SEMTECH SC2442H

SC2442/H High Performance Wide Input Range Dual Synchronous Buck Controller POWER MANAGEMENT Description Features SC2442 and SC2442H are high performance dual buck ‹ Dual output controller converter controllers that can be configured for a variety ‹ Asynchronous start up mode of synchronous buck applications where efficiency is most ‹ Power up sequencing to prevent latch-ups important. Both converters are synchronized to prevent ‹ Out of phase operation for low input ripple beat frequencies. The dual buck converters are also ‹ Over current protection operated out of phase reducing input ripple, allowing for ‹ Output down to 0.75V fewer input capacitors. ‹ Wide input range, 4.75 to 30V for SC2442 and 4.75 to 36V for SC2442H High frequency operation up to 1.1 MHz reduces the size ‹ Vcc regulator with external PNP transistor of output inductors and capacitors. The controller has ‹ Programmable clock frequency up to 1.1MHz separate power pins for both VCC and GND to improve ‹ Two synchronous bucks for high efficiency at high noise immunity. The VCC supplies can be regulated to 7V current using an external PNP transistor. Other features include: bootstrapping for high side drive supplies, asynchronous ‹ –40 to +125 Deg C operating temperature mode start up, power up sequencing to prevent latch- ‹ Small package TSSOP-24 ‹ Fully WEEE and RoHS Compliant ups, individual soft start for each convertor, bootstrapped drivers for high side N-channel MOSFETs, input side current sensing, dual mode current limit with hiccup, Applications enable and external frequency synchronization. ‹ Point of load converter applications ‹ DSL applications with multiple output voltages The SC2442 operates over the range of 4.75V to 30V ‹ Power management for mixed signal applications and SC2442H operates over the range of 4.75V to 36V. ‹ Cable modems and set top boxes. Typical Application Circuit R1 MAX 30V/36V (H) VIN+ R2 Q1 R5 R3 R4 L1 C1 VOUT1 Q5 Q3 C6 C2 OC1 R9 R7 C7 OC2 RTN RTN Q2 D1 D2 3 4 R6 VIN OC1 U1 L2 2 21 BDI OC2 VOUT2 C4 AVCC 1 9 Q4 AVCC GD1H PVCC 13 11 R8 C3 PVCC GD1L R10 7 16 SS1 GD2H C5 18 14 SS2 GD2L RTN PH1 23 10 ROSC PH1 SS1 BST1 6 8 R13 R14 FB1 BST1 C8 C15 5 15 PH2 EA1 PH2 SS2 19 17 BST2 C9 FB2 BST2 C16 OSC 20 12 EA2 PGND R12 22 24 R16 R15 SYNC/EN AGND RTN R11 C10 C11 EA2 RTN R17 C12 R18 C13 FB2 ENA FB1 Revision: June, 2007 1 www.semtech.com SC2442ITSTR SC2442/H POWER MANAGEMENT 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 BST1,BST2toPGND V V V BST1, BST2 SC2442 38 SC2442H 44 VIN toPGND VIN V SC2442 30 SC2442H 36 BDItoPGND VV IN V BDI OC1andOC2toVIN -V 0.3to+0.5 VIN-V , VIN-V OC1 OC2 PC VCC,AVCC toPGND P8 VCC,AVC V BST1toPH1, BST2toPH2 -V 0.3to8 GD1HtoPH1,GD2HtoPH2 GD1L,GD2LtoPGND -V 0.3toPVCC PGND toAGND ±V 0.3 PH1,PH2-veswingwrtPGND (for100nS) -V 1 V V PH1, PH2 AllOtherPinstoAGND -V 0.3toAVCC JunctionTemperature -C 40to+125 ° StorageTemperatureRange -C 60to+150 ° LeadTemperature(Soldering)10Sec. 2C 60 ° Electrical Characteristics Unless specified: T = T = -40 to 125°C, VIN = 24V, V = 7V, Fc = 550KHz A J CC Pl arameter Ss ymbo Tn estCondition Mp i Tx y Mt a Uni UndervoltageLockout StartThreshold A5 VCC rising 46 . 45 . 4V .7 V UVLO UVLOHysteresis A5 VCC falling 0V .1 V HYST PowerSupply OperatingCurrent N8 oload,SYNC/EN=Low 1A 3 m I QSC AC VCC/PVCC Regulated AV VCC,PVC V7 IN>8 60 . 73 . 7V . BDIDriveCurrent V3 IN>AVCC +2V 5 mA I BDI © 2007 Semtech Corp. 2 www.semtech.com SC2442/H POWER MANAGEMENT Electrical Characteristics (Cont.) Unless specified: T = T = -40 to 125°C, VIN = 24V, V = 7V, Fc = 550KHz A J CC Pl arameter Ss ymbo Tn estCondition Mp i Tx y Mt a Uni SoftStart ChargingCurrent 70 13 1A μ I ,I SS1 SS2 DischargeCurrent -2 1 -4 -A μ I ,I SS1 SS2 ErrorAmplifier VoltageFeedbackReference 00 .735 05 .75 0V .76 V ,V FB1 FB2 InputBiasCurrent 5A 00 n I EABIAS (1) 7B 0 d OpenLoopGain G DC (1) G3 BW MHz UnityGainBandwidth OutputSource/SinkCurrent 2A m (1) 1S V/μ OutputSlewRate (1) 8S 0 n PWMtoOutputDelay Oscillator Fc requencyRange F1 01 . 1z . MH Cc lockFrequency FK R0 OSC =60 40 9 50 5 6z 1 kH (1) I0 nternal 3V . OscillatorPeakVoltage (1) I5 nternal 1V . OscillatorValleyVoltage Sync/EnableInput EnableThresheldVoltage S8 YNC/ENpinVoltagerising 10 . 2V . V SYEN DisableThresheldVoltage S8 YNC/ENpinVoltagefalling 00 . 1V . V SYEN (1) S0 YNC/ENpin<0.8V 5S n DisableLowtoShutDownDelay SyncInputHighLevel TV TL V SYEN SyncInputLowLevel TV TL V SYEN CurrentLimit OC1,OC2CurrentLimitSense -5 80 -5 10 -V 12 m V V OC1, OC2 FeedbackThresholdforHiccup 05 .450 00 .52 0V .61 V ,V FB1 FB2 (1) 8S 0 n OC SensetoDriveTurnOffDelay T OCDLY © 2007 Semtech Corp. 3 www.semtech.com SC2442/H POWER MANAGEMENT Electrical Characteristics (Cont.) Unless specified: T = T = -40 to 125°C, VIN = 24V, V = 7V, Fc = 550KHz A J CC Pl arameter Ss ymbo Tn estCondition Mp i Tn y Ms i Unit GateDriveOutputs (1) S+ oure/Sink 0A .5 HighSideGateDrive I ,I GDH+ GDH- (1) S+ oure/Sink 0A .5 LowSideGateDrive I ,I GDL+ GDL- GateDriveRiseTime C =0 1000pF 3S n T OUT RISE GateDriveFallTime C =0 1000pF 3S n T OUT FALL Mx aximumDutyCycle D2 ma F5 orPWM1andPWM 84 9% Mn inimumDutyCycle D2 mi F0 orPWM1andPWM % 1S 00 n DT eadTimeBetweenGateDrives DEAD NOTES: (1) Guaranteed by design, not tested in production (2) This device is sensitive to ESD. Use of standard ESD handling precautions is required. Pin Configuration Ordering Information Temp.Range Top View Pe artNumber Packag (T ) A AGND AVCC SC2442ITSTR BDI ROSC TC SSOP-24 -40°Cto+125° SYNC/EN VIN SC2442HITSTR OC1 OC2 (1) SC2442ITSTRT EA1 EA2 TC SSOP-24 -40°Cto+125° FB1 FB2 (1) SC2442HITSTRT SS1 SS2 BST1 BST2 GD2H GD1H PH1 PH2 GD1L GD2L Notes: PGND PVCC Only available in tape and reel packaging. A reel contains 2500 devices. (24 Pin TSSOP) (1) Lead free devices © 2007 Semtech Corp. 4 www.semtech.com SC2442/H POWER MANAGEMENT Pin Descriptions Pe in# Pn inNam PinFunctio 1C A. VC Supplyvoltageforanalogcircuit RegulatedbytheBDIpin to7VfromVINusinganexternalPNPtransistor. 2I B. D BasedriveforAVCC/PVCCregulator 3N VI Inputsupplyvoltage.Maximumis30VforSC2442and36VforSC2442H. 41 O. C HighsidecurrentsenseforVOUT1.Thresholdis100mV 51 E. A ErroramplifieroutputforcompensationfortheVOUT1 61 F. B Feedbackinputforthe VOUT1 71 SS Softstartpinfor VOUT1.AcapacitortoAGNDsetsthesoftstartperiod. 81 B. ST BoostcapacitorconnectionfortheVOUT1highsidegatedrive ConnectanexternalcapacitorandadiodeasshownintheTypicalApplicationCircuit. 9H GD1 GatedriveforthehighsideMOSFETofVOUT1. 180degreesoutofphasewithGD2H. 11 0 P. H Switchingnodefor VOUT1externalinductorconnection 1L 1 G. D1 Gatedriveforlow sideMOSFETof VOUT1 1D 2 P. GN Powergroundforgatedrivereturncurrents 1C 3 P. VC Supplyvoltageforoutputdrivers 1L 4 G. D2 Gatedriveforlow sideMOSFETof VOUT2 12 5 P. H Switchingnodefor VOUT2externalinductorconnection 1H 6 GD2 GatedriveforthehighsideMOSFETofVOUT2.180degreesoutofphasewithGD1H. 12 7 B. ST BoostcapacitorconnectionfortheVOUT2highsidegatedrive Connectanexternalcapacitorandadiode asshownintheTypicalApplicationCircuit. 12 8 SS Softstartpinfor VOUT2.AcapacitortoAGNDsetsthesoftstartperiod. 12 9 F. B FeedbackinputfortheVOUT2 22 0 E. A ErroramplifieroutputforcompensationfortheVOUT2 22 1 O. C Highsidecurrentsensefor VOUT2.Thresholdis100mV 2N 2 S. YNC/E OscillatorsynchronizationandPWMEnablepin 2C 3 ROS Oscillatorfrequencyprogrammingpin.ConnectaresistortoAGNDtosetclockfrequency. 2D 4 A. GN Analogsignalground © 2007 Semtech Corp. 5 www.semtech.com SC2442/H POWER MANAGEMENT Block Diagram © 2007 Semtech Corp. 6 www.semtech.com SC2442/H POWER MANAGEMENT Application Information Sync and Enable Undervoltage Lockout When the SYNC/EN pin is pulled below 1V, all output The undervoltage lockout circuitry monitors the AVCC pin. drives are turned off and both SS pins are discharged to During undervoltage lockout all output drives are turned ground. When the SYNC/EN pin is pulled high above off and both SS pins are discharged to ground. Typically, 1.8V, normal operation occurs. When an external clock for AVCC increasing, normal operation will not occur until signal is applied that is marginally higher in frequency to AVCC reaches 4.6V. For AVCC falling, undervoltage lock- that set by the ROSC resistor, the internal oscillator will out will not occur until AVCC falls below 4.5V. synchronize to this signal. The external signal should have TTL compatible transition. Voltage Regulator Operating Frequency Using an external PNP transistor as shown in the Typical Applications Circuit, the SC2442/H provide a regulated The operating frequency is set by a resistor from ROSC AVCC supply. The same AVCC with adequate filtering can pin to AGND. ROSC sets the clock frequency Fc that is be connected to PVCC to provide power for the output twice the operating frequency of each converter. The drives. The AVCC is regulated at 7V typical which provides clock frequency is given by optimum drive for most low Voltage power MOSFETs. The BDI pin will provide at least 3 mA to regulate the external Fc = 33,000 / ROSC PNP. Fc is in kHz and ROSC is in kOhm. For VIN voltages below 8V, the PNP pass transistor will always be operating in saturation and it is recommended Current Limiting to connect VIN directly to AVCC and PVCC so long as maximum input voltage is below 8V. The BDI pin may be The SC2442/H provide cycle-by-cycle current limiting by left unconnected. Alternately if an additional supply <8V is sensing the current in the input line. A non inductive resistor available in addition to VIN, it can be used for separately should be used for precise current sensing and limiting. powering both the VCCs. When the voltage drop across a sense resistor in the input line exceeds 105 mV, the PWM pulse is latched off and is Soft Start and Hiccup Mode not reset until the next clock cycle. Overcurrent condition affects only the high side driver. An RC filter should be The SC2442/H controllers utilize asynchronous start up placed across the sense resistor as shown in the Typical to provide glitch free output rise times. During start up, the Application Circuit to reduce noise due to turn-on spikes. SS1 and SS2 pins are held low and the gate drive signals The filter capacitor should be connected between VIN and are also pulled low. Once AVCC reaches 4.6V and above, respective OCx pins for proper filtering. Typically a ceramic the SS capacitors are charged by a 10 μA internal current or similar low esr capacitor is placed between the current source. The error amplifier outputs are clamped by the re- sense resistor and the switching circuit. If this capacitor spective SSx voltages. As the SSx pin voltage goes above value is large, it can significantly distort the current the oscillator valley voltage of 1.5V, the high-side driver feedback waveform aross the sense resistors. This should will begin switching. The low-side driver will not begin be taken into account while designing the overcurrent switching until the SSx voltage has reached 3.3V. protection circuit. During normal operation, the SC2442/H will enter hiccup Gate Drive Considerations mode if the SS pin voltage is above 3.3V and the FB pin voltage is below 0.525V (70% of 0.750V). If this occurs The SC2442/H provide high side gate drive with the GDxH and GDxL signals will go low and the SS pin will bootstrapping as shown in the Typical Application Circuit. begin to sink 2 μA. The 2 μA of sink current will slowly A ceramic capacitor is recommended between each BSTx discharge the SS capacitor until its voltage reaches 1V, pin to the corresponding Phase Node. Each gate drive can which will trigger the SS pin to begin sourcing 10 μA. The source and sink a minimum of 0.5A current with 100 nS convertor will operate in the asynchronous mode during dead time between transistions to prevent shoot throughs. hiccup. © 2007 Semtech Corp. 7 www.semtech.com SC2442/H POWER MANAGEMENT Application Information (Contd) 4.75-6V 0.075R, 1/4W R1 VIN J1-1 QD1 8 7 6 5 0.06R, 1/4W R2 FDS6982S TP2 C2 C7 R3 R4 3.3V/0.6A P1166.473T L1 100R VOUT1 J1-2 C8 100R 1 2 QBQT 10 nF 3.3R C22 R7 C3 C14 OC1 1 2 3 4 J2-1 100 uF 4V J1-3 C23 2R R5 OC2 RTN TP1 10 nF PVCC J2-2 QD2 8 7 6 5 D1 D2 TP3 RTN 3 4 FDS6982S VIN OC1 U1 1.8V/1A J2-4 L2 2 21 P1166.223T C10 BDI OC2 1 2 VOUT2 1 9 AVCC GD1H QBQT C4 C15 13 11 15 uF R9 R10 J2-3 PVCC GD1L 1 2 3 4 2R 100 uF 4V R6 7 16 SS1 GD2H 3.3R C11 R8 18 14 SS2 GD2L RTN 23 10 PH1 C25 15 uF C24 ROSC PH1 SS1 BST1 6 8 1 nF 1 nF FB1 BST1 0.22 uF C16 C12 2.2 uF R18 5 15 PH2 R17 R16 R19 EA1 PH2 SS2 BST2 19 17 0.1 uF C17 FB2 BST2 100R 100R 14K 34K OSC 20 12 C13 2.2 uF EA2 PGND R11 40.2K 22 24 SYNC/EN AGND R14 R15 10K 10K ENA 47 pF C21 C20 47 pF EA1 EA2 R13 C19 R12 C18 220K 4.7 nF 100K 10 nF FB2 FB1 Fig 1) Application Circuit for 5V to 3.3V/1.8V Low Power Dual Synchronous Buck Convertor Input 5V 3.3V Output 1.8V Output Fig 2) Input and output rise times with full load © 2007 Semtech Corp. 8 www.semtech.com 10K 56 uF 10V 5R 2.2 uF 2.2 uF SC2442ITSTR SCH SCH 2.2 uF 2.2 uF SC2442/H POWER MANAGEMENT Application Information (Contd) Fig 3) Switching waveforms at Phase Node with full load. Fig 4) Output ripple and noise at full load Top trace: 1.8V/1A Bottom trace: 3.3V/0.6A Top trace: 3.3V Output Bottom trace: 1.8V Output Fig 5) 1.8V Transient response for 10% to 100% step load Fig 6) 3.3V Transient response for 10% to 100% step load © 2007 Semtech Corp. 9 www.semtech.com SC2442/H POWER MANAGEMENT Outline Drawing - TSSOP-24 Land Pattern - TSSOP-24 Contact Information Semtech Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 Phone: (805)498-2111 FAX (805)498-3804 © 2007 Semtech Corp. 10 www.semtech.com