Synchronous Buck Controller

Synchronous Buck Controller with Dual-Level VOUT Transition Support POWER MANAGEMENT POWER MANAGEMENT Description The SC475A is a versatile, constant on-time synchronous buck, pseudo-fixed-frequency, PWM controller intended for notebook computers and other battery operated portable devices. The SC475A contains all the features needed to provide cost-effective control of system elements needing voltage slewing. An integrated switch provides two resistorprogrammable DC output voltages controlled by the G0 input. www.DataSheet4U.com SC475A Features VOUT Programmable 0.75V to 5.25V with Integrated Transition Support VBAT Range 3V to 25V Soft Shutoff at Output Current Sense Using Low-side RDS(ON) or Resistor Sensing Adjustable Cycle-by-Cycle Valley Current Limit 325kHz Fixed-Frequency Constant On-Time for Fast Dynamic Response and Reduced Output Capacitance Automatic Smart Power Save† Internal Soft-Start Over-Voltage/Under-Voltage Fault Protection Power Good Output with Transition Blanking 1μA Typical Shutdown Current 500μA Typical Operating Current Tiny 3×3mm, 16 Pin MLP Package Low External Part Count Industrial Temperature Range 0.85% Internal Reference 1A/3A Non-Overlapping Gate Drive with SmartDriver™ Technology High Efficiency > 90% Device is Fully WEEE and RoHS Compliant †Patent The output voltage is adjustable from 0.75V to 5V. Additional features include cycle-by-cycle current limit, voltage soft-start, under-voltage protection, programmable over-current protection, soft shutdown, automatic power save and non-overlapping gate drive. The SC475A provides an enable input and a power good output which is automatically blanked during output voltage transitions. The constant on-time topology provides fast dynamic response. The excellent transient response means that SC475A based solutions require less output capacitance than competing fixed-frequency converters. Switching frequency is constant until a step in load or line voltage occurs, at which time the pulse density and frequency will increase or decrease to counter the change in output voltage. After the transient event, the controller frequency returns to steady state operation. At light loads, the automatic power save mode reduces the SC475A frequency for improved efficiency. Pending Applications Notebook/Sub-Notebook Graphics Voltage Controllers Tablet PCs Embedded Applications September 25, 2006 1 www.semtech.com SC475A POWER MANAGEMENT Typical Application Circuit VCC C4 D1 VBAT R4 C3 Q1 G0 www.DataSheet4U.com 16 15 14 G0 C2 L1 VOUT 1 2 C1 VCC Q2 3 4 DH ILIM NC 13 LX BST VCC DL EN 12 11 10 9 EN PGOOD VOUT U1 PGOOD SC475A RTN NC VOUT FB GND 5 6 7 8 R3 D0 R1 R2 © 2006 Semtech Corp. 2 www.semtech.com SC475A POWER MANAGEMENT Absolute Maximum Rating Exceeding the specifications below may result in permanent damage to the device or device malfunction. Operation outside of the parameters specified in the Electrical Characteristics section is not implied. Exposure to Absolute Maximum rated conditions for extended periods of time may affect device reliability. Parameter DH, BST to GND (DC) DH, BST to GND (transient - 100nsec max) DL to GND (DC) DL to GND (transient - 100nsec max) Symbol Min -0.3 -2.0 -0.3 -2.0 -0.3 -2.0 -0.3 -0.3 -0.3 -0.3 Max +30 +33 +6.0 +6.0 +25 +28 +6.0 +0.3 +6.0 VCC + 0.3 +125 +150 o Units V V V V V V V o o LX to GND (DC) www.DataSheet4U.com LX to GND (transient - 100nsec max) BST to LX RTN to GND VCC to RTN D0, EN, FB, G0, ILIM, PGOOD, VOUT to RTN Operating Junction Temperature Range Storage Temperature Range Thermal Resistance, Junction to Ambient(1) Peak IR Reflow Temperature, (10-40sec) ESD Rating (Human Body Model) TJ TSTG -40 -60 45 C C θJA TPKG C/Watt o +260 2 C kV Note: 1) Calculated from package in still air, mounted 3” to 4.5”, 4 layer FR4 PCB with thermal vias under the exposed pad per JESD51 standards. Electrical Characteristics Test Conditions: VBAT = 15V, VOUT = 1.5V, TA = 25 oC, 0.1% resistor dividers; VCC = 5.0V. Parameter Input Supplies VBAT Input Voltage VCC Input Voltage VCC Shutdown Current VCC Operating Current Controller FB On-Time Threshold Output Voltage Adjust Range(1) D0 Pull-Down Resistance © 2006 Semtech Corp. Conditions Min 25°C Typ Max -40° to 85°C Min Max Units 3.0 4.5 EN = 0V FB > 0.8V 1 500 25 5.5 5 1000 V V μA μA 0 to 85°C -40 to 85°C 0.75 0.7436 0.7564 0.7425 0.7575 0.75 5.25 40 V V Ω D0 to RTN; G0 = RTN 15 3 www.semtech.com SC475A POWER MANAGEMENT Electrical Characteristics (continued) 25°C Parameter Conditions Min Regulation Line Regulation Error Load Regulation Error Timing www.DataSheet4U.com On-Time Minimum On-Time Minimum Off-Time Maximum Duty Cycle Soft-Start Soft-Start Time Analog Inputs/Outputs VOUT Input Resistance FB Input Bias Current Current Sense Zero Crossing Detector Threshold Power Good Power Good Threshold Threshold Delay Time(1) Voltage Transition Blank Time(1) Leakage Fault Protection ILIM Source Current ILIM Comparator Offset Current Limit (Negative) Output Under-Voltage Fault LX - GND FB with Respect to Nominal 10 0 80 -30 9 -10 60 -35 11 +10 100 -25 μA mV mV % G0 Transition 1% Hysteresis Typical -20% 5 32 1 -17% -23% V μs clks μA LX - GND 0 -7 +7 mV 500 -1 +1 kΩ μA IOUT = ILIM/2 1000 μs VBAT = VOUT + 0.2 FB < 0.7V VOUT = 1.1V 250 100 350 85 80 225 275 ns ns ns % Typical Application Circuit Typical Application Circuit 0.04 0.3 %/V % Typ Max Min Max -40° to 85°C Units © 2006 Semtech Corp. 4 www.semtech.com SC475A POWER MANAGEMENT Electrical Characteristics (continued) 25°C Parameter Fault Protection (continued) Steady-State Over-Voltage Fault Steady-State Over-Voltage Fault Delay www.DataSheet4U.com G0 Transition Over-Voltage Fault Smart Power Save Threshold Over-Temperature Shutdown(1) Logic Inputs/Outputs Logic Input High Voltage Logic Input Low Voltage EN Input Bias Current G0 Input Bias Current Power Good Output Low Voltage Gate Drivers Shoot-Through Protection Delay(1) DL Pull-Down Resistance DL Sink Current DL Pull-Up Resistance DL Source Current DH Pull-Down Resistance DH Pull-Up Resistance(2) DH Sink/Source Current VDL = 2.5V BST - LX = 5V BST - LX = 5V VDH = 2.5V VDL = 2.5V DH or DL Rising 30 0.8 3.1 2 1.3 2 2 1.3 4 4 4 1.6 ns Ω A Ω A Ω Ω A EN, G0 EN, G0 EN = 5V G0 = 5V RPWRGD = 10kΩ to VCC 5 -1 0 1.2 0.4 +1 10 0.4 V V μA μA V FB with Respect to Nominal FB Forced 50mV Above Over-Voltage Fault Threshold FB with Respect to Nominal; Valid for 32 cycles after G0 Transition FB with Respect to Nominal Latching, >10°C Hysteresis +20 5 +17 +23 % μs Conditions Min Typ Max Min Max -40° to 85°C Units +50 +8 160 % % °C Notes: 1) Guaranteed by design. 2) Semtech’s SmartDriver™ FET drive first pulls DH high with a pull-up resistance of 10Ω (typical) until LX = 1.5V (typical). At this point, an additional pull-up device is activated, reducing the resistance to 2Ω (typical). This negates the need for an external gate or boost resistor. © 2006 Semtech Corp. 5 www.semtech.com SC475A POWER MANAGEMENT Pin Configuration DH NC G0 ILIM Ordering Information Device SC475AMLTRT(1) SC475AEVB 12 11 10 T 9 7 8 Package(2) MLPQ-16 3X3 Evaluation Board 16 15 14 13 LX BST www.DataSheet4U.com 1 2 3 4 5 TOP VIEW EN PGOOD VOUT FB VCC DL Notes: 1) Available in tape and reel packaging only. A reel contains 3000 devices. 2) Available in lead-free packaging only. This product is fully WEEE, RoHS and J-TD-020B compliant. This component and all homogenous subcomponents are RoHS compliant. 6 GND RTN NC MLPQ16: 3X3 16 LEAD Marking Information 475A yyww xxxx Marking for the 3x3mm MLPQ 16 Lead Package nnn = Part Number (Example: 475A) yyww = Date Code (Example: E652) xxxx = Semtech Lot No. (Example: E901) © 2006 Semtech Corp. D0 6 www.semtech.com SC475A POWER MANAGEMENT Pin Descriptions Pin 1 2 3 4 www.DataSheet4U.com 5 Pin Name LX BST VCC DL GND RTN NC D0 FB VOUT PGOOD EN ILIM G0 NC DH PAD Pin Function Switching (phase) node. Boost capacitor connection for high-side gate drive. 5V power input for the internal circuits and gate drive outputs. Gate drive output for the low-side external MOSFET. Power ground. This is the return point for the DL driver output, and the reference point for the ILIM and zero cross circuits. Return or analog ground for the FB input and FB resistor divider . Connect to GND directly at the IC. All feedback components should connect to this ground. Not connected internally — leave unconnected or connect to GND. Drain of the internal MOSFET which is controlled by G0. Feedback sense point. The FB threshold is 0.75V; the resistor divider ratio between VOUT and FB sets the output voltage. This ratio can be modified using the G0 input to switch a resistor in or out at D0. Output voltage sense point for determining On-Time. Open-drain power good indicator - a high impedance indicates power is good. An external pull-up resistor is required. Enable input - connect EN to RTN to disable the SC475A. Current limit sense point — to program the current limit connect a resistor from ILIM to LX or to a current sense resistor. Control input for the D0 MOSFET. A logic low energizes the D0 MOSFET, pulling D0 to ground. Not connected internally — leave unconnected or connect to GND. Gate drive output for the high-side external MOSFET. Mounting pad. Not connected internally - connect to system ground plane through preferably one large vias or multiple smaller vias. 6 7 8 9 10 11 12 13 14 15 16 T © 2006 Semtech Corp. 7 www.semtech.com SC475A POWER MANAGEMENT Block Diagram +5V VBAT BST ILIM Valley I-Limit DH LX +5V QB R VCC UVLO www.DataSheet4U.com DRV 0.75V REF S Q RTN VOUT DL DRV TON Predictor VOUT FB D0 Control and Status G0 EN PGD PAD GND +5V Power Good © 2006 Semtech Corp. 8 www.semtech.com SC475A POWER MANAGEMENT Applications Information SC475A Synchronous Buck Controller The SC475A is a synchronous power su