SEMTECH SC192

SC192 Synchronous Buck Converter with Integrated Power Devices POWER MANAGEMENT Description Features The SC192 is a synchronous step-down converter with ‹ 2.7V to 7V Input Range ‹ Output Adjustable from 0.75V to Vin integrated power devices designed for battery operated systems. The internal power switches reduce system ‹ Fixed Frequency or PSAVE for Maximum Efficiency Over Wide Load Current Range size and cost. In addition, an efficiency of 95% can be ‹ 700mA Guaranteed Output Current achieved for significant line and load ranges. The SC192 is designed for single-cell Li-Ion battery applications, but ‹ No Schottky Diode Required also performs well in fixed 3.3V or 5V input circuits. ‹ 35μA Quiescent Current ‹ 100% Duty Cycle in Dropout The SC192 has a flexible clocking scheme. It can be ‹ 95% Efficiency synchronized to an external oscillator, fixed to the inter- ‹ Fast Transient Response nal oscillator, or allowed to modulate the frequency dur- ‹ Over Temperature Protection ing light loads (PSAVE) for maximum battery life, by the ‹ Space-saving Micro Lead-Frame Package method called pulse frequency modulation (PFM). Shut- MLPD-10 3x3 down places the switches in a high impedance state and turns off all control circuitry to achieve a typical quies- Applications cent current of 0.1μA. ‹ Cell Phones ‹ Cordless Phones Line and load regulation is to +/-0.5% of the output volt- ‹ Notebook and Subnotebook Computers age. The internal MOSFET switches provide >1A peak ‹ PDAs and Mobile Communicators current to provide a DC output of at least 700mA. Grounding the ILIM pin reduces the current limit by half. ‹ 1 Li-Ion or 3 NiMH/NiCd Powered Devices The SC192 can achieve 100% duty cycle for excellent low dropout performance and comes in a tiny MLPD-10, 3 x 3 package having a maximum height of 1mm. Typical Application Circuit SC192 L1 Vout = 0.75V to Vin Vin = 2.7V to 7V 1 9 LX VIN C1 R1 8 C5 EN 5 C6 ADJ 6 ILIM R2 10 PGND 2 7 BP SYNC/PWM C4 C3 R8 34 GND COMP Revision 8, March 26, 2007 1 www.semtech.com SC192 POWER MANAGEMENT PRELIMINARY Absolute Maximum Ratings 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. Pl arameter Sm ymbo Ms aximu Unit VV IN input -0.3 t-V 0.3ot 7 o.7 5 IN SV YNC/PWM Input -0.3 t-V 0.3o t 7 o .7 5 SYNC EV N Input -0.3 t-V 0.3ot 7 o .7 5 EN PV GND to GND -V 0.3 to 0.3 PGDN LV X Voltage -V 1 to VIN +1 LX IV LIM Voltage -V 0.3 to VIN + 0.3 ILIM AV DJ Voltage -V 0.3 to VIN + 0.3 ADJ CV OMP Voltage -V 0.3 to VIN + 0.3 COMP BV P Voltage VV IN - 0.3 to VIN + 0.3 BP ° Thermal Impedance Junction to Ambient θ *57 C/W JA Ot utput Short Circuit to GND Cs ontinuous SC LI X Current +A 1.6 LX Peak IR Reflow Temperature ° SC192IMLTR (Soldering) 10s - 30s T 240 C LEAD SC192IMLTRT (Soldering) 20s - 40s 260 ° ST torage Temperature -65 to +160 C S * Tied to PCB with 1 square inch, 2 ounce copper. Note: This device is ESD sensitive. Use of ESD handling precautions is required. Electrical Characteristics Unless otherwise noted: VIN = 3.6V, SYNC/PWM = VIN, ILIM = VIN, EN = VIN, T =-40 to 85°C. Typical values are at T = +25°C. A A Pl arameter Ss ymbo Cn ondition Mp i Tx y Ms a Unit 7 IV nput Voltage Range 25 .7 5V . IN AV DJ Regulation Voltage 05 .73109 .7 0V .76 ADJ AI DJ Input Current A0 DJ = 0.75V -0 5 5A0 n ADJ OV utput Voltage Adjust Range V V V OUT ADJ IN LG ine Regulation RE -5 0.5 +% 0. LINE (1) Load Regulation REG Peak Inductor Current = 060% . LOAD 0 to 700mA PR -Channel On Resistance I=3 200mA 0. Ω DSP LX NR -Channel On Resistance I=4 200mA 0. Ω DSN LX © 2007 Semtech Corp. 2 www.semtech.com SC192 POWER MANAGEMENT Electrical Characteristics Cont. Unless otherwise noted: VIN = 3.6V, SYNC/PWM = VIN, ILIM = VIN, EN = VIN, T =-40 to 85°C. Typical values are at T = +25°C. A A Pl arameter Ss ymbo Cn ondition Mp i Tx y Ms a Unit I I0 LIM = GND 40 2 60 0 7A 8 m LIM(P) P-Channel Current Limit ILIM = V 80 4010 20 1A 56 m IN IS5 YNC/PWM = GND, PSAVE Mode 4515 0 1A 6 m LIM(N) N-Channel Current Limit -0 320-0 42 -A 52 m QI uiescent current S5 YNC/PWM = GND, PSAVE Mode 305A μ Q ° SI hutdown Current EN = 0, LX = Open, T = 25C1 μA SD A LI X leakage Current PMOSV1 IN = 5.5V, LX = 0V, EN = 0V μA LXP LI X leakage Current NMOS V0 IN = 5.5V, LX = 5.5V, EN = 0V-A 2 μ LXN Of scillator Frequency 60 50 70 5 8z 3 kH OSC Sf YNC Frequency Range 50 00 1z 00 kH SYNC DD uty Cycle Range S0 YNC/PWM = GND, PSAVE Mode201% 0 UV VLO Threshold 25 .35 25 . 2V .6 UVL UV VLO Hysteresis 5V 0 m UVLHYS ° Thermal Shutdown 160 C LV ogic Input High E2 N, SYNC/PWM, ILIM V IH LV ogic Input Low E8 N, SYNC/PWM, ILIM 0V . IL LI ogic Input Current High E2 N, SYNC/PWM, ILIM -2 μA IH LI ogic Input Current Low E2 N, SYNC/PWM, ILIM -2 μA IL Notes: (1) Load regulation limits are specified from 0 to 700mA. This specification is calculated based on parameters measured individually and is not a tested parameter. See the load regulation limit graph on page 13 for more detailed view of performance. © 2007 Semtech Corp. 3 www.semtech.com SC192 POWER MANAGEMENT PRELIMINARY Pin Configuration Ordering Information (1) DEVICE PACKAGE SC192IMLTR MLPD-10 3x3 TOP VIEW (2) SC192IMLTRT VIN 1 10 PGND Sd C192EVB Evaluation Boar BP 2 9 LX Note: GND 3 8 EN (1) Only available in tape and reel packaging. A reel contains COMP 4 7 SYNC/PWM 3000 devices. T ADJ 5 6 ILIM (2) Lead free product. This product is fully WEEE and RoHS compliant. MLPD-10: 3X3 10 LEAD Pin Descriptions Pe in #Pn in Nam Pin Functio 1N VI Input power supply voltage; this input goes directly to the internal MOSFET switches. 2P B Bypass capacitor pin; an external capacitor combined with an internal resistor provides a filtered supply voltage for the internal control circuitry. Connect a 0.1uF capacitor from BP to ground. 3DG. N Analog ground 4PC. OM Compensation pin for the error amplifier 5J AD Output adjust pin; connect to a resistor divider to set the output voltage. 6M ILI Digital current limit select input. Connect ILIM to GND for 0.6A current; connect ILIM to VIN for 1.2A current limit. 7M SYNC/PW Oscillator synchronization input. Tie to VIN for forced PWM mode, GND to enable power save mode, or an external clock signal for frequency synchronization. 8N E Enable digital input; a high input enables the SC192 a low disables the device and reduces quiescent current to 0.1uA. In shutdown, LX becomes high impedance. 9XL. Inductor connection to the switching FETs 1D 0P. GN Power Ground Td Thermal Pa Pad for heatsinking purposes. Connect to ground plane using multiple vias. Not connected internally. © 2007 Semtech Corp. 4 www.semtech.com SC192 POWER MANAGEMENT Block Diagram BP VIN - Plimit V ILIM amp + Current amp OSC and slope SY N C / generation PW M Control logic - LX PW M comp + CO M P PG ND - ADJ Error amp + V 750mV Nlimit comp EN G ND © 2007 Semtech Corp. 5 www.semtech.com - + - + SC192 POWER MANAGEMENT PRELIMINARY Description Forced PWM Description If SYNC/PWM is DC high, the forced PWM mode is en- The SC192 step-down, pulse-width-modulated (PWM), abled. This ensures that the switching frequency of the DC-DC converter has an adjustable output range from 0.75V to the input voltage. The device has an internal converter is maintained over the full range of output loads. This means that the current reversal threshold of synchronous rectifier and does not require a schottky the NMOS is changed to a negative value and the 100% diode on the LX pin. duty cycle and power save modes are also disabled. At moderate to heavy loads, the converter operates in the PWM mode with a fixed frequency of 750kHz. At light loads the converter enters the power save mode by 100% Duty-Cycle Operation Normally the control loop constrains the duty cycle of modulating the frequency, pulse-frequency-modulation the converter with minimum on and off times, but if the (PFM) which achieves high efficiency under light load output voltage droops to the lower power-save thresh- conditions. old and the ON time is not terminated by the PWM com- Normal Mode parator or PMOS current limit, then the next PMOS on time is allowed to extend until either the PWM compara- This is a standard fixed frequency current mode topol- tor or PMOS current limit trips. This is then followed by a ogy. The current feedback is through the PMOS current minimum off time. This maximum on time/minimum off path and is amplified and summed with the internal slope time is allowed to continue until the upper power-save compensation network and DC offset. The voltage feed- back loop is through the resistor divider attached to the threshold is reached. This allows the part to go into a dropout mode of operation if the input supply collapses ADJ pin. The transconductance error amplifier output is down to the output voltage. If this happens, the output the compensation (COMP) pin with the usual external voltage is equal to the input voltage minus the voltage compensation network attached. The PWM COMP pin drop across the P-channel MOSFET. closes the loop by comparing the summed current feed- back and the COMP signal to determine the length of the Soft Start ON time. The period is set by the on-board oscillator or The soft start mode is enabled after every shutdown cycle external clock attached to the SYNC pin. to limit inrush current from the battery. In conjunction with the frequency foldback this controls the maximum Power Save Mode If SYNC/PWM is DC low, power save mode is used at current during start-up. The PMOS current limit is stepped from 25%, to 50%, to 75%, and then 100% by an inter- light loads to improve efficiency. When the output cur- nal 2ms timer. As soon as the part reaches regulation, rent reaches a low enough level, the part goes into a soft start mode is disabled. voltage hysteresis mode of operation. The current level for this is set to be the current reversal protection on the NMOS device. The output voltage is then allowed to decay to a lower threshold with the part in a reduced quiescent current (PSAVE) state. After this lower thresh- old is reached the part is reawoken to normal operation, but with a current offset on the COMP pin to drive the output voltage regulation point to be above an upper threshold point. However the offset is removed once the upper threshold is reached. If the load current is now sufficiently large the part will return to normal regulation, if not another PSAVE cycle will start. Frequency Foldback When the ADJ pin is low the output switching frequency is folded back in several discrete steps to protect against a short to GND on the output and improve inrush cur- rent control during start-up. © 2007 Semtech Corp. 6 www.semtech.com SC192 POWER MANAGEMENT Evaluation Board Schematic VIN TP7 R6 R7 R5 EN 1k 1k 100k SW1 TP8 DIP ILIM TP1 VIN TP4 TP5 U1 LX VOUT 1 10 VIN VIN PGND L1 2 9 1.8V BP LX TP3 10uH COMP 3 8 GND EN R1 4 7 C5 442k COMP SYNC 47pF 5 6 ADJ ILIM EN SC192 C1 C3 C4 10uF 0.1uF 470pF R2 C2 C6 TP6 309k 0.1uF 22uF SYNC R8 SYNC 28k R3 100k TP2 R4 GND 100k GND © 2007 Semtech Corp. 7 www.semtech.com 1 6 2 5 3 4 SC192 POWER MANAGEMENT PRELIMINARY Evaluation Board Gerber Plots BOTTOM COPPER TOP COPPER BOTTOM SILKSCREEN TOP SILKSCREEN © 2007 Semtech Corp. 8 www.semtech.com SC192 POWER MANAGEMENT Applications Information Selecting Components When selecting components for the an SC192 application the main factors are typically performance, size and cost. For higher performance the designer will select higher values of input and output capacitors to reduce ripple current and voltage. However, for an application that can tolerate higher ripple, less expensive and smaller compo- nents can be utilized. The schematics below show two possibilities. The first shows the use of 10μF capacitors on the input and output with L1 = 10μH, while the second shows the use of smaller less expensive 4.7μF capacitors and L1 = 4.7μH. The only circuit consideration for choosing one over the other is the compensation components C4 & R8. When these components are in place the values of R2 can be chosen for a given output voltage. The values that should be used are indicated in Table 1 below. Using a different value for R1 is not advised since this will change the loop characteristics and may cause the supply to become unstable. Any output voltage is achievable using R1 of 442k and then selecting R2 to achieve the desired output voltage. The equation for VOUT is: R1 ⎛ ⎞ Vout= +1 • 0.75 ⎜ ⎟ R2 ⎝ ⎠ Because the SC192 has external compensation the use of small inexpensive ceramic capacitors can be used for the output capacitor allowing the designer greater flexibility. 1 10 VIN VIN PGND L1 2 9 VOUT BP LX 10uH 3 8 GND EN 4 7 C5 R1 COMP SYNC 47pF 442k 5 6 ADJ ILIM C1 C3 C4 C6 SC192 10uF 0.1uF 470pF 10uF R2 R8 12k 1 10 VIN VIN PGND L1 2 9 VOUT BP LX 4.7uH 3 8 GND EN 4 7 C5 R1 COMP SYNC 47pF 442k 5 6 ADJ ILIM C1 C3 C4 C6 SC192 4.7uF 0.1uF 470pF 4.7uF R2 R8 6.19k © 2007 Semtech Corp. 9 www.semtech.com SC192 POWER MANAGEMENT PRELIMINARY Applications Information Cont. TABLE 1 CF C C CCF 6 6 6 6 6 = = = = = C C C C Co o o o ou u u u ut t t t t = = = = = 1 1 1 1 10 0 0 0 0u u u u uF F F CF C C CCF 6 6 6 6 6 = = = = = C C C C Co o o o ou u u u ut t t t t = = = = = 2 2 2 2 22 2 2 2 2u u u u uF F F CF C C CCF 6 6 6 6 6 = = = = = C C C C Co o o o ou u u u ut t t t t = = = = = 4 4 4 4 4.....7 7 7 7 7u u u u uF F F VT V VV2 VT O O O O OU U U U UT T T R R R2 R2 R2 2 LLH LLH L1 1 1 1 1 = = = = = 1 1 1 1 10 0 0 0 0u u u u uH H H LH L LLH L1 1 1 1 1 = = = = = 1 1 1 1 10 0 0 0 0u u u u uH H H LH L LLH L1 1 1 1 1 = = = = = 4 4 4 4 4.....7 7 7 7 7u u u u uH H H 3k .3V 130 2k .5V 187 C4 = 470pF C4 = 470pF C4 = 470pF 1k .8V 309 R8 = 12k R8 = 28k R8 = 6.19k 1k .5V 442 1M .0V 1.30 The plots below were taken at Vin = 3.6V, Vout = 1.8V, with the compensation components listed in Table 1. The upper plot is LX, the middle plot is output voltage, the lower plot is the current transient of 0.1A to 0.6A PSAVE, Cout = 20uF, Lout = 10uH PWM, Cout = 20uF, Lout = 10uH PSAVE, Cout = 10uF, Lout = 10uH PWM, Cout = 10uF, Lout = 10uH © 2007 Semtech Corp. 10 www.semtech.com SC192 POWER MANAGEMENT Applications Information Cont. PSAVE, Cout = 4.7uF, Lout = 4.7uH PWM, Cout = 4.7uF, Lout = 4.7uH Inductor Selection The inductor values listed in Table 1 will work for nearly f = Switching frequency L = Inductor Value all combinations of output current and output voltages. After selecting 4.7uH or 10uH for the inductor value two ΔI = Peak-to-peak inductor ripple current L additional inductor parameters should be considered. The I = Maximum inductor current L current rating of the inductor and the DC resistance. V = Output voltage OUT The DC resistance has a great impact on efficiency due V = Input voltage IN C = Output Capacitance to copper losses. However, small inductors tend to have OUT higher DC resistance. Therefore a compromise between I = Output Current OUT size and efficiency will need to be made. I = Maximum DC Output Current OUT(MAX) The inductor current must be chosen to prevent the in- ductor from saturation. The most conservative approach Output Capacitor Selection Because the SC192 has external compensation avail- would be to select an inductor with a saturation current slightly above the maximum current capability of the able, low ESR ceramic capacitors can be used. This elimi- SC192 which is 1.56A peak current for ILIM = Vin or nates the need for bulky tantalum capacitors. Values for 780mA for ILIM = GND. the output capacitors in Table 1 will work for nearly all A more accurate design of the inductor would be to rate combinations of output current and output voltages. The equation for determining the size of the output capaci- the inductor for the maximum output current plus the inductor ripple current that can be calculated as follows: tor in terms of minimizing the ripple voltage is given as follows: ΔIL IL(MAX)= IO(MAX ) + 1 ⎛ ⎞ 2 ΔVO=ΔIL• + ESR ⎜ ⎟ 8• COUT• f ⎝ ⎠ V OU T ⎛ ⎞ ⎜1- ⎟ Input Capacitor Selection V IN ⎜ ⎟ ΔIL= • V OUT The input ripple current can be reduced with properly L•f ⎜ ⎟ ⎜ ⎟ selecting the input capacitor. Again, values for the input ⎝ ⎠ capacitors in Table 1 will work for nearly all combina- tions of input current and output voltages. The input ca- pacitor should be rated for the maximum input ripple current calculated as: © 2007 Semtech Corp. 11 www.semtech.com SC192 POWER MANAGEMENT PRELIMINARY Applications Information Cont. Load Regulation at Vin = 3.6V 0.45 IOUT 0.40 IRMS= V OUT•VIN -V OUT• 0.35 VIN 0.30 0.25 Vo = 1.8V Vo = 2.5V The worst case RMS ripple current occurs at a duty cycle 0.20 0.15 IOUT 0.10 of 0.5 and its value at that point is . 0.05 2 0.00 Ceramic capacitors are recommended for input capaci- 1 20 40 60 80 100 200 300 400 500 600 Ouput Current (mA) tors because of their low ESR and high ripple current capabilities. In addition, it is advised that the input ca- pacitor be placed as close to the input pin of the IC as Efficiency at Vin = 5V possible. 100 95 Layout Considerations 90 85 PCB layout is of utmost importance because the switch- 80 Vo = 3.3V ing frequency is 750kHz with peak currents over 1A. A 75 careful layout will avoid potential stability and EMI prob- 70 lems. Traces should be as wide and as short as possible. 65 60 Keep the input capacitor as close to the package as pos- 1 10 30 50 70 90 200 400 600 sible. This will help minimize large loop areas. Keep the Load Current (mA) power ground and analog ground separated and tie the two together at one common point. Notice the top cop- Efficiency at Vin = 3.6V per Gerber plot (see Page 8), pin 3 and pin 10 are tied together under the package. Be aware of the high cur- 100 rent paths and avoid tying signal grounds to the high power grounds where the signal paths might experience large 95 fluctuations in voltages as high currents pass though Vo = 2.5V 90 copper traces. Vo = 1.8V 85 80 1 10305070 90 200 400 600 Load Current (mA) Line Regulation At Iout = 300mA 0.10 0.08 0.06 Vo = 1.8V 0.04 0.02 0.00 2.7 3.0 3.3 3.6 3.9 4.2 4.5 4.8 Input Voltage (Volts) © 2007 Semtech Corp. 12 www.semtech.com Load Regulation (%) Efficiency (%) Efficiency (%) Line Regulation (%) SC192 POWER MANAGEMENT Line Regulation at I = 300mA OUT SC192 Load Regulation Limits 1.0 0.14 0.9 0.12 0.8 0.10 0.7 0.6 0.08 0.5 Vo = 2.5V 0.06 0.4 0.04 0.3 Load Reg Max 0.2 0.02 Load Reg Typ 0.1 Load Reg Min 0.00 0.0 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 00.2 0.4 0.6 0.811.2 Input Voltage (Volts) Peak Inductor Current (Amps) Oscillator Frequency vs Temperature Over V IN Oscillator Frequency vs V Over Temperature IN 760 760 755 755 750 Vin = 2.7 V 750 745 Vin = 3.6V 745 Vin = 5.5V 740 Temp = -40C 740 Temp = 0C 735 Temp = 25C 735 Temp = 85C 730 Temp = 125C 730 725 725 720 720 715 715 710 710 -60 -40 -20 0 20 40 60 80 100 120 140 22.533.544.555.5 6 O Temp ( C) V (Volts) in Shutdown Current vs Temperature 0.9 0.8 0.7 0.6 0.5 Vin = 3.6V 0.4 0.3 0.2 0.1 0 -40 0 25 85 125 O Temperature ( C) © 2007 Semtech Corp. 13 www.semtech.com Fosc (kHz) Line Regulation (%) Shutdown Current (µA) Fosc (kHz) Load Regulation (%) SC192 POWER MANAGEMENT PRELIMINARY Outline Drawing - MLPD-10, 3 x 3 DIMENSIONS A E B INCHES MILLIMETERS DIM MIN NOM MAX MIN NOM MAX - - A .031 .039 0.80 1.00 - - A1 .000 .002 0.00 0.05 - (.008) - - (0.20) - A2 b .007 .009 .011 0.18 0.23 0.30 E C .074 .079 .083 1.87 2.02 2.12 D .042 .048 .052 1.06 1.21 1.31 PIN 1 E .114 .118 .122 2.90 3.00 3.10 INDICATOR e .020 BSC 0.50 BSC (LASER MARK) L .012 .016 .020 0.30 0.40 0.50 N 10 10 aaa .003 0.08 bbb .004 0.10 A SEATING PLANE aaa C A1 C A2 C 1 2 LxN D N bxN e bbb C A B NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS TERMINALS. Marking Information Top Marking 192 yyww yy = two-digit year of manufacture ww = two-digit week of manufacture © 2007 Semtech Corp. 14 www.semtech.com SC192 POWER MANAGEMENT Land Pattern - MLPD-10, 3 x 3 K DIMENSIONS DIM INCHES MILLIMETERS (.112) (2.85) C G .075 1.90 H .055 1.40 H (C) G Z K .087 2.20 P .020 0.50 X .012 0.30 Y .037 0.95 Y X .150 3.80 Z 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 Visit us at: www.semtech.com © 2007 Semtech Corp. 15 www.semtech.com