaining good noise immunity. 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. Therefore, the recommended value range for R4 is 59kΩ for good noise immunity or 221kΩ for reduced no load input current. The external resistor R3, combined with an external 100pF feed forward capacitor (C5 in Figure 1), delivers enhanced transient response for extreme pulsed load applications and reduces ripple in light load conditions. The external resistors set the output voltage according to the following equation: VO = 0.6V · 1 + R3 R4 or solving for R3: R3 = VO - 1 · R4 0.6V Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202004C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013 DATA SHEET AAT2114A 2.5A Low-Noise, Fast Transient 3MHz Step-Down Regulator The typical circuit shown in the AAT2114A evaluation schematic is intended to be general purpose and suitable for most applications. In applications where transient load steps are more severe and the restriction on output voltage deviation is more stringent, some simple adjustments can be made. The schematic in Figure 1 shows the configuration for improved transient response in an application where the output is stepped down to 1.2V. The adjustments consist of increasing the value of the feed forward capacitor C5 to 100pF. VOUT (V) R4 = 59.0kΩ R3 (kΩ) R4 = 221kΩ R3 (kΩ) 1.0 1.2 1.5 1.8 2.5 3.3 39.2 59 88.7 118 187 267 147 221 332 442 698 1M Table 2: Feedback Resistors for Various Output Voltages. Thermal Calculations There are three types of losses associated with the AAT2114A 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 losses is given by: PLOSS(RES) = IO2 · RDS(ON)H · VO VIN + RDS(ON)L · VIN - VO VIN + (tSW · FSW · IOUT + IQ) · VIN IQ is the step-down converter quiescent current. The term tSW is the time to charge up the gate capacitor of the high-side P-channel MOSFET, and used to estimate the full load step-down converter switching losses. 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 QFN33-16 package, which is 43°C/W. TJ(MAX) = PTOTAL · ΘJA + TAMB Layout Considerations The suggested PCB layout for the AAT2114A is shown in Figures 2 and 3. The following guidelines should be used to help ensure a proper layout. 1. The input capacitor (C1) should connect as close as possible to VP and PGND. 2. C2, C3 and L1 should be connected as close as possible. The connection of L1 to the LX pin should be as short as possible. 3. The feedback trace or FB pin should be separate from any power trace and connect as close 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 PGND 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. 5. Connect unused signal pins to ground to avoid unwanted noise coupling. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202004C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013 13 DATA SHEET AAT2114A 2.5A Low-Noise, Fast Transient 3MHz Step-Down Regulator U1 VIN 10 11 12 C1 10μF C6 Open R1 10Ω 9 VP LX VP LX VP LX AAT2114A N/C VCC FB C4 0.1μF N/C SGND EN 7 EN PGND 1 U1 C1, C2, C3 C4 C5 L1 R1 R3, R4 2 13 VOUT L1 0.47μH 14 R3 59kΩ 15 C5 100pF 1.2V/2.5A 16 C2 10μF 4 C3 10μF C7 Open 8 R4 59kΩ 5 N/C 3 6 QFN 33 -16 AAT2114AIVN, Skyworks, 3MHz Fast Transient, 2.5A Step-Down Converter, QFN33-16, 3x3mm GRM188R60J106ME47D, Murata, Cap, MLC, 10μF/6.3V, 0603 0.1μF/6.3V, 0402 UMK105CG101JV-F10nF, Taiyo Yuden, 100pF/50V, 0402 252012T-R47N2R1, TDK, 0.47μH, ISAT = 3.7A, DCR = 0.047Ω, 2.5x2x1.2mm, shielded chip inductor Carbon film resistor, 10Ω, 1%, 0201 Carbon film resistor, 59kΩ, 1%, 0402 Figure 1: AAT2114AIVN Evaluation Board Schematic and Bill of Materials. Figure 2: AAT2114AIVN Evaluation Board Top Side Layout. 14 Figure 3: AAT2114AIVN Evaluation Board Bottom Side Layout. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202004C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013 DATA SHEET AAT2114A 2.5A Low-Noise, Fast Transient 3MHz Step-Down Regulator Ordering Information Package Output Marking1 Part Number (Tape and Reel)2 QFN33-16 Adjustable (VFB = 0.6V) M7XYY AAT2114AIVN-0.6-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 Information QFN33-163 Pin 1 Dot By Marking 0.230 ± 0.050 Pin 1 Identification 0.500 ± 0.050 1.250 ± 0.050 5 C0.3 13 9 1.250 ± 0.050 Top View 0.025 ± 0.025 Bottom View 0.214 ± 0.036 0.900 ± 0.100 3.000 ± 0.050 0.400 ± 0.100 3.000 ± 0.050 1 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 manufacturing process. A solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder connection. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202004C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013 15 DATA SHEET AAT2114A 2.5A Low-Noise, Fast Transient 3MHz Step-Down Regulator Copyright © 2012, 2013 Skyworks Solutions, Inc. All Rights Reserved. Information in this document is provided in connection with Skyworks Solutions, Inc. (“Skyworks”) products or services. These materials, including the information contained herein, are provided by Skyworks as a service to its customers and may be used for informational purposes only by the customer. Skyworks assumes no responsibility for errors or omissions in these materials or the information contained herein. Skyworks may change its documentation, products, services, specifications or product descriptions at any time, without notice. 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Additional information, including relevant terms and conditions, posted at www.skyworksinc.com, are incorporated by reference. 16 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202004C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013