AAT1154 SwitchReg step-down switching converter ideal applications whe
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1MHz Step-Down DC/DC Converter General Description
AAT1154 SwitchReg step-down switching converter ideal applications where high efficiency, small size, ripple critical. Able deliver with internal power MOSFET, current-mode controlled provides high efficiency. Fully internally compensated, AAT1154 simplifies system design lowers external parts count. AAT1154 available Pb-free SOP-8 package rated over -40°C +85°C temperature range.
AAT1154
SwitchReg
Range: 2.7V 5.5V Fixed Adjustable VOUT: 1.0V 4.2V Output Current Efficiency Integrated Resistance Power Switch Internally Compensated Current Mode Control 1MHz Switching Frequency Constant Pulse Width Modulation (PWM) Mode Output Ripple With Light Load Internal Soft Start Current Limit Protection Over-Temperature Protection SOP-8 Package -40°C +85°C Temperature Range
Applications
Cable/DSL Modems Computer Peripherals High Efficiency Conversion from 3.3V Supply Network Cards Set-Top Boxes
Typical Application
INPUT
AAT1154
1.5H
0.1F 120F OUTPUT
1154.2006.09.1.6
1MHz Step-Down DC/DC Converter Descriptions
AAT1154
Symbol
Function
Feedback input pin. This must connected converter output. used converter output regulate desired value. Ground connection. Enable input pin. When connected high, AAT1154 normal operation; when connected low, powered down. This should left floating. Power supply: supplies power internal circuitry. Input supply voltage converter power stage. Inductor connection pins. These pins should connected output inductor. Internally, Pins connected drain P-channel switch.
Configuration
SOP-8
1154.2006.09.1.6
1MHz Step-Down DC/DC Converter Absolute Maximum Ratings1
25°C, unless otherwise noted. Symbol
VCC, VESD
AAT1154
Description
VCC, Operating Junction Temperature Range Rating2
Value
-0.3 -0.3 -0.3 3000
Units
Thermal Characteristics3
Symbol
Description
Thermal Resistance Maximum Power Dissipation 25°C)4
Value
Units
°C/W
Recommended Operating Conditions
Symbol
Description
Ambient Temperature Range
Rating
Units
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. Human body model 100pF capacitor discharged through 1.5k resistor into each pin. Mounted demo board (FR4, still air). Derate 9.1mW/°C above 25°C. 1154.2006.09.1.6
1MHz Step-Down DC/DC Converter Electrical Characteristics
-40°C +85°C, unless otherwise noted. Typical values 25°C. Symbol
VOUT VUVLO VUVLO(HYS) ISHDN ILIM RDS(ON)H VOUT (VOUT*VIN) VOUT/VOUT FOSC VEN(L) VEN(H) THYS
AAT1154
Description
Input Voltage Range Output Voltage Tolerance Under-Voltage Lockout Under-Voltage Lockout Hysteresis Quiescent Supply Current Shutdown Current Current Limit High Side Switch Resistance Efficiency Load Regulation Line Regulation Oscillator Frequency Enable Threshold Enable Threshold High Over-Temperature Shutdown Threshold Over-Temperature Shutdown Hysteresis
Conditions
VOUT 0.2V 5.5V, IOUT Rising Falling Load, 5.5V 25°C 25°C IOUT ILOAD 2.7V 5.5V 25°C
-5.0
Units
1000
±2.6 0.75
1154.2006.09.1.6
1MHz Step-Down DC/DC Converter Typical Characteristics
Efficiency Load Current
(VIN VOUT 3.3V)
AAT1154
RDS(ON) Temperature
Efficiency
2.7V 3.6V
4.2V
RDS(ON)
0.01
5.5V
Output Current
Temperature (°C)
Oscillator Frequency Variation Supply Voltage
RDS(ON)
(IDS
RDS(ON)
Variation
0.25
-0.25
-0.5
Input Voltage
Input Voltage
Oscillator Frequency Variation Temperature
(VIN
Enable Threshold
Enable Threshold Input Voltage
EN(H)
Variation
EN(L)
Temperature (°C)
Input Voltage
1154.2006.09.1.6
1MHz Step-Down DC/DC Converter Typical Characteristics
Output Voltage Temperature
(IOUT
AAT1154
Line Regulation
(VOUT 3.3V)
Output Voltge Error
Variation
0.3A
-0.2 -0.4 -0.6 -0.8
3.0A
Temperature (°C)
Input Voltage
Over-Temperature Current Input Voltage
(VOUT 3.3V)
-1.0
Load Regulation
(VIN 5.0V; 3.3V)
Output Current
Output Error
70°C
-2.0 -3.0 -4.0 -5.0 -6.0 -7.0 -8.0 -9.0 -10.0
85°C 100°C
3.75 4.25 4.75 5.25
0.01
Input Voltage
Load Current
Non-Switching Operating Current Temperature
Over-Temperature Shutdown Current Temperature
(VOUT 3.3V; 5.0V; 1.5H)
Operating Current (mA)
5.5V
5.0V
2.7V
3.6V
4.2V
Output Current
Temperature (°C)
Temperature (°C)
1154.2006.09.1.6
1MHz Step-Down DC/DC Converter Typical Characteristics
Inrush Output Overshoot Characteristics
Load)
AAT1154
Inrush Output Overshoot Characteristics
Load)
Inductor Current
Inductor Current
Inductor Current (top trace)
Inductor Current (top trace)
Voltage (bottom traces)
Voltage (bottom traces)
Input Output
Input Output
Time (ms)
Time (ms)
Output Ripple
(IOUT 3.0A; VOUT 3.3V; 5.0V)
Output Ripple
(IOUT 3.0A; VOUT 3.3V; 5.0V)
Output Ripple (mV)
Output Ripple (top) (mV)
Inductor Current (bottom)
Inductor Current (bottom)
300µF 6.3VCeramic C3325X5R0J107M
200F 6.3V Ceramic C3325X5R0J107M
Time
Time
Tantalum Output Ripple
(IOUT 3.0A; VOUT 3.3V; 5.0V)
Loop Crossover Gain Phase
Output Ripple (top) (mV)
-100 -120
Gain (dB)
Phase 100F 100F 100F 6.3V Ceramic C3225X5R0J107M
-135 -180 100000
Phase (degrees)
Inductor Current (bottom)
120F 6.3V Tantalum Vishay 594D127X96R3C2T
10000
Time
Frequency (Hz)
1154.2006.09.1.6
1MHz Step-Down DC/DC Converter Typical Characteristics
Loop Crossover Gain Phase
AAT1154
Transient Response
(IOUT 3.0A; VOUT 3.3V; 5.0V)
100F 6.3V Ceramic C3325X5R0J107M
120F 6.3V Tantalum Vishay 594D127X96R3C2T Phase
Phase (degrees)
Inductor Current (bottom)
Gain (dB)
10000
Output Voltage (top) (mV)
-100 -200 -300 -400 -500 -600 -700
Gain
-135 -180 100000
Frequency (Hz)
Time
Transient Response
(IOUT 3.0A; VOUT 3.3V; 5.0V)
100F 6.3V Ceramic C3325X5R0J107M
Tantalum Transient Response
(IOUT 3.0A; VOUT 3.3V; 5.0V)
Inductor Current (bottom)
Inductor Current (bottom)
Output Voltage (top) (mV)
Output Voltage (top) (mV)
-100 -200 -300 -400 -500 -600 -700
-100 -200 -300 -400 -500 -600 -700 120F 6.3V Tantalum Vishay 594D127X96R3C2T
Time
Time
1154.2006.09.1.6
1MHz Step-Down DC/DC Converter Functional Block Diagram
2.7V 5.5V
AAT1154
LOGIC
Temp. Sensing
Applications Information
Main Control Loop
AAT1154 peak current mode step-down converter. inner wide bandwidth loop controls inductor peak current. inductor current sensed flows through internal P-channel MOSFET. fixed slope compensation signal then added sensed current maintain stability duty cycles greater than 50%. inner loop appears voltage-programmed current source parallel with output capacitor. voltage error amplifier output programs current loop necessary inductor current force constant output voltage load line conditions. feedback resistive divider internal, dividing output voltage error amplifier reference voltage error amplifier limited gain. This eliminates need external compensation components, while still providing sufficient loop gain good load regulation. crossover frequency phase margin output capacitor value. Duty cycle extends 100% input voltage approaches output voltage. Thermal shutdown protection disables device event short-circuit overload condition.
Soft Start/Enable
Soft start controls current limit when input voltage enable applied. limits current surge seen input eliminates output voltage overshoot. When pulled low, enable input forces device into low-power, non-switching state. total input current during shutdown less than 1µA.
Power Signal Source
Separate small signal ground power supply pins isolate internal control circuitry from switching noise. addition, pass filter (shown Figure filters noise associated with power switching.
Current Limit Over-Temperature Protection
Over-temperature current limit circuitry protects AAT1154 external Schottky diode during overload, short-circuit, excessive ambient temperature conditions. junction over-temperature threshold 140°C nominal 15°C hysteresis. Typical graphs over-temperature load current input voltage ambient temperature shown Typical Characteristics section this document.
1154.2006.09.1.6
1MHz Step-Down DC/DC Converter
3.5V 5.5V VOUT 3.3V AAT1154-3.3 1.5µH
AAT1154
100µF
100k
10µF 0.1µF
B340LA
120µF
Murata 10µF 6.3V GRM42-6X5R106K6.3 Vishay120µF 6.3V 594D127X96R6R3C2T 0603ZD104M Vishay Sprague 100µF 595D107X0016C 100µF B340LA Diodes Inc. CDRH6D28-1.5µH Sumida Options MuRata 100µF 6.3V GRM43-2 107M 100µF 6.3V (two three parallel) 100µF 6.3V C3325X5R0J107M 100µF 6.3V (two three parallel)
Figure 3.3V, Output.
Inductor
output inductor selected limit ripple current full load current maximum input voltage. Manufacturer's specifications list both inductor current rating, which thermal limitation, peak current rating, which determined inductor saturation characteristics. inductor should show appreciable saturation under normal load conditions. During overload short-circuit conditions, inductor exceed peak current rating without affecting converter performance. Some inductors have sufficient peak average current ratings result excessive losses high resistance (DCR). losses associated with effect total converter efficiency must considered. load ripple current maximum input voltage, maximum peak-to-peak ripple current 0.9A. Assuming input voltage ripple, output inductance required
VOUT VOUT VIN(MAX)
3.3V 3.3V 1MHz 5.25V
1.36H
factor fraction full load (30%) selected ripple current maximum input voltage. corresponding inductor current
IRMS
peak-to-peak ripple current which fixed inductor selection above. peak-to-peak current full load current, peak current full load will 115% full load. 1.5µH inductor selected from Sumida CDRH6D38 series 4.0A current rating with height 4mm. full load, inductor loss 99mW loss efficiency.
1154.2006.09.1.6
1MHz Step-Down DC/DC Converter
Schottky Freewheeling Diode
Schottky average current load current multiplied minus duty cycle. VOUT 3.3V, average diode current
3.3V 5.0V
AAT1154
output voltage. highest when input voltage double output voltage where half load current.
IRMS
With 125°C maximum junction temperature 120°C/W thermal resistance, maximum average current
IAVG J(MAX)- 125°C 70°C 1.14A 0.4V
high tantalum capacitor with value about times input ceramic capacitor also required when using 10µF smaller ceramic input bypass capacitor. This dampens input oscillations that occur source inductance resonating with converter input impedance.
VFWD
Output Capacitor
With external compensation components, output capacitor strong effect loop stability. Larger output capacitance will reduce crossover frequency with greater phase margin. 200µF ceramic capacitor provides sufficient bulk capacitance stabilize output during large load transitions characteristics necessary very output ripple. ripple current given
IRMS (VOUT VFWD) (VIN VOUT)
overload, short-circuit, excessive ambient temperature conditions, AAT1154 enters overtemperature shutdown mode, protecting AAT1154 output Schottky. this mode, output current limited internally until junction temperature reaches temperature limit (see over-temperature characteristics graphs). diode reverse voltage must rated withstand input voltage. Surface Mount Schottky Diodes
Diodes Inc. ROHM Micro Semi B340LA RB050L-40 5820SM 0.45V 0.45V 0.46V
Input Capacitor Selection
primary function input capacitor provide impedance loop edges pulsed current drawn AAT1154. ESR/ESL ceramic capacitor ideal this function. minimize stray inductance, capacitor should placed closely possible This also keeps high frequency content input current localized, minimizing radiated conducted while facilitating optimum performance AAT1154. Proper placement input capacitor shown layout Figure Ceramic capacitors ideal. size required will vary depending load, output voltage, input voltage source impedance characteristics. Typical values range from 10µF. input capacitor current varies with input voltage
ceramic output capacitor, dissipation current associated output ripple negligible. Tantalum capacitors with sufficiently meet output ripple requirements generally have current rating much greater than that actually seen this application. maximum tantalum output capacitor
VRIPPLE
where peak-to-peak inductor ripple current. zero associated with tantalum capacitor, smaller values than those required with ceramic capacitors provide more phase margin with greater loop crossover frequency.
1154.2006.09.1.6
1MHz Step-Down DC/DC Converter
AAT1154
Figure AAT1154 Fixed Output Side Layout.
Figure AAT1154 Fixed Output Bottom Side Layout.
Layout
Figures display suggested layout fixed output AAT1154. following guidelines should used help ensure proper layout. connection from input capacitor Schottky anode should short possible. input capacitor should connect closely possible (Pins (Pin should connected closely possible. connection from cathode Schottky node should short possible. feedback trace (Pin should separate from power trace connect closely possible load point. Sensing along high-current load trace degrade load regulation. resistance trace from load return (Pin should kept minimum. This will help minimize error regulation differences potential internal reference ground load return. required order provide cleaner power source AAT1154 control circuitry.
RMS2 RDS(ON)
RDS(ON) losses
IRMS
Internal switch current duty cycle forward drop Schottky diode.
peak-to-peak inductor ripple current. simplified form calculating RDS(ON) switching losses given
DS(ON)
where AAT1154 quiescent current. Once total losses have been determined, junction temperature derived. thermal resistance (JA) SOP-8 package mounted printed circuit board still 110°C/W. TAMB TAMB maximum ambient temperature resultant maximum junction temperature.
Thermal
losses associated with AAT1154 output switching MOSFET switching losses conduction losses. conduction losses associated with RDS(ON) characteristics output switching device. full load condition, assuming continuous conduction mode (CCM), accurate calculation RDS(ON) losses derived from following equations:
1154.2006.09.1.6
1MHz Step-Down DC/DC Converter
Design Example
(See Figures reference) IOUT IRIPPLE VOUT TMAX Full Load 3.3V 1MHz 70°C
AAT1154
AAT1154 Junction Temperature
RDS(ON)
3.3V 20ns 1MHz
0.539 Watts
TJ(MAX)= TAMB 70°C 110°C 0.54W 129°C
Inductor Selection
VOUT
Diode
IDIODE= 3.3V 1.02A
0.35
3.3V 1.25H
standard value 1.5µH Sumida Inductor Series CDRH6D38.
3.3V 3.3V 0.82A 1.5H 1MHz 5.25V
PDIODE IDIODE
0.35V 1.01A 0.354W
Given ambient thermal resistance 120°C/W from manufacturer's data sheet, TJ(MAX) diode
IOUT
0.41A 3.41A
J(MAX) 70°C 120°C 0.354W 112°C
Efficiency Load Current
(VIN VOUT 3.3V)
Efficiency
0.01
Output Capacitor
output capacitor value required sufficient loop phase margin depends type capacitor selected. ceramic capacitor, minimum value 200µF required. tantalum capacitor, lower values acceptable. While relatively higher associated with tantalum capacitor will give more phase margin more dampened transient response, output voltage ripple will higher.
Output Current
Figure Input, 3.3V Output.
1154.2006.09.1.6
1MHz Step-Down DC/DC Converter
120µF Vishay 594D tantalum capacitor ripple current rating 1.48Arms case size. Although smaller case sizes sufficiently rated this ripple current, their level would result excessive output ripple. requirement tantalum capacitor estimated examples shown, ceramic capacitor located closely possible. provides impedance path sharp edges associated with input current. required, depending upon impedance characteristics looking back into source. serves dampen input oscillations that arise from source that highly inductive. most applications, where source sufficient bulk capacitance directly AAT1154 through large traces planes, required. When operating AAT1154 evaluation board bench, required inductance wires running from laboratory power supply evaluation board.
AAT1154
IRMS
VRIPPLE 0.82A
(VOUT (VIN VOUT)
3.65V 240mArms 1.5H 1MHz
Adjustable Output
applications requiring output other than fixed outputs available, version externally programmed. Resistors Figure force output regulate higher than accurate results (less than error outputs), select 10k. Once been selected, calculated. 1.25V output with 10k, 2.5k. 0.25 2.5k Figures display suggested layout adjustable output AAT1154.
three 1812 100uF 6.3V ceramic capacitors parallel also provide sufficient phase margin. associated with ceramic capacitors also reduces output ripple significantly over that seen with tantalum capacitors. Temperature rise ripple current dissipation also reduced.
Input Capacitor
input capacitor ripple
IRMS
1.42 Arms
2.7V 5.5V
VOUT 1.25V 2.55k AAT1154-1. 1.5µH
100µF
100k
10µF 0.1µF 10.0k
B340LA
120µF
Murata 10µF 6.3V GRM42-6X5R106K6.3 Vishay 120µF 6.3V 594D127X96R6R3C2T 0603ZD104M Vishay Sprague 100µF 595D107X0016C 100µF B340LA Diodes Inc. CDRH6D28-1.5µH Sumida Options MuRata 100uF 6.3V GRM43-2 107M 100µF 6.3V (two three parallel) 100µF 6.3V C3325X5R0J107M 100µF 6.3V (two three parallel)
Figure AAT1154 Evaluation Board With Adjustable Output.
1154.2006.09.1.6
1MHz Step-Down DC/DC Converter
AAT1154
Figure Evaluation Board Adjustable Output Side Layout.
Figure Evaluation Board Adjustable Output Bottom Side Layout.
Capacitors Part Number
C4532X5ROJ107M GRM43-2 107M GRM43-2 476K GRM42-6 106K 594D127X_6R3C2T 595D107X0016C
Manufacturer
MuRata MuRata MuRata Vishay Vishay
Capacitance (µF)
Voltage
16.0
Temp
Case
1812 1812 1812 1206
Inductors Part Number
CDRH6D38-4763-T055 N05D B1R5M NP06DB B1R5M LQH55DN1R5M03 LQH66SN1R5M03
Manufacturer
Sumida Taiyo Yuden Taiyo Yuden MuRata MuRata
Inductance (µH)
(Amps)
0.014 0.025 0.022 0.022 0.016
Height (mm)
Type
Shielded Non-Shielded Shielded Non-Shielded Shielded
Diodes Manufacturer
Diodes Inc. ROHM Micro Semi
Part Number
B340LA RB050L-40 5820SM
0.45V 0.45V 0.46V
1154.2006.09.1.6
1MHz Step-Down DC/DC Converter Ordering Information
Output Voltage
1.0V (Adj. VOUT 1.0V) 1.8V 2.5V 3.3V
AAT1154
Package
SOP-8 SOP-8 SOP-8 SOP-8
Marking
115410 115418 115425 115433
Part Number (Tape Reel)1
AAT1154IAS-1.0-T1 AAT1154IAS-1.8-T1 AAT1154IAS-2.5-T1 AAT1154IAS-3.3-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 Information
SOP-8
3.90 0.10
4.90 0.10
6.00 0.20
0.375 0.125
1.55 0.20
0.175 0.075
0.235 0.045 0.825 0.445
0.42 0.09
1.27
dimensions millimeters.
Sample stock generally held part numbers listed BOLD.
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. Customers advised obtain latest version relevant information verify, before placing orders, that information being relied current complete. products sold subject terms conditions sale supplied time order acknowledgement, including those pertaining warranty, patent infringement, limitation liability. AnalogicTech warrants performance semiconductor products specifications applicable time sale accordance with AnalogicTech's standard warranty. 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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1154.2006.09.1.6
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