AAT1146 SwitchReg member AnalogicTech's Total Power Management IC(TPMI

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AAT1146 SwitchReg member AnalogicTech's Total Power Management IC(TPMI

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Fast Transient 400mA Step-Down Converter General Description
AAT1146 SwitchReg member AnalogicTech's Total Power Management IC(TPMICTM) product family. 1.4MHz stepdown converter with input voltage range 2.7V 5.5V output voltage 0.6V. optimized react quickly load variation. AAT1146 available fixed voltage versions with internal feedback programmable version with external feedback resistors. deliver 400mA load current while maintaining load quiescent current. 1.4MHz switching frequency minimizes size external components while keeping switching losses low. AAT1146 designed maintain high efficiency throughout operating range, which critical portable applications. AAT1146 available Pb-free, space-saving 2.0x2.1mm SC70JW-8 package rated over -40°C +85°C temperature range.
AAT1146
SwitchReg
Range: 2.7V 5.5V VOUT Fixed Adjustable from 0.6V Load Quiescent Current Efficiency 400mA Output Current 1.4MHz Switching Frequency 120s Soft Start Fast Load Transient Over-Temperature Protection Current Limit Protection 100% Duty Cycle Low-Dropout Operation Shutdown Current SC70JW-8 Package Temperature Range: -40°C +85°C
Applications
Cellular Phones Digital Cameras Handheld Instruments Microprocessor Core Power PDAs Handheld Computers Devices
Typical Application (Fixed Output Voltage)
AAT1146 AGND PGND PGND PGND
4.7H 4.7F
4.7F
1146.2006.04.1.3
Fast Transient 400mA Step-Down Converter Descriptions
AAT1146
Symbol
AGND PGND
Function
Enable pin. Feedback input pin. This connected either directly converter output external resistive divider adjustable output. Input supply voltage converter. Switching node. Connect inductor this pin. internally connected drain both high- low-side MOSFETs. Non-power signal ground pin. Main power ground return pins. Connect output input capacitor return.
Configuration
SC70JW-8 (Top View)
PGND PGND PGND AGND
1146.2006.04.1.3
Fast Transient 400mA Step-Down Converter Absolute Maximum Ratings1
Symbol
VOUT TLEAD
AAT1146
Description
Input Voltage Operating Junction Temperature Range Maximum Soldering Temperature leads, sec)
Value
-0.3 -0.3 -0.3
Units
Thermal Information
Symbol
Description
Maximum Power Dissipation Thermal Resistance2
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. Derate 6.25mW/°C above 25°C. 1146.2006.04.1.3
Fast Transient 400mA Step-Down Converter Electrical Characteristics1
-40°C +85°C, unless otherwise noted. Typical values 25°C, 3.6V. Symbol Description Conditions
Rising Hysteresis Falling IOUT 400mA, 2.7V 5.5V Load, 0.6V Adjustable Version AGND PGND 0.45 0.40 5.5V, VIN, 2.7V 5.5V 0.6V Output, Load 25°C 0.6V Output >0.6V Output From Enable Output Regulation 25°C -3.0 +3.0
AAT1146
Units
Step-Down Converter Input Voltage VUVLO VOUT VOUT ISHDN ILIM RDS(ON)H RDS(ON)L ILXLEAK VLinereg VOUT IOUT ROUT FOSC THYS VEN(L) VEN(H) Enable Threshold Enable Threshold High Input Current UVLO Threshold Output Voltage Tolerance Output Voltage Range Quiescent Current Shutdown Current P-Channel Current Limit High Side Switch Resistance Side Switch Resistance Leakage Current Line Regulation Threshold Voltage Accuracy Leakage Current Impedance Start-Up Time Oscillator Frequency Over-Temperature Shutdown Threshold Over-Temperature Shutdown Hysteresis
VOUT 5.5V -1.0
AAT1146 guaranteed meet performance specifications over -40°C +85°C operating temperature range assured design, characterization, correlation with statistical process controls.
1146.2006.04.1.3
Fast Transient 400mA Step-Down Converter Typical Characteristics
Efficiency Load
(VOUT 1.8V; 4.7H)
AAT1146
Regulation
(VOUT 1.8V)
2.7V
Output Error
Efficiency
3.6V
4.2V
4.2V
-0.5
3.6V 2.7V
1000
-1.0
1000
Output Current (mA)
Output Current (mA)
Efficiency Load
(VOUT 2.5V; 6.8H)
Regulation
(VOUT 2.5V)
2.7V
Output Error
4.2V
Efficiency
5.0V 4.2V 3.6V
5.0V
-0.5
3.6V 3.0V
-1.0
1000
1000
Output Current (mA)
Output Current (mA)
Efficiency Load
(VOUT 3.3V; 6.8H)
Regulation
(VOUT 3.3V; 6.8µH)
3.6V
Output Error
5.0V
Efficiency
4.2V 5.0V
4.2V
-0.5
3.6V
-1.0
1000
1000
Output Current (mA)
Output Current (mA)
1146.2006.04.1.3
Fast Transient 400mA Step-Down Converter Typical Characteristics
Soft Start
(VIN 3.6V; VOUT 1.8V; IOUT 400mA)
AAT1146
Line Regulation
(VOUT 1.8V)
Enable Output Voltage (top)
-1.0 -2.0 -3.0 -4.0 -5.0
0.40 0.30
Accuracy
0.20 0.10 0.00 -0.10 -0.20 -0.30 -0.40
IOUT 10mA
Inductor Current (bottom)
IOUT IOUT 400mA
-0.2 -0.4
Time (100s/div)
Input Voltage
Output Voltage Error Temperature
(VIN 3.6V; 1.8V; IOUT 400mA)
15.0 12.0
Switching Frequency Temperature
(VIN 3.6V; VOUT 1.8V)
Output Error
Variation
-3.0 -6.0 -9.0 -12.0 -15.0
-1.0
-2.0
Temperature (°C)
Temperature (°C)
Frequency Input Voltage
Load Quiescent Current Input Voltage
Frequency Variation
-1.0
VOUT 1.8V
Supply Current
85°C
25°C
VOUT 2.5V
-2.0 -3.0 -4.0
VOUT 3.3V
-40°C
Input Voltage
Input Voltage
1146.2006.04.1.3
Fast Transient 400mA Step-Down Converter Typical Characteristics
P-Channel RDS(ON) Input Voltage
120°C 100°C 120°C
AAT1146
N-Channel RDS(ON) Input Voltage
RDS(ON)
RDS(ON)
100°C
25°C 85°C
25°C 85°C
Input Voltage
Input Voltage
Load Transient Response
(1mA 300mA; 3.6V; VOUT 1.8V; 10F; 100pF)
1.90 1.85
Load Transient Response
(300mA 400mA; 3.6V; VOUT 1.8V; 4.7F)
Load Inductor Current (200mA/div) (bottom)
Load Inductor Current (200mA/div) (bottom)
Output Voltage (top)
300mA
Output Voltage (top)
1.80 1.75 400mA 300mA
Time (50s/div)
Time (50s/div)
Load Transient Response
(300mA 400mA; 3.6V; VOUT 1.8V; 10F)
1.90 1.85
Load Transient Response
(300mA 400mA; 3.6V; VOUT 1.8V; 10F; 100pF)
1.850 1.825
Load Inductor Current (200mA/div) (bottom)
Load Inductor Current (200mA/div) (bottom)
400mA 300mA
Output Voltage (top)
1.75
Output Voltage (top)
1.80
1.800 1.775
400mA 300mA
Time (50s/div)
Time (50s/div)
1146.2006.04.1.3
Fast Transient 400mA Step-Down Converter Typical Characteristics
Line Response
(VOUT 1.8V 400mA)
AAT1146
Output Ripple
(VIN 3.6V; VOUT 1.8V; IOUT 1mA)
Output Voltage coupled) (top) (mV)
1.82 1.81
-100 -120
0.30
0.25
Inductor Current (bottom)
Output Voltage (top)
0.20 0.15 0.10
Input Voltage (bottom)
1.80 1.79 1.78 1.77 1.76
0.05 0.00 -0.05 -0.10
Time (25s/div)
Time (10µs/div)
Output Ripple
(VIN 3.6V; VOUT 1.8V; IOUT 400mA)
Output Voltage coupled) (top) (mV)
-100 -120
Inductor Current (bottom)
Time (500ns/div)
1146.2006.04.1.3
Fast Transient 400mA Step-Down Converter Functional Block Diagram
AAT1146
note
Voltage Reference
Logic
INPUT
PGND AGND
Note: adjustable version, internal feedback divider omitted tied directly internal error amplifier.
Functional Description
AAT1146 high performance 400mA 1.4MHz monolithic step-down converter. been designed with goal minimizing external component size optimizing efficiency over complete load range. Apart from small bypass input capacitor, only small filter required output. Typically, 4.7H inductor 4.7F ceramic capacitor recommended (see table values). fixed output version requires only three external power components (CIN, COUT, adjustable version programmed with external feedback voltage, ranging from 0.6V
input voltage. additional feed-forward capacitor also added external feedback provide improved transient response (see Figure dropout, converter duty cycle increases 100% output voltage tracks input voltage minus RDSON drop P-channel highside MOSFET. input voltage range 2.7V 5.5V. converter efficiency been optimized load conditions, ranging from load 400mA. internal error amplifier compensation provides excellent transient response, load, line regulation. Soft start eliminates output voltage overshoot when enable input voltage applied.
1146.2006.04.1.3
Fast Transient 400mA Step-Down Converter
AAT1146
Enable
100pF
AAT1146
PGND PGND PGND AGND
VOUT =1.8V
118k 4.7H
4.7F
GND2 AAT1146 SC70JW-8 CDRH3D16-4R7 4.7F 0805 6.3V 0805
Figure Enhanced Transient Response Schematic.
Control Loop
AAT1146 peak current mode step-down converter. current through P-channel MOSFET (high side) sensed current loop control, well short circuit overload protection. fixed slope compensation signal added sensed current maintain stability duty cycles greater than 50%. peak current mode loop appears voltage-programmed current source parallel with output capacitor. output voltage error amplifier programs current mode loop necessary peak switch current force constant output voltage load line conditions. Internal loop compensation terminates transconductance voltage error amplifier output. fixed voltage versions, error amplifier reference voltage internally program converter output voltage. adjustable output, error amplifier reference fixed 0.6V.
into low-power, non-switching state. total input current during shutdown less than
Current Limit Over-Temperature Protection
overload conditions, peak input current limited. minimize power dissipation stresses under current limit short-circuit conditions, switching terminated after entering current limit series pulses. Switching terminated seven consecutive clock cycles after current limit been sensed series four consecutive clock cycles. Thermal protection completely disables switching when internal dissipation becomes excessive. junction over-temperature threshold 140°C with 15°C hysteresis. Once over-temperature over-current fault conditions removed, output voltage automatically recovers.
Soft Start Enable
Soft start limits current surge seen input eliminates output voltage overshoot. When pulled low, enable input forces AAT1146
Under-Voltage Lockout
Internal bias circuits controlled input. Under-voltage lockout (UVLO) guarantees sufficient bias proper operation internal circuitry prior activation.
1146.2006.04.1.3
Fast Transient 400mA Step-Down Converter Applications Information
Inductor Selection
step-down converter uses peak current mode control with slope compensation maintain stability duty cycles greater than 50%. output inductor value must selected inductor current down slope meets internal slope compensation requirements. internal slope compensation adjustable low-voltage fixed versions AAT1146 0.24A/sec. This equates slope compensation that inductor current down slope 1.5V output 4.7H inductor. show appreciable saturation under normal load conditions. Some inductors meet peak average current ratings result excessive losses high DCR. Always consider losses associated with effect total converter efficiency when selecting inductor. 4.7H CDRH3D16 series inductor selected from Sumida 105m 900mA current rating. full load, inductor loss 17mW which gives 2.8% loss efficiency 400mA, 1.5V output.
AAT1146
Input Capacitor
Select 4.7F ceramic capacitor input. estimate required input capacitor size, determine acceptable input ripple level (VPP) solve calculated value varies with input voltage maximum when double output voltage.
0.75 0.75 1.5V 0.24 4.7H
This internal slope compensation adjustable (0.6V) version low-voltage fixed versions. When externally programming 0.6V version 2.5V, calculated inductance 7.5H.
0.75
0.75 0.24A
2.5V 7.5H
this case, standard 6.8H value selected. high-voltage fixed versions (2.5V), 0.48A/ sec. Table displays inductor values AAT1146 fixed adjustable options. Manufacturer's specifications list both inductor current rating, which thermal limitation, peak current rating, which determined saturation characteristics. inductor should
CIN(MIN)
Always examine ceramic capacitor voltage coefficient characteristics when selecting proper value. example, capacitance 10F, 6.3V, ceramic capacitor with 5.0V applied actually about
Configuration
0.6V Adjustable With External Feedback Fixed Output
Output Voltage
1.2V 1.5V, 1.8V 2.5V, 3.3V 0.6V 3.3V Table Inductor Values.
Inductor
2.2H 4.7H 6.8H 4.7H
1146.2006.04.1.3
Fast Transient 400mA Step-Down Converter
maximum input capacitor current
AAT1146
IRMS
Since inductance short trace feeding input voltage significantly lower than power leads from bench power supply, most applications exhibit this problem. applications where input power source lead inductance cannot reduced level that does affect converter performance, high tantalum aluminum electrolytic should placed parallel with ESR, bypass ceramic. This dampens high network stabilizes system.
input capacitor ripple current varies with input output voltage will always less than equal half total load current.
0.52
Output Capacitor
output capacitor limits output ripple provides holdup during large load transitions. 4.7F ceramic capacitor typically provides sufficient bulk capacitance stabilize output during large load transitions characteristics necessary output ripple. output voltage droop load transient dominated capacitance ceramic output capacitor. During step increase load current, ceramic output capacitor alone supplies load current until loop responds. Within three switching cycles, loop responds inductor current increases match load current demand. relationship output voltage droop during three switching cycles output capacitance estimated
ILOAD VDROOP
IRMS(MAX)
term appears both input voltage ripple input capacitor current equations maximum when twice VIN. This input voltage ripple input capacitor current ripple maximum duty cycle. input capacitor provides impedance loop edges pulsed current drawn AAT1146. 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 (C2) 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. Errors loop phase gain measurements also result.
COUT
Once average inductor current increases load level, output voltage recovers. above equation establishes limit minimum value output capacitor with respect load transients. internal voltage loop compensation also limits minimum output capacitor value 4.7F. This effect loop crossover frequency (bandwidth), phase margin, gain margin. Increased output capacitance will reduce crossover frequency with greater phase margin.
1146.2006.04.1.3
Fast Transient 400mA Step-Down Converter
AAT1146
Figure AAT1146 Evaluation Board Side.
Figure Exploded View Evaluation Board Side Layout.
Figure AAT1146 Evaluation Board Bottom Side. maximum output capacitor ripple current given
VOUT (VIN(MAX) VOUT) VIN(MAX)
IRMS(MAX)
Dissipation current ceramic output capacitor typically minimal, resulting less than degrees rise hot-spot temperature.
output regulate voltage higher than 0.6V. limit bias current required external feedback resistor string while maintaining good noise immunity, minimum suggested value 59k. Although larger value will further reduce quiescent current, will also increase impedance feedback node, making more sensitive external noise interference. Table summarizes resistor values various output voltages with either good noise immunity 221k reduced load input current.
VOUT 1.5V 0.6V 88.5k
Adjustable Output Resistor Selection
applications requiring adjustable output voltage, 0.6V version externally programmed. Resistors Figure program
1146.2006.04.1.3
Fast Transient 400mA Step-Down Converter
adjustable version AAT1146, combined with external feedforward capacitor Figure delivers enhanced transient response extreme pulsed load applications. addition feedforward capacitor typically requires larger output capacitor stability. VOUT
1.85
AAT1146
Thermal Calculations
There three types losses associated with AAT1146 step-down converter: switching losses, conduction losses, quiescent current losses. Conduction losses associated with RDS(ON) characteristics power output switching devices. Switching losses dominated gate charge power output switching devices. full load, assuming continuous conduction mode (CCM), simplified form losses given
(RDSON(HS) RDSON(LS) [VIN VO])
221k
113K 150K 187K 221K 261K 301K 332K 442K 464K 523K 715K 1.00M
19.6 29.4 39.2 49.9 59.0 68.1 78.7 88.7
PTOTAL
(tsw
step-down converter quiescent current. term used estimate full load stepdown converter switching losses.
Table Adjustable Resistor Values With 0.6V Step-Down Converter.
Enable
AAT1146
PGND PGND PGND AGND
118k VOUT 4.7H
4.7F
GND2
AAT1146 SC70JW-8 CDRH3D16-4R7 0805 4.7F 0805
Figure AAT1146 Adjustable Evaluation Board Schematic.
1146.2006.04.1.3
Fast Transient 400mA Step-Down Converter
condition where step-down converter dropout 100% duty cycle, total device dissipation reduces
PTOTAL RDSON(HS)
AAT1146
Since RDS(ON), quiescent current, switching losses vary with input voltage, total losses should investigated over complete input voltage range. Given total losses, maximum junction temperature derived from SC70JW-8 package which 160°C/W.
feedback trace (Pin should separate from power trace connect closely possible load point. Sensing along high-current load trace will degrade load regulation. external feedback resistors used, they should placed closely possible (Pin minimize length high impedance feedback trace. resistance trace from load return PGND (Pins 6-8) should kept minimum. This will help minimize error regulation differences potential internal signal ground power ground. high density, small footprint layout achieved using inexpensive, miniature, nonshielded, high inductor. evaluation board available with this inductor shown Figure total solution footprint area 40mm2.
TJ(MAX) PTOTAL TAMB
Layout
suggested layout AAT1146 shown Figures following guidelines should used help ensure proper layout. input capacitor (C2) should connect closely possible (Pin PGND (Pins 6-8). should connected closely possible. connection should short possible.
Figure Minimum Footprint Evaluation Board Using 2.0mm 1.6mm 0.95mm Inductor.
1146.2006.04.1.3
Fast Transient 400mA Step-Down Converter Step-Down Converter Design Example
Specifications
TAMB 1.8V 400mA (adjustable using 0.6V version), Pulsed Load ILOAD 300mA 2.7V 4.2V (3.6V nominal) 1.4MHz 85°C
AAT1146
1.8V Output Inductor
1.8V 5.4H
(use 4.7H; Table
Sumida inductor CDRH3D16, 4.7H, 105m.
1.8V 1.8V 156mA 4.7H 1.4MHz 4.2V
IPKL1
0.4A 0.068A 0.468A
0.4A2 105m 17mW
1.8V Output Capacitor
VDROOP 0.1V
ILOAD 0.3A 6.4F; 10µF 0.1V 1.4MHz VDROOP (VO) (VIN(MAX) 1.8V (4.2V 1.8V) 45mArms VIN(MAX) 4.7H 1.4MHz 4.2V
COUT
IRMS
Pesr IRMS2 (45mA)2
1146.2006.04.1.3
Fast Transient 400mA Step-Down Converter
Input Capacitor
Input Ripple 25mV
AAT1146
3.11F; 4.7F 25mV 1.4MHz 0.4A
IRMS
0.2Arms
IRMS2 (0.2A)2 0.2mW
AAT1146 Losses
(RDSON(HS) RDSON(LS) [VIN -VO])
PTOTAL
(tsw
0.42 (0.725 1.8V [4.2V 1.8V])
4.2V
(5ns 1.4MHz 0.4A 70A) 4.2V 126mW
TJ(MAX) TAMB PLOSS 85°C (160°C/W) 126mW 105.1°C
1146.2006.04.1.3
Fast Transient 400mA Step-Down Converter
Adjustable Version (0.6V device) VOUT
1.85
AAT1146
19.6 29.4 39.2 49.9 59.0 68.1 78.7 88.7
221k1
75.0 1000
Fixed Version VOUT
0.6-3.3V
Used
Table Evaluation Board Component Values.
Manufacturer
Sumida Sumida Sumida MuRata MuRata Coilcraft Coiltronics Coiltronics Coiltronics
Part Number
CDRH3D16-2R2 CDRH3D16-4R7 CDRH3D16-6R8 LQH2MCN4R7M02 LQH32CN4R7M23 LPO3310-472 SD3118-4R7 SD3118-6R8 SDRC10-4R7
Inductance
Current
1.20 0.90 0.73 0.40 0.45 0.80 0.98 0.82 1.30
0.072 0.105 0.170 0.80 0.20 0.27 0.122 0.175 0.122
Size (mm) LxWxH
3.8x3.8x1.8 3.8x3.8x1.8 3.8x3.8x1.8 2.0x1.6x0.95 2.5x3.2x2.0 3.2x3.2x1.0 3.1x3.1x1.85 3.1x3.1x1.85 5.7x4.4x1.0
Type
Shielded Shielded Shielded Non-Shielded Non-Shielded Shielded Shielded Shielded
Table Typical Surface Mount Inductors.
reduced quiescent current, 221k.
1146.2006.04.1.3
Fast Transient 400mA Step-Down Converter
Manufacturer
MuRata MuRata MuRata
AAT1146
Part Number
GRM219R61A475KE19 GRM21BR60J106KE19 GRM21BR60J226ME39
Value
4.7F
Voltage
6.3V 6.3V
Temp.
Case
0805 0805 0805
Table Surface Mount Capacitors.
1146.2006.04.1.3
Fast Transient 400mA Step-Down Converter Ordering Information
Output Voltage1
1.875
AAT1146
Package
SC70JW-8 SC70JW-8
Marking2
QMXYY OXXYY
Part Number (Tape Reel)3
AAT1146IJS-1.875-T1 AAT1146IJS-0.6-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
SC70JW-8
0.50 0.50 0.50
1.75 0.10
0.225 0.075 2.00 0.20
2.20 0.20
0.048REF
0.85 0.15
1.10
0.15 0.05
0.100
0.45 0.10 2.10 0.30
dimensions millimeters.
Contact Sales other voltage options. assembly date code. 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.
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Arques Avenue, Sunnyvale, 94085 Phone (408) 737-4600 (408) 737-4611
1146.2006.04.1.3
0.05 0.05

AAT1146 SwitchReg member AnalogicTech's Total Power Management IC(TPMI

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