600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass

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600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass

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AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch General Description
AAT1171 SwitchReg dynamically controls operating voltage WCDMA CDMA power amplifier inside single-cell, lithium-ion battery-powered systems. AAT1171 outputs voltage between 0.6V 3.6V, thereby optimizing amplifier efficiency both high transmit levels. AAT1171 output voltage controlled analog signal from baseband processor. deliver 600mA continuous load current while maintaining 45µA load quiescent current. 2MHz switching frequency minimizes size external components while keeping switching losses low. further improve system efficiency, bypass MOSFET transistor also included allow powered directly from battery. AAT1171 maintains high efficiency thoughout entire load range Light Load (LL) mode, forced into Pulse Wide Modulation (PWM) mode noise operation synchronized external clock. AAT1171 available Pb-free, space-saving TDFN33-12 package rated over -40°C +85°C temperature range.
SwitchReg
Range: 2.7V 5.5V Variable Output Voltage: 0.6V 3.6V 600mA Output Current Input: 0.2V 1.2V High Output Accuracy: 45µA Load Quiescent Current Internal Soft Start Limits Startup Current Output Voltage Overshoot Synchronizable External 19.8MHz System Clock Over-Temperature Current Limit Protection Integrated Bypass MOSFET 2MHz Operation PWM/LL Control with Override Fast Start-Up: 50µs (AAT1171-4, AAT1171-5) 150µs (AAT1171-1) 100% Duty Cycle Operation <30µs Output Voltage Response Time 3x3mm 12-Pin TDFN Package Temperature Range: -40°C +85°C
Applications
WCDMA CDMA Cellular Phones, Smartphones, Feature Phones, etc. Express Card PCMCIA Data Cards
Typical Application
4.7F COUT 4.7F 4.7F 2.2H 0.6V 3.6V COUT 4.7H 0.6V 3.6V
AAT1171-1/ AAT1171-4
BYPASS MODE/SYNC GNDx2 VOUT
AAT1171-5
BYPASS MODE/SYNC VOUT
VCC2 VCONT VREF VCC2 Baseband Processor
GNDx2 VREF
VCC2 VCONT VCC2
Baseband Processor
1171.2007.08.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch Descriptions
Symbol
VOUT
Function
connected. Feedback input pin. This connected converter output. used complete control loop, regulating output voltage desired value. When bypass mode, resistance MOSFET connected between this VIN. Bias supply. Supply power internal circuitry. Connect input power pass filter with decoupling AGND. Analog ground. Connect return small signal components this pin. Control voltage input from DAC. Input voltage between 0.2V 1.2V control output voltage converter. Force 1.3V bypass switch enable. Enable DC/DC converter, active high. Enable control bypass DC/DC converter when transmitting full power from battery voltage. Active high. This used program device between mode: HIGH Mode Only Mode: operation loads above 100mA variable switching frequency loads below 100mA Connecting SYNC system clock (19.8MHz) will override internal clock force switching frequency external clock frequency divided Input supply voltage converter. Must closely decoupled. Main power ground. Connect output input capacitor return. Switching node. Connect inductor this pin. connected internally drain both low- high-side MOSFETs. Exposed paddle (bottom). Connect ground directly beneath package.
AGND BYPASS MODE/SYNC
PGND
Configuration
TDFN33-12 (Top View)
VOUT VOUT AGND
PGND MODE/SYNC BYPASS
1171.2007.08.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch Absolute Maximum Ratings1
Symbol
VCC, VOUT TLEAD
Description
Input Voltage Bias Power VOUT DAC, BYPASS, MODE/SYNC Operating Junction Temperature Range Maximum Soldering Temperature leads, sec)
Value
-0.3 -0.3 -0.3
Units
Thermal Information2
Symbol
Description
Maximum Power Dissipation, 25°C Thermal Resistance, 25°C
Value
Units
°C/W
Stresses above those listed Absolute Maximum Ratings cause permanent damage device. Functional operation conditions other than operating conditions specified implied. Only Absolute Maximum Rating should applied time. Mounted board. 1171.2007.08.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch Electrical Characteristics1
-40°C +85°C, unless otherwise noted. 3.6V; typical values 25°C. Symbol
VUVLO VOUT VDACIN ISHDN ILIM RDS(ON)H RDS(ON)L RDS(ON)BP ILXLEAK VOUT/VOUT VOUT/ VOUT/VIN ROUT VOUT FOSC THYS tVOUTS
Description
Input Voltage UVLO Threshold UVLO Hysteresis VOUT Programmable Range Input Voltage Range from Quiescent Current Shutdown Current P-Channel Current Limit High Side Switch Resistance Side Switch Resistance Bypass Switch Resistance Leakage Current Load Regulation Line Regulation Feedback Impedance Output Voltage Accuracy Oscillator Frequency Over-Temperature Shutdown Threshold Over-Temperature Shutdown Hysteresis Light Load Load Current Threshold Output Voltage Settling Time
Conditions
Rising
Units
Load, Light Load Load, PWM, Bias Current AGND PGND 25°C
VDAC 1.3V BYPASS 5.5V, ILOAD 500mA
VDAC 0.6V, ILOAD
1.746
1.854
VOUT 0.6V VOUT(MAX), MODE/SYNC
AAT1171 guaranteed meet performance specifications over -40°C +85°C operating temperature range assured design, characterization, correlation with statistical process controls.
1171.2007.08.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch Electrical Characteristics1
-40°C +85°C, unless otherwise noted. 3.6V; typical values 25°C. Symbol Description Conditions
5.5V AAT1171-1: High, MODE/SYNC High, VDAC 1.2V AAT1171-4/AAT1171-5: High, MODE/SYNC High, VDAC 1.2V Sync 19.8MHz2 VSYNC -1.0 -1.0
Units
PWM/Light Load/EN VEN(L) Enable Threshold VEN(H) Enable Threshold High Input Current SYNC FSYNC VSYNC(H) VSYNC(L) ISYNC Input Gain Turn-On Enable Response Time
Synchronization Frequency SYNC High Level Threshold SYNC Level Threshold SYNC Current Output Voltage/DAC Voltage3
19.8
AAT1171 guaranteed meet performance specifications over -40°C +85°C operating temperature range assured design, characterization, correlation with statistical process controls. Please contact Sales other synchronization frequencies. Please contact Sales other output voltage/DAC voltage gains. 1171.2007.08.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch Typical Characteristics
Efficiency Output Current
Mode; VOUT 3.3V)
Load Regulation
Mode; VOUT 3.3V)
Output Voltage Error
3.9V
Efficiency
5.0V 3.6V
4.2V 5.0V
-0.5
4.2V
1000
-1.0
1000
Output Current (mA)
Output Current (mA)
Efficiency Output Current
(PWM Mode; VOUT 3.3V)
Load Regulation
(PWM Mode; VOUT 3.3V)
Output Voltage Error
Efficiency
5.0V
3.6V
4.2V 5.0V
3.6V
-0.5
4.2V
1000
1000
-1.0
Output Current (mA)
Output Current (mA)
Efficiency Output Current
Mode; VOUT 2.5V) 3.0V
Output Voltage Error
Load Regulation
Mode; VOUT 2.5V)
Efficiency
5.0V 4.2V
4.2V 5.0V
-0.5
3.0V
1000
-1.0
1000
Output Current (mA)
Output Current (mA)
1171.2007.08.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch Typical Characteristics
Efficiency Output Current
(PWM Mode; VOUT 2.5V)
Load Regulation
(PWM Mode; VOUT 2.5V)
Output Voltage Error
Efficiency
3.0V 4.2V 5.0V
5.0V 3.0V
4.2V
-0.5
1000
-1.0
1000
Output Current (mA)
Output Current (mA)
Efficiency Output Current
Mode; VOUT 1.8V) 2.7V 4.2V 3.6V
Output Voltage Error
Load Regulation
Mode; VOUT 1.8V)
Efficiency
1000
3.6V 4.2V
-0.5
2.7V
-1.0
1000
Output Current (mA)
Output Current (mA)
Efficiency Output Current
(PWM Mode; VOUT 1.8V)
Load Regulation
(PWM Mode; VOUT 1.8V)
Output Voltage Error
2.7V 3.6V 4.2V
Efficiency
1000
3.6V 4.2V
2.7V
-0.5
-1.0 1000
Output Current (mA)
Output Current (mA)
1171.2007.08.0.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch Typical Characteristics
Output Voltage Supply Voltage
Mode; VOUT 1.5V)
1.514 1.514
Output Voltage Supply Voltage
(PWM Mode; VOUT 1.5V)
Output Voltage
1.510 1.506 1.502 1.498
Output Voltage
IOUT 50mA IOUT 300mA
1.510 1.506 1.502 1.498
IOUT 50mA IOUT 300mA IOUT 600mA
IOUT 600mA
1.494
1.494
Supply Voltage
Supply Voltage
Output Voltage Temperature
(VIN 3.6V; VOUT 1.8V; VDAC 0.6V;
Output Voltage Error
-0.5 -1.0 -1.5 0.05
Bypass Mode Dropout Voltage Load Current
Dropout Voltage
0.00 -0.05 -0.10 -0.15 -0.20 -0.25 -0.30 1000
Temperature (°C)
Load Current (mA)
Supply Current Supply Voltage
Load; Mode)
Supply Current Supply Voltage
Load; Mode)
Supply Current (mA)
Supply Current (µA)
VOUT 1.8V
VOUT 1.8V
VOUT 0.6V
VOUT 0.6V
Supply Voltage
Supply Voltage
1171.2007.08.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch Typical Characteristics
P-Channel RDS(ON) Input Voltage
Bypass RDS(ON) Input Voltage
120°C 85°C
120°C
85°C
RDS(ON)
RDS(ON)
25°C
25°C
Input Voltage
Input Voltage
Switching Frequency Temperature
(VIN 3.6V; VOUT 1.8V;
Output Voltage Voltage
(VIN 4.2V; Mode)
Switching Frequency (MHz)
2.06
Output Voltage
2.04 2.02 2.00 1.98 1.96 1.94 1.92 1.90 -40.0 -20.0 20.0 40.0 60.0 80.0
25°C 85°C -40°C
Temperature (°C)
Voltage
Heavy Load Switching Waveform
(VIN 3.6V; VOUT 1.8V; COUT 4.7µF; 2.2µH) VOUT coupled) 20mV/div 200mA/div
2V/div
Time (200ns/div)
1171.2007.08.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch Typical Characteristics
Light Load Switching Waveform
(PWM Mode; 4.2V; VOUT 0.6V; COUT 4.7µF; 2.2µH) VOUT coupled) 20mV/div 100mA/div
Light Load Switching Waveform
Mode; 4.2V; VOUT 0.6V; COUT 4.7µF; 2.2µH) VOUT coupled) 20mV/div 200mA/div
2V/div
2V/div
Time (200ns/div)
Time (1µs/div)
Transient Response Mode
(VIN 3.6V; COUT 4.7µF; 2.2µH) VOUT 1V/div
3.3V
Transient Response Mode
(VIN 3.6V; COUT 4.7µF; 2.2µH) VOUT 1V/div
3.3V
0.6V 1.2V 1.2V
0.6V
VDAC 0.5V/div
0.2V
VDAC 0.5V/div
0.2V
Time (25µs/div)
Time (25µs/div)
Bypass Transient Response
(PWM Mode; 3.6V; COUT 4.7µF; 2.2µH)
3.5V
Bypass Transient Response
Mode; 3.6V; COUT 4.7µF; 2.2µH)
3.5V
VOUT 1V/div
0.6V
VOUT 1V/div
0.6V
VBYP 1V/div
VBYP 1V/div
Time (25µs/div)
Time (25µs/div)
1171.2007.08.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch Typical Characteristics
Bypass Transient Response
Mode; 4.2V; COUT 4.7µF; 2.2µH)
Enable Soft Start
(VIN 3.6V; VOUT 1.8V; 3.9; COUT 4.7µF; 2.2µH) VOUT 1V/div
1.8V
4.2V
VOUT 1V/div
0.6V 1.3V
Enable 2V/div
VDAC 0.5V/div
200mA/div
0.2V
Time (25µs/div)
Time (20µs/div)
Load Transient Response
(VIN 4.2V; VOUT 3.3V; COUT 4.7µF; 2.2µH) VOUT coupled) 20mV/div
3.51V
Load Transient Response
(VIN 3.6V; VOUT 1.8V; COUT 4.7µF; 2.2µH) VOUT coupled) 20mV/div
1.914V
3.26V
1.798V 500mA
525mA
IOUT 200mA/div
250mA
IOUT 100mA/div
200mA
Time (20µs/div)
Time (20µs/div)
(VOUT 1.5V; COUT 4.7µF; 2.2µH) 0.5V/div
3.6V 3.0V
Line Transient Response
1.56V
VOUT coupled) 50mV/div
1.44V
Time (50µs/div)
1171.2007.08.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch Functional Block Diagram
VOUT
Comp Error
Logic
BYPASS
MODE/SYNC
MODE/SYNC Interface
AGND
PGND
Functional Description
AAT1171 600mA 2MHz peak current mode synchronous step-down (buck) converter designed operate from single-cell lithium-ion battery with 2.7V 4.2V input range. output voltage dynamically programmed input voltage. maximize converter efficiency over load conditions, converter automatically transitions variable frequency light load (LL) mode when load less than 100mA. When combined with very quiescent current, mode maintains high efficiency over complete load range. noise sensitive applications, converter forced into fixed frequency mode. Provisions also made synchronization converter external system clock. synchronous buck converter power output devices sized 230m 600mA full load output current. addition converter output, additional resistance bypass MOSFET (85m) connected between battery input converter output (VIN VOUT),
bypassing converter output inductor improve headroom extend WCDMA full power range. This reduces battery voltage necessary WCDMA power amplifier meet linearity requirements, thus extending operating time. dual mode systems, bypass mode also used when WCDMA power amplifier mode. Bypass mode activated setting bypass input high forcing baseband output voltage 1.3V. AAT1171 requires only three external components operation (CIN, COUT, LX). high 2MHz switching frequency reduces inductor size required 2.2µH AAT1171-1/AAT1171-4 4.7µH AAT1171-5. This reduces resistance improves converter efficiency while minimizing inductor footprint height. output voltage converter regulated within 0.5% will settle less than 30µs (according WCDMA specifications) response step change input. Under-voltage lockout, internal compensation, softstart, over-current, over-temperature protection also included.
1171.2007.08.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch
Output Voltage Control
output voltage programmed input voltage. output gain AAT1171
LL/PWM Control
control modes available with AAT1171: mode mode. mode maintains fixed switching frequency regardless load. fixed switching frequency gives advantage lower output ripple simplified output input noise filtering. mode also provides faster output voltage response changes voltage. mode, converter transitions variable switching frequency load decreases below 100mA. Above 100mA, where switching losses longer dominate, switching frequency fixed. mode's effect output voltage response time most notable when transitioning from high output voltage voltage. When converter mode, inductor current reversed output voltage actively discharged synchronous MOSFET. While mode, output voltage discharged load only, resulting slower response transition from high voltage. mode, apply logic level high MODE/SYNC pin; mode, apply logic level MODE/SYNC pin.
VOUT VDAC
input voltage range 0.2V 1.2V, which corresponds output voltage range 0.6V 3.6V (see Figure 1.3V level, bypass switch activated output voltage level equivalent input voltage minus bypass MOSFET (RDS(ON)(bp)) drop.
Bypass Mode
bypass mode, AAT1171 bypasses output inductor, connecting input directly output through RDS(ON) MOSFET. Bypass mode initiated applying 1.3V input applying logic high bypass input. When activated, logic level must applied bypass input pin. bypass MOSFET current limited 600mA.
3.6V
Output
BYPASS MODE
0.6V
0.2V
1.2V 1.3V
Output
Figure VOUT VDAC.
1171.2007.08.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch
Soft Start/Enable
AAT1171 soft-start control prevents output voltage overshoot limits inrush current when either input power enable input applied. When pulled low, enable input forces converter into low-power, non-switching state with less than bias current.
Current Limit Short-Circuit Protection
high-side P-channel MOSFET current limit comparator limits peak inductor current 1.6A. mode, synchronous MOSFET current limit comparator limits peak negative inductor current, output capacitor discharge current limited bypass mode, bypass MOSFET current limited 600mA. event overload short-circuit condition, current limit protects load AAT1171 power devices. Upon removal short-circuit fault condition, AAT1171 output automatically recovers regulated level.
Dropout Operation
conditions where input voltage drops output voltage level, converter duty cycle increases 100%. 100% duty cycle approached, minimum off-time initially forces high-side on-time exceed 2MHz clock period, reducing converter switching frequency. Once input drops level where output longer regulated, high-side P-channel MOSFET enabled continuously 100% duty cycle. output voltage then tracks input voltage minus drop high side P-channel MOSFET RDS(ON).
Thermal Overload Protection
maximum junction temperature limited AAT1171 over-temperature shutdown protection circuitry. Both step-down converter bypass MOSFET disabled when junction temperature reaches 140°C. Normal operation resumes once junction temperature drops 125°C.
UVLO Shutdown
Under-voltage lockout (UVLO) circuitry monitors input voltage disables converter when input voltage drops 2.4V, guaranteeing sufficient operating input voltage maintain output voltage regulation control. rising input voltage, UVLO circuitry enables converter 200mV above shutdown level 2.6V.
External Synchronization
AAT1171 switching frequency synchronized external square wave clock MODE/SYNC input. external clock frequency range logic levels which AAT1171 will remain synchronized listed Electrical Characteristics table this datasheet.
1171.2007.08.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch Applications Information
Inductor Selection
step-down converter uses peak current mode control with slope compensation maintain stability duty cycles greater than 50%. Because required slope compensation varies with output voltage, AAT1171 varies slope compensation match output voltage. This allows single inductor value output voltage levels. inductor value 2.2µH AAT1171-1/AAT1171-4 4.7µH AAT11715. Manufacturer's specifications list both inductor current rating, which thermal limitation, peak current rating, which determined saturation characteristics. inductor should show appreciable saturation under normal load conditions. inductor ripple current varies with both input voltage output voltage peaks maximum input voltage with output half input voltage. typical AAT1171, this corresponds 4.2V input voltage 2.1V output voltage. With suggested 2.2µH inductor, this corresponds 239mA peak-to-peak ripple current. 600mA load current, peak inductor current would 718mA. order prevent saturation under normal load conditions, peak inductor current should less than inductor saturation current. overall device efficiency.
0.6A2 0.14 50mW 0.6A 3.4V 0.6A 50mW
2.2µH inductor selected AAT1171 evaluation board 140m 0.91A current rating. 600mA load current, inductor loss 50mW which gives 2.4% loss efficiency 600mA 3.4V output voltage with inductor that measures 3.2x3.2x1.2mm.
Output Capacitor Selection
AAT1171-1/AAT1171-4 designed with 4.7µF ceramic output capacitors, while AAT1171-5 designed with 10µF ceramic output capacitors. Although larger output capacitor provides improved response large load transients, also limits output voltage rise fall time response input. stable operation, with sufficient phase gain margin, internal voltage loop compensation limits minimum output capacitor value 4.7µF. Increased output capacitance will reduce crossover frequency with greater phase margin. output voltage droop load transients dominated output capacitor. During step increase load current, output capacitor supplies load current while control loop responds. Within three switching cycles, inductor current increases match load current demand. relationship output voltage droop during three switching cycles output capacitance estimated
COUT
IPK(MAX)
VIN(MAX) 4.2V 2.2µH 2MHz
0.6A
0.6A 0.12A 0.72A
Some inductors meet peak average current requirements result excessive losses high DCR. Always consider losses associated with effect total converter efficiency when selecting inductor. inductor losses estimated using full load output current. output inductor losses then calculated estimate their effect
ILOAD VDROOP
Once average inductor current increases load level, output voltage recovers. above equation establishes limit minimum output capacitor value necessary meet given output voltage droop requirement (VDROOP) given load transient.
1171.2007.08.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch
maximum output capacitor ripple current
VOUT (VIN(MAX) VOUT) VIN(MAX)
input capacitor ripple current varies with input output voltage will always less than equal half total load current.
IRMS(MAX)
Dissipation current ceramic output capacitor typically minimal, resulting less than degrees rise hot-spot temperature.
0.52
Input Capacitor Selection
ceramic capacitor suggested input capacitor with typical values ranging from 4.7µF 10µF. estimate required input capacitance size, determine acceptable input ripple level (VPP) solve shown below. calculated value varies with input voltage maximum when double output voltage. Always examine ceramic capacitor voltage coefficient characteristics when selecting proper value. example, voltage coefficient 10µF 6.3V ceramic capacitor, with applied voltage capacitance decreases 6µF.
IRMS(MAX)
term appears both input voltage ripple input capacitor current equations maximum when twice therefore, input voltage ripple input capacitor current ripple maximum duty cycle. input capacitor provides impedance loop edges pulsed current drawn AAT1171. ESR/ESL ceramic capacitors ideal this function. minimize stray inductance, capacitor should placed closely possible This keeps high frequency content input current localized, minimizing input voltage ripple. proper placement input capacitor (C1) seen evaluation board layout Figure laboratory test set-up typically consists long wires running from bench power supply evaluation board input voltage pins. inductance these wires, along with low-ESR ceramic input capacitor, create high network that affect converter performance. This problem often becomes apparent form excessive ringing output voltage during load transients with errors loop phase gain measurements. Since inductance short trace feeding input voltage significantly lower than power leads from bench power supply, most applications exhibit this problem.
CIN(MIN)
maximum input capacitor current
IRMS
1171.2007.08.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch
applications where input power source lead inductance cannot reduced level that does affect converter performance, high tantalum aluminum electrolytic capacitor Figure should placed parallel with ESR, bypass ceramic capacitor. This dampens high network stabilizes system.
Thermal Calculations
There three types losses associated with AAT1171 step-down converter: switching losses, conduction losses, quiescent current losses. Conduction losses associated with RDS(ON) characteristics power MOSFET devices. Switching losses dominated gate charge power MOSFET devices. AAT1171 main synchronous power MOSFETs sized have similar RDS(ON) values that track with input voltage. full load, assuming continuous conduction mode (CCM), simplified form stepdown converter losses given
Programming Gain
output voltage dynamically controlled input voltage. output gain fixed typical response time 0.2V 1.2V pulsed signal input less than 30µs. gain reduced external resistive divider input, shown evaluation board schematic Figures output gain 10k, 4.99k.
PTOTAL RDS(ON) (tSW
GDAC)R2 2)10k 4.99k GDAC
step-down converter quiescent current. term used estimate full load switching losses, which dominated gate charge losses.
AAT1171-1/AAT1171-4
2.2H
VOUT VOUT AGND
PGND MODE/SYNC BYPASS
VOUT 4.7F 4.7F
ENABLE
BYPASS SYNC
Figure AAT1171-1/AAT1171-4 Evaluation Board Schematic.
1171.2007.08.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch
AAT1171-5
4.7H
PGND
VOUT VOUT AGND
VOUT 4.7F
MODE/SYNC BYPASS
ENABLE
BYPASS SYNC
Figure AAT1171-5 Evaluation Board Schematic.
1171.2007.08.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch
condition where buck converter 100% duty cycle dropout, total device dissipation reduces
PTOTAL RDS(ON)
Layout
suggested layout AAT1171 shown Figures following guidelines should used ensure proper layout. input capacitor (C1) should connect closely possible (Pin PGND (Pin 11). should connected closely possible. connection should short possible. trace connected VOUT (Pins tied bypass path, well feedback path control loop. bypass mode, full load current delivered directly from battery input; therefore, this trace should sufficient handle current bypass current limit level. resistance trace from load return PGND (Pin should kept minimum. This minimizes error regulation differences potential internal signal ground power ground. good thermal coupling, vias required from TDFN exposed paddle ground plane. diameter should 0.3mm 0.33mm positioned 1.2mm grid.
bypass mode, bypass MOSFET RDS(ON)(bp) used determine losses. power MOSFET RDS(ON) increases with decreasing input voltage associated losses maximum minimum input voltage (2.7V).
PTOTAL RDS(ON)(bp)
Since RDS(ON), quiescent current, switching losses vary with input voltage, total losses should investigated over complete input voltage range. After calculating total losses, maximum junction temperature derived from TDFN33-12 package which typically 50°C/W.
TJ(MAX) PTOTAL TAMB
Figure AAT1171 Evaluation Board Side Layout.
Figure AAT1171 Evaluation Board Bottom Side Layout.
1171.2007.08.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch Step-Down Converter Design Example
Specifications
VO(BUCK) 0.6V 3.4V with TAMB 2.7V 4.2V (3.6V nominal) 2.0MHz 85°C
Output Inductor
2.2µH Copper Electronics SD3112, 2.2µH, 140m.
IL1(MAX)
2.1V 2.1V 239mA 2.2µH 2.0MHz 4.2V
maximum inductor ripple current occurs duty cycle maximum input voltage.
IPKL1
IL1(MAX) 0.6A 0.118A 0.718A
0.6A2 140m 50mW
Output Capacitor
Specify that VDROOP 0.2V 600mA load pulse.
ILOAD 0.6A 4.5µF 0.2V 2.0MHz VDROOP (VO) (VIN(MAX) 3.4V (4.2V 3.4V) 69mArms VIN(MAX) 4.7µH 2.0MHz 4.2V
COUT IRMS
PESR IRMS2 (69mA)2 24µW
1171.2007.08.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch
Input Capacitor
Specify maximum input voltage ripple 25mV.
CIN(MIN)
3.4µF 25mV 2.0MHz 0.6A
IRMS
0.3Arms
IRMS2 (0.3A)2 0.45mW
AAT1171 Losses
PTOTAL RDS(ON) (tsw 0.62 0.29 (5ns 2.0MHz 0.6A 60µA) 4.2V 104mW
TJ(MAX) PTOTAL TAMB 104mW 50°C/W 5.2°C 70°C 75.2°C
AAT1171 Dropout Losses
PTOTAL RDS(ON)(HS) 0.62 310m 100µA 3.5V 112mW
TJ(MAX) PTOTAL TAMB 112mW 50°C/W 5.6°C 70°C 75.6°C
1171.2007.08.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch
Manufacturer
www.avxcorp.com Murata www.murata.com www.tdk.com Taiyo Yuden www.t-yuden.com
Value
10µF 4.7µF 10µF 4.7µF 10µF 4.7µF
Device
Output Capacitor Output Input Capacitor Input Capacitor Output Capacitor Output Input Capacitor Input Capacitor Output Capacitor Output Input Capacitor Input Capacitor
Voltage
6.3V 6.3V 6.3V
Case Size
0805 0805 0603 0805 0805 0603 0805 0805 0603
Part Number
0805ZD106KAT GRM21BR61A475KA73L GRM188R60J475KE19D GRM21BR61A106K C2012X5R1A475K C1608X5ROJ475K C2012X5R1A106K LMK212BJ475MG JMK107BJ475MA
Manufacturer
Cooper Electronics www.cooperet.com Sumida www.sumida.com ABCO Electronics www.abco.co.kr
Value
2.2µH 4.7µH 2.2µH 4.7µH 2.2µH 2.2µH
Part Number
SD3118-2R2 SD3112-4R7-R CDRH2D11/HP CDRH2D11/HP LPF2010-2R2M LPF2010-2R2M
ISAT
1.12A 0.8A 1.1A 0.75A
IRMS
0.91A 0.74A 1.3A 0.85A 0.52A 0.55A
140m 246m 238m 200m 110m
Case Size (mm)
3.1x3.1x1.2 3.1x3.1x1.2 3.2x3.2x1.2 3.2x3.2x1.2 2.0x2.0x1.0 2.0x2.0x1.4
Table Suggested Component Selection.
1171.2007.08.1.1
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch Ordering Information
Package
TDFN33-12 TDFN33-12 TDFN33-12
Marking1
RXXYY XCXYY XDXYY
Part Number (Tape Reel)2
AAT1171IWP-1-T1 AAT1171IWP-4-T1 AAT1171IWP-5-T1
AnalogicTech products offered Pb-free packaging. term "Pb-free" means semiconductor products that compliance with current RoHS standards, including requirement that lead exceed 0.1% weight homogeneous materials. more information, please visit website
Package Information3
TDFN33-12
Index Area
Detail
0.43 0.05
3.00 0.05
2.40 0.05
C0.3
0.45 0.05
Indicator (optional)
3.00 0.05
1.70 0.05
View
Bottom View Detail
0.75 0.05
0.05 0.05
Side View
dimensions millimeters.
assembly date code. Sample stock generally held part numbers listed BOLD. leadless package family, which includes QFN, TQFN, DFN, TDFN STDFN, exposed copper (unplated) lead terminals manufacturing process. solder fillet exposed copper edge cannot guaranteed required ensure proper bottom solder connection. 1171.2007.08.1.1
0.23 0.05
0.23 0.05
AAT1171
600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass Switch
Advanced Analogic Technologies, Inc. AnalogicTech cannot assume responsibility circuitry other than circuitry entirely embodied AnalogicTech product. circuit patent licenses, copyrights, mask work rights, other intellectual property rights implied. AnalogicTech reserves right make changes their products specifications discontinue product service without notice. Except provided AnalogicTech's terms conditions sale, AnalogicTech assumes liability whatsoever, AnalogicTech disclaims express implied warranty relating sale and/or AnalogicTech products including liability warranties relating fitness particular purpose, merchantability, infringement patent, copyright other intellectual property right. order minimize risks associated with customer's applications, adequate design operating safeguards must provided customer minimize inherent procedural hazards. Testing other quality control techniques utilized extent AnalogicTech deems necessary support this warranty. Specific testing parameters each device necessarily performed. AnalogicTech AnalogicTech logo trademarks Advanced Analogic Technologies Incorporated. other brand product names appearing this document registered trademarks trademarks their respective holders.
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1171.2007.08.1.1

600mA Voltage-Scaling Step-Down Converter Power Amplifiers with Bypass

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