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AP1539
18V 4A 300KHz BUCK CONVERTER
Features
* * * * * * * * * * Input voltage: 3.6V to 18V Output voltage: 0.8V to VCC Output current: up to 4A Duty ratio: 0% to 99% PWM control Oscillation frequency: 300KHz typ. Soft-start like, Current limit and Enable function Thermal Shutdown function Built-in internal SW P-channel MOS SOP-8L-DEP: Available in "Green" Molding Compound (No Br, Sb) Lead Free Finish / RoHS Compliant (Note 1)
General Description
AP1539 consists of step-down switching regulator with PWM control. These devices include a reference voltage source, oscillation circuit, error amplifier, internal PMOS. AP1539 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 99%. This converter also contains an error amplifier circuit as well as a soft-start circuit that prevents overshoot at startup. An enable function, an over current protect function and a short circuit protect function are built inside, and when OCP or SCP happens, the operation frequency will be reduced from 300KHz to 50KHz. 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-DEP mini-package, providing such outstanding features as low current consumption. Since this converter can accommodate an input voltage up to 18V, 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
Ordering Information
AP 1539 SDP G - 13
Package SDP : SOP-8L-DEP Green G : Green Packing
13 : Tape & Reel
Device AP1539SDPG-13
Notes:
Package Code SDP
Packaging (Note 2) SOP-8L-DEP
13" Tape and Reel Part Number Suffix Quantity 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.
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AP1539
18V 4A 300KHz BUCK CONVERTER
Pin Assignments
SOP-8L-DEP (Dual Exposed Pads)
( Top View ) Vss Vss Output Output
FB
1
8
1
EN 2 OCSET 3 7 6
2
VCC 4
(Note 3)
5
Notes:
3. Exposed pad 1 is connected to VSS and exposed pad 2 is connected to Output. The board layout for exposed pads needs to be considered to avoid short circuit.
Pin Descriptions
Pin Name FB Pin No. 1 Description Feedback pin Power-off 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
EN
2
OCSET VCC Output VSS
3 4 5, 6 7, 8
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AP1539
18V 4A 300KHz BUCK CONVERTER
Block Diagram
Output Oscillation Circuit Vcc PWM-Switched Control Circuit Thermal Shutdown VEN 90uA Vss
+
Reference Voltage Source with Soft Start
FB
-
EN
OCSET
Absolute Maximum Ratings
Symbol ESD HBM ESD MM VCC VFB VEN VOUT PD TJ TST Parameter Human Body Model ESD Protection Machine Model ESD Protection VCC Pin Voltage Feedback Pin Voltage EN Pin Voltage Switch Pin Voltage Power Dissipation Operating Junction Temperature Range Storage Temperature Range Rating 7 450 VSS - 0.3 to VSS + 20 VSS - 0.3 to VCC VSS - 0.3 to VCC VSS - 0.3 to VCC Internally limited -40 to +125 -65 to +150 Unit KV V V V V V mW
o o
C 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
Notes:
Parameter Input Voltage (Note 4) Output Current Operating Ambient Temperature
Min 3.6 0 20
Max 18 4 +85
Unit V A o C
4. For the operations in low input voltage, AP1539 can tolerate down to 3.6V but max output current loading will be less than 4A. For nominal applications in such low input voltage range, especially lower than 4V, a higher ROCSET with larger heat sink is recommended.
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AP1539
18V 4A 300KHz BUCK CONVERTER
Electrical Characteristics
(VIN = 12V, TA = 25C, unless otherwise specified) Symbol Parameter Conditions VFB Feedback Voltage IOUT = 0.1A IFB Feedback Bias Current IOUT = 0.1A Current Consumption During ISHDN VEN = 0V Power Off VOUT Line Regulation / VIN VOUT Load Regulation / VOUT fOSC Oscillation Frequency Frequency of Current Limit or fOSC1 Short Circuit Protection VIH EN Pin Input Voltage VIL ISH EN Pin Input Leakage Current ISL IOCSET OCSET Pin Bias Current RDS(ON) Internal MOSFET RDS(ON) EFFI TSHDN THYS JC
Notes:
Min 0.784 240 2.0 75 -
Typ. 0.8 0.1 10 1 0.2 300 50 20 -10 90 90 50 92 150 55 26
Max 0.816 0.5 2 0.5 400 0.8 105 -
Unit V A A % % KHz KHz V A A A m % C C
o
VIN = 5V~18V IOUT = 0.1 to 4A Measure waveform at SW pin Measure waveform at SW pin Evaluate oscillation at SW pin Evaluate oscillation stop at SW pin EN Pin High EN Pin Low -VIN = 5V, VFB = 0V VIN = 12V, VFB = 0V VIN = 12V, VOUT = 5V IOUT = 4A
Efficiency
Thermal shutdown threshold Thermal shutdown hysteresis Thermal Resistance SOP-8L-DEP (Note 5) Junction-to-Case
C/W
5. Test condition for SOP-8L-DEP: Devices mounted on 2oz copper, minimum recommended pad layout on top & bottom layer with thermal vias, double sided FR-4 PCB.
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AP1539
18V 4A 300KHz BUCK CONVERTER
Typical Application Circuit
VOUT = 5V/4A RA 6.8K
VIN ROCSET COCSET 3.9K Option C IN 470uF CVcc 0.1uF R EN 100K CEN 0.1uF
Vcc
Output
L1 22uH Cc Option (Note 8)
AP 1539
OCSET EN FB V SS
+ -
C
+ -
COUT 470uF (Note 7)
0.1uF
D1 (Note 6)
RB 1.3K
VOUT =V FB x (1+ R A /RB ) R B = 0.7K~5 K ohm
Notes: 6. Suggested DIODES Power Schottky P/N: B540 series or PDS540. 7. Suggested COUT for VOUT < 1V; 680F. 8. Typical feedback compensation (Cc): 5600pF.
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AP1539
18V 4A 300KHz BUCK CONVERTER
Typical Performance Characteristics
VIN vs. Frequency
326 324 322 320 FOSC (kHz) 318 316 314 312 310 308 306 0 2 4 6 8 10 V IN (V) 12 14 16 18 (V OUT = 3.3V, IOUT = 0.2A)
0.820 0.815 0.810 V FB (V) 0.805 0.800 0.795 0.790 0.785 0.780 0 2 4 6 8 10 V IN (V) 12 14 16 18
VIN vs. VFB
(V OUT = 3.3V, IOUT = 0.2A)
Line Regulation
3.40 3.35 3.30 V OUT (V) V OUT (V) 3.25 3.20 3.15 3.10 3.05 3.00 0 2 4 6 8 10 V IN (V) 12 14 16 18 (V OUT = 3.3V, IOUT = 0.2A) 3.35 3.34 3.33 3.32 3.31 3.30 3.29 3.28 3.27 3.26 3.25 0.0 0.5
Load Regulation
(V IN = 12V)
1.0
1.5
2.0 2.5 IOUT (A)
3.0
3.5
4.0
Efficiency
100 90 80 Efficiency (%) 70 60 50 40 30 20 10 0 0.0 1.0 2.0 IOUT (A) VOUT=3.3V VOUT=5V 3.0 4.0 (V IN = 12V)
Switch Current Limit
7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 0 2 4 (TA = 25 )
Current Limit (A)
ROCSET=6.8k ROCSET=4.7k 6 8 10 V IN (V) 12 14 16 18
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AP1539
18V 4A 300KHz BUCK CONVERTER
Typical Performance Characteristics
Current Limit vs. Temperature
(V IN = 12V, ROCSET = 6.8k) 9.0 8.5 8.0 Current Limit (A) 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 -25 0 25 50 75 Ambient Temperature (C) 100
(Continued)
VOUT Ripple (VIN=12V, VOUT=3.3V, IOUT=0.1A)
VOUT Ripple (VIN=12V, VOUT=3.3V, IOUT=4.0A)
Load Transient Response (VIN =12V, VOUT =3.3V, IOUT =0.1~4A)
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AP1539
18V 4A 300KHz BUCK CONVERTER
Test Circuit
Oscillation open VCC OUTPUT FB open
A
VCC
OUTPUT
FB
OCSET
A
+
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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AP1539
18V 4A 300KHz BUCK CONVERTER
Functional Descriptions
PWM Control The AP1539 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 AP1539 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 (90uA 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 operates with inductors of 22H to 33H. The inductor value can be derived from the following equation:
L=
(VIN - VOUT )TON
2 x I L x f osc
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 4A, IL=0.6A. 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 (4A+0.3A). 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 RDS(ON) = IOCSET x R OCSET
IPEAK
where,
> IOUT (MAX) +
VIN - VOUT FSxL
( I) 2
I =
x
VOUT VIN
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, higher than 18V or ambient temperature over 100C, higher ROCSET is recommended. The recommended minimum ROCSET value is summarized below: VOUT (V) 0.8 1.0 1.2 1.8 2.5 3.3 5.0 VIN (V) 12V 3.9K 3.9K 3.9K 3.9K 3.9K 3.9K 3.9K
VRIPPLE = I L 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. Connect FB circuits (R1, R2, C1) as closely as possible and keep away from inductor flux for pure VFB. 2. Connect C3 to Vcc and Vss pin as closely as possible to get good power filter effect. 3. Connect R4 to Vcc and OCSET pin as closely as possible. 4. Connect ground side of the C2 & D1 & C4 as closely as possible and use ground plane for best performance.
5V 6.8K 6.8K 6.8K 6.8K 6.8K 6.8K N/A
18V 4.7K 4.7K 4.7K 4.7K 4.7K 4.7K 5.6K
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AP1539
18V 4A 300KHz BUCK CONVERTER
Functional Description
(Continued)
Keep the gap of exposed pads from short circuit. Top Side Layout Guide
Recommended exposed-pads gap: 30~40mil (0.75~1mm)
Use vias to conduct the heat into the backside of PCB layer. The heat sink at output (SW) pins should be allowed for maximum solder-painted area. Bottom Side Layout Guide
Brown: IC exposed pads. Red: recommended layout. Reference pads layout dimension: Output: 90 x 50 mil Vss: 90 x 60 mil
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AP1539
18V 4A 300KHz BUCK CONVERTER
Functional Description
VIN R4 C2 R5 C6 C7 Option
(Continued)
Vcc L1 VOUT R1
Output
AP1539
OCSET EN V SS FB
C1 Option
+ -
C8
+ -
C4
C3
D1
R2
Figure: Layout numbering comparison.
Marking Information
(1) SOP-8L-DEP
( Top View )
8 5
Logo Part No. AP1539 YY WW X X E
1 4
G : Green YY : Year : 08, 09,10~ WW : Week : 01~52; 52 represents 52 and 53 week X : Internal Code SOP-8L-DEP
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AP1539
18V 4A 300KHz BUCK CONVERTER
Package Information
(1) Package type: SOP-8L-DEP
(All Dimensions in mm)
1.8 1.65
8 8 5
C L
1.8 0.95 8x-1.55
EXPOSED PAD
5
3.85/3.95
5.90/6.10
5.4
2.35
1.0
C L
Top View
1 4
0.3/0.5
9(all side)
1
4
Land Pattem Recommendation (Unit: mm)
0.35Typ.
45
8x-0.60
6x-1.27
4.85/4.95 0.685 2.05Typ.
1 4
EXPOSED PAD
0.254
Gauge Plane Seating Plane
1.15Typ.
2.15Typ.
0.9
C L
0/0.13
0.20
0.15/0.25
0 /
R0
8
.1
1.63Max.
1.4/1.5
1.27Typ.
View"A"
0.62/0.82 View"A"
8
5
1.7
C L
1.7
0.713
Bottom view
IMPORTANT NOTICE Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other changes without further notice to any product herein. Diodes Incorporated does not assume any liability arising out of the application or use of any product described herein; neither does it convey any license under its patent rights, nor the rights of others. The user of products in such applications shall assume all risks of such use and will agree to hold Diodes Incorporated and all the companies whose products are represented on our website, harmless against all damages. LIFE SUPPORT Diodes Incorporated products are not authorized for use as critical components in life support devices or systems without the expressed written approval of the President of Diodes Incorporated.
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