AP1533

AP1533 PWM CONTROL 1.8A STEP-DOWN CONVERTER Features • • • • • • • • • • Input voltage: 4V to 23V Output voltage: 0.8V to VCC Output current: 1.8A up to peak 2A 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: Available in “Green” Molding Compound (No Br, Sb) Lead Free Finish/ RoHS Compliant (Note 1) General Description AP1533 consists of step-down switching regulator with PWM control. These devices include a reference voltage source, oscillation circuit, error amplifier, internal PMOS. AP1533 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 mini-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 Typical Application Circuit L1 Output 33uH CC Optional FB VSS D1* RB 1.3K RA 6.8K VOUT=5V/1.8A VIN ROCSET COCSET 3.3K Option C IN 470uF CVcc 0.1uF R EN 100K C EN 0.1uF Vcc AP1533 OCSET EN + - C + - COUT 470uF 0.1uF VOUT = V FB x (1+ R A /RB ) R B= 0.7K~5K ohm * Suggested DIODES Power Schottky P/N: B340 series or PDS340. AP1533 Rev. 4 DS31192 1 of 9 www.diodes.com JULY 2009 © Diodes Incorporated AP1533 PWM CONTROL 1.8A STEP-DOWN CONVERTER Ordering Information AP 1 5 3 3 S G - 13 Package S : SOP-8L Green G : Green Packing 13 : Tape & Reel Device AP1533SG-13 Notes: Package Code S Packaging (Note 2) SOP-8L 13” Tape and Reel Quantity Part Number Suffix 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 AP1533 OCSET 3 VCC 4 SOP-8L 6 5 Output Output 8 7 VSS VSS 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 AP1533 Rev. 4 DS31192 2 of 9 www.diodes.com JULY 2009 © Diodes Incorporated AP1533 PWM CONTROL 1.8A STEP-DOWN CONVERTER Block Diagram Output Oscillation Circuit VCC PWM-Switched Control Circuit Thermal Shutdown VEN 90uA VSS + FB Reference Voltage Source EN OCSET Absolute Maximum Ratings Symbol ESD MM VCC VFB VEN VOUT PD TJ TST Caution: Parameter 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 8 500 VSS - 0.3 to VSS + 24 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 KV V V V V V mW o o ESD HBM Human Body Model ESD Protection C 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. 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 AP1533 Rev. 4 DS31192 3 of 9 www.diodes.com JULY 2009 © Diodes Incorporated AP1533 PWM CONTROL 1.8A STEP-DOWN CONVERTER Electrical Characteristics (VIN = 12V, TA = 25°C, 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 Efficiency VIN = 5V~23V IOUT = 0.1 to 1.8A 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=1.8A Min 0.784 240 2.0 75 - Typ. 0.8 0.1 10 1 0.2 300 50 20 -10 90 110 80 91 150 55 134 22 Max 0.816 0.5 2 0.5 400 0.8 105 150 110 - Unit V µA µA % % KHz KHz V µA µA µA mΩ % °C °C o TSHDN Thermal shutdown threshold THYS Thermal shutdown hysteresis Thermal Resistance θJA SOP-8L (Note 3) Junction-to-Ambient Thermal Resistance θJC SOP-8L (Note 3) Junction-to-Case Notes: C/W C/W o 3. Test condition: Device mounted on FR-4 PCB, 2”x2”, 2oz copper, minimum recommended pad layout, single side. For better thermal performance, larger copper pad for heatsink is needed. AP1533 Rev. 4 DS31192 4 of 9 www.diodes.com JULY 2009 © Diodes Incorporated AP1533 PWM CONTROL 1.8A STEP-DOWN CONVERTER Typical Performance Characteristics VIN vs. Frequency 320 318 316 314 312 310 308 306 304 302 300 0 2 4 (VOUT=3.3V; IOUT=0.2A) (Continued) VIN vs. VFB 0.820 0.815 0.810 VFB (V) 0.805 0.800 0.795 0.790 0.785 0.780 (VOUT=3.3V; IOUT=0.2A) FOSC (kHz) 6 8 10 12 14 16 18 VIN (V) 20 22 24 0 2 4 6 8 10 12 14 16 18 20 22 24 VIN (V) Line Regulation 3.40 3.35 3.30 VOUT (V) 3.20 3.15 3.10 3.05 3.00 0 2 4 6 8 10 12 14 16 18 20 22 24 VIN (V) VOUT (V) 3.25 (VOUT=3.3V; IOUT=0.2A) 3.25 3.24 3.23 3.22 3.21 3.20 3.19 3.18 3.17 3.16 3.15 0 0.5 Load Regulation (VIN=12V) 1 IOUT (A) 1.5 2 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 0 0.5 Efficiency Efficiency (%) VOUT=3.3V VOUT=5V 1 IOUT (A) 1.5 2 AP1533 Rev. 4 DS31192 5 of 9 www.diodes.com JULY 2009 © Diodes Incorporated AP1533 PWM CONTROL 1.8A STEP-DOWN CONVERTER Typical Performance Characteristics VOUT Ripple ( VIN = 12V; VOUT = 3.3V; IOUT = 0.1A ) (Continued) VOUT Ripple (VIN = 12V; VOUT = 3.3V; IOUT = 1.8A ) 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 AP1533 Rev. 4 DS31192 6 of 9 www.diodes.com JULY 2009 © Diodes Incorporated AP1533 PWM CONTROL 1.8A STEP-DOWN CONVERTER Functional Description PWM Control The AP1533 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 AP1533 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 (90μA 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 22µH to 33µH. The inductor value can be derived from the following equation: L= VIN − VOUT VOUT × 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 1.8A, ∆IL=0.27A. 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 (1.8A+0.135A). 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 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 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 × R DS(ON) = IOCSET × R OCSET (ΔI) IPEAK > IOUT(MAX) + 2 where, ΔI = VIN − VOUT VOUT × fs × L VIN V RIPPLE = 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. 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 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 minimum ROCSET value is summarized below: VIN (V) 4 5 12 18 23 VOUT (V) 0.8 3.3 5 12 12 ROCSET (Ω) 3.9K 3.3K 3.3K 3.3K 4.7K The maximum ROCSET value should not exceed AP1533 maximum current output. AP1533 Rev. 4 DS31192 7 of 9 www.diodes.com JULY 2009 © Diodes Incorporated AP1533 PWM CONTROL 1.8A STEP-DOWN CONVERTER Marking Information (1) SOP-8L ( Top View ) 8 5 Logo Part Number AP1533 YY WW X X 1 4 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) AP1533 Rev. 4 DS31192 8 of 9 www.diodes.com JULY 2009 © Diodes Incorporated AP1533 PWM CONTROL 1.8A 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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