850kHz 700mA Synchronous Buck DC/DC Converter General Description

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850kHz 700mA Synchronous Buck DC/DC Converter General Description

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AAT1151
850kHz 700mA Synchronous Buck DC/DC Converter General Description
AAT1151 SwitchRegis member AnalogicTech's Total Power Management IC(TPMICTM) product family. step-down switching converter ideal applications where high efficiency required over full range output load conditions. 2.7V 5.5V input voltage range makes AAT1151 ideal single-cell lithiumion/polymer battery applications. Capable more than 700mA with internal MOSFETs, currentmode controlled provides high efficiency using synchronous rectification. Fully integrated compensation simplifies system design lowers external parts count. device operates fixed 850kHz switching frequency enters mode light load current maintain high efficiency across load conditions. AAT1151 available MSOP-8 QFN33-16 packages rated over -40°C +85°C temperature range.
SwitchReg
Range: 2.7V 5.5V Efficiency High Initial Accuracy 110m RDS(ON) Internal Switches <1µA Shutdown Current 850kHz Switching Frequency Fixed VOUT Adjustable VOUT 1.0V Integrated Power Switches Synchronous Rectification Current Mode Operation Internal Compensation Stable with Ceramic Capacitors Optimum Efficiency Load Conditions Internal Soft Start Over-Temperature Protection Current Limit Protection MSOP-8 QFN33-16 Packages -40°C +85°C Temperature Range
Applications
Cellular Phones Digital Cameras Players Notebook Computers PDAs USB-Powered Equipment Wireless Notebook Adapters
Typical Application
INPUT
10µF
AAT1151
3.0µH ENABLE OUTPUT SGND 0.1µF PGND 22µF
1151.2005.11.1.4
AAT1151
850kHz 700mA Synchronous Buck DC/DC Converter Descriptions
MSOP-8 QFN33-16
Symbol
Function
Feedback input pin. This connected converter output. used output converter regulate desired value internal resistive divider. adjustable output, external resistive divider connected this model. Signal ground. Connect return small signal components this pin. (See board layout rules.) Enable input pin. logic high enables converter; logic forces AAT1151 into shutdown mode reducing supply current less than 1µA. should left floating. Bias supply. Supplies power internal circuitry. Connect input power pass filter with decoupling SGND. Input supply voltage converter power stage. Must closely decoupled PGND. Connect inductor these pins. Switching node internally connected drain both high- low-side MOSFETs. Main power ground return pin. Connect output input capacitor return. (See board layout rules.) internally connected. Exposed paddle (bottom); connect PGND directly beneath package.
SGND
PGND
Configuration
MSOP-8 (Top view) QFN33-16 (Top view)
SGND
PGND PGND PGND PGND
SGND SGND
1151.2005.11.1.4
AAT1151
850kHz 700mA Synchronous Buck DC/DC Converter Absolute Maximum Ratings1
Symbol
VCC, VESD
Description
VCC, Operating Junction Temperature Range Rating2
Value
-0.3 VP+0.3 -0.3 VCC+0.3 -0.3 3000
Units
Thermal Characteristics3
Symbol
Description
Thermal Resistance (MSOP-8) Maximum Power Dissipation (MSOP-8) 25°C)4 Thermal Resistance (QFN33-16) Maximum Power Dissipation (QFN33-16) 25°C)5
Value
Units
°C/W °C/W
Recommended Operating Conditions
Symbol
Description
Ambient Temperature Range
Value
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. Derate 6.7mW/°C above 25°C. Derate 20mW/°C above 25°C. 1151.2005.11.1.4
AAT1151
850kHz 700mA Synchronous Buck DC/DC Converter Electrical Characteristics1
-40°C 85°C, unless otherwise noted. Typical values 25°C. Symbol
VOUT VUVLO VUVLO(HYS) ISHDN ILIM RDS(ON)H RDS(ON)L VOUT (VOUT*VIN) VOUT/VOUT FOSC VEN(L) VEN(H) THYS
Description
Input Voltage Range Output Voltage Tolerance
Conditions
VOUT 5.5V, IOUT 700mA Rising Falling 5.5V Load, 4.2V 25°C 5.5V 25°C 25°C 25°C IOUT 300mA, 3.5V 4.2V, ILOAD 700mA 2.7V 5.5V 25°C
-3.0
+3.0
Units
Under-Voltage Lockout Under-Voltage Lockout Hysteresis Input Current Input High Current Quiescent Supply Current Shutdown Current Current Limit High Side Switch Resistance Side Switch Resistance Efficiency Load Regulation Line Regulation Oscillator Frequency Enable Threshold Enable Threshold High Over-Temperature Shutdown Threshold Over-Temperature Shutdown Hysteresis
±0.9 ±0.1
1200
AAT1151 guaranteed meet performance specifications over -40°C +85°C operating range assured design, characterization, correlation with statistical process controls.
1151.2005.11.1.4
AAT1151
850kHz 700mA Synchronous Buck DC/DC Converter Typical Characteristics
Load Supply Current Input Voltage
Frequency Input Voltage
Supply Current (µA)
85°C Frequency (kHz)
-40°C
25°C
Input Voltage
Input Voltage
Output Voltage Temperature
1.794 1.792
Load Line Regulation
4.2V 3.6V 2.7V
Output Voltage
VOUT Error
1.79 1.788 1.786 1.784 1.782 1.78
-1.0 -2.0 -3.0
1000
Temperature (°C)
Load Current (mA)
Switching Frequency Temperature
1200
AAT1151 Efficiency
(VOUT 2.5V; 4.2µH)
1000
Frequency (kHz)
Efficiency
1000 10000
Temperature (°C)
Output Current (mA)
1151.2005.11.1.4
AAT1151
850kHz 700mA Synchronous Buck DC/DC Converter Typical Characteristics
Output Ripple 1.8V, 50mA, 3.6V Circuit Figure
Line Transient Response 1.8V, 50mA Circuit Figure
Output Voltage coupled) (top) (mV)
Inductor Current (bottom)
Output Voltage (bottom) (mV)
-0.2
Input Voltage (top)
Time (2µs/div)
Time (20µs/div)
Output Ripple 1.8V, 0.7A, 3.6V Circuit Figure
Line Transient Response 1.8V, 0.7A Circuit Figure
Output Voltage coupled) (top) (mV)
Inductor Current (bottom)
Output Voltage (bottom) (mV)
-0.5
Input Voltage (top)
Time (2µs/div)
Time (20µs/div)
Load Transient Response 50mA 0.7A 3.6V Circuit Figure
Output Voltage (top) (mV) coupled)
-100 -120
Soft Start 1.8V, 0.7A, 3.6V Circuit Figure
Enable (top) Output (middle)
Inductor Current (bottom)
Inductor Current (bottom)
-0.5
-0.5
Time (200µs/div)
Time (200µs/div)
1151.2005.11.1.4
AAT1151
850kHz 700mA Synchronous Buck DC/DC Converter Typical Characteristics
Output Ripple Circuit Figure
Ripple (mV)
2.7V
3.6V
4.2V
1000
Output Current (mA)
1151.2005.11.1.4
AAT1151
850kHz 700mA Synchronous Buck DC/DC Converter Functional Block Diagram
2.7V- 5.5V
1.0V
LOGIC
Temp. Sensing
SGND
PGND
Operation
Control Loop
AAT1151 peak current mode buck converter. inner, wide bandwidth loop controls peak current output inductor. output inductor current sensed through P-channel MOSFET (high side) also used short-circuit overload protection. fixed slope compensation signal added sensed current maintain stability. 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. voltage feedback resistive divider internal, dividing output voltage error amplifier reference voltage 1.0V. voltage error amplifier does have large gain typical most error amplifiers. This eliminates need external compensation components, while still providing sufficient loop gain load regulation. voltage loop crossover frequency phase margin output capacitor value only.
PFM/PWM Operation
Light load efficiency maintained Pulse Frequency Modulation (PFM) control. AAT1151 control forces peak inductor current minimum level regardless load demand. medium high load demand, this effect circuit operation normal controls take over. reduces switching frequency light loads, thus reducing associated switching losses.
Soft Start/Enable
Soft start increases inductor current limit point discrete steps when input voltage enable input applied. limits current surge seen input eliminates output voltage overshoot. When pulled low, enable input forces AAT1151 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 noise associated with output MOSFET switching. pass filter schematic Figure filters noise associated with power switching.
1151.2005.11.1.4
AAT1151
850kHz 700mA Synchronous Buck DC/DC Converter
Efficiency Load Current
2.7V-4.2V 100k 0.1µF 100k AAT1151-QFN Pgnd Pgnd Pgnd
(VOUT 1.8V)
1.8V
Efficiency
3.3µH 2x22µF
2.7V
10µF
3.6V
4.2V
Murata 10µF 6.3V GRM42-6X5R106K6.3 C3-C4 MuRata 22µF 6.3V GRM21BR60J226ME39L 0805 Sumida CDRH3D16-4R7NC CDRH3D16-3R3NC
1000
Load Current (mA)
Figure AAT1151 Evaluation Board.
Current Limit Over-Temperature Protection
overload conditions, peak input current limited. load impedance decreases output voltage falls closer zero, more power dissipated internally, raising device temperature. Thermal protection completely disables switching when internal dissipation becomes excessive, protecting device from damage. junction over-temperature threshold 140°C with 10°C hysteresis.
peak average current ratings result excessive losses high DCR. Always consider losses associated with effect total converter efficiency when selecting inductor. load ripple maximum input voltage, maximum peak-topeak ripple current 280mA. inductance value required 2.84µH.
VOUT VOUT 1.5V 1.5V 4.2V 850kHz
Inductor
output inductor selected limit ripple current some predetermined value, typically full load current maximum input voltage. 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. During overload transient conditions, average current inductor meet exceed current limit point AAT1151. These conditions tolerate greater saturation inductor without degradation converter performance. Some inductors meet
2.84µH factor fraction full load selected ripple current maximum input voltage. ripple current full load current, peak current will 120% full load. Selecting standard value 3.0µH gives ripple current. 3.0µH inductor selected from Sumida CDRH5D28 series 2.4A current rating. full load, inductor loss 24mW, which amounts 1.6% loss efficiency.
1151.2005.11.1.4
AAT1151
850kHz 700mA Synchronous Buck DC/DC Converter
Input Capacitor
primary function input capacitor provide impedance loop edges pulsed current drawn AAT1151. ESR/ESL ceramic capacitor ideal this function. minimize stray inductance, capacitor should placed close possible This keeps high frequency content input current localized, minimizing radiated conducted while facilitating optimum performance AAT1151. Ceramic capacitors ideal this function. size required will vary depending load, output voltage, input voltage source impedance characteristics. typical value around 10µF. input capacitor current varies with input voltage output voltage. equation current input capacitor
VOUT (VIN VOUT)
IRMS
ceramic capacitor, that dissipation current capacitor concern. Tantalum capacitors with sufficiently meet output voltage ripple requirements also have current rating well beyond that actually seen this application.
Layout
Figures through display suggested layout AAT1151. following guidelines should used help ensure proper layout. input capacitor (C1) should connect closely possible VPOWER (Pin PGND (Pin should connected closely possible. connection node should short possible. feedback trace (Pin should separate from power trace connect closely possible load point. Sensing along high-current load trace will degrade load regulation. resistance trace from load return PGND (Pin should kept minimum. This will help minimize error regulation differences potential internal signal ground power ground. pass filter provide cleaner bias source AAT1151 active circuitry. should placed closely possible SGND (Pin (Pin Figures
IRMS
input capacitor ripple current reaches maximum when times output voltage where approximately half load current. Losses associated with input ceramic capacitor typically minimal issue. Proper placement input capacitor seen reference design layout Figures
Output Capacitor
Since there external compensation components, output capacitor strong effect loop stability. Lager output capacitance will reduce crossover frequency with greater phase margin. 1.5V design using 4.1µH inductor, 22µF capacitors provide stable output. addition assisting stability, output capacitor limits output ripple provides holdup during large load transitions. output capacitor ripple current given
1151.2005.11.1.4
AAT1151
850kHz 700mA Synchronous Buck DC/DC Converter
Figure MSOP Evaluation Board Layer.
Figure MSOP Evaluation Board Bottom Layer.
Figure Evaluation Board Side.
Figure Evaluation Board Bottom Side.
R4=10k
2.7V-5.5V 100k 10µF AAT1151-1.0
1.25V 0.7A 2.55k
3.3µH
22µF
Pgnd
Murata 10µF 6.3V GRM42-6X5R106K6.3 MuRata 22µF 6.3V GRM21BR60J226ME39L 0805 Sumida CDRH3D16-3R3
Output Voltage
Figure VOUT Adjustable Output Using AAT1151-1.0V.
Figure Adjustable Output Schematic.
1151.2005.11.1.4
AAT1151
850kHz 700mA Synchronous Buck DC/DC Converter
Thermal Calculations
There types losses associated with AAT1151 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), simplified form total losses given Once total losses have been determined, junction temperature derived from MSOP-8 package.
TAMB
Adjustable Output
applications requiring output other than fixed available, version programmed externally. Resistors Figure force output regulate higher than volt. should times less than internal resistance (recommended 10k). Once selected, calculated. 1.25 volt output with 10.0k, 2.55k.
(RDSON(HS) RDSON(LS) (VIN VO))
where AAT1151 quiescent current.
0.25 2.55k
1151.2005.11.1.4
AAT1151
850kHz 700mA Synchronous Buck DC/DC Converter
Design Example
Specifications IOUT IRIPPLE VOUT TAMB 0.7A Full Load 1.5V 2.7V 4.2V (3.6V nominal) 850kHz 85°C
Maximum Input Capacitor Ripple:
IRMS 0.35Arms,
IRMS2 0.352 0.6mW
Inductor Selection:
VOUT 1.5V 1.5V 4.05µH 0.7A 850kHz 4.2V
Select Sumida inductor CDRH3D16 3.3µH 1.8mm height.
1.5V 1.5V 340mA 3.3µH 850kHz 4.2V
IOUT
0.7A 0.17A 0.87A
(0.7)2 31mW
Output Capacitor Ripple Current:
IRMS VOUT (VIN VOUT) 1.5V (4.2V 1.5V) 99mArms 3.3µH 850kHz 4.2V
Pesr IRMS2 50µW
1151.2005.11.1.4
AAT1151
850kHz 700mA Synchronous Buck DC/DC Converter
AAT1151 Dissipation:
PTOTAL (RDSON(H) RDSON(L) (VIN -VO)) (tsw
(0.7A)2 (0.2 1.5V 0.187 (4.2V 1.5V))
4.2V
(20nsec 850kHz 0.7A 0.3mA) 4.2V 0.145W
TJ(MAX) TAMB PLOSS 85°C 150°C/W 0.145W 107°C (MSOP-8)
85°C 50°C/W 0.145W 92°C (QFN33-16)
Surface Mount Inductors
Manufacturer
TaiyoYuden Toko Sumida Sumida Sumida MuRata MuRata MuRata
Part Number
NPO5DB4R7M A914BYW-3R5M-D52LC CDRH5D28-3R0 CDRH5D28-4R2 CDRH5D18-4R1 LQH55DN4R7M03 LQH66SN4R7M03 CDRH3D16-3R3
Value
4.7µH 3.5µH 3.0µH 4.2µH 4.1µH 4.7µH 4.7µH 3.3µH
Current
1.4A 1.34A 2.4A 2.2A 1.95A 2.7A 2.2A 1.1A
0.038 0.073 0.024 0.031 0.057 0.041 0.025 0.063
Size (mm)
Type
Shielded Shielded Shielded Shielded Shielded Non-Shielded Shielded Shielded
Surface Mount Capacitors
Manufacturer
MuRata MuRata MuRata MuRata
Part Number
GRM40 106K GRM42-6 106K GRM21BR60J226ME39L GRM21BR60J106ME39L
Value
10µF 10µF 22µF 10µF
Voltage
6.3V 6.3V 6.3V 6.3V
Temp.
Case
0805 1206 0805 0805
1151.2005.11.1.4
AAT1151
850kHz 700mA Synchronous Buck DC/DC Converter Ordering Information
Output Voltage1
1.0V (Adj VOUT 1.0V) 1.0V (Adj VOUT 1.0V) 1.8V 1.8V 2.5V 2.5V 3.3V
Package
MSOP-8 QFN33-16 MSOP-8 QFN33-16 MSOP-8 QFN33-16 MSOP-8
Marking2
JHXYY JHXYY JIXYY JIXYY JJXYY JJXYY NKXYY
Part Number (Tape Reel)3
AAT1151IKS-1.0-T1 AAT1151IVN-1.0-T1 AAT1151IKS-1.8-T1 AAT1151IVN-1.8-T1 AAT1151IKS-2.5-T1 AAT1151IVN-2.5-T1 AAT1151IKS-3.3-T1
Package Information
MSOP-8
1.95
3.00 0.10
4.90 0.10
0.60 0.20 0.254 0.95 3.00 0.10 0.95 0.15 0.85 0.10 0.65 0.30 0.08
0.075 0.075
dimensions millimeters.
Contact local sales office custom options. assembly date code. Sample stock generally held part numbers listed BOLD. 1151.2005.11.1.4
GAUGE PLANE
0.155 0.075
AAT1151
850kHz 700mA Synchronous Buck DC/DC Converter
QFN33-16
Identification
0.230 0.05
3.000 0.05
Marking
0.400 0.05
3.000 0.05
0.500 0.05
View
Bottom View
1.55 0.15 0.025 0.025 0.203 0.0254
Side View
dimensions millimeters.
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.
Advanced Analogic Technologies, Inc.
Arques Avenue, Sunnyvale, 94085 Phone (408) 737-4600 (408) 737-4611
1151.2005.11.1.4
0.850 0.05

850kHz 700mA Synchronous Buck DC/DC Converter General Description

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