ACT4060A Rev 1, 25-Jun-09 Wide Input 2A Step Down Converter FEATURES GENERAL DESCRIPTION • • • • • • • • • • The ACT4060A is a current-mode step-down DC/DC converter that provides up to 2A of output current at 400kHz switching frequency. The device utilizes Active-Semi’s proprietary high voltage process for operation with input voltages up to 24V. 2A Output Current Up to 96% Efficiency 4.5V to 24V Input Range 10µA Shutdown Supply Current The ACT4060A provides fast transient response and eases loop stabilization while providing excellent line and load regulation. This device features a very low ON-resistance power MOSFET which provides peak operating efficiency up to 96%. In shutdown mode, the ACT4060A consumes only 10μA of supply current. 400kHz Switching Frequency Adjustable Output Voltage Cycle-by-Cycle Current Limit Protection Thermal Shutdown Protection Frequency FoldBack at Short Circuit This device also integrates protection features including cycle-by-cycle current limit, thermal shutdown and frequency fold-back at short circuit. Stability with Wide Range of Capacitors, Including Low ESR Ceramic Capacitors • SOP-8 Package The ACT4060A is available in a SOP-8 package and requires very few external devices for operation. APPLICATIONS • • • • • • • TFT LCD Monitors Portable DVDs Car-Powered or Battery-Powered Equipments Set-Top Boxes Telecom Power Supplies DSL and Cable Modems and Routers Termination Supplies TYPICAL APPLICATION CIRCUIT BS Up to 24V SW IN 2.5V/2A ACT4060A ENABLE EN G FB COMP + Innovative PowerTM -1- www.active-semi.com Copyright © 2009 Active-Semi, Inc. ACT4060A Rev 1, 25-Jun-09 ORDERING INFORMATION PART NUMBER TEMPERATURE RANGE PACKAGE PINS PACKING ACT4060ASH -40°C to 85°C SOP-8 8 TUBE ACT4060ASH-T -40°C to 85°C SOP-8 8 TAPE & REEL PIN CONFIGURATION BS 1 8 N/C IN 2 7 EN SW 3 6 COMP G 4 5 FB ACT4060ASH SOP-8 PIN DESCRIPTIONS PIN NAME 1 BS Bootstrap. This pin acts as the positive rail for the high-side switch’s gate driver. Connect a 10nF capacitor between BS and SW. 2 IN Input Supply. Bypass this pin to G with a low ESR capacitor. See Input Capacitor in the Application Information section. 3 SW 4 G Ground. 5 FB Feedback Input. The voltage at this pin is regulated to 1.293V. Connect to the resistor divider between output and ground to set output voltage. 6 COMP Compensation Pin. See Stability Compensation in the Application Information section. 7 EN Enable Input. When higher than 1.3V, this pin turns the IC on. When lower than 0.7V, this pin turns the IC off. Output voltage is discharged when the IC is off. When left unconnected, EN is pulled up to 4.5V with a 2µA pull-up current. 8 N/C Not Connected. Innovative PowerTM DESCRIPTION Switch Output. Connect this pin to the switching end of the inductor. -2- www.active-semi.com Copyright © 2009 Active-Semi, Inc. ACT4060A Rev 1, 25-Jun-09 ABSOLUTE MAXIMUM RATINGSc PARAMETER VALUE UNIT -0.3 to 28 V SW Voltage -1 to VIN + 1 V BS Voltage VSW - 0.3 to VSW + 8 V EN, FB, COMP Voltage -0.3 to 6 V Continuous SW Current Internally Limited A Junction to Ambient Thermal Resistance (θJA) 105 °C/W Maximum Power Dissipation 0.76 W Operating Junction Temperature -40 to 150 °C Storage Temperature -55 to 150 °C 300 °C IN Supply Voltage Lead Temperature (Soldering, 10 sec) c: Do not exceed these limits to prevent damage to the device. Exposure to absolute maximum rating conditions for long periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VIN = 12V, TA = 25°C, unless otherwise specified.) PARAMETER SYMBOL TEST CONDITIONS Input Voltage VIN VOUT = 3.3V, ILOAD = 0A to 1A Feedback Voltage VFB 4.5V ≤ VIN ≤ 24V, VCOMP = 1.5V MIN TYP 4.5 1.267 1.293 MAX UNIT 24 V 1.319 V High-Side Switch On Resistance RONH 0.18 Ω Low-Side Switch On Resistance RONL 4.5 Ω SW Leakage Current Limit COMP to Current Limit Transconductance VEN = 0 ILIM GCOMP Error Amplifier Transconductance GEA Error Amplifier DC Gain AVEA Switching Frequency 2.4 DMAX 10 µA 2.85 A VIN = 12V, VOUT = 5V 1.8 A/V ΔICOMP = ±10µA 650 µA/V 4000 V/V fSW Short Circuit Switching Frequency Maximum Duty Cycle 0 350 400 450 kHz VFB = 0 60 kHz VFB = 1.1V 95 % Minimum Duty Cycle VFB = 1.4V Enable Threshold Voltage Hysteresis = 0.1V Enable Pull-Up Current Pin pulled up to 4.5V typically when left unconnected 2 Supply Current in Shutdown VEN = 0 10 IC Supply Current in Operation VEN = 3V, VFB = 1.4V 0.55 mA Thermal Shutdown Temperature Hysteresis = 10°C 160 °C Innovative PowerTM -3- 0.7 1 0 % 1.3 V µA 20 µA www.active-semi.com Copyright © 2009 Active-Semi, Inc. ACT4060A Rev 1, 25-Jun-09 FUNCTIONAL BLOCK DIAGRAM IN EN COMP ENABLE REGULATOR & REFERENCE BS CURRENT SENSE AMPLIFIER ERROR AMPLIFIER 1.293V 0.18Ω HIGH-SIDE POWER SWITCH PWM COMP FB FOLDBACK CONTROL OSCILLATOR & RAMP SW LOGIC 4.5Ω LOW-SIDE POWER SWITCH THERMAL SHUTDOWN G reference. If FB is lower than the reference voltage, COMP tends to go higher to increase current to the output. Current limit happens when COMP reaches its maximum clamp value of 2.55V. FUNCTIONAL DESCRIPTION As seen in Functional Block Diagram, the ACT4060A is a current mode pulse width modulation (PWM) converter. The converter operates as follows: The Oscillator normally switches at 400kHz. However, if FB voltage is less than 0.7V, then the switching frequency decreases until it reaches a typical value of 60kHz at VFB = 0.5V. A switching cycle starts when the rising edge of the Oscillator clock output causes the High-Side Power Switch to turn on and the Low-Side Power Switch to turn off. With the SW side of the inductor now connected to IN, the inductor current ramps up to store energy in the magnetic field. The inductor current level is measured by the Current Sense Amplifier and added to the Oscillator ramp signal. If the resulting summation is higher than the COMP voltage, the output of the PWM Comparator goes high. When this happens or when Oscillator clock output goes low, the High-Side Power Switch turns off and the Low-Side Power Switch turns on. At this point, the SW side of the inductor swings to a diode voltage below ground, causing the inductor current to decrease and magnetic energy to be transferred to output. This state continues until the cycle starts again. Shutdown Control The ACT4060A has an enable input EN for turning the IC on or off. When EN is less than 0.7V, the IC is in 10μA low current shutdown mode and output is discharged through the Low-Side Power Switch. When EN is higher than 1.3V, the IC is in normal operation mode. EN is internally pulled up with a 2μA current source and can be left unconnected for always-on operation. Note that EN is a low voltage input with a maximum voltage of 6V, it should never be directly connected to IN. Thermal Shutdown The ACT4060A automatically turns off when its junction temperature exceeds 160°C. The High-Side Power Switch is driven by logic using BS as the positive rail. This pin is charged to VSW + 6V when the Low-Side Power Switch turns on. The COMP voltage is the integration of the error between FB input and the internal 1.293V Innovative PowerTM -4- www.active-semi.com Copyright © 2009 Active-Semi, Inc. ACT4060A Rev 1, 25-Jun-09 APPLICATIONS INFORMATION Input Capacitor Output Voltage Setting The input capacitor needs to be carefully selected to maintain sufficiently low ripple at the supply input of the converter. A low ESR capacitor is highly recommended. Since large current flows in and out of this capacitor during switching, its ESR also affects efficiency. Figure 1: Output Voltage Setting VOUT The input capacitance needs to be higher than 10µF. The best choice is the ceramic type, however, low ESR tantalum or electrolytic types may also be used provided that the RMS ripple current rating is higher than 50% of the output current. The input capacitor should be placed close to the IN and G pins of the IC, with the shortest traces possible. In the case of tantalum or electrolytic types, they can be further away if a small parallel 0.1µF ceramic capacitor is placed right next to the IC. RFB1 ACT4060A FB RFB2 Figure 1 shows the connections for setting output voltage. Select the proper ratio of the feedback resistors RFB1 and RFB2 based on output voltage. Typically, use RFB2 ≈ 10kΩ determine RFB1 from the following equation: the two the and ⎛ V ⎞ R FB1 = R FB 2 ⎜ OUT − 1 ⎟ 1 . 293 V ⎝ ⎠ Output Capacitor (1) The output capacitor also needs to have low ESR to keep low output voltage ripple. The output ripple voltage is: VRIPPLE = I OUTMAX K RIPPLE R ESR Inductor Selection The inductor maintains a continuous current to the output load. This inductor current has a ripple that is dependent on the inductance value: higher inductance reduces the peak-to-peak ripple current. The trade off for high inductance value is the increase in inductor core size and series resistance, and the reduction in current handling capability. In general, select an inductance value L based on ripple current requirement: L= VOUT × (VIN − VOUT ) VIN fSW IOUTMAX K RIPPLE + (2) where VIN is the input voltage, VOUT is the output voltage, fSW is the switching frequency, IOUTMAX is the maximum output current, and KRIPPLE is the ripple factor. Typically, choose KRIPPLE = 30% to correspond to the peak-to-peak ripple current being 30% of the maximum output current. 2.5V 3.3V 5V L 6.8μH 6.8μH 10μH 15μH 22μH Innovative PowerTM where IOUTMAX is the maximum output current, KRIPPLE is the ripple factor, RESR is the ESR of the output capacitor, fSW is the switching frequency, L is the inductor value, and COUT is the output capacitance. In the case of ceramic output capacitors, RESR is very small and does not contribute to the ripple. Therefore, a lower capacitance value can be used for ceramic type. In the case of tantalum or electrolytic capacitors, the ripple is dominated by RESR multiplied by the ripple current. In that case, the output capacitor is chosen to have sufficiently low ESR. Use a Schottky diode as the rectifier to conduct current when the High-Side Power Switch is off. The Schottky diode must have current rating higher than the maximum output current and a reverse voltage rating higher than the maximum input voltage. Typical Inductor Values 1.8V (3) Rectifier Diode Table 1: 1.5V 2 28 × fSW LC OUT For ceramic output capacitor, typically choose a capacitance of about 22µF. For tantalum or electrolytic capacitors, choose a capacitor with less than 50mΩ ESR. With this inductor value, the peak inductor current is IOUT × (1 + KRIPPLE/2). Make sure that this peak inductor current is less that the 3A current limit. Finally, select the inductor core size so that it does not saturate at 3A. Typical inductor values for various output voltages are shown in Table 1. VOUT VIN -5- www.active-semi.com Copyright © 2009 Active-Semi, Inc. ACT4060A Rev 1, 25-Jun-09 STEP 2. Set the zero fZ1 at 1/4 of the cross over frequency. If RCOMP is less than 15kΩ, the equation for CCOMP is: STABILITY COMPENSATION Figure 2: Stability Compensation C COMP = COMP ACT4060A CCOMP CCOMP = 1.2 ×10 −5 VOUT COUT RCOMP The feedback loop of the IC is stabilized by the components at the COMP pin, as shown in Figure 2. The DC loop gain of the system is determined by the following equation: 1 .3V AVEA GCOMP I OUT CCOMP2 = The second pole P2 is the output pole: 1 Table 2: Typical Compensation for Different Output Voltages and Output Capacitors (7) 2 πR COMP C COMP (13) Table 2 shows some calculated results based on the compensation method above. (6) The first zero Z1 is due to RCOMP and CCOMP: fZ1 = COUT RESRCOUT RCOMP Though CCOMP2 is unnecessary when the output capacitor has sufficiently low ESR, a small value CCOMP2 such as 100pF may improve stability against PCB layout parasitic effects. (5) I OUT 2 π V OUT C OUT (12) And the proper value for CCOMP2 is: (4) G EA 2 π AVEA C COMP (11) (F) ⎛ 1.1 × 10 −6 ⎞ RESRCOUT ≥ Min⎜⎜ ,0.012 × VOUT ⎟⎟ (Ω) ⎝ COUT ⎠ The dominant pole P1 is due to CCOMP: fP 2 = (10) STEP 3. If the output capacitor’s ESR is high enough to cause a zero at lower than 4 times the cross over frequency, an additional compensation capacitor CCOMP2 is required. The condition for using CCOMP2 is: c: CCOMP2 is needed only for high ESR output capacitor fP1 = (F) If RCOMP is limited to 15kΩ, then the actual cross over frequency is 3.4 / (VOUTCOUT). Therefore: CCOMP2 AVDC = 1 .8 × 10 −5 R COMP VOUT COUT RCOMP CCOMP 2.5V 22μF Ceramic 8.2kΩ 2.2nF 3.3V 22μF Ceramic 12kΩ 1.5nF 5V 22μF Ceramic 15kΩ 1.5nF The following steps should be used to compensate the IC: 2.5V 47μF SP CAP 15kΩ 1.5nF 3.3V 47μF SP CAP 15kΩ 1.8nF STEP 1. Set the cross over frequency at 1/10 of the switching frequency via RCOMP: 5V 47μF SP CAP 15kΩ 2.7nF 2.5V 470μF/6.3V/30mΩ 15kΩ 15nF 3.3V 470μF/6.3V/30mΩ 15kΩ 22nF 5V 470μF/6.3V/30mΩ 15kΩ 27nF And finally, the third pole is due to RCOMP and CCOMP2 (if CCOMP2 is used): fP 3 = 1 (8) 2πRCOMP CCOMP2 R COMP = 2π VOUT C OUT f SW 10 G EA GCOMP × 1 .3V = 1.7 × 10 8 VOUT C OUT (Ω) (9) Figure 4 shows an example ACT4060A application circuit generating a 3.3V/2A output. but limit RCOMP to 15kΩ maximum. Innovative PowerTM -6- www.active-semi.com Copyright © 2009 Active-Semi, Inc. ACT4060A Rev 1, 25-Jun-09 Separate noise sensitive traces, such as the voltage feedback path, compensation from noisy sources such as inductor, diode, input capacitor. ACT4060A PCB Layout Guidelines. Place all the power components (Diode, Inductor, filter Capacitors) as close as possible. Use short and wide trace between them. Place components, such as compensation, feedback network and boost-trap capacitors, as close to the IC as possible. If double layer PCB is used, it is good if the bottom layer is almost fill as ground. Use ground planes for power ground and signal ground, connect signal ground and power ground at single point close to the IC GND. Ceramic cap C1 is closely placed across VIN and GND of the IC, as close as possible. Arrange the power components so that the switching current loop curl in the same direction. Figure 3: ACT4060A PCB Layout Reference R3 EN R2 C2 R1 Multiple Vias 8 7 6 5 GND GND U1 1 2 3 4 INPUT C4 C3 VIN+ D1 OUTPUT VOUT C1 L1 Innovative PowerTM -7- www.active-semi.com Copyright © 2009 Active-Semi, Inc. ACT4060A Rev 1, 25-Jun-09 Figure 4: ACT4060A 3.3V/2A Output Applicationc VIN C3 BS Up to 24V IN ENABLE L1 SW VOUT IC1 ACT4060A EN G R1 FB COMP C2 + R2 C4 D1 C1 R3 c: D1 is a 40V, 3A Schottky diode with low forward voltage, an IR 30BQ040 or SK34 equivalent. C4 can be either a ceramic capacitor (Panasonic ECJ-3YB1C226M) or SP-CAP (Specialty Polymer) Aluminum Electrolytic Capacitor such as Panasonic EEFCD0J470XR. The SP-Cap is based on aluminum electrolytic capacitor technology, but uses a solid polymer electrolyte and has very stable capacitance characteristics in both operating temperature and frequency compared to ceramic, polymer, and low ESR tantalum capacitors. Table 3: ACT4060A Bill of Materials (Apply for 3.3V Output Application) ITEM 1 DESCRIPTION MANUFACTURER QTY REFERENCE IC, ACT4060A Active-Semi 15µH ± 20%, ISAT = 2.7A, IDC = [email protected] ΔT = 40°C Taiyo Yuden NR 8040T 150M 15µH ± 10%, ISAT = 2.88A, IDC = [email protected] ΔT = 40°C Wurth Electronik 744776115 10µH ± 20%, ISAT = 3.4A, IDC = [email protected]ΔT = 40°C Taiyo Yuden NR 6045T 100M 10µH ± 10%, ISAT = 2.95A, IDC = [email protected] ΔT = 40°C Wurth Electronik 74477510 Schottky Diode SK34/40V, 3A, SMB Transys electronics 1 Schottky Diode B340C/40V, 3A, SMB Diodes Inc 1 4 Ceramic cap 10µF/35V, X7R, 1210 Murata, TDK,Taiyo Yuden 1 C1 5 Ceramic cap 2.2nF/6.3V, X7R, 0603 Murata, TDK,Taiyo Yuden 1 C2 6 Ceramic cap 10nF/50V, X7R, 0603 Murata, TDK,Taiyo Yuden 1 C3 Ceramic cap 22µF/10V, X7R, 1210 Murata, TDK,Taiyo Yuden SP cap 47µF/6.3V, 50mΩ Kemet, Panasonic 1 C4 2 3 7 8 Resistor, 15.5kΩ, 1/16W, 1%, 0603 9 Resistor, 10kΩ, 1/16W, 1%, 0603 10 Resistor, 12kΩ, 1/16W, 5%, 0603 Innovative PowerTM 1 U1 1 L1 D1 R1 FengHua, Neohm, Yageo 1 R2 R3 -8- www.active-semi.com Copyright © 2009 Active-Semi, Inc. ACT4060A Rev 1, 25-Jun-09 Figure 5: ACT4060A 5V/2A Output Applicationc VIN C3 BS Up to 24V IN ENABLE L1 SW VOUT IC1 ACT4060A EN G R1 FB COMP C2 + R2 C4 D1 C1 R3 c: D1 is a 40V, 3A Schottky diode with low forward voltage, an IR 30BQ040 or SK34 equivalent. C4 can be either a ceramic capacitor (Panasonic ECJ-3YB1C226M) or SP-CAP (Specialty Polymer) Aluminum Electrolytic Capacitor such as Panasonic EEFCD0J470XR. The SP-Cap is based on aluminum electrolytic capacitor technology, but uses a solid polymer electrolyte and has very stable capacitance characteristics in both operating temperature and frequency compared to ceramic, polymer, and low ESR tantalum capacitors. Table 4: ACT4060A Bill of Materials (Apply for 5V Output Application) ITEM 1 2 DESCRIPTION MANUFACTURER IC, ACT4060A Active-Semi 15µH ± 20%, ISAT =2.7A, IDC = [email protected] ΔT = 40°C Taiyo Yuden NR 8040T 150M 15µH ± 10%, ISAT = 2.88A, IDC = [email protected] ΔT = 40°C Wurth Electronik 744776115 QTY REFERENCE 1 U1 1 L1 1 D1 Schottky Diode SK34/40V, 3A, SMB Transys electronics Schottky Diode B340C/40V, 3A, SMB Diodes Inc 4 Ceramic cap 10µF/35V, X7R, 1210 Murata, TDK, Taiyo Yuden 1 C1 5 Ceramic cap 2.2nF/6.3V, X7R, 0603 Murata, TDK, Taiyo Yuden 1 C2 6 Ceramic cap 10nF/50V, X7R, 0603 Murata, TDK, Taiyo Yuden 1 C3 Ceramic cap 22µF/10V, X7R, 1210 Murata, TDK, Taiyo Yuden SP cap 47µF/6.3V, 50mΩ Kemet, Panasonic 1 C4 3 7 8 Resistor, 28.7kΩ, 1/16W, 1%, 0603 9 Resistor, 10kΩ, 1/16W, 1%, 0603 10 Resistor, 15kΩ, 1/16W, 5%, 0603 Innovative PowerTM R1 FengHua, Neohm, Yageo 1 R2 R3 -9- www.active-semi.com Copyright © 2009 Active-Semi, Inc. ACT4060A Rev 1, 25-Jun-09 TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 4, unless otherwise specified.) Efficiency vs. Output Current Efficiency vs. Output Current Efficiency (%) 80 70 80 VIN = 12V 60 50 40 30 VIN = 7V 70 VIN = 12V 60 50 40 30 20 20 10 10 0 0 10 100 1000 10 10000 100 Efficiency vs. Output Current Maximum Output Current vs. Duty Cycle Maximum Output Current (mA) 40 20 VOUT = 3.3V 0 10 100 1000 ACT4060A-004 VIN = 12V 60 5000 ACT4060A-003 VIN = 5V 4000 3000 2000 1000 0 10000 0 20 40 60 80 100 Duty Cycle (% ) Output Current (mA) Switching Frequency vs. Input Voltage Feedback Voltage vs. Temperature 400 Feedback Voltage (V) 405 395 390 ACT4060A-006 1.33 ACT4060A-005 410 Switching Frequency (kHz) 10000 Output Current (mA) 80 385 1000 Output Current (mA) 100 Efficiency (%) VOUT = 5V 90 Efficiency (%) VIN = 7V ACT4060A-002 VOUT = 2.5V 90 100 ACT4060A-001 100 1.31 1.29 1.27 VOUT = 2.5V IOUT = 1A 380 1.25 4 6 8 10 12 14 16 18 -50 20 Innovative PowerTM 0 100 50 150 Temperature (°C) Input Voltage (V) - 10 - www.active-semi.com Copyright © 2009 Active-Semi, Inc. ACT4060A Rev 1, 25-Jun-09 TYPICAL PERFORMANCE CHARACTERISTICS CONT’D (Circuit of Figure 4, unless otherwise specified.) Shutdown Current vs. Input Voltage Shutdown Current (µA) ACT4060A-007 25 20 15 10 5 0 5 10 15 20 25 Input Voltage (V) Innovative PowerTM - 11 - www.active-semi.com Copyright © 2009 Active-Semi, Inc. ACT4060A Rev 1, 25-Jun-09 PACKAGE OUTLINE SOP-8 PACKAGE OUTLINE AND DIMENSIONS D C SYMBOL θ e B DIMENSION IN MILLIMETERS DIMENSION IN INCHES MIN MAX MIN MAX A 1.350 1.750 0.053 0.069 A1 0.100 0.250 0.004 0.010 A2 1.350 1.550 0.053 0.061 B 0.330 0.510 0.013 0.020 C 0.190 0.250 0.007 0.010 D 4.700 5.100 0.185 0.201 E 3.800 4.000 0.150 0.157 E1 5.800 6.300 0.228 0.248 e 1.270 TYP 0.050 TYP L 0.400 1.270 0.016 0.050 θ 0° 8° 0° 8° Active-Semi, Inc. reserves the right to modify the circuitry or specifications without notice. Users should evaluate each product to make sure that it is suitable for their applications. Active-Semi products are not intended or authorized for use as critical components in life-support devices or systems. Active-Semi, Inc. does not assume any liability arising out of the use of any product or circuit described in this datasheet, nor does it convey any patent license. Active-Semi and its logo are trademarks of Active-Semi, Inc. For more information on this and other products, contact [email protected] or visit http://www.active-semi.com. For other inquiries, please send to: 2728 Orchard Parkway, San Jose, CA 95134-2012, USA Innovative PowerTM - 12 - www.active-semi.com Copyright © 2009 Active-Semi, Inc.