AAT1152 SwitchRegis member AnalogicTechTM's Total Power ManagementIC p

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AAT1152 SwitchRegis member AnalogicTechTM's Total Power ManagementIC p

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850kHz Synchronous Buck DC/DC Converter General Description
AAT1152 SwitchRegis member AnalogicTechTM's Total Power ManagementIC product family. Step-down switching converter ideal applications where high efficiency, small size, ripple critical. Able deliver with internal Power MOSFETs, current-mode controlled provides high efficiency using synchronous rectification. Fully internally compensated, AAT1152 simplifies system design lowers external part count. AAT1152 features Power Good (POK) function which monitors output, alerting system output voltage falls regulation. AAT1152 available MSOP-8 package, rated over 85°C.
AAT1152
SwitchReg
5.5V supply input Fixed output voltage: 1.1V-4.2V with increment output current Integrated resistance power switches Synchronous rectification efficiency Power Good signal Internally compensated current mode control High initial accuracy: 850kHz switching frequency Constant mode output ripple with light load Internal softstart Current limit protection Over-Temperature protection MSOP-8 package
Preliminary Information
Applications
Computer Peripherals Boxes Network Cards Cable/DSL Modems High efficiency conversion from 3.3V supply
Typical Application
INPUT
100k
10µF
AAT1152
4.1µH
ENABLE OUTPUT SGND 0.1µF PGND 47µF
1152.2003.01.0.9
850kHz Synchronous Buck DC/DC Converter Descriptions
AAT1152
Symbol
SGND PGND
Function
Feedback input Signal Ground Converter enable Small Signal Filtered Bias Supply Input supply converter power stage Inductor connection Power Good indicator. Open-drain output when VOUT falls regulation. Power ground return output stage
Configuration
MSOP-8
SGND
PGND
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850kHz Synchronous Buck DC/DC Converter Absolute Maximum Ratings
Symbol
VCC, VEN, VPOK TLEAD VESD
AAT1152
(TA=25°C unless otherwise noted) Value
-0.3 VP+0.3 -0.3 VCC+0.3 -0.3 3000
Description
VCC, POK, Operating Junction Temperature Range Maximum Soldering Temperature leads, sec) Rating
Units
Note: 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. Note Human body model 100pF capacitor discharged through 1.5K resistor into each pin.
Thermal Characteristics
Symbol
Description
Maximum Thermal Resistance (MSOP-8) Maximum Power Dissipation (MSOP-8)
Value
Units
°C/W
Note Mounted demo board.
Recommended Operating Conditions
Symbol
Description
Ambient Temperature Range
Rating
Units
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850kHz Synchronous Buck DC/DC Converter Electrical Characteristics
values 25°C) Symbol
VOUT ILIM VOUT (VOUT*VIN) VOUT/VOUT FOSC RDSON(H) RDSON(L) VEN(H) VEN(L) VUVLO VUVLO(hys) THYS ISHDN VTH(POK) RPOK
AAT1152
(VIN 85°C unless otherwise noted. Typical
Description
Operation Voltage Output Voltage Tolerance Current Limit Quiescent Supply Current Load Regulation Line Regulation Oscillator frequency High-side Switch On-resistance Low-side Switch On-resistance Enable input high voltage Enable input voltage Enable Leakage Current Undervoltage Lockout Undervoltage Lockout Hysteresis Over Temp Shutdown Threshold Over Temp Shutdown Hysteresis Shutdown current Power Good Threshold Power Good Pull-Down On-Resistance
Conditions
IOUT 500mA 25°C Full temp
-1.0 -2.0
+1.0 +2.0
Units
25°C load, 4.2V, ILOAD 5.5V 25°C 25°C 25°C 5.5V 5.5V 5.5V rising falling
1000
5.5V Ramping Ramping Down
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850kHz Synchronous Buck DC/DC Converter Typical Characteristics
High Side RDS(ON) Temperature
AAT1152
Side RDS(ON) Temperature
3.6V 2.7V RDS(ON)
RDS(ON)
3.6V 2.7V 5.5V 4.2V
4.2V
5.5V
Temperature (°C)
Temperature (°C)
RDS(ON) Input Voltage
Enable Threshold Input Voltage
Enable Threshold
High Side RDS(ON)
VEN(H)
Side
VEN(L)
Input Voltage
Input Voltage
Oscillator Frequency Variation Supply Voltage
Oscillator Frequency Variation Temperature VIN=3.6V
Variation
-0.5 -1.5
Variation
Supply Voltage
Temperature (°C)
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850kHz Synchronous Buck DC/DC Converter Typical Characteristics
Output Voltage Temperature IOUT=900mA, VOUT=1.5V
Output Voltage Error
-0.2 -0.6 -1.0
AAT1152
Line Regulation VOUT=1.5V
0.25 0.15
2.7V
Accuracy
IOUT 1.0A
0.05 -0.05 -0.15 -0.25
3.6V
IOUT 0.4A
Temperature (°C)
Input Voltage
Load Regulation VOUT= 1.5V, VIN=3.6V
Load Regulation VOUT=3.3V, VIN=5.0V
VOUT Error
Error
1050
IOUT (mA)
Output Current
Efficiency Input Voltage VOUT=1.5V
Loop Gain Phase Output Capacitor 3.6V IOUT 0.3A
Efficiency
Gain (dB)
0.4A
100µF
Phase
47µF 69µF
Phase (degrees)
-135 -180 -225 1000
47µF
Gain
69µF 100µF
Input Voltage
Frequency (kHz)
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850kHz Synchronous Buck DC/DC Converter Typical Characteristics
Load Input Current Temperature
AAT1152
Non-Switching Temperature
Operating Current (µA)
5.5V
5.0V
Input Current (mA)
5.5V 5.0V 4.2V 2.7V
4.2V
3.6V
2.7V
3.6V
Temperature (°C)
Temperature (°C)
Switching Waveform
VOUT 50mV/div V(LX) 2V/div Inductor Current 500mA/div
Transient Response
500mA/div
VIN=3.6V VOUT=1.5V IOUT=1.2A
VIN=3.6V VOUT=1.5V ILOAD=0.25 1.2A 500nsec/div 20µs/div
Output Ripple 1.5V, Load
VOUT 5mV/div BW=20MHz VIN=3.6V VOUT=1.5V IOUT=0A 2V/div 500nsec/div VOUT 5mV/div BW=20MHz VIN=3.6V VOUT=1.5V IOUT=1A 2V/div
Output Ripple 1.5V, Load
500nsec/div
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850kHz Synchronous Buck DC/DC Converter Typical Characteristics
Output Ripple 3.3V, Load
VOUT 5mV/div BW=20MHz VIN=5.0V VOUT=3.3V IOUT=0A 2V/div 500nsec/div VOUT 5mV/div BW=20MHz VIN=5.0V VOUT=3.3V IOUT=1A 2V/div 500nsec/div
AAT1152
Output Ripple 3.3V, Load
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850kHz Synchronous Buck DC/DC Converter Functional Block Diagram
2.7V- 5.5V
AAT1152
1.0V
LOGIC
Temp. Sensing Power Good
SGND
PGND
Applications Information
DC-DC Synchronous Buck Converter Control Loop
AAT1152 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. feedback resistive divider internal, dividing output voltage error amplifier reference voltage 1.0V. error amplifier does have large gain typical most error amplifiers. This eliminates need external compensation components while still providing sufficient loop gain load regulation. crossover frequency phase margin output capacitor value only.
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. enable input, when pulled low, forces AAT1152 into power non-switching state. total input current during shutdown less that 1µA.
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850kHz Synchronous Buck DC/DC Converter
AAT1152
Enable 2V/div
VOUT 1V/div 0.5A/div VIN=3.6V VOUT=1.5V IL=1A
200µsec/div
Figure Inrush Limit
Power Signal Source
Separate small signal ground power supply pins isolate internal control circuitry from noise associated with output MOSFET switching. pass filter schematic figures filters noise associated with power switching.
Current Limit Over-temperature protection
overload conditions peak input current limited. Figure displays current limit characteristics. 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 15°C hysteresis.
Current Limit Characteristic
5.0V 3.3V Figure schematic
VOUT
=3.6V 1.5V Figure schematic
IOUT
Figure
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850kHz Synchronous Buck DC/DC Converter
Power Good
1152 features integrated Power Good (POK) comparator open-drain output signal. goes when converter's output more below nominal regulation voltage when device shutdown. Connect pull-up resistor from converter's input output. Typical resistor pull-up values range from 100k 10k.
AAT1152
factor fraction full load selected ripple current maximum input voltage. corresponding inductor current IRMS 1.0A
Inductor
output inductor selected limit ripple current some predetermined value, typically 2040% 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 over load short circuit conditions, average current inductor meet exceed ILIMIT point AAT1152 without effecting converter performance. Some inductors have sufficient 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 peak ripple current inductance value required 3.9µH. VOUT 1.5V 1.5V 11.0A 830kHz 4.2V
peak peak ripple current which fixed inductor selection above. peak peak current full load current peak current full load will 115% full load. 4.1µH inductor selected from Sumida CDRH5D18 series 1.95 current rating. full load inductor loss 57mW which amounts 3.8% loss efficiency.
Input Capacitor
primary function input capacitor provide impedance loop edges pulsed current drawn AAT1152. 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 AAT1152. 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 maximum current input capacitor
IRMS
1VIN
3.9µH
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
1152.2003.01.0.9
850kHz Synchronous Buck DC/DC Converter
100k AAT1152-1.0 10µF 100k 0.1µF 2.7µH 100µF
AAT1152
Vin+ 3.3V
2.55k 1.25V1A
Sgnd Pgnd
Murata 10µF 6.3V GRM42-6X 5R106K6.3 MuRata 100µF 6.3V GRM43-2 107M 100µF 6.3V Sumida CDRH4D28-2R
Figure 3.3V 1.25V converter
Output Capacitor
Since there external compensation components, output capacitor strong effect loop stability. Larger output capacitance will reduce crossover frequency with greater phase margin. 1.5V design using inductor, 47µF capacitor provides stable loop with degrees phase margin crossover frequency kHz. Doubling capacitance 100µF reduces crossover frequency half while increasing phase margin degrees. addition assisting stability, output capacitor limits output ripple provides holdup during large load transitions. 100µF ceramic capacitor provides sufficient bulk capacitance
stabilize output during large load transitions characteristics necessary output ripple. output capacitor ripple current given
(VOUT VFWD) (VIN VOUT)
IRMS
ceramic capacitor dissipation current capacitor concern. Tantalum capacitors, with sufficiently meet output voltage ripple requirements, also have current rating much greater than that actually seen this application.
1152.2003.01.0.9
850kHz Synchronous Buck DC/DC Converter
100k AAT1152-1.5 100µF 4.1µH
AAT1152
Vin+ 2.7V-5.5V 10µF 100k 0.1µF
1.5V
Sgnd Pgnd
Murata 10µF 6.3V GRM42-6X5R106K6.3 MuRata 100µF 6.3V GRM43-2 107M 100µF 6.3V Sumida CDRH5D 18-4R
1.5V Efficiency IOUT
2.7V
Efficiency
4.2V
1000
3.6V
Iout (mA)
Figure Lithium-Ion 1.5V Output Converter
Figure AAT1152 Layout Layer
Figure AAT1152 Layout Bottom Layer
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850kHz Synchronous Buck DC/DC Converter
Adjustable Output
applications requiring output other than fixed outputs available, version programmed externally. Resistors figure force output regulate higher than Volt. should times less than internal MegOhm resistance pin. Once selected calculated. 1.25V output with 10.0k, 2.55k.
AAT1152
Layout Considerations
Figures display suggested layout AAT1152. most critical aspect layout placement input capacitor proper operation must placed close possible AAT1152.
Thermal Calculations
There types losses associated with AAT1152 output switching MOSFET, switching losses conduction losses. conduction losses associated with Rds(on) characteristics output switching device. full load, assuming continuous conduction mode (CCM), simplified form total losses
0.25 10.0k 2.55k
PLOSS
(RDSON(H) RDSON(L) (VIN VO))
Once total losses have been determined junction temperature derived from MSOP-8 package.
Design Example
Specifications IOUT 1.0A IRIPPLE full load VOUT 1.5V (3.6V nominal)
Maximum Input Capacitor Ripple:
IRMS 0.5ARMS VINMAX VINMAX
ESRCOUT IRMS2 0.52 1.25mW
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850kHz Synchronous Buck DC/DC Converter
Inductor Selection:
VOUT 1.5V 1.5V 3.9µH 1.0A 830kHz 4.2V
AAT1152
Select Sumida inductor CDRH5D18 4.1µH height.
1.5V 1.5V 280mA 4.1µH 830kHz 4.2V
IOUT
1.0A 0.14A 1.14A
=57mW
Output Capacitor Dissipation:
IRMS VOUT (VIN VOUT) 1.5V (4.2V 1.5V) =82mARMS 4.1µH 830kHz 4.2V
PESR ESRCOUT IRMS2 .0822 33µW
AAT1152 Dissipation:
(RDSON(H) RDSON(L) (VIN -VO)) (tsw
(0.14 1.5V 0.145 (3.6V 1.5V)) 3.6V
(20nsec 830kHz 1.0A 0.3mA) 3.6V 0.203W
TJ(MAX) TAMB PLOSS 85°C 150°C/W 0.203W 115°C
1152.2003.01.0.9
850kHz Synchronous Buck DC/DC Converter
Table Surface Mount Inductors
Manufacturer
TaiyoYuden Toko Sumida Sumida MuRata MuRata
AAT1152
Part Number
NPO5DB4R7M A914BYW-3R5M-D52LC CDRH5D28-4R2 CDRH5D18-4R1 LQH55DN4R7M03 LQH66SN4R7M03
Value
4.7µH 3.5µH 4.2µH 4.1µH 4.7µH 4.7µH
Current
1.4A 1.34A 2.2A 1.95A 2.7A 2.2A
.038 .073 .031 .057 .041 .025
Size (mm)
Type
Shielded Shielded Shielded Shielded Non-shielded Shielded
Table Surface Mount Capacitors
Manufacturer
MuRata MuRata MuRata MuRata
Part Number
C4532X5ROJ107M GRM43-2 107M GRM43-2 476K GRM40 106K GRM42-6 106K
Value
100µF 100µF 47µF 10µF 10µF
Voltage
6.3V 6.3V 6.3V 6.3V 6.3V
Temp.
Case
1812 1812 1812 0805 1206
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850kHz Synchronous Buck DC/DC Converter Ordering Information
Output Voltage 1.0V 1.1V 1.2V 1.5V 1.8V 2.0V 2.5V 3.0V 3.3V Package MSOP-8 MSOP-8 MSOP-8 MSOP-8 MSOP-8 MSOP-8 MSOP-8 MSOP-8 MSOP-8 Marking Part Number (Tape Reel) AAT1152IKS-1.0-T1 AAT1152IKS-1.1-T1 AAT1152IKS-1.2-T1 AAT1152IKS-1.5-T1 AAT1152IKS-1.8-T1 AAT1152IKS-2.0-T1 AAT1152IKS-2.5-T1 AAT1152IKS-3.0-T1 AAT1152IKS-3.3-T1
AAT1152
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
0.075 0.075 0.65 0.30 0.08
dimensions millimeters.
GAUGE PLANE
0.155 0.075
1152.2003.01.0.9
850kHz Synchronous Buck DC/DC Converter
AAT1152
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, advise customers 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
1152.2003.01.0.9

AAT1152 SwitchRegis member AnalogicTechTM's Total Power ManagementIC p

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