SP6121 Low Voltage, Synchronous Step Down PWM Controller Ideal for 2A to 10A, Small Footprint, DC-DC Power Converters FEATURES V 1 8 PDRV CC Optimized for Single Input Voltage - 3V to 5.5V SP6121 High Efficiency: Greater than 95% possible GND 2 7 NDRV 8 Pin nSOIC Accurate, 500kHz Fixed Frequency Operation V FB 3 6 I SET Fast Transient Response I COMP 4 5 SENSE 500A, I (25A in Shutdown) Q Internal, 0.4 V/ms, Soft Start Circuit Now Available in Lead Free Packaging Precision 1% Reference Resistor Programmable Output Voltage APPLICATIONS Lossless Adjustable Current Limit with Supply Bias for High Side R Sensing DS(ON) - DSP 0% to 100% Duty Cycle Range - Microprocessor Core High Side PMOS Switch Negates Need for - I/O & Logic External Charge Pump Video Cards Output Over Voltage Protection Board Level Supply in Hiccup Mode Current Limit Protection Distributed Power Systems DESCRIPTION The SP6121 is a fixed frequency, voltage mode, synchronous PWM controller designed to work from a single 5V or 3.3V input supply, providing excellent AC and DC regulation for high efficiency power conversion. The operating frequency is internally set at 500kHz, permitting the use of small, surface mount inductors and capacitors. Requiring only few external components, the SP6121 packaged in an 8-pin SOIC, is especially suited for low voltage applications where cost, small size and high efficiency are critical. With its low voltage capability and inherent 100% duty cycle operation, the SP6121 allows low dropout operation in the event of a low input supply voltage condition. TYPICAL APPLICATION CIRCUIT 3.3V V RSET IN C IN RV CC 47F 5 2.3k Ceramic 6.3V Q1 1.9V 8A 1.8H V PDRV CC V OUT CB L1 SP6121 3.3F Q2 C GND NDRV DS OUT U1 470F x 2 R1 5.2k I V SET FB I COMP SENSE RZ R2 10k 10k CZ CP 3.7nF 50pF Q1 = FAIRCHILD FDS6375 Q2 = FAIRCHILD FDS6690A L1 = PANASONIC ETQ-P6F1R6SFA DS = STMICROELECTRONICS STPS2L25BU C = SANYO 4TPB470M OUT Date: 11/29/04 SP6121 Low Voltage, Synchronous Step Down PWM Controller Copyright 2004 Sipex Corporation 1ABSOLUTE MAXIMUM RATINGS V ...................................................................................................... 7V CC These are stress ratings only and functional All other pins ............................... -0.3V to V +0.3V CC operation of the device at these ratings or any other Peak Output Current < 10s above those indicated in the operation sections of PDRV, NDRV....................................................... 2A the specifications below is not implied. Exposure to Storage Temperature ...................... -65C to 150C absolute maximum rating conditions for extended Lead Temperature (Soldering, 10 sec) ..........300C periods of time may affect reliability. ESD Rating ............................................... 2kV HBM ELECTRICAL CHARACTERISTICS Unless otherwise specified: 0C < T < 70C, 3.0V < V < 5.5V, C = 22nF, C = C = 3.3nF, V = 1.25V, I = I = V , GND=0V A CC COMP PDRV NDRV FB SET SENSE CC PARAMETER MIN TYP MAX UNITS CONDITIONS QUIESCENT CURRENT V Supply Current - 0.5 1.0 mA No Switching CC V Supply Current (Disabled) - 25 60 A COMP = 0V CC ERROR AMPLIFIER Error Amplifier Transconductance 600 s COMP Sink Current 15 35 65 AV = 1.35V, COMP=0.8V, No Faults FB COMP Source Current 15 35 65 AV =1.15V, COMP=1.8V FB COMP Output Impedance 3 M V Input Bias Current 100 nA FB ERROR AMPLIFIER REFERENCE Initial Accuracy 1.238 1.250 1.262 V Trimmed with Error Amp in Unity Gain Error Amplifier Reference over 1.225 1.250 1.275 V Line, Load and Temperature OSCILLATOR & DELAY PATH Internal Oscillator Frequency 440 500 560 kHz Maximum Duty Cycle 100 - - % COMP = 2V Minimum Duty Cycle - - 0 % COMP = 0.8V Minimum PDRV Pulse Width 100 ns V > 4.5V, Ramp up COMP voltage CC until PDRV starts switching CURRENT LIMIT Internal Current Limit Threshold 125 160 195 mV V - V , T = 25C ISET ISENSE A ISET Sink Current 25 30 35 AV =5V, T = 25C ISET A Current Limit Threshold and 0.33 %/C ISET Temperature Coefficient Current Limit Time Constant 15 s ISENSE Input Bias Current - - 100 nA SOFT START, SHUTDOWN, UVLO Internal Soft Start Slew Rate 0.4 V/ms Measured at COMP pin on the transition from shutdown Internal Soft Start Delay Time 1.5 ms COMP charging to PDRV switching COMP Discharge Current 150 300 A COMP = 0.5V, Fault Initiated COMP Clamp Voltage 0.6 0.7 0.8 V V = 1.3V FB COMP Clamp Current 100 A COMP = 0.5V, V =1.15V FB Date: 11/29/04 SP6121 Low Voltage, Synchronous Step Down PWM Controller Copyright 2004 Sipex Corporation 2