SEMTECH SC1110

SC1110 Sink and Source DC/DC Controller for Termination Power Supply Applications POWER MANAGEMENT Features Description The SC1110 is a low-cost, full featured, synchronous ‹ Generates termination voltages for active termina- voltage-mode controller designed to generate tion schemes termination voltage in double data rate (DDR) memory ‹ 1% set point accuracy systems and other applications where wide data bus ‹ For ±7A output current, transient regulation is need to be actively terminated. Synchronous control of better than ±80mV the MOSFET half bridge allows power flowing ‹ V pin available for external 50% resistive divider REFIN bi-directionally. The termination voltage can be tightly to allow termination voltage track of the chip set regulated to track the chipset voltage, i.e. to be exactly voltage 50% of that at all times. ‹ Buffered V for system usage REFOUT ‹ R sensing for over current protection in hiccup DSON The SC1110 is ideal for low cost implementation of mode termination voltage supplies. SC1110 features include ‹ Soft start and logic input enabling temperature compensated voltage reference, triangle ‹ 250kHz switching for best transient and efficiency wave oscillator and current sense comparator circuitry, performance and allows the use of inexpensive N-channel power ‹ Gate drive capable for 0.5A sourcing and sinking MOSFETs. The SC1110 operates at a fixed 250kHz, providing an Applications optimum compromise between efficiency, transient performance, external component size, and cost. ‹ For DDR memory systems ‹ For active termination schemes in high speed logic systems Typical Application Circuit REFOUT +5Vcc + C1 R1 R2 R3 C10,11 C7 C8,9 Vin 2.5V 0.01 5k 1.24k 10 U1 R4 1.0 2 x 10uF 2 x 560uF C2 SC1110 1k C4 0.1 0.022 _ 1 14 VCC REFOUT SS/ENBL 2 13 SS/ENBL REFIN R5 C3 1k 0.1 3 12 OCSET SENSE C5 R6 PWRGD 0.047 4.7k 4 11 PWRGD COMP C25 0.1 5 10 GND BSTL D1 MBRM120 6 9 PHASE BSTH R7 Q1 C6 L1 2.2 1.0 7 8 Si9426DY 800 nH DL DH + R8 Q2 2.2 Si9426DY C12-14 C15-24 Vout = 1.25V @ 7A 3 x 560uF 10 x 10uF _ C10-14: Sanyo, 4SP560M C8,9,15-24: TDK, CC3216AX5R0J106K L1: Panasonic, ETQP6F0R8L or Falco, QPIP1205-809-3 Q1,Q2 options: Si9426DY, FDS6890A, IRF7401 D1: ON Semi (Motorola) 1 Revision: July 20, 2004 www.semtech.com SC1110 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 V,V BSTL to GND -V 0.5 to 14 CC IN PGND to GND +50V . PHASE to GND -V 0.3 to 18 BSTH to PHASE 1V 4 Thermal Impedance Junction to Case 4W 5 °C/ θ JC Thermal Resistance Junction to Ambient θ 1W 15 °C/ JA OT perating Temperature Range 0C to 70 ° A ST torage Temperature Range -C 65 to +150 ° STG LT ead Temperature (Soldering) 10 Sec. 3C 00 ° LEAD EV SD Rating (Human Body Model) 2V k ESD Electrical Characteristics o Unless specified: V = 4.75V to 12.6V; GND = PGND = 0V; FB = V ; V = 12V; V = 12V; T = 25 C CC O BSTL BSTH-PHASE J Ps arameter Cn ondition Mp i Tx y Ms a Unit Power Supply SV upply Voltage 46 .4 1V 2. CC Supply Current 821A m LV ine Regulation = 2.5V ± 0.5V, V = V/5 2 @ 0A 0% . O O IN Under Voltage Lockout Turn-On Threshold 4V .15 Turn-Off Threshold 3V .95 Error Amplifier Transconductance 2S m Open Loop DC Gain 5B 0 d B) andwidth - 3dB(0 Unity gain crossover 70MHz 5z 0 kH COMP Source Capability ±A 250 µ Input Bias 25 µA Oscillator Oscillator Frequency 20 25 25 5 2z 7 kH Oscillator Max Duty Cycle 95 09% Ramp Height 1V www.semtech.com  2004 Semtech Corp. 2 SC1110 POWER MANAGEMENT Electrical Characteristics (Cont.) o Unless specified: V = 4.75V to 12.6V; GND = PGND = 0V; FB = V ; V = 12V; V = 12V; T = 25 C CC O BSTL BSTH-PHASE J Ps arameter Cn ondition Mp i Tx y Ms a Unit Timing Minimum Off-Time 2s 00 n Dn ead Time G0 uaranteed by characterizatio8s n MOSFET Drivers Peak DH Sink/Source Current BSTH - DH = 4.5V, DH - PHASE = 3.0V0A .5 DH - PHASE = 1.5V 0.1 Peak DL Sink/Source Current BSTL - DL = 4.5V, DL - GND = 3.0V0A .5 DL - GND = 1.5V 0.1 Protection OV vercurrent Set Isource =0 2.2V 10 8 20 0 2A 2 µ OCSET Soft Start CV harge Current =8 1.5V 120 1A µ SS DV ischarge Current =1 1.5V 23 µA SS Power Good Upper Threshold 1% 12 Lower Threshold 8% 8 PI WRGD Voltage Low =5 2mA 0V . PWRGD Reference REFOUT Source Current 3A m OF ffset RE=5 1.25V -5 mV IN Enable Threshold 00 .5505 .6 0V .6  2004 Semtech Corp. 3 www.semtech.com SC1110 POWER MANAGEMENT Timing Diagrams SIMULA SIMULA SIMULA SIMULA SIMULATION W TION W TION W TION W TION WA A A A AVEF VEF VEF VEF VEFORMS ORMS ORMS ORMS ORMS 2.5V and 1.25V ramp up Output current of the VTT supply www.semtech.com  2004 Semtech Corp. 4 SC1110 POWER MANAGEMENT Pin Configuration Ordering Information (1) (1)(2) Device Package Temp Range (T ) J S4 C1110CSTRTSC O-1 0° to 125° S4 C1110TSTRT TSSOP-1 Notes: (1) Only available in tape and reel packaging. A reel contains 2500 devices. (2) Lead free product. (14 Pin SOIC or TSSOP) Pin Descriptions Pe in #Pn in Nam Pin Functio 1CV. C Chip Supply Voltage 2LS. S/ENB Soft start/Enable 3TO. CSE Current limit set point 4DP. WRG Logic high indicates correct output 5DG. N Ground 6EP. HAS Phase node connection between MOSFETs 7LD. Low side driver output 8HD. High side driver output 9HB. ST High side driver supply 1L 0B. ST Low side driver supply 1P 1C. OM Error amplifier output, compensation 1E 2S. ENS Error amplifier negative input 1N 3R. EFI Error amplifier positive input 1T 4R. EFOU Buffered reference voltage NOTE: NOTE: NOTE: NOTE: NOTE: (1) All logic level inputs and outputs are open collector TTL compatible.  2004 Semtech Corp. 5 www.semtech.com SC1110 POWER MANAGEMENT Block Diagram Applications Information THEORY OF OPERATION fier. When the oscillator output voltage drops below the error amplifier output voltage, the comparator output Synchronous Buck Converter goes high. This pulls DL low, turning off the low-side FET, V power is provided by a synchronous, voltage- and DH is pulled high, turning on the high-side FET (once TERMINATION mode pulse width modulated (PWM) controller. This sec- the cross-current control allows it). When the oscillator tion has all the features required to build a high efficiency voltage rises back above the error amplifier output volt- synchronous buck converter for termination of power age, the comparator output goes low. This pulls DH low, application. turning off the high-side FET, and DL is pulled high, turn- ing on the low-side FET (once the cross-current control The output voltage of the synchronous converter is set allows it). and controlled by the output of the error amplifier. The external resistive divider generates reference voltage for As SENSE increases, the output voltage of the error the error amplifier from the chipset voltage which is amplifier decreases. This causes a reduction in the on- usually 2.5V. The inverting input of the error amplifier time of the high-side MOSFET connected to DH, hence receives its voltage from the SENSE pin. lowering the output voltage. The internal oscillator uses an on-chip capacitor and Under Voltage Lockout trimmed precision current sources to set the oscillation The under voltage lockout circuit of the SC1110 assures frequency to 250kHz. The triangular output of the oscil- that both the high-side MOSFET driver outputs remain in lator sets the reference voltage at the inverting input of the off state whenever the supply voltage drops below the PWM comparator. The non-inverting input of the com- set parameters. Lockout occurs if V falls below 4.1V. CC parator receives it’s input voltage from the error ampli- Normal operation resumes once V rises above 4.2V. CC www.semtech.com  2004 Semtech Corp. 6 SC1110 POWER MANAGEMENT Applications Information Soft Start synchronous switcher turns off and SS/ENABLE starts Initially, SS/ENABLE sources 10µA of current to charge to sink 2µA. When SS/ENABLE reaches 0.8V, it then starts to source 10µA and a new cycle begins. an external capacitor. The outputs of the error amplifiers are clamped to a voltage proportional to the voltage on SS/ENABLE. This limits the on-time of the high-side Hiccup Mode MOSFETs, thus leading to a controlled ramp-up of the During power up, the SS/ENABLE pin is internally pulled output voltages. low until VCC reaches the undervoltage lockout level of 4.2V. Once V has reached 4.2V, the SS/ENABLE pin is CC released and begins to source 10µA of current to the R Current Limiting DS(ON) The current limit threshold is set by connecting an exter- external soft-start capacitor. As the soft-start voltage nal resistor from the V supply to OCSET. The voltage rises, the output of the internal error amplifier is clamped CC drop across this resistor is due to the 200µA internal to this voltage. When the error signal reaches the level of the internal triangular oscillator, which swings from 1V sink sets the voltage at the pin. This voltage is compared to 2V at a fixed frequency of 250 kHz, switching occurs. to the voltage at the PHASE node. This comparison is made only when the high-side drive is high to avoid false As the error signal crosses over the oscillator signal, the current limit triggering due to uncontributing measure- duty cycle of the PWM signal continues to increase until ments from the MOSFET’s off-voltage. When the voltage the output comes into regulation. If an over-current con- dition has not occurred the soft-start voltage will con- at PHASE is less than the voltage at OCSET, an overcurrent condition occurs and the soft start cycle is initiated. The tinue to rise and level off at about 2.2V.  2004 Semtech Corp. 7 www.semtech.com SC1110 POWER MANAGEMENT Typical Characteristics CH1: Vout_ripple CH2: Phase node Vin = 2.5V Vout = 1.25V Iout = 7A 95% 90% 85% 80% 75% 70% 65% 60% 012345 6789 10 11 12 Current, A 1.0% 0.5% 0.0% -0.5% -1.0% 01 234 56 7 8 9 10 11 12 Current, A www.semtech.com  2004 Semtech Corp. 8 Efficiency Regulation SC1110 POWER MANAGEMENT Evaluation Board Top View Bottom View  2004 Semtech Corp. 9 www.semtech.com SC1110 POWER MANAGEMENT Evaluation Board (Cont.) Bottom Copper Top Copper Midlayer 1 Midlayer 2 www.semtech.com  2004 Semtech Corp. 10 SC1110 POWER MANAGEMENT Outline Drawing - SO-14 Land Pattern - SO-14  2004 Semtech Corp. 11 www.semtech.com SC1110 POWER MANAGEMENT Outline Drawing - TSSOP-14 Land Pattern - TSSOP-14 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  2004 Semtech Corp. 12