AP1534SG-13

AP1534 PWM CONTROL 2A STEP-DOWN CONVERTER Description Pin Assignments AP1534 consists of step-down switching regulator with PWM control. These devices include a reference voltage source, oscillation circuit, error amplifier, internal PMOS. (Top View) 8 VSS FB 1 AP1534 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 minimize external component count. EN 2 AP1534 7 VSS OCSET 3 6 Output VCC 4 5 Output SO-8 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 SO-8 mini-packages, 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. Features Applications • • • • • • • • • • Input voltage: 3.6V to 18V Output voltage: 0.8V to VCC Duty ratio: 0% to 99% PWM control Oscillation frequency: 300KHz typical Current limit, Enable function Thermal Shutdown function Built-in internal SW P-channel MOS SO-8: Available in “Green” Molding Compound (No Br, Sb) Lead Free Finish/RoHS Compliant (Note 1) Notes: • • • • • • • PC Motherboard LCD Monitor Graphic Card DVD-Video Player Telecom Equipment ADSL Modem Printer and other Peripheral Equipment Microprocessor Core Supply 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. Typical Application Circuit    22uH L1 Vcc V IN R OCSET COCSET 5.6K Option CIN CVcc 0.1uF REN 100K CC Optional AP1534 RA 6.8K + FB OCSET 470uF VOUT =5V/2A Output V SS EN CEN 0.1uF D1 B240A (Note 2) - + C 0.1uF - COUT 470uF RB 1.3K Note: VOUT = VFB x (1+RA /RB) RB = 0.7K~5KΩ Notes: 2. Suggested DIODES Power Schottky P/N: B240/B340 series. AP1534 Document number: DS31314 Rev. 6 - 2 1 of 9 www.diodes.com April 2011 © Diodes Incorporated AP1534 PWM CONTROL 2A STEP-DOWN CONVERTER Pin Descriptions Pin Name Pin No. Description FB 1 EN 2 OCSET 3 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 VCC 4 IC power supply pin Output 5, 6 Switch Pin. Connect external inductor/diode here. Minimize trace area at this pin to reduce EMI VSS 7, 8 GND Pin Functional Block Diagram Output Oscillation Circuit Reference Voltage Source Vcc + PWM-Switched Control Circuit FB - Thermal Shutdown VEN EN 100uA Vss OCSET Absolute Maximum Ratings Symbol ESD HBM ESD MM Parameter Human Body Model ESD Protection Machine Model ESD Protection Rating Unit 4.5 150 KV V VCC VCC Pin Voltage VSS - 0.3 to VSS + 20 V VFB Feedback Pin Voltage VSS - 0.3 to VCC V VEN EN Pin Voltage VSS - 0.3 to VIN V VOUT Switch Pin Voltage VSS - 1.0 to VIN V PD Power Dissipation Internally limited mW TJ Operating Junction Temperature Range TST Caution: Storage Temperature Range -40 to +125 o C -65 to +150 o C 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. AP1534 Document number: DS31314 Rev. 6 - 2 2 of 9 www.diodes.com April 2011 © Diodes Incorporated AP1534 PWM CONTROL 2A STEP-DOWN CONVERTER Recommended Operating Conditions Symbol Parameter VIN Input Voltage IOUT Output Current TA Operating Ambient Temperature Min Max Unit 3.6 18 V 0 2 -20 A o 85 C Electrical Characteristics (VIN = 12V, TA = 25°C, unless otherwise specified) Symbol VFB IFB ISW Parameter Conditions Feedback Voltage IOUT = 0.1A Feedback Bias Current IOUT = 0.1A Min Typ. Max Unit 0.784 0.8 0.816 V - 0.1 0.5 µA Switch Current -- 2.0 - - A Current Consumption During Power Off VEN = 0V - 10 - µA Line Regulation VIN = 5V~18V - 1 2 % Load Regulation IOUT = 0.1 to 2A - 0.2 0.5 % fOSC Oscillation Frequency Measure waveform at SW pin 240 300 400 KHz fOSC1 Frequency of Current Limit or Short Circuit Measure waveform at SW pin Protect - 50 - KHz 2.0 - - Evaluate oscillation stop at SW pin - - 0.8 -- - 20 - µA -- - -10 - µA -- µA ISHDN ∆VOUT / VIN ∆VOUT /VOUT VIH VIL ISH ISL EN Pin Input Voltage EN Pin Input Leakage Current IOCSET OCSET Pin Bias Current RDS(ON) Internal MOSFET RDS(ON) EFFI Efficiency Evaluate oscillation at SW pin 75 90 105 VIN = 5V, VFB = 0V - 160 - VIN = 12V, VFB = 0V - 100 - VIN = 12V, VOUT = 5V, IOUT = 2A - 91 - V mΩ % TSHDN Thermal shutdown threshold - 150 - °C THYS Thermal shutdown hysteresis - 55 - °C - 127 - o C/W - o C/W θJA θJC Notes: Thermal Resistance Junction-to-Ambient Thermal Resistance Junction-to-Case SO-8 (Note 3) SO-8 (Note 3) - 28 3. Test condition for SO-8: Device mounted on FR-4 substrate PC board, 2oz copper, with minimum recommended pad layout. For better thermal performance, larger copper pad for heatsink is needed. AP1534 Document number: DS31314 Rev. 6 - 2 3 of 9 www.diodes.com April 2011 © Diodes Incorporated AP1534 PWM CONTROL 2A STEP-DOWN CONVERTER Typical Performance Characteristics 0.820 326 VOUT = 3.3V, IOUT = 0.2A 324 VOUT = 3.3V, IOUT = 0.2A 0.815 322 0.810 FOSC (kHz) 320 0.805 VFB (V) 318 316 314 0.800 0.795 312 0.790 310 0.785 308 306 0 2 4 6 8 10 12 VIN (V) VIN vs. Frequency 14 16 0.780 18 3.0% 2 4 6 8 10 12 VIN (V) VIN vs. VFB 14 16 18 1.0% VOUT = 3.3V, IOUT = 0.2A 0.8% 2.0% VIN = 5V, VOUT = 3.3V 0.6% VOUT CHANGE (%) VOUT CHANGE (%) 0 1.0% 0.0% -1.0% 0.4% 0.2% 0.0% -0.2% -0.4% -0.6% -2.0% -0.8% -3.0% 0 2 4 6 8 10 12 VIN (V) Line Regulation 100 14 16 18 -1.0% 0.0 0.5 1.0 1.5 IOUT (A) Load Regulation 2.0 VOUT = 3.3V 90   EFFICIENCY (%) 80 70 VOUT = 5V 60 50 40 30 20 10 0 0.0 0.5 AP1534 Document number: DS31314 Rev. 6 - 2 1.0 IOUT (A) Efficiency 1.5 2.0 4 of 9 www.diodes.com April 2011 © Diodes Incorporated AP1534 PWM CONTROL 2A STEP-DOWN CONVERTER Typical Performance Characteristics (cont.) VOUT Ripple (VIN = 5V, VOUT = 3.3V, IOUT = 0.1A) VOUT Ripple (VIN = 5V, VOUT = 3.3V, IOUT = 2A) Test Circuit VCC OUTPUT FB Oscillation open open OCSET A EN + - VSS Enable function test VCC + - A OUTPUT VCC OUTPUT OCSET EN FB VSS Feedback function test FB OCSET EN VSS + V - Operation function test AP1534 Document number: DS31314 Rev. 6 - 2 5 of 9 www.diodes.com April 2011 © Diodes Incorporated AP1534 PWM CONTROL 2A STEP-DOWN CONVERTER Functional Description PWM Control Inductor Selection The AP1534 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. For most designs, the operates with inductors of 22µH to 33µH. The inductor value can be derived from the following equation: Under Voltage Lockout The under voltage lockout circuit of the AP1534 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. V − VOUT VOUT L = IN × fS × ΔI VIN Where ΔIL 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=0.3A. 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). 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 overcurrent condition is triggered. The current limit threshold is given by the following equation: IPEAK × RDS(ON) = IOCSET × R OCSET ( ΔI) IPEAK > IOUT (MAX) + 2 VIN − VOUT VOUT × FS × L 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 ΔI. The above equation is recommended for input voltage range of 5V to 18V. For input voltage lower than 5V or ambient temperature over 100°C, higher ROCSET is recommended. The recommended summarized below: VIN (V) 4 5 12 18 minimum VOUT (V) 1 3.3 5 12 AP1534 Document number: DS31314 Rev. 6 - 2 ROCSET ROCSET (Ω) 6.8K 5.6K 3.9K 4.7K 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 1/2 the DC load current. A low ESR input capacitor sized for maximum RMS current must be used. A 470µF low ESR capacitor for most applications is sufficient. Output Capacitor Selection where, ΔI = Input Capacitor Selection value is 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. VRIPPLE= ΔIL × 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. 6 of 9 www.diodes.com April 2011 © Diodes Incorporated AP1534 PWM CONTROL 2A STEP-DOWN CONVERTER Functional Description (cont.) 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 SO-8 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. Bottom Side Layout Guide Connect FB circuits (RA, RB, CC) as closely as possible and keep away from inductor flux for pure VFB. Connect CVCC 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 CIN & D1 & COUT as closely as possible and use ground plane for best performance. Connect FB circuits closer and keep away from L1. 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. Top Side Layout Guide Vcc VIN R4 + - C7 Option C2 EN + C3 - C6 C1 Option AP1534 FB OCSET R5 L1 Output VOUT R1 + V SS D1 C8 + C4 - R2 Layout numbering comparison AP1534 Document number: DS31314 Rev. 6 - 2 7 of 9 www.diodes.com April 2011 © Diodes Incorporated AP1534 PWM CONTROL 2A STEP-DOWN CONVERTER Ordering Information   AP 1534 S G - 13 Package S : SO-8 Green Packing G : Green 13 : Tape & Reel 13” Tape and Reel Part Number Suffix Device Package Code Packaging (Note 4) Quantity AP1534SG-13 S SO-8 2500/Tape & Reel Note: -13 4. 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. Marking Information (1) SO-8 ( Top View ) 5 8 Logo G : Green YY : Year : 08, 09,10~ represents 52 and 53 week WW : Week : 01~52; 52 X : Internal Code AP1534 YY WW X X Part Number 1 4 Package Outline Dimensions (All Dimensions in mm) 0.254 (1) Package Type: SO-8 E1 E A1 L Gauge Plane Seating Plane Detail ‘A’ 7°~9° h 45° A2 A A3 Detail ‘A’ b e SO-8 Dim Min Max A 1.75 A1 0.10 0.20 A2 1.30 1.50 A3 0.15 0.25 b 0.3 0.5 D 4.85 4.95 E 5.90 6.10 E1 3.85 3.95 e 1.27 Typ h 0.35 L 0.62 0.82 θ 0° 8° All Dimensions in mm D AP1534 Document number: DS31314 Rev. 6 - 2 8 of 9 www.diodes.com April 2011 © Diodes Incorporated AP1534 PWM CONTROL 2A STEP-DOWN CONVERTER IMPORTANT NOTICE DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION). 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