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Document overview
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Technical content
Features
Patented X-EMITM Inductor Technology Enables Trace Inductors in PC Board Material Excellent EMI Performance Efficiency up to 90% 9µA Quiescent Current under Very Light Loads Wide Input Voltage Range — 2.7V to 5.5V Adjustable Output Voltage Down to .0V Output DC Current — up to 650mA High Light-load Efficiency via Automatic PSAVE Mode Ultra-fast Transient Response — <µs Temperature Range — -40 to +85°C Shutdown Current — 0.µA (typical) Requires Tiny 220nH Inductor Requires Only μF of Output Capacitance External Switching Frequency Synchronization Protection Features Including Over-Current Protection Output Short-Circuit Protection Thermal Shutdown Protection Offered in SOIC 8 Lead Package Lead-free, halogen-free, and RoHS/WEEE Compliant AEC-Q00 Qualified Version Available
Applications
HDTV, Set Top Boxes, Gaming Consoles POL Applications White Goods Automotive AEC-Q00 Qualified Applications
Description
The SC220/Q is a 20MHz X-EMI™ ()-enabled step-down regulator optimized for power low voltage rails from 2.7 to 5.5V input voltage. X-EMI™ inductor technology enables inductors to be drawn directly on the PC board. This technology meets or exceeds the EMI performance of chip inductors and eliminates the need for discrete inductors. The SC220/Q uses a unique constant frequency, self- oscillating control loop architecture to provide excellent transient performance. Under light loads, the device operates in Power Save mode(PSAVE) maintaining a typical quiescent current of 9µA. At moderate to heavy loads, this part operates in PWM mode with a constant switching frequency of 20MHz. This high switching fre - quency offers the advantages of using small and low cost external components like a µF external capacitor and a small 220nH inductor (including X-EMI TM PCB trace inductors). The device provides adjustable output voltages down to .0V and an output current up to 650mA. An EN pin can be used to synchronize to an external source and includes de-glitching to reduce noise sensitivity. The SC220/Q is available in SOIC 8 lead package. The SC220Q is an AEC-Q00 qualified version. Note : Purchase of SC220/Q includes royalty-free right to use X-EMITM inductor technology with no addi- tional cost. Typical Application Circuit January 5, 203 SC220 SC220Q A G N D S W V O U T VIN L, 220 nH C O U T 1 µF E N E nable F B A V IN P V IN C IN 1 µF R 1 R 2P G N D V O U T=1.8V up to 650 m A 2.7~5.5V
Ordering Information
SC220STRT ()(2) SOIC 8 Lead SC220QSTRT ()(2)(3) SOIC 8 Lead SC220EVB Evaluation Board SC220QEVB Evaluation Board Notes: () Available in tape and reel only. A reel contains 2,500 devices. (2) Device is lead-free, halogen-free, and RoHS/WEEE compliant. (3) Device is AEC-Q00 qualified. xxxxx = S em tech Lot N um ber nnnnn = P art N um ber yyw w = D ate code SC220 yyww xxxxx P G N D A G N D A V IN FB E N S W V O U T P V IN SOIC 8 Lead, θJA = 38 °C/W xxxxx = S em tech Lot N um ber nnnnnn = P art N um ber yyw w = D ate code SC220Q yyww xxxxx
Exceeding the above specifications may result in permanent damage to the device or device malfunction. Operation outside of the parameters specified in the Electrical Characteristics section is not recommended. Notes: () All voltage values in this section are with respect to PGND pin voltage. (2) Tested according to JEDEC standard JESD22-A4-B. (3) Calculated from package in still air, mounted to 3 x 4.5 (in), 4 layer FR4 PCB with thermal vias under the exposed pad per JESD5 standards. Absolute Maximum Ratings Recommended Operating Conditions Thermal Information Thermal Resistance, Junction to Ambient (2) (°C/W)....38 Unless otherwise specified: AVIN=PVIN = 3.6V, EN = AVIN = PVIN, CIN=COUT =.0μF, L=220nH. TA = 25°C for typical values, -40°C < TA = TJ < 85°C for minimum and maximum values. Parameter Symbol Condition Min Typ Max Units POWER SUPPLY Input Voltage VIN 2.7 5.5 V Input Quiescent Current IVIN_Q No load, no switching 9 40 µA Shutdown Current IVIN_SD EN = 0V .0 µA POWER SWITCH PMOS On Resistance 400 mΩ NMOS On Resistance 360 mΩ OSCILLATOR Switching Frequency fOSC PWM Mode 6 20 24 MHz REGULATION Output Voltage Tolerance() VOUT_TOL -4.0 4.0 % Current Limit ILIMIT 850 300 mA Soft-Start() tSS EN pin low to high 40 µs
Electrical Characteristics
Parameter Symbol Condition Min Typ Max Units Feedback Leakage Current IFB µA ENABLE EN Input High Voltage Threshold VENH .2 V EN Input “Low” Voltage Threshold VENL 0.4 V EN Input High Current IENH VEN= VIN -.0 .0 µA EN Input Low Current IENL VEN= AGND -.0 .0 µA Minimum Synchronization Frequency fSYN_MIN Square wave applied at EN pin 3 MHz PROTECTION Over Temp Thermal Shutdown() TOT 50 °C Thermal Shutdown Hysteresis() THYST 5 °C Notes () Guaranteed by design. Not tested in production. Electrical Characteristics (continued) Unless otherwise specified: AVIN=PVIN = 3.6V, EN = AVIN = PVIN, CIN=COUT =.0μF, L=220nH. TA = 25°C for typical values, -40°C < TA = TJ < 85°C for minimum and maximum values.
Pin # Pin Name Pin Function SW Switching output node — connect to the output LC filter. 2 PVIN Power input supply voltage (2.7 to 5.5V). 3 VOUT Input for sensing the output of LC filter. 4 FB Input for regulation of output LC filter — Using R and R2 to set the output voltage, VOUT = VFB x (+ R/R2). (Please refer to the typical application circuit diagram on page ). 5 EN Enable Input — when low, circuit draws <µA. Apply a square wave clock at EN to synchronize the switching frequency with an external clock. It is recommended that the externally applied clock frequency should not be above 20MHz.
6 AVIN Input supply voltage
7 AGND Analog ground
8 PGND Power ground
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Efficiency vs. VIN Input Voltage (V) IOUT = mA IOUT = 50mA IOUT = 300mA Efficiency vs. Load Current Load Current (A) Efficiency VOUT = .8V VIN = 3.7V 0.00 0.0 0. 30 % 40 % 50 % 60 % 70 % 00 % VIN = 4.2V 80 % 90 % VIN = 2.7V Efficiency VOUT = .8V Typical Characteristics Switching Frequency vs. VIN Switching Frequency vs. VIN Input Voltage (V) IOUT = 650mA Switching Frequency (MHz) 5.0 0.0 5.0 20.0 22.5 2.5 7.5 2.5 7.5 VOUT = .8V 5.0 IOUT = 450mA IOUT = 300mA IOUT = 200mA Input Voltage (V) IOUT = 650mA Switching Frequency (MHz) 5.0 0.0 5.0 20.0 22.5 2.5 7.5 2.5 7.5 VOUT = .0V 5.0 IOUT = 450mA IOUT = 300mA IOUT = 200mA Load Regulation Output Voltage (V) .77 .79 .80 .78 Nominal VOUT = .8V VIN = 3.7V VIN = 4.2V VIN = 5.0V VIN = 2.7V Load Current (A) 0.00 0.0 0. 0 % 20 % Efficiency vs. Load Current (Chip Inductor vs. X-EMITM Inductor) Load Current (A) Efficiency VOUT = .8V VIN = 3.7V 0.00 0.0 0. VIN = 4.2V VIN = 2.7V 30 % 40 % 50 % 60 % 70 % 00 % 80 % 90 % 0 % 20 % Dashed Lines: Efficiency with X-EMITM Inductor Solid Lines: Efficiency with chip Inductor 30 % 40 % 50 % 60 % 70 % 00 % 80 % 90 % 0 % 20 %
Load Transient Response Load Transient Response Typical Characteristics (Continuous) VIN = 3.7V, VOUT = 2.0V, IOUT = 0mA - 650mA Time (1µs/div) VOUT (ac coupled) 00mV/div. IOUT 200mA/div. VIN = 3.7V, VOUT = 2.0V, IOUT = 200mA - 500mA Time (1µs/div) VOUT (ac coupled) 50mV/div. IOUT 200mA/div. Steady State Operation (IOUT = 50mA) Steady State Operation (IOUT = 300mA) Time (200ns/div) IOUT 50mA/div. VIN = 3.6V, VOUT = .8V, IOUT = 50mA IL 200mA/div. VSW 2V/div. Time (50ns/div) IOUT 200mA/div. VIN = 3.6V, VOUT = .8V, IOUT = 300mA IL 200mA/div. VSW 2V/div. Output Hard Short Time (500ns/div) VOUT V/div. VIN = 5.0V, VOUT = .8V, IOUT = 650mA IL 500mA/div. IOUT 500mA/div. Input Quiescent Current vs. Temperature Temperature (°C) Quiescent Current (µA) -40 -20 0 20 40 80 8.5 20.0 9.0 9.5 VIN = 5.5V, EN = High, FB = High 60 00
Start-up Operation Disable Operation Typical Characteristics (Continuous) VIN = 3.7V, VOUT = .8V, IOUT = 0mA EN 5V/div. VOUT V/div. IOUT 0mA/div. VIN 2V/div. VIN = 3.7V, VOUT = .8V, IOUT = 0mA EN 5V/div. VOUT V/div. IOUT 0mA/div. VIN 2V/div. Time (20µs/div) Time (100µs/div) Start-up Operation Disable Operation VIN = 3.7V, VOUT = .8V, IOUT = 650mA EN 5V/div. VOUT V/div. IOUT 500mA/div. VIN 2V/div. VIN = 3.7V, VOUT = .8V, IOUT = 650mA EN 5V/div. VOUT V/div. IOUT 500mA/div. VIN 2V/div. Time (20µs/div) Time (20µs/div)
The SC220/Q is a step-down regulator capable of deliver- ing a lower voltage from an input supply voltage of 2.7V to 5.5V with high efficiency. Using a unique control archi- tecture, the SC220/Q is capable of delivering a peak efficiency of 90%, while maintaining efficiency over 80% during light load condition. The converter operates at 20MHz switching frequency with pulse width modulation (PWM) at moderate to heavy loads up to 650mA. Under light load, the converter operates in power save (PSAVE) mode. Control Scheme The SC220/Q operates with a self-oscillating control method based on the output voltage ripple. This control loop compares the output voltage to an internal V refer- ence to regulate the output voltage directly, adjusting the turn-on and turn-off time of the power switches such that the output voltage at the load is held at a precise value. This architecture gives a single-cycle response to transient events. To maintain constant frequency, a phase locked loop (PLL) is included to synchronize the switching with an internal clock. This PLL adjusts the effective upper and lower thresholds of the comparator, thus maintaining a constant frequency. Under transient conditions the voltage control loop determines the required switching pattern to best maintain the output voltage. After a short transient, the PLL will bring the switching frequency back to normal. At extreme duty cycles, where the frequency control loop may not be able to maintain frequency lock even under steady-state conditions, frequency may fall, but the output voltage regulation will be maintained by the main voltage control loop. This unique architecture helps to achieve the excellent line and load transient response. Operating Modes The SC220/Q operates in two modes over a wide range of load currents. At moderate to high load, it operates in PWM mode with its switching frequency held constant. Under light loads, the converter enters PSAVE mode auto- matically. With the typical 220nH inductor, the transition between PWM and PSAVE mode typically occurs in the range of 00-200mA, depending on the input and output voltages. At very light loads, the SC220/Q maintains high efficiency by shutting down all but the most essential circuit blocks, maintaining a typical quiescent current of about 9µA. In this mode, some circuitry used to control absolute DC accuracy is turned off. In that case, there may be a small DC shift (tens of mV) between normal opera - tion and this ‘no-load’ state. However, in the case of a load transient, the system will turn on the high-side FET within nanoseconds as a discontinuous pulse is issued. The tran- sition to PWM mode can occur within that nominal on-time, giving superior no load to full load transient response. The transition from PWM mode to PSAVE mode is con - trolled by sensing the minimum value of the ripple current. When it drops below a threshold level for 32 con- secutive cycles, the transition to PSAVE mode is initiated. Once in PSAVE, the regulation is maintained by modulat- ing the time between fixed current pulses. When a new pulse is required by the loop before the existing pulse has terminated, the loop determines that the load cannot be maintained in PSAVE mode. This prompts an instanta - neous switch from PSAVE mode back to PWM mode. Enable and Start-up The SC220/Q is enabled by applying a voltage higher than .2V on EN pin pin, and it is disabled when the applied voltage is pulled below the logic low threshold. The EN pin can also be used to set the switching fre - quency: if a digital clock is fed to EN, the SC220/Q will sense this as a valid enable signal and the external clock will be used rather than the internal 20MHz oscillator. The SC220/Q has an internal soft start circuit that limits the inrush current during start-up with a stepped current limit. Over the course of about 40μs, the SC220/Q is stepped in increments of one quarter of the nominal current limit to full current limit, thereby reducing the worst-case surge current that might otherwise be reflected to the input current. Current Limit The SC220/Q integrates a current limit feature to protect itself and the external components during over load con- dition. When the current in the high-side PMOS switch exceeds the current limit, the PMOS switch is turned off. Applications InformationApplications Information
The high-side switch is then held off for a period sufficient to allow inductor current to decay. When the output voltage is close to the nominal regulation point, this will look similar to constant current limiting. As the output voltage falls, imposed off-time is such that the frequency will drop so that the inductor will have appropriate time to reset. This may cause the average current to reduce, giving a mild ‘fold-back’ characteristic to the current limit, where the average load current drops as the output voltage collapses (although the peak current maintains its nominal value). In a short-circuit condition, the system runs continuously at this reduced frequency. Load Transient Response The SC220/Q features excellent regulation during line and load transients. This is due to the nature of the proprietary control method and the high di/dt allowed by the use of a small inductor. This allows for best performance while providing the benefit of using a small low cost output capacitor. VOUT shows only tens of milivolts of ripple voltage during a load current step change of mA to 650mA within hundreds of nanoseconds, using a μF output capacitor. (See the typical performance curves on page 7). X-EMI™ Inductor Technology The SC220/Q is the industry’s first buck regulator that enables designers to draw their own inductors directly on the PC board. This patented technology is called as X- EMI™ inductor technology and is different from conventional PCB trace inductors. Conventional PCB trace inductors can be used with high-frequency switchers, but they exhibit significant EMI issues. X-EMI™ inductor tech - nology solves these EMI problems and can meet or exceed the EMI performance of conventional chip inductors. X-EMITM technology works by placing two small air-core inductors adjacent to one another in anti-phase position, where the magnetic fields of each inductor partially cancel one another to reduce EMI. The net flux from the two inductors, partially cancels the wide leakage paths caused by the wide geometry, while still storing the energy of the inductors in series. This approach uses multiple air core inductors implemented using printed circuit traces. Because these traces may be located on internal layers of the PCB, inductors can be designed with almost no impact on the available PCB area for components on the surface of the board. (See the efficiency curves using X-EMI™ inductor technology on page 6). External Components The input and output capacitors used for the operation of the SC220/Q should be multilayer ceramic capacitors, preferably with X7R or X5R dielectric. SC220/Q is opti - mized to operate with the input and output capacitance of μF typical. In practice, the self-resonant frequency of surface mount capacitors of this type is well below 20MHz ripple frequency, so efforts to minimize output ripple may best be focused on minimizing the inductance of the output capacitor and the length of the circuit path to ground rather than on increasing the capacitance value of the output capacitor. The inductor should be a high current inductor rated for currents at least up to A. Typical power inductors may be too lossy at 20MHz unless specifically designed for high frequency operation. For inductor value of 220nH, it may be preferred to use wire-wound RF chokes, many of which are rated for appropriate currents. Some Recommended External Components Value Manufacturer Part Number Package L 0.22μH Coilcraft XFL2005-22ME 2x2mm 0.24μH Coilcraft 0603LS-24XJL 0603 CIN μF Murata GRM55R6C05KA2 0402 COUT μF Murata GRM55R6C05KA2 0402 Applications Information (Cont.) Figure . Top view of an evaluation board with X-EMI inductor
Applications Information (Cont.) PCB Layout Considerations Fundamental layout rules must be followed since the layout is critical for achieving the desirable performance. Poor layout can degrade the performance of the DC-DC converter and can contribute to EMI problems, ground bounce, and resistive voltage losses, and possibly poor regulation and instability. The following guidelines are recommended when devel - oping a PCB layout: The input capacitor, C IN should be placed as close to the PVIN and PGND pins as possible. This capacitor provides a low impedance loop for the pulsed currents present at the buck converter’s input. Use short wide traces to connect this capacitor as close to the IC as possible. This will minimize EMI and input voltage ripple by localizing the high frequency current pulses. Keep the SW pin traces as short as possible to minimize pickup of high frequency switching edges to other parts of the circuit. COUT and L should be connected as close as possible between the SW and GND pins, with a direct return to the GND pin from COUT. Route the output voltage feedback/sense path away from the inductor and SW node to minimize noise and magnetic interference to the output feedback/ sense path. Use a ground plane referenced to the PGND pin, and the ground connection of the input and output capacitors should be put on this plane and close to each other if possible, and as close to the PGND pin as possible. Use several vias to connect to the component side ground to further reduce noise and interference on sensitive circuit nodes. If possible, minimize the resistance from the VOUT and AGND pin to the load. This will reduce the voltage drop on the ground plane and improve the load regulation. And it will also improve the overall efficiency by reducing the copper losses on the output and ground planes.
Outline Drawing — SOIC 8 Lead S E E D E TA IL D E T A IL AA .050 B S C .236 B S C .010 .150 .189 .154 .193 .012 - 0.25
1.27 B S C
6.00 B S C
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Land Pattern —SOIC 8 Lead (.205) (5.20) ZG Y P (C ) 3.00.118 1.27.050 0.60.024 2.20.087 7.40.291 X IN C H E S D IM E N S IO N S Z P Y X D IM C G M ILLIM E TE R S T H IS LA N D P A T T E R N IS F O R R E F E R E N C E P U R P O S E S O N LY . C O N S U LT Y O U R M A N U F A C T U R IN G G R O U P T O E N S U R E Y O U R C O M P A N Y 'S M A N U F A C T U R IN G G U ID E LIN E S A R E M E T . N O T E S : R E F E R E N C E IP C -S M -782A , R LP N O . 300A .2.
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