ACT6390/ACT6391 Rev0, 13-May-08 1.7A/2.5A PWM Step-Up DC/DC Converters In MSOP FEATURES • • • • GENERAL DESCRIPTION Greater than 90% Efficiency The ACT6390/ACT6391 are high-performance, fixed-frequency, current-mode PWM step-up DC/DC converters that incorporate internal power MOSFETs. The ACT6390 includes an integrated 0.2Ω power MOSFET that supports peak currents of up to 1.7A, while the ACT6391’s integrated 0.15Ω power MOSFET supports currents of up to 2.5A. Adjustable Output Voltage Up to 12V Internal 14V Power MOSFET Two Peak Current Options: − ACT6390: 1.7A, 0.2Ω − ACT6391: 2.5A, 0.15Ω • Selectable 700kHz/1.3MHz Frequency • • • • • The ACT6390 and ACT6391 both utilize simple external loop compensation and a pin-selectable fixed-frequency of either 700kHz or 1.3MHz, allowing optimization between component size, cost, and AC performance across a wide range of applications. Additional functions include an externally programmable soft-start function for easy inrush current control, internal over-voltage protection (OVP), cycle-by-cycle current limit protection, and thermal shutdown. Integrated Over-Voltage Protection (OVP) Programmable Soft-Start Function Thermal Shutdown Cycle-by-Cycle Over-Current Protection Small MSOP-8 Package APPLICATIONS • • • • Both the ACT6390 and the ACT6391 are available in the small 8-pin MSOP-8 package. TFT LCD Monitors Battery-Powered Equipment Set-Top Boxes DSL and Cable Modems and Routers SIMPLIFIED APPLICATION CIRCUIT VIN 2.7V to 5.5V ON OFF 1.3MHz 700kHz IN EN ACT6390 ACT6391 SW FREQ VOUT R1 SS FB COMP G Innovative PowerTM -1- R2 www.active-semi.com Copyright © 2008 Active-Semi, Inc. ACT6390/ACT6391 Rev0, 13-May-08 ORDERING INFORMATION PART NUMBER CURRENT LIMIT TEMPERATURE RANGE PACKAGE PINS PACKAGING ACT6390MH-T 1.7A -40°C to 85°C MSOP-8 8 TAPE & REEL ACT6391MH-T 2.5A -40°C to 85°C MSOP-8 8 TAPE & REEL PIN CONFIGURATION COMP 1 FB 2 EN 3 G 4 ACT6390 ACT6391 8 SS 7 FREQ 6 IN 5 SW MSOP-8 PIN DESCRIPTIONS PIN NAME 1 COMP 2 FB Feedback Input. Connect this pin a resistor divider from the output to set the output voltage. FB is regulated to 1.24V. 3 EN Enable Control. Connect to a logic high level to enable the IC. Connect to a logic low level to disable the IC. When unused, connect EN pin to IN (do not leave pin floating). 4 G 5 SW 6 IN 7 FREQ 8 SS Innovative PowerTM DESCRIPTION Error Amplifier Compensation Node. Connect to a resistor RC and capacitor CC in series to ground. Ground. Switch Output. Connect this pin to the inductor and the schottky diode. To minimize EMI, minimize the PCB trace path between this pin and the input bypass capacitor. Supply Input. Bypass to G with a 1µF or larger capacitor. Frequency Setting Pin. A logic low sets the switching frequency at 700kHz. A logic high sets the switching frequency at 1.3MHz. This pin has an internal 5.5µA pull-down current. Soft Start Control Input. Connect a capacitor from this pin to G to set soft-start timing duration (tSS = 2.2 x 105 x CSS). SS is discharged to ground in shutdown. SS may be left unconnected if soft start is not desired. -2- www.active-semi.com Copyright © 2008 Active-Semi, Inc. ACT6390/ACT6391 Rev0, 13-May-08 ABSOLUTE MAXIMUM RATINGSc PARAMETER VALUE UNIT SW to G -0.3 to 14 V IN, EN, FB, FREQ, COMP to G -0.3 to 6 V SS to G -0.3 to VIN + 0.3 V Continuous SW Current Internally Limited A Junction to Ambient Thermal Resistance (θJA) 200 °C/W Maximum Power Dissipation 0.5 W Operating Junction Temperature -40 to 150 °C Storage Temperature -55 to 150 °C 300 °C 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. Innovative PowerTM -3- www.active-semi.com Copyright © 2008 Active-Semi, Inc. ACT6390/ACT6391 Rev0, 13-May-08 ELECTRICAL CHARACTERISTICS (VIN = VEN = 3V, VFREQ = 0V, TA = 25°C, unless otherwise specified.) PARAMETER TEST CONDITIONS MIN TYP Switch Voltage Rating Input Voltage Under Voltage Lockout Threshold 2.7 VIN Rising 2.2 Under Voltage Lockout Hysteresis Supply Current in Shutdown Switching Frequency Maximum Duty Cycle VFB = 1.0V, Switching 5.5 V 2.5 V mV ACT6390 1 4 ACT6391 1.4 4 0.1 10 µA EN = G mA FREQ = G 490 700 910 kHz FREQ = IN 900 1300 1700 kHz FREQ = G 80 86 92 FREQ = IN 86 1.22 VFB = 1.27V FB Voltage Line Regulation VFB from 2.6V to 5.5V Error Amplifier Trans-conductance ∆I = 5µA Error Amplifier Output Current VFB = 1.15V and 1.35V, VCOMP = 1.1V Switch Current Limit VFB = 1V, Duty Cycle = 65% Current Sense Trans-resistance V 0.35 FB Input Current Switch Leakage Current 12 0.2 FB Feedback Voltage Switch On Resistance UNIT 65 VFB = 1.3V, Not Switching Quiescent Supply Current 2.35 MAX 70 1.24 1.26 V 0 80 nA 0.05 0.15 %/V 150 240 µs 11 µA ACT6390 1.2 1.7 2.3 ACT6391 1.8 2.5 3.4 ACT6390 0.2 0.4 ACT6391 0.15 0.3 VSW = 12V, EN = G 15 ACT6390 0.45 ACT6391 0.3 Soft Start Pin Bias Current VSS = 1.2V Soft Start Reset Resistance VSS = 1.2V, VEN = 0V Logic High Threshold EN, FREQ Logic Low Threshold EN, FREQ EN Input Current VEN = 0V or 5V FREQ Pull-down Current VFREQ = 3V 2 A Ω µA V/A 4.5 7 µA 110 220 Ω 1.4 2.5 % V 0.4 V 0 1 µA 5.5 8.5 µA Thermal Shutdown Temperature 160 °C Thermal Shutdown Hysteresis 20 °C Innovative PowerTM -4- www.active-semi.com Copyright © 2008 Active-Semi, Inc. ACT6390/ACT6391 Rev0, 13-May-08 FUNCTIONAL BLOCK DIAGRAM IN EN 4.5µA SOFT START COMP ERROR AMPLIFIER ERROR COMPARATOR + SW CONTROL AND DRIVE LOGIC + 1.24V - FB SS CLOCK SLOPE COMPENSATION + CURRENT SENSE AMPLIFIER 5.5µA FUNCTIONAL DESCRIPTION G (1) t SS = 2 . 2 × 10 5 × C SS The ACT6390 and ACT6391 are highly efficient step-up DC/DC converters that employ a currentmode, fixed frequency pulse-width modulation (PWM) architecture with excellent line and load regulation. Frequency Selection The ACT6390 and ACT6391 include a pinselectable operating frequency drive FREQ to a logic high for 1.3MHz operation, drive FREQ to a logic low for 700kHz operation. The ACT6390 and ACT6391 operate at constant switching frequency under medium to high load current conditions. At light loads, these devices operate in a pulse-skipping mode in order to improve light-load efficiency. Selectable operating frequency, in combination with the external compensation network, allows a wide range of flexibility in optimizing total solution size and cost. FREQ is internally pulled down by 5.5µA, this pin may be left unconnected to achieve a 700kHz operating frequency. Soft-Start The ACT6390 and ACT6391 both offer a programmable soft-start function which minimizes inrush current during startup. The soft-start period is programmed by connecting a capacitor (CSS) between SS and G. Operation of the soft-start function is as follows: when the IC is disabled, SS is actively discharged to G. Upon enabling the IC, CSS is charged with a 4.5µA current so that the voltage at SS increases in a controlled manner. The peak inductor current is limited by the voltage at SS, so that the input current is limited until the soft-start period expires, and the regulator can achieve its full output current rating. Setting the Output Voltage The ACT6390 and ACT6391 both feature external adjustable output voltages of up to 12V. To program the output voltage, simply connect a resistive voltage divider between the output, FB, and G, with resistors set according to the following equation: ⎡⎛ V R1 = R 2 × ⎢⎜⎜ OUT ⎣⎝ VFB ⎞ ⎤ ⎟⎟ − 1⎥ ⎠ ⎦ (2) Where VFB is 1.24V. The soft-start period can be calculated as a simple function of the soft-start capacitor using the equation: Innovative PowerTM - OSCILLATOR + FREQ -5- www.active-semi.com Copyright © 2008 Active-Semi, Inc. ACT6390/ACT6391 Rev0, 13-May-08 Inductor Selection As a step-up converter, the switch duty cycle (D) is determined by the input voltage (VIN) and output voltage (VOUT), as given by the following formula: D= VOUT − VIN VOUT ∆IL (3) For example: VIN = 3.3V, VOUT = 12V, fSW = 700kHz IOUT = 250mA, η = 85%, FREQ = G, K = 0.4 ⎛V ⎞ L = ⎜⎜ IN ⎟⎟ ⎝ VOUT ⎠ (4) I L (DC ) VIN V ×D DT = IN L L × fSW VOUT × IOUT VIN × η Assuming the minimum input voltage is 3V and low cost external components are used, yielding a low efficiency of just 80%. (6) IL (DC ,MAX ) = ∆IL (MAX ) = Solving equations (3),(4),(5) and (6) for the inductor value, ⎞ (VOUT − VIN ) η ⎟⎟ × ⎠ IOUT × fSW K (11) Select L = 10µH (5) Where η is typical efficiency. ⎛V L = ⎜⎜ IN ⎝VOUT ⎛ VOUT − VIN ⎞ η ⎜⎜ ⎟⎟ × ⎝ IOUT × fSW ⎠ K 0.85 ⎞ ⎛ 3.3V ⎞ ⎛ 12V − 3.3V =⎜ × ⎟ ⎜ ⎟ ≈ 7.99µH ⎝ 12V ⎠ ⎝ 250mA ×700kHz 0.4 ⎠ IL(DC) is the inductor DC current, given by: IL (DC ) = 2 2 Where: ∆IL is the inductor ripple current in steady state, typically chosen to be about 0.3, and ∆ IL = (10) 1.75 × fSW Where RCS is the current sense trans-resistance, RCS is 0.45Ω for ACT6390, and RCS = 0.3Ω for ACT6391. Define K= (VOUT − VIN ) × RCS L > LMIN = 250 mA ×12V = 1.25 A 3V × 0.8 3V × (12V − 3V ) = 0.32 A 12V ×10 µH × 700 kHz IPEAK (MAX ) = 1.25 A + 2 (7) (12) 1 0.32 A = 1.41A 2 (13) (14) For stability, This equation can be used to determine the correct trade-off between efficiency, current ripple, size and cost. LMIN = (12V − 3.3V ) × 0.45 Ω = 3.2 µH (15) 1.75 × 700kHz Which meets the slope compensation requirement. When selecting an inductor make sure that the inductors maximum DC current and saturation current exceed the maximum operation point, calculated by: I ×V IL (DC ,MAX ) = OUT (MAX ) OUT (8) VIN (MIN ) × η Loop Compensation REF FB 2 + - EA GM COMP 3 RCOMP CCOMP2 and CCOMP 1 IL(PEAK ,MAX ) = IL(DC,MAX ) + ∆IL(MAX ) 2 IOUT (MAX ) ×VOUT 1 VIN (MIN ) [VOUT −VIN (MIN ) ] = + × (9) VIN (MIN ) × η 2 VOUT × L × fSW The ACT6390 and ACT6391 feature a simple loop compensation scheme. Simple follow the procedure detailed below to determine suitable compensation components. For best results be sure to prototype to confirm the values, and adjust the compensation network (by inspecting the transient response, for example) as needed to optimize results for your particular application. If the output voltage is greater than two times of input voltage, that means the duty cycle is greater than 50%, the slope compensation is required for stability. When operating in this condition ensure that the inductor value is greater than LMIN: Innovative PowerTM When the converter operates with continuous inductor current, a right-half-plane zero exits in the loop’s gain-frequency response. To ensure stability, -6- www.active-semi.com Copyright © 2008 Active-Semi, Inc. ACT6390/ACT6391 Rev0, 13-May-08 CCOMP2, the cross-over frequency (unity gain-frequency) should be less than one-fifth of the right-half-plane zero fZ(RHP), and lower than one-fifteenth of switching frequency fsw. CCOMP2 = VIN × R LOAD 2 2VOUT × π × L Choose fC = CCOMP (16) For example: (3.3V )2 × ⎛⎜ 1 fZ (RHP ) , then calculate CCOMP: 5 fZ (RHP) R V G = FB × LOAD × M (1 − D ) VOUT RCS 2πfC = VIN × VFB RLOAD × GM × 2 RCS × 2πfC VOUT RCOMP K⎞ ⎛ RCS × VOUT × IOUT ⎜1 + ⎟ 2⎠ ⎝ = α × VFB × GM × VIN × η (17) CCOMP = α= (19) (20) The output capacitor is chosen to set the output pole for canceling the RCOMP, CCOMP zero. RLOAD × COUT 48Ω × 33µF = = 233kΩ CCOMP 6.8nF (29) If a ceramic capacitor is used with an assumed ESR of 20mΩ, (21) fZ (ESR ) = CCOMP2 is optional and can be used when the output capacitor has significant ESR. The ESR will form a zero as follows: 1 = 241kHz 2π × 33 µF × 20 mΩ (30) fZ(ESR) > fC Since the zero frequency is greater than the pole frequency ,CCOMP2 can be omitted. (22) If a tantalum capacitor is used, whose ESR is about 0.5Ω, If this zero occurs at a higher frequency than the cross-over frequency, it can be ignored. Otherwise, it should be canceled with the pole set by capacitor Innovative PowerTM RCOMP × CCOMP 180kΩ × 6.8nF = = 25.5 µF (28) RLOAD ⎛ 12V ⎞ ⎜ ⎟ ⎝ 0.25 A ⎠ RCOMP = GM: is the trans-conductance of the error amplifier. 1 2π × RESR × COUT (26) COUT can be chosen to be either 22µF or 33µF, choose 33µF to reduce droop. VFB: is the feedback voltage, 1.24V fZ (ESR ) = 200 mV 1 = 60 12V COUT = η: is the typical efficiency. RCOMP × CCOMP RLOAD 3.3V ×1.24V 48Ω 150µS × × = 6.26nF (25) 2 0.45Ω 2π ×11.56kHz (12V ) ⎛ 0.4 ⎞ 0.45Ω ×12V × 250mA⎜1 + ⎟ 2 ⎠ ⎝ RCOMP = = 186.3kΩ (27) 1 ×1.24V ×150µS × 3.3V × 0.85 60 Choose RCOMP = 180kΩ K: is defined in equation (4) COUT = 1 fZ (RHP ) = 11.56 kHz 5 Assume that 200mV of transient droop can be accepted: (18) α is the transient droop percentage which can be accepted, calculated by: ∆VOUT VOUT (24) Choose CCOMP = 6.8nF Where: α= 12V ⎞ ⎟ ⎝ 250mA ⎠ ≈ 57.8kHz = 2 2 × (12V ) × π ×10 µH Choose fC = Select RCOMP to meet the transient-droop requirements. V ×I ⎛ K⎞ α ×VFB × GM × RCOMP = RCS × OUT OUT × ⎜1 + ⎟ VIN × η ⎝ 2⎠ (23) If the value of CCOMP2 calculated by (23) is smaller than 10pF, CCOMP2 can be omitted. 2 fZ (RHP ) = COUT × RESR RCOMP -7- www.active-semi.com Copyright © 2008 Active-Semi, Inc. ACT6390/ACT6391 Rev0, 13-May-08 fZ (ESR) = 1 = 9.64kHz 2π × 33µF × 0.5 Ω (31) fZ(ESR) < fC RESR × COUT 0.5 Ω × 33µF = = 70.8 pF RCOMP 233kΩ Choose CCOMP2 = 82pF CCOMP2 = (32) Rectifier Selection For optimal performance, the rectifier should be a Schottky rectifier that is rated to handle both the output voltage as well as the peak switch current. Over Voltage Protection The ACT6390 and ACT6391 both feature internal automatic over-voltage protection (OVP). Once the outputs achieve regulation, if the voltage at FB falls below 0.125V the controller will automatically disable and latch off, preventing the controller from running open-loop and potentially damaging the IC and load. To re-enable the converters, simply cycle the EN pin or remove and reapply power to the input. Shutdown Drive EN low to disable the IC and reduce the supply current to just 0.1µA. As with all nonsynchronous step-up DC/DC converters, the external Schottky diode provides a DC path from the input to the output in shutdown. As a result, the output drops to one diode voltage drop below the input in shutdown. Thermal Shutdown The ACT6390 and ACT6391 both feature integrated thermal overload protection. Both devices are automatically disabled when their junction temperatures exceed 160°C, and automatically re-enable when the die temperature decreases by 20°C. Innovative PowerTM -8- www.active-semi.com Copyright © 2008 Active-Semi, Inc. ACT6390/ACT6391 Rev0, 13-May-08 TYPICAL PERFORMANCE CHARACTERISTICS (VIN = VEN = 3.3V, FREQ = G, TA = 25°C, unless otherwise specified.) ACT6390 Efficiency vs. Output Current FREQ = IN L = 2.7µH 80 85 FREQ = G L = 5.4µH 75 VIN = 5V VOUT = 12V 90 Efficiency (%) 85 70 65 FREQ = G L = 10µH 80 FREQ = IN L = 5.4µH 75 70 65 60 60 55 55 50 50 0 10 100 0 1000 10 ACT6390 Efficiency vs. Output Current ACT6390 No Load Supply Current vs. VIN 80 Supply Current (mA) 85 FREQ = G L = 10µH 75 FREQ = IN L = 5.4µH 70 65 60 0.36 FREQ = IN L = 5.4µH ACT6390-004 VIN = 3.3V VOUT = 12V 90 1000 0.40 ACT6390-003 95 100 Output Current (mA) Output Current (mA) Efficiency (%) ACT6390-002 VIN = 3.3V VOUT = 5V 90 Efficiency (%) ACT6390 Efficiency vs. Output Current 95 ACT6390-001 95 0.32 0.28 FREQ = G L = 10µH 0.24 55 0.20 50 0 10 100 1000 2.5 3 3.5 Output Current (mA) 4 4.5 5 5.5 VIN (V) 2200 ACT6390-005 Maximum Output Current (mA) ACT6390 Maximum Output Current vs. Input Voltage FREQ = G 1800 1400 VOUT = 5V VOUT = 9V 1000 600 VOUT = 12V 200 0 2.5 3.1 3.7 4.3 4.9 5.5 Input Voltage (V) Innovative PowerTM -9- www.active-semi.com Copyright © 2008 Active-Semi, Inc. ACT6390/ACT6391 Rev0, 13-May-08 TYPICAL PERFORMANCE CHARACTERISTICS (VIN = VEN = 3.3V, FREQ = G, TA = 25°C, unless otherwise specified.) ACT6391 Efficiency vs. Output Current Efficiency (%) 85 80 85 FREQ = IN L = 4.7µH 75 VIN = 5V VOUT = 12V 90 Efficiency (%) FREQ = G L = 5.4µH 70 65 FREQ = IN L = 4.7µH 80 75 FREQ = G L = 10µH 70 65 60 60 55 55 50 50 0 10 100 0 1000 10 ACT6391 Efficiency vs. Output Current 85 80 75 Supply Current (mA) FREQ = G L = 10µH 0.40 FREQ = IN L = 4.7µH 70 65 60 ACT6391-009 VIN = 3.3V VOUT = 12V 90 1000 ACT6391 No Load Supply Current vs. VIN ACT6391-008 95 100 Output Current (mA) Output Current (mA) Efficiency (%) ACT6391-007 VIN = 3.3V VOUT = 9V 90 ACT6391 Efficiency vs. Output Current 95 ACT6391-006 95 VOUT = 12V 0.36 FREQ = IN L = 4.7µH 0.32 FREQ = G L = 10µH 0.28 0.24 55 0.20 50 0 10 100 1000 2.5 3 3.5 Output Current (mA) 4 4.5 5 5.5 VIN (V) 2400 ACT6391-010 Maximum Output Current (mA) ACT6391 Maximum Output Current vs. Input Voltage FREQ = G 2000 VOUT = 5V 1600 VOUT = 9V 1200 800 400 VOUT = 12V 0 2.5 3 3.5 4 4.5 5 Input Voltage (V) Innovative PowerTM - 10 - www.active-semi.com Copyright © 2008 Active-Semi, Inc. ACT6390/ACT6391 Rev0, 13-May-08 PACKAGE OUTLINE MSOP-8 PACKAGE OUTLINE AND DIMENSIONS e C DIMENSION IN SYMBOL MILLIMETERS MIN MAX DIMENSION IN INCHES MIN MAX A 0.820 1.100 0.032 0.043 A1 0.020 0.150 0.001 0.006 A2 0.750 0.950 0.030 0.037 b 0.250 0.380 0.010 0.015 C 0.090 0.230 0.004 0.009 D 2.900 3.100 0.114 0.122 E 2.900 3.100 0.114 0.122 E1 4.750 5.050 0.187 0.199 E E1 L b A2 D e A A1 θ 0.650 TYP 0.026 TYP L 0.400 0.800 0.016 0.031 θ 0° 6° 0° 6° 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 lifesupport 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@example.com or visit http://www.active-semi.com. For other inquiries, please send to: 1270 Oakmead Parkway, Suite 310, Sunnyvale, California 94085-4044, USA Innovative PowerTM - 11 - www.active-semi.com Copyright © 2008 Active-Semi, Inc.