ACT4070 ACTIVE-SEMI | Alldatasheet
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Innovative Products. Active Solutions. Copyright © 2006 Active-Semi, Inc. www.active-semi.com - 1 - 3A Output Current Up to 95% Efficiency 4.5V to 30V Input Range 6µA Shutdown Supply Current 400kHz Switching Frequency Adjustable Output Voltage Cycle-by-Cycle Current Limit Protection Thermal Shutdown Protection Internal Soft Start Function Frequency Fold Back at Short Circuit Stability with Wide Range of Capacitors, Including Low ESR Ceramic Capacitors SOP-8/EP (Exposed Pad) Package The ACT4070 is a current -mode step -down DC/DC converter that generates up to 3A output current at 400kHz switching frequency. The device utilizes Active -Semi’s proprietary ISOBCD30 process for operation with input voltage up to 30V. Consuming only 6 μA in shutdown mode, the ACT4070 is highly efficient with peak efficiency at 95% when in operation. Protection features include cycle -by-cycle current limit, thermal shutdown, and frequency fold back at short circuit. The device also includes an internal soft start function to prevent overshoot. The ACT4070 is available in SOP -8/EP exposed pad package and requires very few external devices for operation. GENERAL DESCRIPTION TYPICAL APPLICATION CIRCUIT TFT LCD Monitors or Televisions and HDTV Portable DVD Players Car-Powered or Battery-Powered Equipment Set-Top Boxes Telecom Power Supplies DSL and Cable Modems and Routers
FEATURES
APPLICATIONS
Rev 0, 12/2006 Wide Input 3A Step Down Converter
Innovative Products. Active Solutions. Copyright © 2006 Active-Semi, Inc. www.active-semi.com - 2 - ACT4070
ORDERING INFORMATION
TEMPERATURE RANGE PACKAGE PINS PACKING ACT4070YH -40°C to 85°C SOP-8/EP 8 TUBE ACT4070YH-T -40°C to 85°C SOP-8/EP 8 TAPE & REEL PIN CONFIGURATION PIN DESCRIPTION PIN NUMBER PIN NAME PIN DESCRIPTION 1 BS Bootstrap. This pin acts as the positive rail for the high-side switch’s gate driver. Connect a 10nF between this pin and SW. 2 IN Input Supply. Bypass this pin to G with a low ESR capacitor. See Input Capacitor in Application Information section. 3 SW Switch Output. Connect this pin to the switching end of the inductor. 4 G Ground. 5 FB Feedback Input. The voltage at this pin is regulated to 1.222V. Connect to the resistor divider between output and ground to set output voltage. 6 COMP Compensation Pin. See Compensation Technique in Application Information sec- tion. 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. This pin has a small internal pull up current to a high level voltage when pin is not con- nected. 8 N/C Not Connected. EP EP Exposed Pad shown as dashed box. The exposed thermal pad should be con- nected to board ground plane and pin 4. The ground plane should include a large exposed copper pad under the package for thermal dissipation (see package out- line). The leads and exposed pad should be flush with the board, without offset from the board surface. SOP-8/EP
Innovative Products. Active Solutions. Copyright © 2006 Active-Semi, Inc. www.active-semi.com - 3 - ACT4070 ABSOLUTE MAXIMUM RATINGS PARAMETER VALUE UNIT IN to G -0.3 to +34 V EN to G -0.3 to VIN + 0.3 V BS to SW -0.3 to +8 V FB, COMP to G -0.3 to 6 V Continuous SW Current Internally limited A Junction to Ambient Thermal Resistance (θJA) 46 °C/W Maximum Power Dissipation 1.8 W Operating Junction Temperature -40 to 150 °C Storage Temperature -55 to 150 °C Lead Temperature (Soldering, 10 sec) 300 °C SW to G -1 to VIN + 1 V
ELECTRICAL CHARACTERISTICS
(VIN = 12V, TA= 25°C, unless otherwise specified.) PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT Input Voltage VIN VOUT = 2.5V, ILOAD = 0A to 3A 4.5 30 V Feedback Voltage VFB 1.198 1.222 1.246 V High-Side Switch On Resistance RONH 100 mΩ Low-Side Switch On Resistance RONL 10 Ω SW Leakage VEN = 0, VIN = 12V, VSW = 0V 0 10 µA Current Limit ILIM 3.5 5 A COMP to Current Limit Transcon- ductance GCOMP ΔILOAD/ΔICOMP 3 A/V Error Amplifier Transconductance GEA ΔICOMP = ±10µA 550 µA/V Error Amplifier DC Gain AVEA 4000 V/V Switching Frequency fSW 340 400 460 kHz Short Circuit Switching Frequency VFB = 0V 40 kHz Maximum Duty Cycle DMAX VFB = 1.1V, PWM mode 90 % Minimum Duty Cycle VFB = 1.4V, PFM mode 0 % Enable Threshold Voltage Hysteresis = 0.1V 0.7 1 1.3 V Enable Pull Up Current Pin pulled up to VIN when left uncon- nected 2 µA Supply Current in Shutdown VEN = 0 6 20 µA IC Supply Current in Operation VEN = 3V, not switching 0.85 2 mA Thermal Shutdown Temperature Hysteresis = 10°C 160 °C : Do not exceed these limits to prevent damage to the device. Exposure to absolute maximum rating conditions for long periods ma y affect device reliability.
Innovative Products. Active Solutions. Copyright © 2006 Active-Semi, Inc. www.active-semi.com - 4 - ACT4070 FUNCTIONAL BLOCK DIAGRAM FUNCTIONAL DESCRIPTION As seen in the Functional Block Diagram , the ACT4070 is a current mode pulse width modulation (PWM) converter. The converter operates as fol- lows: 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 con- nected to IN, the inductor current ramps up to store energy in the its magnetic field. The inductor current level is measured by the Current Sense Amplifier and added to the Oscillator ramp signal. If the result- ing 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 de- crease and magnetic energy to be transferred to output. This state continues until the cycle starts again. The High-Side Power Switch is driven by logic using BS bootstrap pin as the positive rail. This pin is charged to V SW + 6 V w h e n t h e L o w-Side Power Switch turns on. The COMP voltage is the integration of the error between FB input and the internal 1.222V refer- ence. 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 2.65V. The Oscillator normally switches at 400kHz. How- ever, if FB voltage is less than 0.7V, then the switching frequency decreases until it reaches a typical value of 40kHz at VFB = 0V. Shutdown Control The ACT4070 has an enable input EN for turning the IC on or off. When EN is less than 0.7V, the IC is in 6μA 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. Thermal Shutdown The ACT4070 automatically turns off when its junc- tion temperature exceeds 160°C and then restarts once the temperature falls to 150°C.
Innovative Products. Active Solutions. Copyright © 2006 Active-Semi, Inc. www.active-semi.com - 7 - ACT4070 Figure 3: ACT4070 2.5V/3A Output Application : D1 is a 40V, 3A Schottky diode with low forward voltage, an IR 30BQ040 or SK34 equivalent. C4 can be either a ceramic capacito r (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 capa ci- tance characteristics in both operating temperature and frequency compared to ceramic, polymer, and low ESR tantalum capacitors. IC1 ACT4070 BS IN EN COMP FB SW G VIN ENABLE 4.5V to 30V 10µF/35V (CCOMP) 3.3nF (RCOMP) 5.6k (CCOMP2) 220pF 13k 40V L1 10µH/4AC3 10nF R1 14k VOUT C4 (COUT) 22µF/10V ceramic or 47µH/6.3 SP Cap 2.5V/3A
Innovative Products. Active Solutions. Copyright © 2006 Active-Semi, Inc. www.active-semi.com - 8 - ACT4070 TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 3, unless otherwise specified.) Input Voltage (V) 8 10 12 14 16 18 20 22 24 26 28 30 ACT4070-0004 Switching Frequency vs. Input Voltage 350 400 300 Switching Frequency (kHz) 450 500 ACT4070-006 Output Current (A) Surface Temperature vs. Output Current Surface Temperature (°C) 100 120 140 0 0.5 1 1.5 2 2.5 3 VOUT = 5V L = 15µH CIN = 22µF COUT = 22µF VIN = 30V VIN = 20V VIN = 12V ACT4070-0005 Input Voltage (V) Shutdown Supply Current (µA) 5 10 15 20 25 30 Shutdown Supply Current vs. Input Voltage 100 Efficiency (%) Output Current (A) ACT4070-0001 0.01 0.1 1 10 Efficiency vs. Output Current VOUT = 5V L = 15µH CIN = 22µF COUT = 22µF VIN = 20V VIN = 30V VIN = 8V VIN = 12V 100 Efficiency (%) 0.01 0.1 1 10 Output Current (A) ACT4070-0002 Efficiency vs. Output Current VOUT = 2.5V L = 10µH CIN = 22µF COUT = 22µF VIN = 8V VIN = 30V VIN = 12V VIN = 20V -40 Temperature (°C) -20 0 20 40 60 80 100 ACT4070-0003 1.21 1.25 1.27 1.23 1.19 1.17 Feedback Voltage (V) Feedback Voltage vs. Temperature
Innovative Products. Active Solutions. Copyright © 2006 Active-Semi, Inc. www.active-semi.com - 9 - ACT4070 TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 3, unless otherwise specified.) ACT4070-0007 VIN = 12V Load Transient Response VOUT 200mV/div IOUT 100µs/div ACT4070-0008 VIN = 12V Load Transient Response IOUT VOUT 200mV/div 100µs/div ACT4070-0009 VIN = 12V Load Transient Response VOUT 200mV/div IOUT 100µs/div
Innovative Products. Active Solutions. Copyright © 2006 Active-Semi, Inc. www.active-semi.com - 10 - ACT4070 SYMBOL DIMENSION IN MILLIMETERS DIMENSION IN INCHES MIN MAX MIN MAX A 1.350 1.750 0.053 0.069 A1 0.050 0.150 0.002 0.006 A2 1.350 1.550 0.053 0.061 b 0.330 0.510 0.013 0.020 c 0.170 0.250 0.007 0.010 D 4.700 5.100 0.185 0.200 D1 3.202 3.402 0.126 0.134 E 3.800 4.000 0.150 0.157 E1 5.800 6.200 0.228 0.244 E2 2.313 2.513 0.091 0.099 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 sales@active-semi.com or visit http://www.active-semi.com. For other inquiries, please send to:
1270 Oakmead Parkway, Suite 310, Sunnyvale, California 94085-4044, USA
SOP-8/EP PACKAGE OUTLINE AND DIMENSIONS D e b