SEMTECH SC191

SC191 Low Supply Ripple Synchronous Buck Conversion Regulator POWER MANAGEMENT Description F Features eatures The SC191 is a synchronous step-down converter with ‹ Less than 1mV Supply Ripple integrated power devices and an integrated front-end ‹ 2.7V to 5.5V Input Range LDO regulator to minimize input supply ripple. If supply ‹ 330mA Guaranteed Output Current ripple is not a concern, the front-end LDO regulator can be ‹ Fixed Frequency 1MHz Operation bypassed externally to maximize efŢ ciency. ‹ No Schottky Diode Required ‹ Over-Current Protection The internal MOSFET switches provide peak current greater ‹ Over-Voltage Protection than 550mA to achieve a DC output of at least 330mA over ‹ Over-Temperature Protection the rated input voltage range, making the SC191 ideal for ‹ Soft-Start single-cell Li-ion battery applications as well as Ţ xed 3.3V ‹ No External Compensation Required and 5V Ţ xed input applications. The output is a Ţ xed 1.2V ‹ MLPD-8, 2.3mm x 2.3mm Package - ideal for low-voltage microprocessors. Other voltage ‹ WEEE and RoHS Compliant options are available (consult the factory for details). Applications Additional features include internal soft-start to limit in- ‹ Cell Phones rush current, over-current protection, over-temperature ‹ Cordless Phones protection, and over-voltage protection. ‹ Notebook and Subnotebook Computers ‹ PDAs and Mobile Communicators The 1MHz switching frequency allows the use of small ‹ WLAN Peripherals surface mount capacitors and inductors, and no other ‹ Wireless Modules external compensation components are needed. The ‹ 1 Li-Ion or 3 NiMH/NiCd Powered Devices device is available in a low proŢ le (0.8mm max height) 2.3mm x 2.3mm MLPD 8-lead package, minimizing area Patent Pending without compromising performance. Typical Application Circuit L 4.7μH SC191 8 3 VIN LX V V OUT IN 4 EN 5 C IN 2 VOUT PVIN 4.7μF C OUT 1 BP 4.7μF C BP 7 6 PGND GND 4.7μF April 12, 2006 1 www.semtech.com SC191 POWER MANAGEMENT Absolute Maximum Ratings Absolute Maximum Ratings Exceeding the speciŢ cations below may result in permanent damage to the device or device malfunction. Operation outside of the parameters speciŢ ed in the Electrical Characteristics section is not recommended. Parameter Symbol Maximum Units Input Voltage V , V -0.3 to 7.0 V VIN PVIN Enable Input V -0.3 to 7.0 V EN LX Voltage V -1 to V + 1 (7V max) V LX BP Output Voltage V -0.3 to 7.0 V VOUT BP Voltage V 0.3 to 7.0 V BP 1 Thermal Impedance Junction to Ambient θ 135 °C/W JA V Short Circuit to GND t Continuous s OUT SC Storage Temperature T -60 to +160 °C S Junction Temperature T +150 °C JC Peak IR Reţ ow Temperature T 260 °C LEAD 2 ESD Protection Level V 2kV ESD Notes: 1) Calculated from package in still air, mounted to 3” x 4.5”, 4 layer FR4 PCB with thermal vias under the exposed pad as per JESD51 standards. 2) Tested according to JEDEC standard JESD22-A114-B. Electrical Characteristics Unless otherwise noted: V = 3.6V , V = V , T = -40°C to 85°C . Typical values are at T = 25°C. IN EN IN A A Parameter Symbol Conditions Min Typ Max Units Input Voltage Range V 2.7 5.5 V IN Input Voltage Ripple V C = C = 10μF1 mV IN (P-P) IN BP Line Regulation V I = 150mA -0.3 0.3 %/V LINEREG OUT Load Regulation V 0mA < I < 330mA 0.002 %/mA LOADREG OUT P-Channel On Resistance R I = 100mA 0.3 Ω DSP LX N-Channel On Resistance R I = 100mA 0.2 Ω DSN LX Start-Up Time T I = 150mA 1.25 ms START OUT I = 150mA -3 3 % OUT Output Voltage Accuracy ΔV OUT I = 150mA, T = 25°C -1.5 1.5 % OUT A (1) Front End LDO (FELDO) V I = 110mA 300 325 mV BP BP 2 © 2006 Semtech Corp. www.semtech.com SC191 POWER MANAGEMENT Electrical Characteristics (Cont.) Parameter Symbol Conditions Min Typ Max Units P-Channel Current Limit I 550 730 940 mA LIM(P) N-Channel Current Limit I -270 -420 -700 mA LIM(N) Quiescent Current I Switching mode, I = 100μA 2.5 mA Q OUT Shutdown Current I EN tied to GND 0.1 1 μA SD V = 5.5V IN LX Leakage Current PMOS I 0.1 1 μA LXP LX, EN tied to GND V = V = 5.5V IN LX LX Leakage Current NMOS I -20 0.1 μA LXN EN tied to GND Oscillator Frequency f 0.87 1.0 1.12 MHz OSC UVLO Threshold (Lower) V 2.4 2.5 2.6 V UVLO UVLO Hysteresis V 50 mV UVLO-HYS Thermal Shutdown T 145 °C SD Thermal Shutdown T 10 °C SD-HYS Hysteresis Logic Input High V EN pin 1.6 V IH Logic Input Low V EN pin 0.6 V IL Logic Input Current High I EN pin -2 0.1 2 μA IH Logic Input Current Low I EN pin -2 0.1 2 μA IL Note: 1) FELDO tested at I = 110mA. Equivalent to I = 330mA at V = 1.2V. BP OUT OUT © 2006 Semtech Corp. 3 www.semtech.com SC191 POWER MANAGEMENT Pin ConŢ guration Pin ConŢ guration Ordering Information DEVICE PACKAGE MLPD-8LD TOP VIEW (1)(2) SC191AWLTRT (2.3mm x 2.3mm BODY SIZE) SC191AEVB Evaluation Board BP 1 8 LX Notes: PVIN PGND 2 7 1) Available in tape and reel only. A reel contains 3,000 devices. 2) Device is WEEE and RoHS compliant. VIN 3 6 GND EN VOUT 4 5 MLPD-8 2.3mm x 2.3mm 8-lead Output Voltage Options PART V OUT SC191A 1.2V* *Only option currently available - contact Semtech for other voltage options. Marking Information 91A yw nnn = Part Number yw = Datecode 4 © 2006 Semtech Corp. www.semtech.com SC191 POWER MANAGEMENT Block Diagram Voltage 3 VREF1 VIN References PVIN 500mV 2 LDO Error Amp Plimit Front-End Amp LDO Current 1 BP Amp OSC and Slope Generator 8 LX Control Logic VOUT 5 PWM Comp 7 PGND 500mV VREF1 Error Amp Nlimit Comp 6 GND EN 4 Pin Descriptions Pin# Pin Name Pin Function Regulated output, with respect to VIN, of the front-end LDO. A 4.7μF decoupling capacitor 1BP should be connected to this pin. This output is connected directly to the internal switching MOSFETs. 2 PVIN Input power supply for the power devices. 3 VIN Input power supply for the analog functions. Enable (digital input): high input enables the SC191, a low disables and reduces the quiescent 4EN current to < 1μA. In shutdown LX becomes high impedance. 5 VOUT Regulated output voltage and feedback for the SC191. 6 GND Ground: this pin should be connected directly to PGND on the user’s PCB. Power Ground: this pin should be connected directly to GND on the user’s PCB and should 7 PGND be the reference point for the input, output and BP capacitor GND connections. These ground paths should be separate and as short as possible to minimize circuit noise. 8 LX Inductor connection to the switching MOSFETs. © 2006 Semtech Corp. 5 www.semtech.com SC191 POWER MANAGEMENT Applications Information SC191 Detailed Description Current Limit The part has a number of current limit functions. The The SC191 is a step-down, pulse-width-modulated (PWM) front-end LDO regulator has a current limit set at ap- DC-DC converter with a Low Dropout (LDO) pre-regulator. proximately 500mA, which will protect it in the event of a The device has an internal synchronous rectiŢ er and does not require a Schottky diode on the LX pin. The device is pulsed short circuit. The PMOS and NMOS power devices designed to operate as a buck converter in PWM mode of the buck switcher stage are also protected by current limit functions. In the case of a short to ground on the with a Ţ xed-frequency of 1MHz. The SC191 operates as output, the part enters frequency foldback mode which a Ţ xed frequency current mode regulator with the input causes the switching frequency to divide by a factor deter- supply for the switching regulator pre-regulated by a front- end LDO regulator. This technique reduces the supply mined by the output voltage, which prevents the inductor voltage ripple from 10mV, typically seen from a switching current from “stair stepping”. converter, to less than 1mV for the SC191. The supply to Over-Voltage Protection the switcher is regulated to the supply voltage minus ap- Over-voltage protection is provided on the SC191. In the proximately 300mV. Current feedback for the switching regulator is through the PMOS current path, and it is am- event of an over-voltage on the output, the PWM drive is pliŢ ed and summed with the internal slope compensation disabled, tri-stating the LX output and disabling the front- end LDO. network and level shifted. The voltage feedback loop is through an internal feedback divider. Soft-Start The on-time is determined by comparing the summed cur- The soft-start mode is enabled after every shutdown cycle rent feedback and the output of the error ampliŢ er. The to limit in-rush current. In conjunction with the frequency foldback this controls the maximum current during start- period is set by the onboard oscillator. up. The switcher’s PMOS current limit is stepped from 25%, to 50%, to 75%, and then 100% of its typical value EfŢ ciency at moderate to high loads can be improved by shorting the VIN and BP pins together. This bypasses the by a timer driven by the internal oscillator. The oscillator front-end LDO, reducing voltage drop and improving efŢ - frequency is stepped by 1/8, 1/4, 1/2 and 1 under the control of 4 output voltage thresholds. As soon as the ciency at the expense of increasing input supply ripple. part reaches regulation, soft start mode is disabled. Protection Features The SC191 provides the following protection features: Output Filter The SC191 series of synchronous step-down converters have internal loop compensation. The internal compen- • Thermal Shutdown sation is designed to work with a certain output Ţ lter cor- • Current Limit • Over-Voltage Protection ner frequency deŢ ned by the equation: • Soft-Start 1 f = ————— C ——— 2�√ L×C Thermal Shutdown The thermal shutdown feature protects the device from exceeding a junction temperature of 150°C. In thermal The internal compensation is optimized to operate with shutdown the PWM drive is disabled, the LX output is tri- an output Ţ lter, L = 4.7μH and C = 10μF. When select- stated, and the front-end LDO is disabled. The device will OUT ing output Ţ lter components the LC product should not not be enabled again until the temperature reduces by 10°C. If during this time the output falls by greater than vary over a wide range. 60% of its regulation voltage, a soft-start will be invoked. 6 © 2006 Semtech Corp. www.semtech.com SC191 POWER MANAGEMENT Applications Information (Cont.) Table 1: Output Filter Combinations Alternatively, the inductor saturation current should be greater than the switch current limit. Final inductor selec- L (μH) C (μF) OUT tion will depend on various design considerations such 4.7 4.7 as efŢ ciency, EMI, size and cost (see Table 2 for a list of practical inductor options). 4.7 10 10 10 CIN Selection To prevent large input voltage ripple caused by discon- The selection of smaller inductor and capacitor values will tinuous source input current, a low ESR ceramic capacitor move the corner frequency, having an impact on system is required. A minimum value of 4.7μF should be used stability. Due to this issue the practical lower limit for the for sufficient input voltage filtering, and a 10μF capacitor inductor value is 4.7μH. is strongly recommended for optimum input voltage fil- tering. Input voltage ripple of approximately 1mV can be Inductor Selection achieved when CIN = 10μF and the front-end LDO regu- The value of the inductor should be in the range 4.7μH lator is active and pre-regulating the input supply to the to 10μH. The magnitude of the inductor current ripple is switching regulator. dependant on the inductor value and can be determined by the following equation: COUT Selection A 10μF ceramic capacitor is recommended for the out- put filter capacitor. Output voltage ripple is mainly deter- V V mined by the filter capacitor in the following equation: OUT OUT ΔI = ——— 1 + ——— L ( ) L × f V OSC IN ΔV = ΔI × ESR OUT(ESR) L(ripple) COUT This equation demonstrates the relationship between V , IN V and I . To minimize conduction losses and maximize OUT L efŢ ciency, the inductor should have a low DC resistance. X7R or X5R ceramic dielectric capacitors should be used As a minimum requirement, the DC current rating of the because of their low ESR and superior temperature and inductor should be equal to the maximum load current voltage characteristics. Y5V ceramic capacitors should plus half of the inductor current ripple as described by the be avoided due to their widely-varying temperature coef- following equation: Ţ cients. ΔI L I = I + —— L(PK) OUT(MAX) 2 Table 2: Recommended Inductors Value DCR Rated Current I (A) Tolerance Dimensions SAT Manufacturer Part Number (μH) Ω (A) (40°C rise) L drop 25% (± %) (LxWxH mm) TDK LDR655312T-4R7W 4.7 0.206 0.9 - 20 6.5x5.3x1.2 Sumida CDRH3D16LD 4.7 0.073 0.68 - 30 4x4x1.8 Taiyo Yuden LMNP04SB100M 10 0.066 0.9 - 20 5x5x2 Coilcraft LPS3015 10 0.044 - 0.65 20 3x3x1.5 Coilcraft LP06610-103M 10 0.41 - 0.8 20 6.9x3.8x1.0 © 2006 Semtech Corp. 7 www.semtech.com SC191 POWER MANAGEMENT Applications Information (Cont.) Table 3: Recommended Capacitors Value Rated Voltage Temperature Manufacturer Part Number Package Size (μF) (VDC) CoefŢ cient Murata GRM-188R60J475KE19D 4.7 6.3 X5R 0603 Murata GRM-188R60G106ME47D 10 4 X5R 0603 TDK C1608X5R0G106M 10 4 X5R 0603 PCB Layout Considerations ductor and LX node to minimize noise and magnetic inter- Poor layout can degrade the performance of the DC-DC ference. Use a ground plane to further reduce noise. converter and can be a contributory factor in EMI prob- lems, ground bounce and resistive voltage losses. Poor 3) Maximize ground metal on the component side to regulation and instability can result. A few simple design improve the return connection and thermal dissipation. rules can be implemented to ensure good layout: Separation between the LX node and GND should be maintained to avoid coupling of switching noise to the 1) Place the inductor and Ţ lter capacitors as close to the ground plane. device as possible and use short, wide traces between the power components. 4) To further reduce noise interference on sensitive circuit nodes, use a ground plane with several vias connecting 2) Route the output voltage feedback path away from in- all ground planes together. Suggested Layout GND C BP LX VIN SC191 L OUT C IN C OUT VOUT GND Vias to GND Plane 8 © 2006 Semtech Corp. www.semtech.com SC191 POWER MANAGEMENT Typical Characteristics EfŢ ciency vs. Load Current (FELDO Active) EfŢ ciency vs. Load Current (FELDO Bypassed) 100 100 90 90 80 80 70 70 60 60 50 50 V =3V IN V =3V IN 40 40 V =3.6V IN V =3.6V IN 30 30 V =4.2V V =4.2V IN IN 20 20 10 10 0 0 0.0100 0.1000 1.0000 0.0100 0.1000 1.0000 I (A) I (A) OUT OUT Line Regulation (FELDO Active) Line Regulation (FELDO Bypassed) 1.21 1.21 I =1mA I =1mA OUT OUT 1.205 1.205 I =150mA OUT I =150mA OUT I =330mA OUT I =330mA OUT 1.2 1.2 1.195 1.195 1.19 1.19 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 V (V) V (V) IN IN Load Regulation Switching Frequency vs. Temperature 1.01 1.21 1 0.99 1.205 0.98 V =4.2V IN 1.2 0.97 V =3.6V IN V =3V IN 0.96 V =3.6V IN 1.195 0.95 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 -60 -40 -20 0 20 40 60 80 100 120 140 I (A) T (°C) OUT J © 2006 Semtech Corp. 9 www.semtech.com V (V) V (V) EfŢ ciency (%) OUT OUT Switching Frequency (MHz) V (V) EfŢ ciency (%) OUT SC191 POWER MANAGEMENT Typical Characteristics (Cont.) Switching Frequency vs. Input Voltage Quiescent Current vs. Input Voltage 1.005 4 1 3.5 0.995 o T =85 C 3 J 0.99 o T =25 C J 0.985 2.5 o T =-40 C J 0.98 2 0.975 1.5 0.97 0.965 1 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 V (V) V (V) IN IN N-Channel R vs. Temperature P-Channel R vs. Temperature DSON DSON 400 600 350 500 300 400 250 200 300 150 200 100 100 50 0 0 -60 -40 -20 0 20 40 60 80 100 120 140 -60 -40 -20 0 20 40 60 80 100 120 140 T (°C) T (°C) J J Load Transient Response Start-Up V =3.6V, V =1.2V IN OUT V =3.6V, I =300mA IN OUT I OUT 33 to 330mA V OUT 100mV/DIV V OUT 500mV/DIV ENABLE 5V/DIV 200μs/Div 200μs/Div 10 © 2006 Semtech Corp. www.semtech.com RDSON (mΩ) Switching Frequency (MHz) RDSON (mΩ) Quiescent Current (mA) SC191 POWER MANAGEMENT Typical Characteristics (Cont.) Input Voltage Ripple (FELDO Bypassed) Input Voltage Ripple (FELDO Active) V =3.6V, I =300mA, C =10uF, C = not Ţ tted V =3.6V, I =300mA, C =10uF, C = 10uF IN OUT BP IN IN OUT BP IN V OUT 5mV/DIV V OUT 5mV/DIV V V LX LX 2V/DIV 2V/DIV 400ns/Div 400ns/Div Input Voltage Ripple (FELDO Bypassed) V =3.6V, I =300mA, C =20uF, C = not Ţ tted IN OUT BP IN V OUT 5mV/DIV V LX 2V/DIV 400ns/Div © 2006 Semtech Corp. 11 www.semtech.com SC191 POWER MANAGEMENT Outline Drawing - MLPD-8 B A D DIMENSIONS INCHES MILLIMETERS DIM MIN NOM MAX MIN NOM MAX E PIN 1 A .028 .031 0.70 0.75 0.80 .030 INDICATOR A1 .000 .002 0.00 0.02 0.05 .001 (LASER MARK) A2 (.008) (0.20) b .008 .010 .012 0.20 0.25 0.30 D .087 .091 .094 2.20 2.30 2.40 E .087 .091 .094 2.20 2.30 2.40 e .020 BSC 0.50 BSC A L .012 .016 .020 0.30 0.40 0.50 SEATING L1 .016 .020 .024 0.40 0.50 0.60 PLANE aaa C N 8 8 aaa .003 0.08 C A1 bbb .003 0.08 A2 1 2 LxN L1 0.125 CHAMFER N bxN e bbb C A B e/2 NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 12 © 2006 Semtech Corp. www.semtech.com SC191 POWER MANAGEMENT Land Pattern - MLPD-8 DIMENSIONS DIM INCHES MILLIMETERS (.083) (2.10) C C G .047 1.20 G Z P .020 0.50 X .012 0.30 Y .035 0.90 Y Z .118 3.00 X P NOTES: 1. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. Contact Information Semtech Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 Phone: (805) 498-2111 Fax: (805) 498-3804 www.semtech.com © 2006 Semtech Corp. 13 www.semtech.com