AP3469
3A 27V Synchronous Buck Converter
Features General Description
z 3A Output Current
z Wide 4.5V to 27V Operating Input Range z Fixed 340KHZ Frequency
z Integrated Power MOSFET switches z Output Adjustable from 0.925V to 0.8Vin z Up to 93% Efficiency
z Programmable Soft-Start
z Stable with Low ESR Ceramic Output
Capacitors
z Cycle by Cycle Over Current Protection z Short Circuit Protection
z Input Under Voltage Lockout z Package： ESOP-8L
The AP3469 is a monolithic synchronous buck regulator. The device integrates 90 mΩ MOSFETS that provide 3A continuous load current over a wide operating input voltage of 4.5V to 27V. Current mode control provides fast transient response and cycle-by-cycle current limit. An adjustable soft-start prevents inrush current at turn on.
Applications
Distributed Power Systems Networking Systems
FPGA, DSP, ASIC Power Supplies Green Electronics/ Appliances Notebook Computers
Typical Application Circuit
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AP3469
3A 27V Synchronous Buck Converter
Ordering Information
AP3469- X X X
Tape & Reel
Device Package Code Package Part Number
Quantity Suffix
AP3469 R8 ESOP-8L 2500 A Pin Assignments
ESOP-8L
(TOP View) 8SSBS1 7ENVIN2ExposedPad on 6COMPSW3Backside 5FBGND4
Pin Descriptions
Pin Number Name Description
Bootstrap. This pin acts as the positive rail for the high-side switch’s
1 BS gate driver. Connect a 0.01uF capacitor between BS and SW. Input Supply. Bypass this pin to GND with a low ESR capacitor. See
2 VIN Input Capacitor in the Application Information section. 3 SW Switch Output. Connect this pin to the switching end of the inductor.
4 GND Ground.
Feedback Input. The voltage at this pin is regulated to 0.925V.
5 FB Connect to the resistor divider between output and ground to set
output voltage.
Compensation Pin. See Stability Compensation in the Application 6 COMP Information section.
Enable Input. When higher than 2.7V, this pin turns the IC on. When
lower than 1.1V, this pin turns the IC off. Output voltage is discharged 7 EN when the IC is off. This pin should not be left open. Recommend to put
a 150KΩ pull-up resistor to Vin for startup.
Soft-Start Control Input. SS controls the soft-start period. Connect a
capacitor from SS to GND to set the soft-start period. A 0.1uF
8 SS capacitor sets the soft-start period to 13ms. To disable the soft-start
feature, leave SS unconnected. Exposed Pad Exposed Pad. Need to connect to GND pin.
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AP3469
3A 27V Synchronous Buck Converter
Block Diagram
OVP1.1VFB50.3VOSCILLATORRAMP340/120KHzCLKSS80.925VERRORAMPLIFIER6uA4GND OVP1.2V IN<4.10VLOCKOUT2.5VCOMPARATOR IN INTERNALREGULATORSSHUTDOWN 1.5V COMPARATOR
Absolute Maximum Ratings Parameter Value Unit
Input Supply Voltage -0.3 to 30 V
SW Voltage -0.3 to VIN + 0.3 V
BS Voltage VSW – 0.3 to VSW + 6 V
EN, FB, COMP Voltage -0.3 to 5 V
Continuous SW Current Internally limited A
Junction to Ambient Thermal Resistance (θJA)
20 °C/W (Test on Approximately 3 in2 Copper Area 1oz copper FR4 board)
Junction to Ambient Case Resistance (θJC) 10 °C/W SOP-8L Power Dissipation Internally limited W
Maximum Junction Temperature 150 °C
Storage Temperature Range -65 to 150 °C Please refer the MSL
Moisture Sensitivity (MSL) label on the IC package
bag/carton for detail (Note: Exceeding these limits may damage the device. Even the duration of exceeding is very short. Exposure to
absolute maximum rating conditions for long periods may affect device reliability.)
COMP6 CURRENTSENSEAMPLIFIER5V2VIN
1BS
S QR Q CURRENTCOMPARATOR3SW
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AP3469
3A 27V Synchronous Buck Converter
Parameter
Input Supply Voltage
Operating Junction Temperature
Recommended Operating Conditions Min 4.5 -20
Max
(1)Unit
(Note (1): Operating the IC over this voltage is very easy to cause over voltage condition to VIN pin, SW pin, BS pin & EN pin)
(Note (2): If the IC experienced OTP, then the temperature may need to drop to <125 degree C to let the IC recover.) Electrical Characteristics (VIN = 12V, TA= 25°C unless otherwise specified.)
Parameter SymbolMin Typ MaxUnit
Test Conditions
Feedback Voltage VFB 4.5V ≤ VIN ≤ 27V 0.900 0.925 0.950V
Feedback Overvoltage Threshold 1.1 V 90 mΩHigh-Side Switch-On Resistance*
70 mΩLow-Side Switch-On Resistance*
High-Side Switch Leakage V 0.1 10 uA EN = 0V, VSW = 0V
Minimum Duty Cycle 3.8 4.5 A Upper Switch Current Limit* From Drain to Source 1.2 A Lower Switch Current Limit* COMP to Current Sense
5.2 A/VGCS Limit Transconductance
Error Amplifier Transconductance GEA = ±10uA 900 uA/V ΔICOMP
AVEA 400 V/VError Amplifier DC Gain*
Switching Frequency fSW 300 340 380KHz
Short Circuit Switching Frequency VFB = 0 100 KHz
7.5 % Dmin Minimum Duty Cycle*
Maximum Duty Cycle Dmax 92 %
EN Shutdown Threshold Voltage 1.1 1.4 2 V VEN Rising EN Shutdown Threshold Voltage
180 mV Hysteresis
EN Lockout Threshold Voltage 2.2 2.5 2.7 V EN Lockout Hysteresis 150 mV
Supply Current in Shutdown VEN = 0 0.3 3.0 uA
= 3V, VFB = 1.0V IC Supply Current in Operation VEN 1.3 1.5 mA
Input UVLO Threshold Rising UVLORising 3.80 4.0 4.40V VEN Input UVLO Threshold Hysteresis 150 mV
Soft-start Current VSS = 0V 6 uA CSS = 0.1uF Soft-start Period 13 mS
Hysteresis =25°C 155 °C Thermal Shutdown Temperature*
Note: * Guaranteed by design, not tested
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AP3469
3A 27V Synchronous Buck Converter
Application Description
AP3469 application circuit, 3.3V/3A output. AP3469 application circuit, 3.3V/3A output with EN function Note: C2 is required for separate EN signal.
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AP3469
3A 27V Synchronous Buck Converter
Output Voltage Setting
that is dependent on the inductance value: higher inductance reduces the peak-to-peak ripple current. The trade off for high inductance value is the increase in inductor core size and series
resistance, and the reduction in current handling capability. In general, select an inductance value
L based on the ripple current requirement:
VOUT•(V IN−VOUT)L=(2) VINfSWIOUTMAXKRIPPLE
where VIN is the input voltage, VOUT is the output voltage, fSW is the switching frequency, IOUTMAX is
the maximum output current, and KRIPPLE is the ripple factor. Typically, choose KRIPPLE = ~ 30% to
correspond to the peak-to-peak ripple current being ~30% of the maximum output current.
With this inductor value, the peak inductor current is IOUT • (1 + KRIPPLE / 2). Make sure that this
peak inductor current is less than the upper switch current limit. Finally, select the inductor core
size so that it does not saturate at the current limit. Typical inductor values for various output
voltages are shown in Table 2. VOUT 1.0V 1.2V1.5V1.8V2.5V3.3V5V9V L 4.7uH 4.7uH10uH10uH10uH10uH10uH22uH Table 2. Typical Inductor Values
VOUT R1 FB R2 Figure1. Output Voltage Setting
Figure 1 shows the connections for setting the output voltage. Select the proper ratio of the two
feedback resistors R1 and R2 based on the output voltage. Typically, use R2 ≈ 10KΩ and
determine R1 from the following equation:
Table1－ Recommended Resistance Values
(1)
R1 R2 VOUT
1.0V 1.0 KΩ 12 KΩ
1.2V 3.0 KΩ 10 KΩ
KΩ 10 KΩ 1.8V 9.53 2.5V 16.9 KΩ 10 KΩ
3.3V 26.1 KΩ 10 KΩ
KΩ 10 KΩ 5V 44.2 12V 121 KΩ 10 KΩ
Inductor Selection
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AP3469
3A 27V Synchronous Buck Converter
Input Capacitor
The input capacitor needs to be carefully selected to maintain sufficiently low ripple at the supply
input of the converter. A low ESR Electrolytic (EC) capacitor is highly recommended. Since large
current flows in and out of this capacitor during switching, its ESR also affects efficiency.
When EC cap is used, the input capacitance needs to be equal to or higher than 100uF.The RMS
ripple current rating needs to be higher than 50% of the output current. The input capacitor should
be placed close to the VIN and GND pins of the IC, with the shortest traces possible. The input
capacitor can be placed a little bit away if a small parallel 0.1uF ceramic capacitor is placed right
next to the IC.
When Vin is >15V, pure ceramic Cin (* no EC cap) is not recommended. This is because the
ESR of a ceramic cap is often too small, Pure ceramic Cin will work with the parasite inductance of
the input trace and forms a Vin resonant tank. When Vin is hot plug in/out, this resonant tank will
boost the Vin spike to a very high voltage and damage the IC.
Output Capacitor
The output capacitor also needs to have low ESR to keep low output voltage ripple. In the case of
ceramic output capacitors, RESR is very small and does not contribute to the ripple. Therefore, a
lower capacitance value can be used for ceramic capacitors. In the case of tantalum or electrolytic
capacitors, the ripple is dominated by RESR multiplied by the ripple current. In that case, the output
capacitor is chosen to have sufficiently low ESR.
For ceramic output capacitors, typically choose two capacitors of about 22uF. For tantalum or
electrolytic capacitors, choose a capacitor with less than 50m
Optional Schottky Diode
During the transition between high-side switch and low-side switch, the body diode of the low side power MOSFET conducts the inductor current. The forward voltage of this body diode is high. An
optional Schottky diode may be paralleled between the SW pin and GND pin to improve overall
efficiency. Table 3 lists example Schottky diodes and their Manufacturers.
Table 3Diode Selection Guide
Vin max
<20V
<20V >20V >20V
Part Number
B130 SK13 B140 SK14
Voltage/Current Rating 30V, 1A 30V, 1A 40V,1A 40V, 1A
Vendor
Lite-on semiconductor corp.Lite-on semiconductor corpLite-on semiconductor corpLite-on semiconductor corp.
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AP3469
3A 27V Synchronous Buck Converter
CCOMP2 is needed only for high ESR output capacitor
Figure 2. Stability Compensation
The feedback loop of the IC is stabilized by the components at the COMP pin, as shown in Figure
2. The DC loop gain of the system is determined by the following equation:
0.925V(4) AVDC=AVEAGCOMP IOUT
The dominant pole P1 is due to CCOMP1
GEA fP1= (5) 2πAVEACCOMP1
Stability Compensation
fP2(6)
The first zero Z1 is due to RCOMP and C
1 fZ1=(7) 2πRCOMPCCOMP1
And finally, the third pole is due to RCOMP and CCOMP2 (if CCOMP2 is used):
1fP3= (8) 2πRCOMPCCOMP2
The following steps should be used to compensate the IC:
STEP1. Set the crossover frequency at 1/10 of the switching frequency via RCOMP:
2πVOUTCOUTfSW (9) RCOMP=
10GEAGCOMP•0.925V
But limit RCOMP to 10KΩ maximum. More than 10 KΩ is easy to cause overshoot at power on.
IOUT =2πVOUTCOUT
The second pole P2 is the output pole:
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AP3469
3A 27V Synchronous Buck Converter
STEP2. Set the zero fZ1 at 1/4 of the crossover frequency. If RCOMP is less than 10KΩ, the
0.637
CCOMP1=(F) (10)
RCOMP×fc
STEP3. If the output capacitor’s ESR is high enough to cause a zero at lower than 4 times the crossover frequency, an additional compensation capacitor CCOMP2 is required. The condition for using CCOMP2 is:
π×COUT ×RESR×fs≥1 (11)
And the proper value for CCOMP2 is:
CR
CCOMP2=OUTESRCOUT(12) RCOMP Though CCOMP2 is unnecessary when the output capacitor has sufficiently low ESR, a small value CCOMP2 such as 100pF may improve stability against PCB layout parasitic effects.
equation for CCOMP is:
Table 4 Component Selection Guide for Stability Compensation
Vin Range
(V) 5 – 12 5 – 15 5 – 15 5 – 15 5 – 15 7 – 15 5 – 12 5 – 15 5 – 23 5 – 27 5 – 27 7 – 27
Vout, (V) 1.0 1.2 1.8 2.5 3.3 5 1.0 1.2 1.8 2.5 3.3 5
Cout
Rcomp,Ccomp,Ccomp2, Inductor, (kΩ) (nF) (pF) (uH)
2.4 6.8 none 4.7 22uF x2Ceramic
470uF/ 6.3V/ 120mΩ
3 6.2 none
3 none 6.2
8 2.2 none 10 2.2 none 10 2.2 none
10 10 680
4.7 10 10 10 10
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AP3469
3A 27V Synchronous Buck Converter
Figure 3. Load Transient Testing VS Compensation Value
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AP3469
3A 27V Synchronous Buck Converter
Typical Performance Characteristics (Vin=12V, Io=0 mA, Temperature = 25 degree C, unless otherwise specified)
Light Load Operation (No load) Heavy Load Operation (3A Load)
Vin=12V, Iin=8.2 mA, Vout=3,3V Vin=12V, Vout=3,3V
Startup Vin=12V, Vout=3.3V, Iout=1A
through Vin. through Enable.
Short Circuit Protection Vin=12V
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AP3469
3A 27V Synchronous Buck Converter
EFFICIENCY vs LOAD CURRENT (Vout=3.3V) 98.094.090.086.082.078.074.070.066.062.0Vin=5EFFICIENCY (%)Vin=12V Vin=23 V 00.511.522.5LOAD CURRENT (A)33.53.313.30753.3053.30253.33.29753.2953.29253.293.28753.2853.28253.283.2775OUTPUT VOLTAGE vsAMBIENT TEMPERATURE OUTPUT VOLTAGE (3.3V) vs LOAD CURRENT3.4OUTPUT VOLTAGE, (V)3.3753.353.3253.33.2753.253.2253.2Vin=23 V Vin=12V Vin=500.511.522.533.54LOAD CURRENT, (A)
350345340335330325320315310SWITCHING FREQUENCY vsAMBIENT TEMPERATUREOUTPUT VOLTAGE, (V)SWITCHING FREQUENCY,(kHz)-50-30-101030507090110130150-50-30-101030507090110130150AMBIENT TEMPERATURE, (C)AMBIENT TEMPERATURE, (C)
SWITCHES RdsON vs JUNCTION TEMPERATURE (Vin=12V)0.130.12SWITCHES RdsON0.110.10.090.080.070.061030507090110130150JUNCTION TEMPERATURE (C)170
100JUNCTION TEMPERATURE, CJUNCTION TEMPERATURE vs LOAD CURRENT (Ta=25C)908070605040302000.511.522.533.5LOAD CURRENT, AVin=23VVin=12VVin=5V
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AP3469
3A 27V Synchronous Buck Converter
Marking Information
AP3469
V YYWW UZ
Internal Code Date code
YY：Year(09=2009,10=2010,11=2011,12=2012...)
WW：Week(01~53) Output Voltage Blank：ADJ
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AP3469
3A 27V Synchronous Buck Converter
Package Information (All Dimensions in mm)
ESOP-8L
Dimensions In Millimeters Symbol
Min Max A 1.35 1.75 A1 0.05 0.25 B 0.31 0.51 C 0.17 0.25 D 4.70 5.10 E 3.70 4.10 e 1.27BSC H 5.80 6.20 L 0.40 1.27 θ 0˚ 8˚
D1 3.10REF E1 2.21REF
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AP3469
3A 27V Synchronous Buck Converter
Tape/Reel
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AP3469
3A 27V Synchronous Buck Converter
IPC/JEDEC J-STD-020D.1 Moisture Sensitivity Levels Table SOAK REQUIREMENTS 1
Accelerated Equivalent
eV eV
Standard FLOOR LIFE 0.40-0.480.30-0.39 TIME TIME TIME
TIME CONDITION CONDITION LEVEL CONDITION (hours)(hours)(hours)
≤30 °C /85% 168 85 °C /85% 1 Unlimited NA NA NA RH +5/-0 RH
≤30 °C /60% 168 85 °C /60%
2 1 year NA NA NA RH +5/-0 RH
2
30 °C /60% 120 168 ≤30 °C /60% 696
60 °C/ 60% RH 2a 4 weeks +5/-0 RH -1/+0 -1/+0 RH
2
30 °C /60% 40 52 ≤30 °C /60% 192
60 °C/ 60% RH 3 168 hours +5/-0 RH -1/+0 -1/+0 RH
30 °C /60% 20 24 ≤30 °C /60% 962
60 °C/ 60% RH 4 72 hours RH +2/-0 +0.5/-0 +0.5/-0 RH
30 °C /60% 15 20 ≤30 °C /60% 722
60 °C/ 60% RH 5 48 hours +2/-0 RH +0.5/-0 +0.5/-0 RH
2 30 °C /60% 10 13 ≤30 °C /60% 48
60 °C/ 60% RH 5a 24 hours +2/-0 RH +0.5/-0 +0.5/-0 RH Time on Label ≤30 °C /60% 30 °C /60%
6 TOL NA NA NA RH (TOL) RH
reflow), should be established with the ‘‘standard’’ soak conditions. Alternatively, if the known activation energy for moisture diffusion
of the package materials is in the range of 0.40 - 0.48 eV or 0.30 - 0.39 eV, the ‘‘accelerated equivalent’’ may be used. Accelerated soak
times may vary due to material properties (e.g .mold compound, encapsulant, etc.). JEDEC document JESD22-A120 provides a method for determining the diffusion coefficient.
Note 2: The standard soak time includes a default value of 24 hours for semiconductor manufacturer’s exposure time (MET) between bake and
bag and includes the maximum time allowed out of the bag at the distributor’s facility. If the actual MET is less than 24 hours the soak
time may be reduced. For soak conditions of 30 °C/60% RH, the soak time is reduced by 1 hour for each hour the MET is less than 24
hours. For soak conditions of 60 °C/60% RH, the soak time is reduced by 1 hour for each 5 hours the MET is less than 24 hours. If the
actual MET is greater than 24 hours the soak time must be increased. If soak conditions are 30 °C/60% RH, the soak time is increased 1
hour for each hour that the actual MET exceeds 24 hours. If soak conditions are 60 °C/60% RH, the soak time is increased 1 hour for
each 5 hours that the actual MET exceeds 24 hours.
Note 1: CAUTION - To use the ‘‘accelerated equivalent’’ soak conditions, correlation of damage response (including electrical, after soak and
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