APW7077/A PWM Step-Up DC-DC Converter Features * * * * * * General Description Low Start-Up Voltage 0.9V The APW7077/A series are multi- function PWM step- Fixed 300kHz Operating Frequency up DC-DC converter with an adaptive voltage mode controller and higher efficiency application from one to four Built-In Internal Soft-Start Circuit cells battery packs. The APW7077/A series are set Low Operating Current PWM operating mode, voltage-mode to follow portable 3.3V and 5V (2.5%) Fixed (APW7077) or application. And built-in driver pin, EXT pin, for con- Adjustable Output Voltage (APW7077A) necting to an external transistor or MOSFET during light load, the device will automatically skip switching High Efficiency Up to 88% at 400mA cycles to maintain high efficiency. The APW7077/A Output Current * * * series consist of PWM controller, reference voltage, High Output Current Up to 1A phase compensation, oscillator, soft-start, driver block. Compact Package: SOT-23-5 It will be provided to operate suitable voltage without Lead Free and Green Devices Available external compensation circuit. The APW7077/A series have fixed voltage and adjustable voltage version (RoHS Compliant) from a wide input voltage ranges 0.7V to 5.5V for stepup DC-DC converter. The start-up is guaranteed at 1V and the device is operating down to 0.7V, and provid- Applications ing up to 300mA loading current. Besides, low quiescent current (switch-off) is guaranteed. * * * * * Cellular and Portable Phones Portable Audio Pin Configuration Camcorders and Digital Still Camera Hand-held Instrument EXT GND EXT GND 4 5 4 PDAs 5 1 2 3 CE VOUT NC SOT-23-5 (Top View) APW7077 1 2 3 FB VDD CE SOT-23-5 (Top View) APW7077A ANPEC reserves the right to make changes to improve reliability or manufacturability without notice, and advise customers to obtain the latest version of relevant information to verify before placing orders. Copyright ANPEC Electronics Corp. Rev. A.6 - Jun., 2008 1 www.anpec.com.tw APW7077/A Ordering and Marking Information Package Code B : SOT-23-5 Temperature Range I : -40 to 85 C Handling Code TR : Tape & Reel Voltage Code 33 : 3.3V 50 : 5.0V Assembly Material L : Lead Free Device G : Halogen and Lead Free Device APW7077/A Assembly Material Handling Code Temperature Range Package Code Voltage Code APW7077 - 33B : 77RX X - Date Code, R : 3.3V APW7077 - 50B : 77ZX X - Date Code, Z : 5.0V APW7077A B : X - Date Code A77X Note : ANPEC lead-free products contain molding compounds/die attach materials and 100% matte tin plate termination finish; which are fully compliant with RoHS. ANPEC lead-free products meet or exceed the lead-free requirements of IPC/JEDEC J-STD020C for MSL classification at lead-free peak reflow temperature. ANPEC defines "Green" to mean lead-free (RoHS compliant) and halogen free (Br or Cl does not exceed 900ppm by weight in homogeneous material and total of Br and Cl does not exceed 1500ppm by weight). Absolute Maximum Ratings Symbol Parameter Value Unit VDD Supply Voltage -0.3 to 7 V VIO Input / Output Pins (CE, FB, EXT) -0.3 to 7 V TA Operating Ambient Temperature Range -40 to 85 C TJ Junction Temperature Range -40 to 150 C TSTG Storage Temperature Range -65 to +150 C 260 C Typical Value Unit 200 C/W TS Maximum Lead Soldering Temperature, 10 Seconds Thermal Characteristics Symbol Parameter Thermal Resistance - Junction to Ambient R JA Copyright ANPEC Electronics Corp. Rev. A.6 - Jun., 2008 SOT-23-5 2 www.anpec.com.tw APW7077/A Electrical Characteristics (for all values TA = 25C, VOUT = 3.3V, unless otherwise noted) APW7077A Symbol Parameter Test Conditions Unit Min. Typ. Max. - 0.9 - V 1.9 - 5.5 V - 0.9 1 V VOUT = 12V, Io<10mA, VDD = VIN 1.9 2.0 - V VDD = 3.3V, VFB = 0.5V 270 300 330 kHz - 1.2 - % 81 88 95 % - 0.5 - % STEP-UP SECTION VIN VDD fSW Minimum Operating Input Voltage Operating Voltage VIN = VDD Start-Up Voltage Io<10mA, VOUT = VDD (<5.5V) Operating Frequency Oscillator Frequency Line Regulation DMAX VOUT = VDD 2.0V<VDD<5.5V Maximum Duty Cycle VFB = 0.5V Maximum Duty Line Regulation 2.0V<VDD<5.5V POWER MOSFET ISOURCE ISINK EXT Output Source Current Duty5%, EXT = VDD-0.4V -70 -110 -150 mA EXT Output Sink Current Duty5%, EXT = 0.4V 80 120 160 mA Output Voltage Range External Divider 2.0 - - V Feedback Voltage ILOAD = 0mA 0.98 1 1.02 V 2.0V<VDD<5.5V - 0.1 - % VFB = 1.4V - 0.03 50 nA 10 25 40 ms - 1.65 - V - 150 - mV VDD = VCE = 3.3V, VFB = 0.5V - 150 230 A VDD = VCE = 3.3V, VFB = 1.1V - 100 150 A Stand-by Current VDD = VCE = 3.3V, VFB = 1.3V - 17 25 A Switch-Off Current VDD = 3.3V, VCE = 0V - 1 2 A Logic LOW (VIL) - - 0.7 V Logic HIGH(VIH) 1.2 - - V VCE = 0V - 1 2 A VCE = 3.3V - 0.07 50 nA CONTROL SECTION VFB Feedback Voltage Line Regulation IFB Feedback Input Current TSS Soft-Start Time Soft-Start Threshold Voltage Duty = 50% Soft-Start Hysteresis Voltage Iq IOFF VCE ICE Operating Current CE Pin Input Current Copyright ANPEC Electronics Corp. Rev. A.6 - Jun., 2008 3 www.anpec.com.tw APW7077/A Electrical Characteristics (Cont.) (for all values TA = 25C, VOUT = 3.3V, unless otherwise noted) APW7077 Symbol Parameter Test Conditions Unit Min Typ Max 0.7 - - V 1 - 5.5 V APW7077_33, Io<10mA - 0.9 - V APW7077_33, 10mA<Io<100mA - 1.1 - V APW7077_50, Io<10mA - 0.9 - V APW7077_50, 10mA<Io<100mA - 1.1 - V Hold Voltage ILOAD = 10mA - 0.7 0.8 V fSW Operating Frequency VOUT = 3.3VX96% 270 300 330 kHz DMAX Maximum Duty Cycle VOUT = 3.3VX96% 81 88 95 % EXT Output Source Current Duty5%, EXT = 2.9V -70 -110 -150 mA EXT Output Sink Current Duty5%, EXT = 0.4V 80 120 160 mA STEP-UP SECTION VIN Minimum Operating Input Voltage Operating Voltage Start-Up Voltage VHOLD POWER MOSFET ISOURCE ISINK CONTROL SECTION VOUT TSS APW7077-33 IIN = 0mA 3.218 3.3 3.383 V APW7077-50 IIN = 0mA 4.875 5 5.125 V 10 25 40 ms - 1.65 - V - 150 - mV VCE = VOUT, VOUT = 0.96VOUT - 200 300 A VCE = VOUT, VOUT = 1.04VOUT - 160 240 A Stand-by Current VCE = VOUT, VOUT = 1.3VOUT - 35 55 A Switch-Off Current VCE = 0V - 1 2 A Logic LOW (VIL) - - 0.7 V Logic HIGH (VIH) 1.2 - - V VCE = 0V - 1 2 A VCE = 2.0V - 0.07 50 nA Soft-Start Time Soft-Start Threshold Voltage Duty = 50% Soft-Start Hysteresis Voltage Iq IOFF VCE ICE Operating Current CE Pin Input Current Copyright ANPEC Electronics Corp. Rev. A.6 - Jun., 2008 4 www.anpec.com.tw APW7077/A Pin Descripition PIN FUNCTION PIN NAME APW7077 APW7077A 1 3 CE Chip enable input. High = operating mode; Low = shutdown mode 5 5 EXT External MOSFET or transistor drive pin. 4 4 GND Ground pins of the circuit. X 2 VDD Supply voltage. X 1 FB VFB. from and VOUT = 1 + R1 3 X NC No internal connection to the pin. 2 X VOUT VOUT Provides bootstrap power to the IC. FB: Internal 1.0V reference voltage. Use a resistor divider to set the output voltage R2 Block Diagram VDD Phase Compensation VOUT VDD VDD NC PWM Controller Error Amp. RAMP GEN. Vref=1.0V Voltage Reference GND EXT Driver PWM Comp. Oscillator Soft-Start VDD CE APW7077 VDD Phase Compensation VDD VDD VDD FB PWM Controller Error Amp. RAMP GEN. Voltage Reference GND Driver EXT PWM Comp. Oscillator Soft-Start VDD CE APW7077A Copyright ANPEC Electronics Corp. Rev. A.6 - Jun., 2008 5 www.anpec.com.tw APW7077/A Typical Application Circuit Application Circuit for APW 7077 10uH/1.5A VIN VOUT=3.3V(APW7077-33) SS12 VOUT=5V(APW7077-50) CE EXT 100uF VOUT APW 7077 APM2300A NC 100uF 10uF GND 1uF Application Circuit for APW7077A 10uH/1.5A VIN 2.5~5.2V 2R2 SS12 9~12V/50mA V OUT =(1+R2/R1)*1.0V FB EXT 4.7uF VDD APW 7077A APM2300A 0.1uF GND CE 1uF 10uF R2 820K/620K R1/75K C FF /1000pF Application Circuit for APW7077A VIN 10uH/1.5A 3~5V SS12 V OUT =(1+R2/R1)*1.0V FB EXT 100uF VDD APM2300A APW 7077A CE GND 10uF 100uF 1uF R2/300K R1/75K C FF /33pF *R1 100K is recommended Copyright ANPEC Electronics Corp. Rev. A.6 - Jun., 2008 6 www.anpec.com.tw APW7077/A Typical Operating Characteristics Start-up/Hold Voltage vs. Output Current 1.6 1.6 1.4 1.4 1.2 1.2 VSTART-up Input Voltage (V) Input Voltage (V) Start-up/Hold Voltage vs. Output Current 1 0.8 Vhold 0.6 VSTART-up 1 0.8 Vhold 0.6 0.4 0.4 0.2 0.2 VOUT=5.0V VOUT=3.3V 0 0 0 50 100 150 200 250 0 300 Output Current (mA) 50 100 150 20 0 25 0 300 Output Current (mA) Efficiency vs. Output Current Efficiency vs. Output Current 100 100 90 90 80 V DD=3V 80 70 Efficiency(%) Efficiency(%) V DD=5V VDD=3.3V 60 50 40 V DD=2V 70 60 50 40 30 30 VOUT=12V L=10F 20 VOUT=5V L=10H 20 1 10 100 1 100 1000 Output Current (mA) Output Current (mA) Copyright ANPEC Electronics Corp. Rev. A.6 - Jun., 2008 10 7 www.anpec.com.tw APW7077/A Typical Operating Characteristics (Cont.) Output Voltage vs. Output Current 5. 0 2 3.315 5. 015 3. 31 5. 0 1 Output Voltage (V) Output Voltage (V) Output Voltage vs. Output Current 3. 32 3.305 VIN=2.5V 3. 3 3.295 VIN=1.2V VIN=2.0V 5. 005 VIN=3.0V 5 4. 995 3. 29 4. 9 9 3.285 4. 985 VIN=1.2V VIN=2.0V VOUT=5.0V VOUT=3.3V 4. 9 8 3. 28 0 200 400 600 8 00 0 10 00 200 Output Current (mA) 4 00 600 8 00 1 0 00 Output Current (mA) Output Voltage vs. Temperature Oscillation Frequency vs. Temperature 3. 40 3 30 3. 38 3 20 Oscillation Frequency (kHz) Output Voltage (V) 3. 36 3. 34 3. 32 3. 30 3. 28 3. 26 3. 24 3 10 3 00 2 90 2 80 3. 22 3. 20 2 70 -40 -20 0 20 40 60 80 -40 Temperature (C) Copyright ANPEC Electronics Corp. Rev. A.6 - Jun., 2008 -20 0 20 40 60 80 Temperature (C) 8 www.anpec.com.tw APW7077/A Typical Operating Characteristics (Cont.) Load Transient Waveform Load Transient Waveform VIN=3.3V, VOUT=5V, IOUT=10mA->300mA->10mA L=10H, COUT=22F+22F+0.1F, Cff=33pF CH1:VOUT, 100mV/DIV, Time=1ms/DIV CH4:IOUT, 200mA/DIV VIN=3.3V, VOUT=12V, IOUT=5mA->50mA->5mA L=10H, COUT=4.7F+0.1F, Cff=560pF CH1:VOUT, 100mV/DIV, Time=1ms/DIV CH4:IOUT, 20mA/DIV EXT Driving Current vs. Supply Voltage EXT Rds,on vs. Supply Voltage 100 160 Rds,on resistance () Sink/Source Current (mA) 140 120 ISINK (EXT=0.4V) 100 80 ISOURCE (EXT=VDD-0.4V) 60 10 EXT to VDD EXT to GND 40 20 1 0 0 1 2 3 4 5 0 6 Supply Voltage (V) Copyright ANPEC Electronics Corp. Rev. A.6 - Jun., 2008 1 2 3 4 5 6 Supply Voltage (V) 9 www.anpec.com.tw APW7077/A Typical Operating Characteristics (Cont.) Feedback Voltage vs. Supply Voltage 250 2.5 200 2 Feedback Voltage (V) Supply Current (A) Supply Current vs. Supply Voltage Switching Mode 150 100 Non Switching Mode 50 1.5 1 0.5 0 0 0 0.5 1 1. 5 2 2.5 3 3.5 4 4.5 5 5.5 0 0.5 1 1.5 Supply Voltage (V) 2.5 3 3.5 4 4.5 5 5.5 Supply Voltage (V) Maximum Duty vs. Supply Voltage Oscillation Frequency vs. Supply Voltage 35 0 100 90 30 0 80 25 0 Maximum Duty (%) Oscillation Frequency (kHz) 2 20 0 15 0 70 60 50 40 30 10 0 20 50 10 0 0 0 0. 5 1 1. 5 2 2. 5 3 3.5 4 4. 5 5 5.5 0 Supply Voltage (V) Copyright ANPEC Electronics Corp. Rev. A.6 - Jun., 2008 0. 5 1 1. 5 2 2. 5 3 3. 5 4 4 .5 5 5. 5 Supply Voltage (V) 10 www.anpec.com.tw APW7077/A Typical Operating Characteristics (Cont.) Feedback Voltage vs. Temperature 1.020 Feedback Voltage (V) 1.015 1.010 1.005 1.000 0.995 0.990 0.985 0.980 -40 - 20 0 20 40 60 80 Temperature (C) Function Description Operation The APW7077/A operation can be best understood by referring to the block diagram. The error amplifier The APW7077/A series are low noise fixed frequency monitors the output voltage via the feedback resistor voltage-mode PWM DC-DC controllers, and consist divider by comparing the feedback voltage with the of start-up circuit, reference voltage, oscillator, loop reference voltage. When the feedback voltage is lower compensation network, PWM control circuit, and low than the reference voltage, the error amplifier output ON resistance driver. will decrease. The error amplifier output is then APW7077 provides on-chip feedback resistor and loop compared with the oscillator ramp voltage at the PWM compensation network, the system designer can get controller. the regulated fixed output voltage 3.3V and 5.0V with When the feedback voltage is higher than the reference a small number of external components, it is optimized voltage, the error amplifier output increases and the for battery powered portable products where large duty cycle decreases. When the external power switch output current is required. APW7077A provides internal is on, the current ramps up in the inductor, storing reference voltage 1.0V and output voltage setting by energy in the magnetic field. When the external power external resistance for higher voltage requirement. The switch is off, the energy stored in the magnetic field is quiescent current is typically 120A (VOUT = 3.3V, transferred to the output filter capacitor and the load. fsw = 300kHz), and can be further reduced to about The output filter capacitor stores the charge while the 1.0A when the chip is disabled (VCE < 0.7V). Copyright ANPEC Electronics Corp. Rev. A.6 - Jun., 2008 11 www.anpec.com.tw APW7077/A Function Description (Cont.) Operation (Cont.) to let output voltage reach to setting voltage without inductor current is higher than the output current, and over shooting issue whenever heavy load or light load then sustains the output voltage until the next switch- condition. The soft-start time 25ms is setting by ing cycle. internal circuit. As the load current decreases, the switch transistor turns Oscillator on for a shorter duty cycle. Under the light load The oscillator frequency is internally set to 300kHz at condition, the controller will skip switching cycles to an accuracy of +/-10% and with low temperature reduce power consumption, therefore, high efficiency coefficient of 3.3%/C. is maintained at light loads. Enable/Disable Operation Fixed Output Voltage (for APW7077 only) The APW7077/A series offer IC shutdown mode by chip The APW7077 VOUT is set by an integrate feedback enable pin (CE pin) to reduce current consumption. resistor network. This is trimmed to a selected voltage When voltage at pin CE is greater than 1.2V, the chip 3.3V or 5.0V with an accuracy of +/-2.5%. will be enabled, which means the controller is in Setting Output Voltage (for APW7077A only) normal operation. When voltage at pin CE is less than 0.7V, the chip is disabled, which means IC is shut- For APW7077A, the output voltage is adjustable. The down and quiescent current become 1A. output voltage is set using the FB pin and a resistor The CE pin is pulled high to VDD(or VOUT) by internal divider connected to the output as shown in the typical resistor, and this resistance is greater than 1M . operating circuit. The internal reference voltage is 1.0V with 2% variation, so the ratio of the feedback resistors Therefore, this chip will enable normally when CE pin sets the output voltage according to the following is floating. equation: V OUT = (1 + Important: DO NOT apply a voltage between 0.7V R2 R1 ) x 1.0V to 1.2V to pin CE as this is the CE pin's hysteresis voltage range. Clearly defined output states can To avoid the thermal noise from feedback resistor, only be obtained by applying voltage out of this (R1+R2) resistance smaller than 1M and 1% variation range. is recommended. Compensation Soft-Start The device is designed to operate in continuous There is a soft-start function integrated in APW7077/ conduction mode. An internal compensation circuit A series to avoid the over shooting when power on. was designed to guarantee stability over the full When power is applied to the device, the soft-start input/output voltage and full output load range. circuit first pumps up the output voltage to let VDD(or Step-Up Converter Operating Mode VOUT) approximately 1.65V at a fixed duty cycle 50%. This is the voltage level at which the controller can The step-up DC-DC controller is designed to operate operate normally. When supply voltage more than in continuous conduction mode (CCM) or discontinuous 1.65V, the internal reference voltage will be ramp up conduction mode (DCM). Copyright ANPEC Electronics Corp. Rev. A.6 - Jun., 2008 12 www.anpec.com.tw APW7077/A Function Description (Cont.) The inductor peak current can be calculated as Step-Up Converter Operating Mode (Cont.) I PK = For a step up converter in a CCM, the duty cycle D is given by D = V OUT - V IN V OUT x I O I L + V IN 2 NOTES: V OUT In higher output voltage or small output current D - On-time duty cycle application, the step-up DC-DC controller operated in IL - Average inductor current discontinuous conduction mode almost. For a step-up IPK - Peak inductor current converter in a DCM, the duty cycle D is given by IO - Desired dc output current V 2 L OUT T S R LOAD V IN D = VIN - Nominal operating dc input voltage V OUT - 1 V IN VOUT - Desired dc output voltage ESR - Equivalent series resistance of the output External components values can be calculated from capacitor these equations, however, the optimized value should obtained through experimental results. Inductor Selection Critical Inductance Value APW7077/A series are designed to work well with a The minimum value of inductor to maintain continuous 6.8 to 12H inductors in most applications 10H is a conduction mode can be determined by the following sufficiently low value to allow the use of a small surface mount coil, but large enough to maintain low equation. L V OUT x D(1 - D) ripple. Lower inductance values supply higher output 2 current, but also increase the ripple and reduce fsw x I O x Ratio efficiency. Higher inductor values not only reduce ripple A system can be designed to operate in continuous and improve efficiency, but also limit output current. mode for load currents above a certain level usually The inductor should have small DCR, usually less 20 to 50% (Ratio define as 0.2~0.5) of full load at than 0.2, to minimize loss. It is necessary to choose minimum input voltage. When IO smaller than (IO*Ratio), an inductor with a saturation current greater than the the controller system will into DCM. peak current which the inductor will encounter in the IL is the ripple current flowing through the inductor, application. which affects the output voltage ripple and core losses. The inductor ripple current is important for a few Based on 20%(Ratio=0.2) current ripple, VOUT=5V, reasons. One reason is the peak switch current will IO=1A and VIN =1.8V system, the inductance value is be the average inductor current (IL) plus IL. calculated as 6.9H and a 6.8H inductor is used. As a side note, discontinuous operation occurs when The inductor current ripple has an expression IL = the inductor current falls to zero during a switching V IN x D cycle, or IL is greater than the average inductor fsw x L current. Therefore, continuous conduction mode occurs The maximum DC input current can be calculated as I L (max) = when IL is less than the average inductor current. V OUT x I O (max) V IN (min) Copyright ANPEC Electronics Corp. Rev. A.6 - Jun., 2008 13 www.anpec.com.tw APW7077/A Function Description (Cont.) Inductor Selection (Cont.) If the regulator will be loaded uniformly, with very little Care must be taken to make sure that the switch will load changes, and at lower current outputs, the input not reach its current limit during normal operation. capacitor size can often be reduced. The size can also be reduced if the input of the regulator is very close to The inductor must also be sized accordingly. It should the source output. The size will generally need to be have a saturation current rating higher than the peak larger for applications where the regulator is supplying inductor current expected. The output voltage ripple is nearly the maximum rated output or if large load steps also affected by the total ripple current. are expected. A minimum value of 10F should be used for the less stressful conditions while a 22F to Output Capacitor 47F capacitor may be required for higher power and The output capacitor is used for sustaining the output dynamic loads. Small ESR Tantalum or ceramic ca- voltage when the external MOSFET or bipolar pacitor should be suitable and the total input ripple transistor is switched on and smoothing the ripple voltage can be calculated voltage. V IN = I L x ESR The output capacitance needed is calculated in Design Example equation. COUT (min) = It is supposed that a step-up DC-DC controller with IO(max) x D 3.3V output delivering a maximum 1000 mA output fsw x VOUT current with 100 mV output ripple voltage powering The ESR is also important because it determines the from a 2.4V input is to be designed. peak to peak output voltage ripple according to the Design parameters: approximated equation: VIN = 2.4V VOUT ESR = IO VOUT = 3.3V IO = 1.0A With 1% output voltage ripple, low ESR capacitor VOUT = 100mV should be used to reduce output ripple voltage. In fsw= 300kHz general, a 100F to 220F low ESR (0.10 to 0.30) Ratio = 0.2 (typical for small output ripple voltage) Tantalum capacitor should be appropriate. The choice Assume the diode forward voltage and the transistor of output capacitors is also somewhat arbitrary and saturation voltage are both 0.3V. Determine the maxi- depends on the design requirements for output voltage mum steady state duty cycle at VIN = 2.4V: ripple. A minimum value of 10F is recommended and D=0.273 may be increased to a larger value. Calculate the maximum inductance value which can Input Capacitor generate the desired current output and the preferred The input capacitor can stabilize the input voltage and delta inductor current to average inductor current ratio: minimize peak current ripple from the source. The size L=10H used is dependant on the application and board layout. Copyright ANPEC Electronics Corp. Rev. A.6 - Jun., 2008 14 www.anpec.com.tw APW7077/A Function Description (Cont.) Design Example(Cont.) The ESR of the output capacitor is 0.05. Therefore, Determine the average inductor current and peak a Tantalum capacitor with value of 33 F to 47F and inductor current: ESR of 0.05 can be used as the output capacitor. However, according to experimental result, 220F IL=1.38A output capacitor gives better overall operational stability IL=0.218A and smaller ripple voltage. Ipk=1.45A Therefore, a 10H inductor with saturation current larger than 1.73 A can be selected as the initial trial. Determine the output capacitance value for the desired output ripple voltage: COUT=33F Component Selection Diode Selection flow backwards through the diode due to the minority The output diode for a boost regulator must be chosen correctly depending on the output voltage and the carriers being swept from the P-N junction. Using output current. The diode must be rated for a reverse Schottky diodes with lower forward voltage drop will voltage equal to or greater than the output voltage used. decrease power dissipation and increase efficiency. The average current rating must be greater than the External Switch Transistor maximum load current expected, and the peak current The APW7077/A can drive up to 110mA of gate drive rating must be greater than the peak inductor current. current. An N-channel MOSFET with a relatively low During short circuit testing, or if short circuit conditions threshold voltage, low gate charge and low RDS(ON) are possible in the application, the diode current is required to optimize overall circuit performance. The rating must exceed the switch current limit. The diode APW7077/A Evaluation Board uses a APM2300A. This is the largest source of loss in DC-DC converters. NMOS device was chosen because it demonstrates The most importance parameters which affect their an RDS_ON of 45m and a total gate charge Qg of efficiency are the forward voltage drop, VF, and the 12nC (typ.). reverse recovery time, trr. The forward voltage drop creates a loss just by having a voltage across the device while a current flowing through it. The reverse recovery time generates a loss when the diode is reverse biased, and the current appears to actually Copyright ANPEC Electronics Corp. Rev. A.6 - Jun., 2008 15 www.anpec.com.tw APW7077/A Layout Consideration Ground Plane If no analog ground plane is available, then this ground must tie directly to the GND pin. The feedback network, One point grounding should be used for the output resistors R1 and R2, should be kept close to the FB power return ground, the input power return ground, pin, and away from the inductor, to minimize copper and the device switch ground to reduce noise. The trace connections that can inject noise into the system. input ground and output ground traces must be thick Prevent connect feedback network on output enough for current to flow through and for reducing ground bounce. decoupling MLCC. Power Signal Traces Input Capacitor Low resistance conducting paths should be used for In APW7077A high output voltage application circuit, the power carrying traces to reduce power loss so as the input voltage (VIN) is tied to chip supply pin (VDD). to improve efficiency (short and thick traces for The input capacitor CIN in VIN must be placed close to connecting the inductor L can also reduce stray the IC. This will reduce copper trace resistance which inductance). Trace connections made to the inductor effects input voltage ripple of the IC. For additional and schottky diode should be minimized to reduce input voltage filtering, a 1F capacitor can be placed power dissipation and increase overall efficiency. in parallel with CIN, close to the VDD pin, to shunt any high frequency noise to ground. Output Capacitor The output capacitor should be placed close to the Inductor output terminals to obtain better smoothing effect on To minimize copper trace connections that can inject the output ripple. noise into the system, the inductor, switch, and The output capacitor, COUT, should also be placed close Schottky diode should be placed as close as possible to the diode. Any copper trace connections for the to minimize the noise coupling into other circuits. COUT capacitor can increase the series resistance, MINIMUM RECOMMENDED FOOTPRINT FOR SUR- which directly effects output voltage ripple and FACE MOUNTED APPLICATIONS efficiency. Surface mount board layout is a critical portion of the Switching Noise Decoupling Capacitor total design. The footprint for the semiconductor On APW7077 fixed voltage application, a 0.1F ceramic packages must be the correct size to insure proper capacitor should be placed close to the VOUT pin and solder connection interface between the board and the GND pin of the chip to filter the switching spikes in the package. With the correct pad geometry, the packages output voltage monitored by the VOUT pin. will self align when subjected to a solder reflow process. Feedback Network On APW7077A application, the feedback networks should be connected directly to a dedicated analog ground plane and this ground plane must connect to the GND pin. Copyright ANPEC Electronics Corp. Rev. A.6 - Jun., 2008 16 www.anpec.com.tw APW7077/A Layout Consideration (Cont.) MINIMUM RECOMMENDED FOOTPRINT FOR SURFACE MOUNTED APPLICATIONS (Cont.) Bottom Layer 1300mil Demo Board Circuit Layout 1600 mil Top Layer Copyright ANPEC Electronics Corp. Rev. A.6 - Jun., 2008 17 www.anpec.com.tw APW7077/A Package Information SOT-23-5 D e E E1 SEE VIEW A b c 0.25 A L 0 GAUGE PLANE SEATING PLANE A1 A2 e1 VIEW A S Y M B O L SOT-23-5 INCHES MILLIMETERS MIN. MIN. MAX. A MAX. 0.057 1.45 A1 0.00 0.15 0.000 A2 0.90 1.30 0.035 0.051 b 0.30 0.50 0.012 0.020 c 0.08 0.22 0.003 0.009 D 2.70 3.10 0.016 0.122 0.118 0.071 E 2.60 3.00 0.102 E1 1.40 1.80 0.055 e 0.95 BSC 0.037 BSC e1 1.90 BSC 0.075 BSC L 0.30 0.60 0 0 8 0.012 0 0.006 0.024 8 Note : 1. Follow JEDEC TO-178 AA. 2. Dimension D and E1 do not include mold flash, protrusions or gate burrs. Mold flash, protrusion or gate burrs shall not exceed 10 mil per side. Copyright ANPEC Electronics Corp. Rev. A.6 - Jun., 2008 18 www.anpec.com.tw APW7077/A Carrier Tape & Reel Dimensions P0 P2 P1 A B0 W F E1 OD0 K0 A0 A OD1 B B T SECTION A-A SECTION B-B H A d T1 Application A H 178.02.00 50 MIN. SOT-23-5 T1 C d 8.4+2.00 13.0+0.50 -0.00 -0.20 1.5 MIN. P0 P1 P2 4.00.10 4.00.10 2.00.05 D0 1.5+0.10 -0.00 D1 1.0 MIN. D 20.2 MIN. W E1 8.00.30 1.750.10 F 3.50.05 T A0 B0 K0 0.6+0.00 3.200.20 3.100.20 1.500.20 -0.40 (mm) Devices Per Unit Package Type Unit Quantity SOT-23-5 Tape & Reel 3000 Copyright ANPEC Electronics Corp. Rev. A.6 - Jun., 2008 19 www.anpec.com.tw APW7077/A Reflow Condition (IR/Convection or VPR Reflow) tp TP Critical Zone TL to TP Ramp-up Temperature TL tL Tsmax Tsmin Ramp-down ts Preheat 25 t 25C to Peak Time Reliability Test Program Test item SOLDERABILITY HOLT PCT TST ESD Latch-Up Method MIL-STD-883D-2003 MIL-STD-883D-1005.7 JESD-22-B, A102 MIL-STD-883D-1011.9 MIL-STD-883D-3015.7 JESD 78 Description 245C, 5 sec 1000 Hrs Bias @125C 168 Hrs, 100%RH, 121C -65C~150C, 200 Cycles VHBM > 2KV, VMM > 200V 10ms, 1tr > 100mA Classification Reflow Profiles Profile Feature Average ramp-up rate (TL to TP) Preheat - Temperature Min (Tsmin) - Temperature Max (Tsmax) - Time (min to max) (ts) Time maintained above: - Temperature (TL) - Time (tL) Peak/Classification Temperature (Tp) Time within 5C of actual Peak Temperature (tp) Ramp-down Rate Time 25C to Peak Temperature Sn-Pb Eutectic Assembly Pb-Free Assembly 3C/second max. 3C/second max. 100C 150C 60-120 seconds 150C 200C 60-180 seconds 183C 60-150 seconds 217C 60-150 seconds See table 1 See table 2 10-30 seconds 20-40 seconds 6C/second max. 6C/second max. 6 minutes max. 8 minutes max. Notes: All temperatures refer to topside of the package. Measured on the body surface. Copyright ANPEC Electronics Corp. Rev. A.6 - Jun., 2008 20 www.anpec.com.tw APW7077/A Classification Reflow Profiles (Cont.) Table 1. SnPb Eutectic Process - Package Peak Reflow Temperatures 3 3 Package Thickness Volume mm <350 Volume mm 350 <2.5 mm 2.5 mm 240 +0/-5C 225 +0/-5C 225 +0/-5C 225 +0/-5C Table 2. Pb-free Process - Package Classification Reflow Temperatures 3 Package Thickness 3 Volume mm <350 Volume mm 350-2000 3 Volume mm >2000 <1.6 mm 260 +0C* 260 +0C* 260 +0C* 1.6 mm - 2.5 mm 260 +0C* 250 +0C* 245 +0C* 2.5 mm 250 +0C* 245 +0C* 245 +0C* * Tolerance: The device manufacturer/supplier shall assure process compatibility up to and including the stated classification temperature (this means Peak reflow temperature +0C. For example 260C+0C) at the rated MSL level. Customer Service Anpec Electronics Corp. Head Office : No.6, Dusing 1st Road, SBIP, Hsin-Chu, Taiwan, R.O.C. Tel : 886-3-5642000 Fax : 886-3-5642050 Taipei Branch : 2F, No. 11, Lane 218, Sec 2 Jhongsing Rd., Sindian City, Taipei County 23146, Taiwan Tel : 886-2-2910-3838 Fax : 886-2-2917-3838 Copyright ANPEC Electronics Corp. Rev. A.6 - Jun., 2008 21 www.anpec.com.tw