SC221 SEMTECH | Alldatasheet
Document overview
- Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
- PDF pages: 14
Technical content
Features
Patented X-EMITM Inductor Technology Enables Trace Inductors in PC Board Material Excellent EMI Performance Efficiency up to 90% 17.5µA Quiescent Current under Very Light Loads Wide Input Voltage Range — 2.7V to 5.5V Adjustable Output Voltage Down to 1.0V Output DC Current — up to 650mA High Light-load Efficiency via Automatic PSAVE Mode Ultra-fast Transient Response — <1µs Temperature Range — -40 to +85°C Shutdown Current — 0.1µA (typical) Requires Tiny 220nH Inductor Requires Only 1μF of Output Capacitance External Switching Frequency Synchronization Protection Features Including Over-Current Protection Output Short-Circuit Protection Thermal Shutdown Protection Offered in MLPD-UT 8 Lead Packages Lead-free, Halogen-free, and RoHS/WEEE Compliant
Applications
HDTV, Set Top Boxes, Gaming Consoles POL Applications White Goods
Description
The SC221 is a 20MHz X-EMI™(1)-enabled step-down regu- lator 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 tech- nology meets or exceeds the EMI performance of chip inductors and eliminates the need for discrete inductors. The SC221 uses a unique constant frequency, self-oscil - lating 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 17.5µA. 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 1µF external capacitor and a small 220nH inductor (including X-EMI TM PCB trace inductors). The device provides adjustable output voltages down to 1.0V 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 SC221 is available in MLPD-UT 8 Lead package. Note 1: Purchase of SC221 includes royalty-free right to use X-EMI TM inductor technology with no addi - tional cost. Typical Application Circuit Revision 2.0 SC221 AGND SW VOUT VIN L, 220nH COUT 1 µF EN Enable FB AVIN PVIN CIN 1 µF R2PGND VOUT=1.8V up to 650mA 2.7~5.5V © 2016 Semtech Corporation
Ordering Information
SC221ULTRT (1)(2) MLPD-UT 8 Lead SC221EVB Evaluation Board Notes: (1) Available in tape and reel only. A reel contains 3000 devices. (2) Device is lead-free, halogen-free, and RoHS/WEEE compliant. SW PVIN VOUT FB PGND AGND AVIN EN MLPD-UT 8 Lead, θJA = 38 °C/W
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: (1) All voltage values in this section are with respect to PGND pin voltage. (2) Tested according to JEDEC standard JESD22-A114-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 JESD51 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 =1.0μF, 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 17.5 60 µA Shutdown Current IVIN_SD EN = 0V 1.0 µA POWER SWITCH PMOS On Resistance 400 mΩ NMOS On Resistance 360 mΩ OSCILLATOR Switching Frequency fOSC PWM Mode 16 20 24 MHz REGULATION Output Voltage Tolerance(1) VOUT_TOL -4.0 4.0 % Current Limit ILIMIT 800 1300 mA Soft-Start(1) tSS EN pin low to high 40 µs
Electrical Characteristics
Parameter Symbol Condition Min Typ Max Units Feedback Leakage Current IFB 1 µA ENABLE EN Input High Voltage Threshold VENH 1.2 V EN Input “Low” Voltage Threshold VENL 0.4 V EN Input High Current IENH VEN= VIN -1.0 1.0 µA EN Input Low Current IENL VEN= AGND -1.0 1.0 µA Minimum Synchronization Frequency fSYN_MIN Square wave applied at EN pin 3 MHz PROTECTION Over Temp Thermal Shutdown(1) TOT 150 °C Thermal Shutdown Hysteresis(1) THYST 15 °C Notes (1) Guaranteed by design. Not tested in production. Electrical Characteristics (continued) Unless otherwise specified: AVIN=PVIN = 3.6V, EN = AVIN = PVIN, CIN=COUT =1.0μF, L=220nH. TA = 25°C for typical values, -40°C < TA = TJ < 85°C for minimum and maximum values.
Pin # Pin Name Pin Function 1 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 R1 and R2 to set the output voltage, VOUT = VFB x (1+ R1/R2). (Please refer to the typical application circuit diagram on page 1). 5 EN Enable Input — when low, circuit draws <1µA. 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
Typical Characteristics (Continuous) Efficiency vs. Load Current Efficiency vs. VIN Efficiency vs. Load Current (Chip Inductor vs. X-EMITM Inductor) Load Regulation Switching Frequency vs. VIN Switching Frequency vs. VIN Efficiency (%) Load Current (A) VOUT = 1.8V VIN = 2.7V VIN = 5.5V VIN = 3.3V 2.5 3 3.5 4 4.5 5 5.5 Efficiency (%) Input Voltage (V) VOUT = 1.8V IOUT = 360mA IOUT = 650mA IOUT = 40mA Efficiency (%) Load Current (A) VOUT = 1.8V Solid Lines: Efficiency with X-EMI TM Inductor Dashed Lines: Efficiency with Chip Inductor VIN = 2.7V VIN = 5.5V VIN = 3.3V 1.77000 1.78000 1.79000 1.80000 1.81000 Output Voltage (V) Load Current (A) Nominal VOUT = 1.8V VIN = 5.5V VIN = 3.3V VIN = 2.7V 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 Switching Frequency (MHz) Input Voltage (V) VOUT = 1.8V Io=200mA Io=300mA Io=450mA Io=650mA 16.60 16.80 17.00 17.20 17.40 17.60 17.80 18.00 18.20 18.40 Switching Frequency (MHz) Input Voltage (V) VOUT = 1V Io=200mA Io=300mA Io=450mA Io=650mA
Typical Characteristics (Continuous) Load Transient Response Load Transient Response Steady State Operation Steady State operation Output Hard Short Input Quiescent Current vs. Temperature VOUT (ac coupled) 100mV/div VIN = 3.6V, VOUT = 1.8V, IOUT = 0mA - 500mA 200us/div 200mA/div VIN = 3.6V, VOUT = 1.8V, IOUT = 80mA - 500mA VOUT (ac coupled) 50mV/div 200us/div 200mA/div VIN = 3.6V, VOUT = 1.8V, IOUT = 50mA IOUT 50mA/div 500ns/div IL 500mA/div VSW 2V/div 50ns/div VIN = 3.6V, VOUT = 1.8V, IOUT = 300mA IL 200mA/div VSW 2V/div IOUT 200mA/div 16.5 17.5 -40 0 40 80 120 160 Quiescent Current (µA) Temperature (°C) VIN= 3.6V, EN = High, FB = High VIN = 5V, VOUT = 1.8V, IOUT = 650mA 500ns/div IL 500mA/div VOUT 1V/div
Typical Characteristics (Continuous) Start-up Operation Shutdown Operation Start-up Operation Shutdown Operation EN 2V/div VIN 2V/div VOUT 1V/div IOUT 50mA/div VIN = 3.6V, VOUT = 1.8V, IOUT = 20mA 100us/div VIN = 3.6V, VOUT = 1.8V, IOUT = 20mA EN 2V/div VIN 2V/div VOUT 1V/div IOUT 50mA/div 200us/div VIN = 3.6V, VOUT = 1.8V, IOUT = 650mA VIN = 3.6V, VOUT = 1.8V, IOUT = 650mA EN 2V/div VIN 2V/div VOUT 1V/div IOUT 500mA/div 200us/div EN 2V/div VIN 2V/div VOUT 1V/div IOUT 500mA/div 200us/div
The SC221 is a step-down regulator capable of delivering a lower voltage from an input supply voltage of 2.7V to 5.5V with high efficiency. Using a unique control architec- ture, the SC221 is capable of delivering a peak efficiency upto 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 SC221 operates with a self-oscillating control method based on the output voltage ripple. This control loop compares the output voltage to an internal 1V reference 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 SC221 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 100-200mA, depending on the input and output voltages. At very light loads, the SC221 maintains high efficiency by shutting down all but the most essential circuit blocks, maintaining a typical quiescent current of about 17.5µA. 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 SC221 is enabled by applying a voltage higher than 1.2V 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 frequency: if a digital clock is fed to EN, the SC221 will sense this as a valid enable signal and the external clock will be used rather than the internal 20MHz oscillator. The SC221 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 SC221 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 SC221 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
runs continuously at this reduced frequency. formance of conventional chip inductors. inductors implemented using printed circuit traces. inductor technology on page 6). are rated for appropriate currents. Figure 1. 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: 1. 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. 2. 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. 3. 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. 4. 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. 5. 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 — MLPD-UT 8 Lead 2.00.079 PIN 1 INDICATOR (LASER MARK) SEATING PLANE C BA aaa C N E 2.10 2.10 1.90 1.90 .083 .083 .075 .075 D e/2 e bxN bbb C A B COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS THE TERMINALS.2. D/2 E/2 E LxN INCHES .020 BSC b .007 bbb aaa N L e D .012 DIM A MIN .000 .020 0.400.30 .004 .003 .014 .079 .016 0.08 0.10 0.35 2.00
0.50 BSC
0.05 0.60 DIMENSIONS MIN 0.00 NOM (.006) MAX .002 .024 NOM 0.50 - (0.1524) CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). NOTES: A
Land Pattern —MLPD-UT 8 Lead INCHES DIMENSIONS P Z X Y C G DIM MILLIMETERS FAILURE TO DO SO MAY COMPROMISE THE THERMAL AND/OR FUNCTIONAL PERFORMANCE OF THE DEVICE. SHALL BE CONNECTED TO A SYSTEM GROUND PLANE. THERMAL VIAS IN THE LAND PATTERN OF THE EXPOSED PAD3. H .067 1.70 K .031 0.80 R .006 0.15 Y R G Z P X (C) 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). H K .030 .106 (.077) .047 0.75 2.70 (1.95) 1.20 0.30 0.50.020 .012 THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. NOTES:
Power Management Products Division
200 Flynn Road, Camarillo, CA 93012
Phone: (805) 498-2111 Fax: (805) 498-3804 www.semtech.com Contact Information SC221 x © Semtech 2016 All rights reserved. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. The information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice. No liability will be accepted by the publisher for any conse - quence of its use. Publication thereof does not convey nor imply any license under patent or other industrial or intellectual property rights. Semtech assumes no responsibility or liability whatsoever for any failure or unexpected operation resulting from misuse, neglect improper installation, repair or improper handling or unusual physical or elec- trical stress including, but not limited to, exposure to parameters beyond the specified maximum ratings or operation outside the specified range. SEMTECH PRODUCTS ARE NOT DESIGNED, INTENDED, AUTHORIZED OR WARRANTED TO BE SUITABLE FOR USE IN LIFE- SUPPORT APPLICATIONS, DEVICES OR SYSTEMS OR OTHER CRITICAL APPLICATIONS. INCLUSION OF SEMTECH PRODUCTS IN SUCH APPLICATIONS IS UNDERSTOOD TO BE UNDERTAKEN SOLELY AT THE CUSTOMER’S OWN RISK. Should a customer purchase or use Semtech products for any such unauthorized application, the customer shall indemnify and hold Semtech and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs damages and attorney fees which could arise. Notice: All referenced brands, product names, service names and trademarks are the property of their respective owners.