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AP1520
PWM CONTROL 2A STEP-DOWN CONVERTER
Features
* * * * * * * * * * Input Voltage: 3.6V to 23V Output Voltage: 0.8V to VCC Duty Ratio: 0% to 100% PWM Control Oscillation Frequency: 300kHz typ. Current Limit, Enable Function Thermal Shutdown Function Built-in Internal SW P-Channel MOS SOP-8L Pb-Free Package SOP-8L: Available in "Green" Molding Compound (No Br, Sb) Lead Free Finish/ RoHS Compliant (Note 1)
General Description
AP1520 consists of step-down switching regulator with PWM control. These devices include a reference voltage source, oscillation circuit, error amplifier and internal PMOS. AP1520 provides low-ripple power, high efficiency and excellent transient characteristics. The PWM control circuit is able to vary the duty ratio linearly from 0 up to 100%. This converter also contains an error amplifier circuit. An enable function, an over current protection and a short circuit protection are built inside, and when OCP or SCP happens, the operation frequency will be reduced from 300kHz to 30kHz. Also, an internal compensation block is built in to minimum external component count. With the addition of an internal P-channel Power MOS, a coil, capacitors, and a diode connected externally, these ICs can function as step-down switching regulators. They serve as ideal power supply units for portable devices when coupled with the SOP- 8L package, providing such outstanding features as low current consumption. Since this converter can accommodate an input voltage up to 23V, it is also suitable for the operation via an AC adapter.
Applications
* * * * * * * * * PC Motherboard LCD Monitor Graphic Card DVD-Video Player Telecom Equipment ADSL Modem Printer and other Peripheral Equipment Microprocessor Core Supply Networking Power Supply
Typical Application Circuit
L1 22uH CC Optional FB VSS D1 RB 1.3K RA 6.8K
VIN ROCSET COCSET 3K Option CIN 680uF CVcc 0.1uF REN 100K CEN 0.1uF
Vcc
Output
VOUT
AP1520
OCSET EN
+ -
C
+ -
COUT 470uF
0.1uF
Note: VOUT = VFB x (1+RA/RB) RB=0.7K~5K ohm
AP1520 Rev. 5 DS31174
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AP1520
PWM CONTROL 2A STEP-DOWN CONVERTER
Ordering Information
AP1520 S X - 13 Package S : SOP-8L Lead Free L : Lead Free G : Green Packing 13 : Tape & Reel
Device
Lead-free
AP1520SL-13 AP1520SG-13
Notes:
Package Code S S
Packaging (Note 2) SOP-8L SOP-8L
13" Tape and Reel Quantity Part Number Suffix 2500/Tape & Reel -13 2500/Tape & Reel -13
1. EU Directive 2002/95/EC (RoHS). All applicable RoHS exemptions applied. Please visit our website at http://www.diodes.com/products/lead_free.html. 2. Pad layout as shown on Diodes Inc. suggested pad layout document AP02001, which can be found on our website at http://www.diodes.com/datasheets/ap02001.pdf.
Pin Assignments
( Top View ) FB 1 EN 2 AP1520 OCSET 3 VCC 4 SOP-8L 6 5 Output Output 8 7 Vss Vss
Pin Descriptions
Pin Name FB EN OCSET VCC Output VSS Pin No. 1 2 3 4 5, 6 7, 8 Description Feedback pin Enable Input pin H: Normal operation (Step-down operation) L: Step-down operation stopped (All circuits deactivated) Add an external resistor to set max output current IC power supply pin Switch Pin. Connect external inductor/diode here. Minimize trace area at this pin to reduce EMI GND Pin
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AP1520
PWM CONTROL 2A STEP-DOWN CONVERTER
Block Diagram
Output Oscillation Circuit Vcc PWM-Switched Control Circuit Thermal Shutdown VEN 100uA Vss + FB Reference Voltage Source with Soft Start
EN
OCSET
Absolute Maximum Ratings
Symbol VCC VFB VEN VOUT PD TOP TST Parameter VCC Pin Voltage Feedback Pin Voltage EN Pin Voltage Switch Pin Voltage Power Dissipation Operating Junction Temperature Range Storage Temperature Range Rating VSS - 0.3 to VSS + 25 VSS - 0.3 to VCC VSS - 0.3 to VIN + 0.3 VSS - 0.3 to VIN + 0.3 Internally limited -20 to +125 -65 to +150 Unit V V V V mW o C o C
Caution: The absolute maximum ratings are rated values exceeding which the product could suffer physical damage. These values must therefore not be exceeded under any conditions.
Recommended Operating Conditions
Symbol VIN IOUT TA Parameter Input Voltage Output Current Operating Ambient Temperature Min 4 0 -25 Max 23 1.8 85 Unit V A o C
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AP1520
PWM CONTROL 2A STEP-DOWN CONVERTER
Electrical Characteristics
Symbol Parameter VFB Feedback Voltage IFB Feedback Bias Current ISW Switch Current Current Consumption During ISHDN Power off VOUT Line Regulation /VIN VOUT Load Regulation /VOUT fOSC Oscillation Frequency Frequency of Current Limit or fOSC1 Short Circuit Protect VIH EN Pin Input Voltage VIL IENH EN Pin Input Leakage Current IENL IOCSET OCSET Pin Bias Current TSS Soft-Start Time TSHDN Thermal shutdown threshold THYS Thermal shutdown hysteresis RDSON Internal MOSFET RDSON EFFI JA JC
Notes:
(VIN = 12V, Ta = 25C, unless otherwise specified)
Conditions IOUT = 0.1A IOUT = 0.1A -VEN = 0V VIN = 5V~23V IOUT = 0.1 to 2A Measure waveform at SW pin Measure waveform at SW pin Evaluate oscillation at SW pin Evaluate oscillation stop at SW pin ----VIN = 5V, VFB = 0V VIN = 12V, VFB = 0V VIN = 12V, VOUT = 5V IOUT = 2A SOP-8L (Note 3) SOP-8L (Note 3)
Min 0.784 2.5 240 10 2.0 75 0.3 -
Typ. 0.8 0.1 10 1 0.2 300 20 -10 90 1 150 55 110 70 92 134 22
Max 0.816 0.5 2 0.5 360 0.8 105 2 150 100 -
Unit V A A A % % kHz kHz V A A A ms C C m %
o
Efficiency Thermal Resistance Junction-to-Ambient Thermal Resistance Junction-to-Case
C/W C/W
o
3. Test condition: Device mounted on FR-4 substrate 2oz copper, minimum recommended pad layout, single side. For better thermal performance, please arrange larger copper pad of layout for heatsink.
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AP1520
PWM CONTROL 2A STEP-DOWN CONVERTER
Typical Performance Characteristics
AP1520 Vin vs. Frequency (Vout=3.3V; Iout=0.2A)
350 345 340
330 325 320 315 310
3.6 4 6 8 10 12 14 16 18
FB (V)
335
0.84 0.83 0.82 0.81 0.80 0.79 0.78 0.77 0.76 0.75 0.74 3.6
AP1520 Vin vs. FB (Vout=3.3V; Iout=0.2A)
Fosc (kHz)
Vin (V)
4
6
8
Vin (V)
10
12
14
16
18
3.40 3.35
AP1520 Line Regulation (Vin=12V; Iout=0.2A)
Vout (V)
3.25 3.20 3.15 3.10
Vout (A)
3.30
5.10 5.09 5.08 5.07 5.06 5.05 5.04 5.03 5.02 5.01 5.00 0.0
AP1520 Load Regulation (Vin=12V)
3.6
4
6
8
Vin (V)
10
12
14
16
18
1.0
2.0
3.0
4.0
Iout (A)
AP1520 Efficiency
100 90 80
Efficiency (%)
70 60 50 40 30 20 10 0 0.0 0.5 1.0 1.5 2.0 Vout:5.0V Vout:3.3V
Iout (A)
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AP1520
PWM CONTROL 2A STEP-DOWN CONVERTER
Typical Performance Characteristics
AP1520 Vout Ripple ( Vin = 12V; Vout = 3.3V; Iout = 0.1A )
(Continued)
AP1520 Vout Ripple ( Vin = 12V; Vout = 3.3V; Iout = 2A )
Test Circuit
Oscillation open VCC OUTPUT OCSET
A
FB
open
A +
VCC
OUTPUT
FB
EN
VSS
-
OCSET EN
VSS
Enable function test
Feedback function test
VCC
+ -
OUTPUT
FB
OCSET EN VSS
+ V
Operation function test
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AP1520
PWM CONTROL 2A STEP-DOWN CONVERTER
Functional Description
PWM Control The AP1520 is a DC/DC converter that employs pulse width modulation (PWM) scheme. Its pulse width varies in the range of 0% to 99%, based on the output current loading. The output ripple voltage caused by the PWM high frequency switching can easily be reduced through an output filter. Therefore, this converter provides a low ripple output supply over a broad range of input voltage & output current loading Under Voltage Lockout The under voltage lockout circuit of the AP1520 assures that the high-side MOSFET driver remains in the off state whenever the supply voltage drops below 3.3V. Normal operation resumes once VCC rises above 3.5V. Current Limit Protection The current limit threshold is set by external resistor ROCSET connected from VCC supply to OCSET pin. The internal sink current IOCSET (90A typical) across this resistor sets the voltage at OCSET pin. When the PWM voltage is less than the voltage at OCSET, an over-current condition is triggered. The current limit threshold is given by the following equation: Inductor Selection For most designs, the operation range with inductors is from 22H to 33H. The inductor value can be derived from the following equation:
L=
VIN - VOUT VOUT x fs x I VIN
Where IL is inductor Ripple Current. Large value inductors lower ripple current and small value inductors result in high ripple current. Choose inductor ripple current approximately 15% of the maximum load current 2A, IL=0.30A. The DC current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation (2A+0.15A). Input Capacitor Selection This capacitor should be located close to the IC using short leads and the voltage rating should be approximately 1.5 times the maximum input voltage. The RMS current rating requirement for the input capacitor of a buck regulator is approximately 12 the DC load current. A low ESR input capacitor sized for maximum RMS current must be used. A 470F low ESR capacitor for most applications is sufficient. Output Capacitor Selection The output capacitor is required to filter the output voltage and provides regulator loop stability. The important capacitor parameters are the 100KHz Equivalent Series Resistance (ESR), the RMS ripples current rating, voltage rating and capacitance value. For the output capacitor, the ESR value is the most important parameter. The output ripple can be calculated from the following formula.
IPEAK x R DS(ON) = IOCSET x R OCSET
(I) IPEAK > IOUT(MAX) + 2
where,
I =
VIN - VOUT VOUT x fs x L VIN
V RIPPLE = IL x ESR
The bulk capacitor's ESR will determine the output ripple voltage and the initial voltage drop after a high slew-rate transient. An aluminum electrolytic capacitor's ESR value is related to the capacitance and its voltage rating. In most case, higher voltage electrolytic capacitors have lower ESR values. Most of the time, capacitors with much higher voltage ratings may be needed to provide the low ESR values required for low output ripple voltage. PCB Layout Guide If you need low TC & TJ or large PD (Power Dissipation), The dual SW pins (5& 6) and Vss pins(7& 8)on the SOP-8L package are internally connected to die pad, The evaluation board should be allowed for maximum copper area at output (SW) pins. 1. 2. 3. 4. Connect FB circuits as closely as possible and keep away from inductor flux for pure VFB. Connect input capacitor to Vcc and Vss pin as closely as possible to get good power filter effect. Connect ROCSET to Vcc and OCSET pin as closely as possible. Connect ground side of the input capacitor & Schottky & output capacitor as closely as possible and use ground plane for best performance.
IPEAK is the output peak current; RDS (ON) is the MOSFET ON resistance; fS is the PWM frequency (300KHz typical). Also, the inductor value will affect the ripple current I. The above equation is recommended for input voltage range of 5V to 18V. For input voltage lower than 5V or ambient temperature over 100C, higher ROCSET is recommended.
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AP1520
PWM CONTROL 2A STEP-DOWN CONVERTER
Marking Information
(1) SOP-8L
( Top View )
8 5
Logo Part Number AP1520 YY WW X X
1 4
L : Lead Free G : Green YY : Year : 08, 09,10~ WW : Week : 01~52; 52 represents 52 and 53 week X : Internal Code
Package Information
(1) Package type: SOP-8L
( All Dimensions in mm )
3.85/3.95
5.90/6.10
0.10/0.20
0.254 0.62/0.82
Gauge Plane Seating Plane
Detail "A"
7~9 1.30/1.50 1.75max. 0.15/0.25
0.35max. 45
7~9
Detail "A"
0/8
1.27typ 4.85/4.95
0.3/0.5
8x-0.60 5.4 6x-1.27 8x-1.55
Land Pattern Recommendation (Unit: mm)
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AP1520
PWM CONTROL 2A STEP-DOWN CONVERTER
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