SC2442ITSTR

SC2442/H High Performance Wide Input Range Dual Synchronous Buck Controller POWER MANAGEMENT Description Features SC2442 and SC2442H are high performance dual buck converter controllers that can be configured for a variety of synchronous buck applications where efficiency is most important. Both converters are synchronized to prevent beat frequencies. The dual buck converters are also operated out of phase reducing input ripple, allowing for fewer input capacitors. ‹ ‹ ‹ ‹ ‹ ‹ ‹ High frequency operation up to 1.1 MHz reduces the size of output inductors and capacitors. The controller has separate power pins for both VCC and GND to improve noise immunity. The VCC supplies can be regulated to 7V using an external PNP transistor. Other features include: bootstrapping for high side drive supplies, asynchronous mode start up, power up sequencing to prevent latchups, individual soft start for each convertor, bootstrapped drivers for high side N-channel MOSFETs, input side current sensing, dual mode current limit with hiccup, enable and external frequency synchronization. ‹ ‹ ‹ ‹ ‹ ‹ Applications ‹ ‹ The SC2442 operates over the range of 4.75V to 30V and SC2442H operates over the range of 4.75V to 36V. ‹ ‹ Typical Application Circuit VIN+ MAX 30V/36V (H) Dual output controller Asynchronous start up mode Power up sequencing to prevent latch-ups Out of phase operation for low input ripple Over current protection Output down to 0.75V Wide input range, 4.75 to 30V for SC2442 and 4.75 to 36V for SC2442H Vcc regulator with external PNP transistor Programmable clock frequency up to 1.1MHz Two synchronous bucks for high efficiency at high current –40 to +125 Deg C operating temperature Small package TSSOP-24 Fully WEEE and RoHS Compliant Point of load converter applications DSL applications with multiple output voltages Power management for mixed signal applications Cable modems and set top boxes. R1 R2 C1 Q1 R3 R5 R4 L1 Q5 Q3 C6 R9 OC1 C7 C4 AVCC 1 PVCC 13 7 R10 18 C5 23 SS1 6 C8 5 SS2 19 C9 OSC 20 R12 22 VI N U1 BD I OC 1 OC 2 AVC C G D 1H P VC C G D 1L SS1 SS2 ROS C FB1 SC2442ITSTR 2 R7 OC2 RTN 3 VOUT1 C2 G D 2H G D 2L PH1 BS T 1 E A1 PH2 FB2 BS T 2 E A2 P G ND S YN C /E N AG ND D1 4 RTN Q2 D2 R6 L2 21 9 VOUT2 Q4 11 R8 C3 16 14 10 PH1 8 BST1 15 PH2 17 BST2 RTN R13 R14 C15 C16 12 24 R15 R16 RTN R11 C10 R17 ENA Revision: June, 2007 C11 C12 R18 EA2 RTN C13 FB2 FB1 1 www.semtech.com 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. Parameter Sy mbol BST1, BST2 to PGND S C 2442 S C 2442H VBST1, VBST2 Maximum U nits V 38 44 VIN to PGND S C 2442 S C 2442H VIN V BD I to PGND V BD I VIN V VIN - VOC1, VIN - VOC2 -0.3 to +0.5 V PVC C , AVC C 8 V -0.3 to 8 V -0.3 to PVC C V ±0.3 V -1 V -0.3 to AVC C V Juncti on Temperature -40 to +125 °C Storage Temperature Range -60 to +150 °C 260 °C 30 36 OC 1 and OC 2 to VIN PVC C , AVC C to PGND BST1 to PH1, BST2 to PH2 GD 1H to PH1, GD 2H to PH2 GD 1L, GD 2L to PGND PGND to AGND PH1, PH2 -ve swi ng wrt PGND (for 100 nS) VPH1, VPH2 All Other Pi ns to AGND Lead Temperature (Solderi ng) 10 Sec. Electrical Characteristics Unless specified: TA = TJ = -40 to 125°C, VIN = 24V, VCC = 7V, Fc = 550KHz Parameter Sy mbol Test C onditions Min Ty p Max U nit Start Threshold VUVLO AVC C ri si ng 4.5 4.6 4.75 V UVLO Hysteresi s VHYST AVC C falli ng 0.15 IQSC No load, SYNC /EN = Low 8 13 mA 6.7 7.0 7.3 V 3 5 U nderv oltage Lockout V Power Supply Operati ng C urrent AVC C /PVC C Regulated BD I D ri ve C urrent © 2007 Semtech Corp. AVC C , PVC C VIN > 8V VIN > AVC C + 2V IBDI 2 mA www.semtech.com SC2442/H POWER MANAGEMENT Electrical Characteristics (Cont.) Unless specified: TA = TJ = -40 to 125°C, VIN = 24V, VCC = 7V, Fc = 550KHz Parameter Sy mbol Test C onditions Min Ty p Max U nit Soft Start C hargi ng C urrent ISS1, ISS2 7 10 13 μA D i scharge C urrent ISS1, ISS2 -1 -2 -4 μA V F B 1, V F B 2 0.735 0.750 0.765 V Error Amplifier Voltage Feedback Reference Input Bi as C urrent Open Loop Gai n (1) Uni ty Gai n Bandwi dth (1) IEABIAS 500 nA GDC 70 dB GBW 3 MHz 2 mA 1 V/μS 80 nS Output Source/Si nk C urrent Output Slew Rate (1) PWM to Output D elay (1) Oscillator Frequency Range Fc C lock Frequency Fc Osci llator Peak Voltage Osci llator Valley Voltage 0.1 ROSC = 60K (1) (1) 490 550 1.1 MHz 610 kHz Internal 3.0 V Internal 1.5 V 2.0 V Sy nc/Enable Input Enable Thresheld Voltage VSYEN SYNC /EN pi n Voltage ri si ng D i sable Thresheld Voltage VSYEN SYNC /EN pi n Voltage falli ng 0.8 SYNC /EN pi n < 0.8V 50 nS D i sable Low to Shut D own D elay (1) 1.8 1.0 V Sync Input Hi gh Level VSYEN TTL V Sync Input Low Level VSYEN TTL V C urrent Limit OC 1, OC 2 C urrent Li mi t Sense VOC1, VOC2 -80 -105 -125 mV Feedback Threshold for Hi ccup V F B 1, V F B 2 0.450 0.525 0.610 V OC Sense to D ri ve Turn Off D elay (1) © 2007 Semtech Corp. 80 TOCDLY 3 nS www.semtech.com SC2442/H POWER MANAGEMENT Electrical Characteristics (Cont.) Unless specified: TA = TJ = -40 to 125°C, VIN = 24V, VCC = 7V, Fc = 550KHz Parameter Sy mbol Test C onditions Min Ty p Min U nits Hi gh Si de Gate D ri ve (1) IGDH+, IGDH- Soure/Si nk + 0 .5 A (1) IGDL+, IGDL- Soure/Si nk + 0 .5 A Gate D ri ve Ri se Ti me TRISE C OUT = 1000 pF 30 nS Gate D ri ve Fall Ti me TFALL C OUT = 1000 pF 30 nS Maxi mum D uty C ycle D max For PWM1 and PWM2 94 % Mi ni mum D uty C ycle D mi n For PWM1 and PWM2 0 % D ead Ti me Between Gate D ri ves TDEAD 100 nS Gate D riv e Outputs Low Si de Gate D ri ve 85 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 Top View Part Number AVCC AGND BDI ROSC SC2442ITSTR VIN SYNC/EN SC2442HITSTR OC1 OC2 EA1 EA2 FB1 FB2 SS1 SS2 BST1 BST2 GD1H GD2H SC2442ITSTRT Package Temp. Range (T A) TSSOP-24 -40°C to +125°C TSSOP-24 -40°C to +125°C (1) SC2442HITSTRT (1) PH2 PH1 GD1L GD2L PGND PVCC Notes: 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 Pin # Pin Name 1 AVCC 2 BDI Base drive for AVCC/PVCC regulator. 3 VIN Input supply voltage. Maximum is 30V for SC2442 and 36V for SC2442H. 4 OC1 High side current sense for VOUT1. Threshold is 100 mV. 5 EA1 Error amplifier output for compensation for the VOUT1. 6 FB1 Feedback input for the VOUT1. 7 SS1 Soft start pin for VOUT1. A capacitor to AGND sets the soft start period. 8 BST1 Boost capacitor connection for the VOUT1 high side gate drive. Connect an external capacitor and a diode as show n in the Typical Application Circuit. 9 GD1H Gate drive for the high side MOSFET of VOUT1. 180 degrees out of phase w ith GD2H. 10 PH1 11 GD1L Gate drive for low side MOSFET of VOUT1. 12 PGND Pow er ground for gate drive return currents. 13 PVCC Supply voltage for output drivers. 14 GD2L Gate drive for low side MOSFET of VOUT2. 15 PH2 16 GD2H Gate drive for the high side MOSFET of VOUT2. 180 degrees out of phase w ith GD1H. 17 BST2 Boost capacitor connection for the VOUT2 high side gate drive. Connect an external capacitor and a diode as show n in the Typical Application Circuit. 18 SS2 Soft start pin for VOUT2. A capacitor to AGND sets the soft start period. 19 FB2 Feedback input for the VOUT2. 20 EA2 Error amplifier output for compensation for the VOUT2. 21 OC2 High side current sense for VOUT2. Threshold is 100 mV. 22 SY NC/EN 23 ROSC Oscillator frequency programming pin. Connect a resistor to AGND to set clock frequency. 24 AGND Analog signal ground. © 2007 Semtech Corp. Pin Function Supply voltage for analog circuit. Regulated by the BDI pin to 7V from VIN using an external PNP transistor. Sw itching node for VOUT1 external inductor connection. Sw itching node for VOUT2 external inductor connection. Oscillator synchronization and PWM Enable pin. 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 drives are turned off and both SS pins are discharged to ground. When the SYNC/EN pin is pulled high above 1.8V, normal operation occurs. When an external clock signal is applied that is marginally higher in frequency to that set by the ROSC resistor, the internal oscillator will synchronize to this signal. The external signal should have TTL compatible transition. The undervoltage lockout circuitry monitors the AVCC pin. During undervoltage lockout all output drives are turned off and both SS pins are discharged to ground. Typically, for AVCC increasing, normal operation will not occur until AVCC reaches 4.6V. For AVCC falling, undervoltage lockout will not occur until AVCC falls below 4.5V. Voltage Regulator Operating Frequency Using an external PNP transistor as shown in the Typical Applications Circuit, the SC2442/H provide a regulated AVCC supply. The same AVCC with adequate filtering can be connected to PVCC to provide power for the output drives. The AVCC is regulated at 7V typical which provides optimum drive for most low Voltage power MOSFETs. The BDI pin will provide at least 3 mA to regulate the external PNP. The operating frequency is set by a resistor from ROSC pin to AGND. ROSC sets the clock frequency Fc that is twice the operating frequency of each converter. The clock frequency is given by Fc = 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 to connect VIN directly to AVCC and PVCC so long as maximum input voltage is below 8V. The BDI pin may be left unconnected. Alternately if an additional supply