2.7V 5.5V Input Range Output Adjustable from 0.75V Fixed Frequency PSA

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2.7V 5.5V Input Range Output Adjustable from 0.75V Fixed Frequency PSA

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2.7V 5.5V Input Synchronous Buck Converter w/Integrated Power Devices
2.7V 5.5V Input Range Output Adjustable from 0.75V Fixed Frequency PSAVE Maximum
SC192
SC192 synchronous step-down converter with integrated power devices designed battery operated systems. internal power switches reduce system size cost. addition, efficiency achieved significant line load ranges. SC192 designed single-cell Li-Ion battery applications, also performs well fixed 3.3V input circuits. SC192 flexible clocking scheme. synchronized external oscillator, fixed internal oscillator, allowed modulate frequency during light loads (PSAVE) maximum battery life, method called pulse frequency modulation (PFM). Shutdown places switches high impedance state turns control circuitry achieve typical quiescent current 0.1µA. Line load regulation +/-0.5% output voltage. internal MOSFET switches provide peak current provide output least 700mA. Grounding ILIM reduces current limit half. SC192 achieve 100% duty cycle excellent dropout performance comes tiny MLPD-10, package having maximum height 1mm.
Efficiency Over Wide Load Current Range 700mA Guaranteed Output Current Schottky Diode Required 35µA Quiescent Current 100% Duty Cycle Dropout Efficiency Fast Transient Response Over Temperature Protection Space-saving Micro Lead-Frame Package MLPD-10
Applications
Cell Phones Cordless Phones Notebook Subnotebook Computers PDAs Mobile Communicators Li-Ion NiMH/NiCd Powered Devices
Typical Application Circuit
Revision April 2004
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SC192
POWER MANAGEMENT Absolute Maximum Ratings
Parameter input SYNC/PWM Input Input PGND Voltage ILIM Voltage Voltage COMP Voltage Voltage Thermal Impedance Junction Ambient Output Shor Circuit Current Peak Reflow Temperature SC192IMLTR (Soldering) SC192IMLTRT (Soldering) Symbol VSYNC VPGDN VILIM VADJ VCOMP Storage Temperature Maximum -0.3 -0.3 -0.3 -0.3 -0.3 -0.3 -0.3 Continuous +1.6 +160
PRELIMINARY
Exceeding specifications below result permanent damage device, device malfunction. Operation outside parameters specified Electrical Characteristics section implied.
Units
Tied with square inch, ounce copper. Note: This device sensitive. handling precautions required.
Electrical Characteristics
Unless otherwise noted: 3.6V, SYNC/PWM VIN, ILIM VIN, VIN, =-40 85°C. Typical values +25°C.
Parameter Input Voltage Range Regulation Voltage Input Current Output Voltage Adjust Range Line Regulation Load Regulation(1) P-Channel Resistance N-Channel Resistance
2004 Semtech Corp.
Symbol IADJ VOUT REGLINE REGLOAD RDSP RDSN
Conditions
0.731
Units Ohms Ohms
0.75
0.769 +0.5
0.75V
-0.5
Peak Inductor Current 700mA 200mA 200mA
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SC192
POWER MANAGEMENT Electrical Characteristics Cont.
Unless otherwise noted: 3.6V, SYNC/PWM VIN, ILIM VIN, VIN, =-40 85°C. Typical values +25°C.
Parameter P-Channel Current Limit
Symbol ILIM(P)
Conditions ILIM ILIM
-320
1200 -420
1560 -520
Units
N-Channel Current Limit Quiescent current Shutdown Current leakage Current PMOS leakage Current NMOS Oscillator Frequency SYNC Frequency Range Duty Cycle Range UVLO Threshold UVLO Hysteresis Thermal Shutdown Logic Input High Logic Input Logic Input Current High Logic Input Current
ILIM(N)
SYNC/PWM GND, PSAVE Mode
ILXP ILXN fOSC fSYNC VUVLHYS
SYNC/PWM GND, PSAVE Mode Open, 25OC 5.5V, 5.5V, 5.5V, SYNC/PWM GND, PSAVE Mode 2.35
1000 2.65
SYNC/PWM, ILIM SYNC/PWM, ILIM SYNC/PWM, ILIM SYNC/PWM, ILIM
Notes: Load regulation limits specified from 700mA. This specification calculated based parameters measured individually tested parameter. load regulation limit graph page more detailed view performance.
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SC192
POWER MANAGEMENT Configuration PRELIMINARY Ordering Information
DEVICE(1) PACKAGE MLPD-10 Evaluation Board
VIEW
COMP PGND SYNC/PWM ILIM
SC192IMLTR SC192IMLTRT(2) SC192EVB
Note: Only available tape reel packaging. reel contains 3000 devices. Lead free product.
MLPD-10: LEAD
Descriptions
Name Function Input power supply voltage; this input goes directly internal MOSFET switches. Bypass capacitor pin; external capacitor combined with internal resistor provides filtered supply voltage internal control circuitry. Connect 0.1uF capacitor from ground. Analog ground. Compensation error amplifier. Output adjust pin; connect resistor divider output voltage. Digital current limit select input. Connect ILIM 0.6A current; connect ILIM 1.2A current limit. Oscillator synchronization input. forced mode, enable power save mode, external clock signal frequency synchronization. Enable digital input; high input enables SC192 disables device reduces quiescent current 0.1uA. shutdown, becomes high impedance. Inductor connection switching FETs. Power Ground.
COMP ILIM SYNC/PWM PGND
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SC192
POWER MANAGEMENT Block Diagram
ILIM
Plimit Current
SYNC/
slope generation
COMP
comp
Control logic
PGND
Error
750mV
Nlimit comp
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SC192
Description SC192 step-down, pulse-width-modulated (PWM), DC-DC converter adjustable output range from 0.75V input voltage. device internal synchronous rectifier does require schottky diode pin. moderate heavy loads, converter operates mode with fixed frequency 750kHz. light loads converter enters power save mode modulating frequency, pulse-frequency-modulation (PFM) which achieves high efficiency under light load conditions. Normal Mode This standard fixed frequency current mode topology. current feedback through PMOS current path amplified summed with internal slope compensation network offset. voltage feedback loop through resistor divider attached pin. transconductance error amplifier output compensation (COMP) with usual external compensation network attached. COMP closes loop comparing summed current feedback COMP signal determine length time. period on-board oscillator external clock attached SYNC pin. Power Save Mode SYNC/PWM low, power save mode used light loads improve efficiency. When output current reaches enough level, part goes into voltage hysteresis mode operation. current level this current reversal protection NMOS device. output voltage then allowed decay lower threshold with part reduced quiescent current (PSAVE) state. After this lower threshold reached part reawoken normal operation, with current offset COMP drive output voltage regulation point above upper threshold point. However offset removed once upper threshold reached. load current sufficiently large part will return normal regulation, another PSAVE cycle will start. Frequency Foldback When output switching frequency folded back several discrete steps protect against short output improve inrush current control during start-up.
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PRELIMINARY
Forced SYNC/PWM high, forced mode enabled. This ensures that switching frequency converter maintained over full range output loads. This means that current reversal threshold NMOS changed negative value 100% duty cycle power save modes also disabled. 100% Duty-Cycle Operation Normally control loop constrains duty cycle converter with minimum times, output voltage droops lower power-save threshold time terminated comparator PMOS current limit, then next PMOS time allowed extend until either comparator PMOS current limit trips. This then followed minimum time. This maximum time/minimum time allowed continue until upper power-save threshold reached. This allows part into dropout mode operation input supply collapses down output voltage. this happens, output voltage equal input voltage minus voltage drop across P-channel MOSFET. Soft Start soft start mode enabled after every shutdown cycle limit inrush current from battery. conjunction with frequency foldback this controls maximum current during start-up. PMOS current limit stepped from 25%, 50%, 75%, then 100% internal timer. soon part reaches regulation, soft start mode disabled.
SC192
POWER MANAGEMENT Evaluation Board Schematic
10uH
C192
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SC192
POWER MANAGEMENT Evaluation Board Gerber Plots COPPER BOTTOM COPPER PRELIMINARY
SILKSCREEN
BOTTOM SILKSCREEN
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SC192
POWER MANAGEMENT Applications Information
Selecting Components When selecting components SC192 application main factors typically performance, size cost. higher performance designer will select higher values input output capacitors reduce ripple current voltage. However, application that tolerate higher ripple, less expensive smaller components utilized. schematics below show possibilities. first shows 10uF capacitors input output with 10uH, while second shows smaller less expensive 4.7uF capacitors 4.7uH. only circuit consideration choosing over other compensation components When these components place values chosen given output voltage. values that should used indicated Table below. Using different value advised since this will change loop characteristics cause supply become unstable. output voltage achievable using 442k then selecting achieve desired output voltage. equation VOUT
0.75 Vout
Because SC192 external compensation small inexpensive ceramic capacitors used output capacitor allowing designer greater flexibility.
C192
C192
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SC192
POWER MANAGEMENT Applications Information Cont.
TABLE
3.3V 2.5V 1.8V 1.5V 1.0V 130k 187k 309k 442k 1.30M 470pF 470pF 470pF 6.19k Cout 10uF 10uH Cout 22uF 10uH Cout 4.7uF 4.7uH
PRELIMINARY
Plots below were taken 3.6V, Vout 1.8V, with compensation components listed Table upper plot middle plot output voltage, lower plot current transient 0.1A 0.6A PSAVE, Cout 20uF, Lout 10uH PWM, Cout 20uF, Lout 10uH
PSAVE, Cout 10uF, Lout 10uH
PWM, Cout 10uF, Lout 10uH
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SC192
POWER MANAGEMENT Applications Information Cont.
PSAVE, Cout 4.7uF, Lout 4.7uH PWM, Cout 4.7uF, Lout 4.7uH
Inductor Selection inductor values listed Table will work nearly combinations output current output voltages. After selecting 4.7uH 10uH inductor value additional inductor parameters should considered. current rating inductor resistance. resistance great impact efficiency copper losses. However, small inductors tend have higher resistance. Therefore compromise between size efficiency will need made. inductor current must chosen prevent inductor from saturation. most conservative approach would select inductor with saturation current slightly above maximum current capability SC192 which 1.56A peak current ILIM 780mA ILIM GND. more accurate design inductor would rate inductor maximum output current plus inductor ripple current that calculated follows:
Switching frequency Inductor Value Peak-to-peak inductor ripple current Maximum inductor current VOUT Output voltage Input voltage COUT Output Capacitance IOUT Output Current IOUT(MAX) Maximum Output Current Output Capacitor Selection Because SC192 external compensation available, ceramic capacitors used. This eliminates need bulky tantalum capacitors. Values output capacitors Table will work nearly combinations output current output voltages. equation determining size output capacitor terms minimizing ripple voltage given follows:
IL(MAX) IO(MAX
COUT
Input Capacitor Selection input ripple current reduced with properly selecting input capacitor. Again, values input capacitors Table will work nearly combinations input current output voltages. input capacitor should rated maximum input ripple current calculated
VOUT VOUT
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SC192
POWER MANAGEMENT Applications Information Cont.
IRMS VOUT VOUT
Load Regulation
PRELIMINARY
Load Regulation 3.6V
0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 Ouput Current (mA) 1.8V 2.5V
IOUT
worst case ripple current occurs duty cycle value that point
IOUT
Ceramic capacitors recommended input capacitors because their high ripple current capabilities. addition, advised that input capacitor placed close input possible. Layout Considerations layout utmost importance because switching frequency 750kHz with peak currents over careful layout will avoid potential stability problems. Traces should wide short possible. Keep input capacitor close package possible. This will help minimize large loop areas. Keep power ground analog ground separated together common point. Notice copper Gerber plot, tied together under package. aware high current paths avoid tying signal grounds high power grounds where signal paths might experience large fluctuations voltages high currents pass though copper traces.
Efficiency
Load Current (mA) 3.3V
Efficiency
Efficiency 3.6V
Efficiency Load Current (mA) 2.5V 1.8V
Marking Information
Mark
0.10 Line Regulation 0.08 0.06
Line Regulation Iout 300mA
two-digit year manufacture two-digit week manufacture
2004 Semtech Corp. www.semtech.com
yyww
1.8V 0.04 0.02 0.00
Input Voltage (Volts)
SC192
POWER MANAGEMENT
Line Regulation Iout 300mA
0.14 Line Regulation 0.12 0.10 0.08 0.06 0.04 0.02 0.00 Input Voltage (Volts) 2.5V
SC192 Load Regulation Limits Load Regulation Peak Inductor Current (Amps)
Load Load Load
Oscillator Frequency Over Temperature
(Volts) -40C 125C Fosc (kHz)
Oscillator Frequency Temperature Over
Fosc (kHz) 3.6V 5.5V
Shutdown Current Temperature
Temperature (OC) Shutdown Current (uA)
3.6V
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SC192
POWER MANAGEMENT Outline Drawing MLPD-10, PRELIMINARY
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SC192
POWER MANAGEMENT Land Pattern MLPD-10,
Contact Information
Semtech Corporation Power Management Products Division Flynn Road, Camarillo, 93012 Phone: (805)498-2111 (805)498-3804
2004 Semtech Corp.
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2.7V 5.5V Input Range Output Adjustable from 0.75V Fixed Frequency PSA

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