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Date: 07/20/05 SP6659 1.5MHz, 600mA Synchronous Buck Regulator © Copyright 2005 Sipex Corporation SP6659 The SP6659 is a 600mA synchronous buck regulator using a constant frequency, current mode architecture. The output voltage can be programmed using an external resistor divider. The 2.5V to 5.5V input voltage range is ideal for portable applications that use a Li-Ion battery. Switching frequency is internally set at 1.5MHz, allowing the use of small surface mount inductors and capacitors. The internal synchronous switch increases efficiency and eliminates the need for an external Schottky diode. The output voltage can be programmed using an external resistor divider. Low output voltages are easily supported with the 0.6V feedback reference voltage. The SP6659 is available in a low profile 5 pin TSOT-23 package.
DESCRIPTION
FEATURES
■ 94% Efficiency Possible ■ 600mA Output Current at VIN = 3V ■ 2.5V to 5.5V Input Voltage Range ■ 1.5MHz constant frequency operation ■ No Schottky Diode Required ■ Output Voltages as low as 0.6V ■ Slope Compensated Current Mode Operation for Excellent Line and Load Transient Response ■ 100 % Duty Cycle in LDO Mode ■ <1µA Shutdown Current, Quiescent Current of 300 µA ■ Over-temperature protected ■ Offered in Low Profile TSOT-23 package
APPLICATIONS
■ Cell Phones ■ Wireless and DSL Modems ■ DSC's ■ Portable Instruments TYPICAL APPLICATION SCHEMATICS Now Available in Lead Free Packaging 1.5MHz, 600mA Synchronous Buck Regulator Preliminary SP6659 4.7µF Ceramic V IN GND V OUT 10µF Ceramic V FB SW 2.2µH R2RUN 22pF 4 3 SP6659
5 Pin TSOT-23
4.7µF Ceramic V IN GND V OUT 10µF Ceramic V OUT SW 2.2µH RUN 1 4 3 Adjustable Fixed
Date: 07/20/05 SP6659 1.5MHz, 600mA Synchronous Buck Regulator © Copyright 2005 Sipex Corporation PIN DESCRIPTION ABSOLUTE MAXIMUM RATINGS These are stress ratings only and functional operation of the device at these ratings or any other above those indicated in the operation sections of the specifications below is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability.
ELECTRICAL CHARACTERISTICS
Note 1: Junction Temperature TJ is calculated from the ambient temperature TA and ower dissipation PD according to the following formula: TJ = TA + PD X 220°C/W PIN # PIN NAME DESCRIPTION 1 RUN Power down control pin. Forcing this pin above 1.5V enables the device. Forcing this pin below 0.3V shuts down the device. 2 GND Ground pin. 3S W Switching node. 4V IN Power supply pin 5V FB / VOUT Adjustable Version: VFB, Feedback Input Pin. Connect FB to the center point of the external resistor divider. The feedback threshold voltage is 0.6V. Fixed Output Version: VOUT, Output Voltage Feedback Pin. An internal resistive divider drops the output voltage down for comparison to the internal reference voltage. Vin=Vrun=3.6V, Io=0mA, Tamb= -40ºC to +85ºC, typical values at 25ºC unless otherwise noted. Parameter Min Typ Max Units Conditions Input Voltage Range 2.5 5.5 V Input DC Supply Current Active Mode 300 400 µA Vfb = 0.5V, Vin = Vrun Shutdown Mode 0.1 1 µA Vin = 3.6V, Vrun = ZeroV 0.5880 0.6000 0.6120 Ta=+25ºC 0.5865 0.6000 0.6135 V 0ºC<Ta<+85ºC 0.5820 0.6000 0.6180 -40ºC < Ta < +85ºC Vfb Input Bias Current 85 300 nA Vfb = 1.0V Vfb Line Regulation -1 0.4 1 %/V Vin = 2.5V to 5.5V Vfb Load Regulation -0.1 0.01 0.1 %/mA ILoad = 0mA to 600mA Regulated Output Voltage 1.455 1.500 1.545 V SP6659EK1-1.5, -40ºC < Ta < +85ºC 1.746 1.800 1.854 V SP6659EK1-1.8, -40ºC < Ta < +85ºC Minimum Output Voltage 0.6 V Peak inductor current 0.7 1.15 1.5 A Vfb = 0.5V Oscillator frequency 0.8 1.4 1.8 mHz Closed Loop, ILoad=100mA P-channel ON resistance 0.4 0.6 Ω I SW = 100mA N-channel ON resistance 0.4 0.6 Ω I SW = -100mA Vrun=ZeroV, Vin = 3.6V Vsw=ZeroV, Vsw = Vin Run Threshold Voltage 0.2 1 1.3 V Run Leakage Current ±0.01 ±1.5 µA ±1.0 µA Vfb (Feedback Voltage) SW Leakage Current ±0.01
Date: 07/20/05 SP6659 1.5MHz, 600mA Synchronous Buck Regulator © Copyright 2005 Sipex Corporation FUNCTIONAL DIAGRAMS Q R Q S VIN 2.7 - 5.5V COUT DRV REF 0.6V BLANKING OSC SLOPE PWM LOGIC COMP R 5 EA OV DET COMP 0.65V VIN SHUTDOWN 0.6V Izero COMP NON- OVERLAP CONTROL ISENSE COMP RS LATCH SW GND VOUT VFB RUN CIN Adjustable Output Version Fixed Output Version Q R Q S VIN 2.7 - 5.5V C OUT DRV REF 0.6V BLANKING OSC SLOPE PWM LOGIC COMP R 5 EA OV DET COMP 0.65V VIN SHUTDOWN 0.6V Izero COMP NON- OVERLAP CONTROL ISENSE COMP RS LATCH SW GND VOUT VOUT RUN C IN
Date: 07/20/05 SP6659 1.5MHz, 600mA Synchronous Buck Regulator © Copyright 2005 Sipex Corporation
APPLICATION INFORMATION
A resistive divider based on the following equation determines the output voltage: VOUT = 0.6 (1+ ) The external resistive divider is connected to the output as shown in Figure 7 . SP6659 GND V FB V OUT Figure 7: Setting the SP6659 Output Voltage. The SP6659 is a monolithic switching mode Step-Down DC-DC converter. It utilizes in- ternal MOSFETs to achieve high efficiency and can generate very low output voltage by using its internal reference at 0.6V. It operates at a fixed switching frequency, and uses slope compensated, current-mode architecture. This Step-Down DC-DC con- verter supplies 600mA of output current at V IN = 3V. The entire input voltage range is from 2.5V to 5.5V. PWM CONTROL Slope compensated current mode PWM control provides stable switching and cycle- by-cycle current limit for excellent load and line responses and protection of the internal main switch (P-Channel MOSFET) as well as the synchronous rectifier (N-Channel MOSFET). During normal operation, the in- ternal P-Channel MOSFET is turned on for a certain time to ramp the inductor current at each rising edge of the internal oscillator, and switched off when the peak inductor current is above the error voltage. The THEORY OF OPERATION current comparator, ICOMP , limits the peak inductor current. When the main switch is off, the synchronous rectifier will be turned on immediately and stay on until either the inductor current starts to reverse, as indi- cated by the current reversal comparator, I ZERO , or the beginning of the next clock cycle. The OVDET comparator controls output transient overshoots by turning the main switch off and keeping it off until the fault is no longer present. OPERATION At very light loads, the SP6659 automati- cally enters Idle Mode (Figure 8). In the Idle Mode, the inductor current may reach zero Amps or reverse on each pulse. The PWM control loop will automatically skip pulses to maintain output regulation. The bottom MOSFET is turned off by the current rever- sal comparator, I ZERO , and the switch volt- age will ring. This is discontinuous mode operation, and is normal behavior for the switching regulator.
duty cycle until it reaches 100%. Where ∆IL is the inductor Ripple Current. mum load current 600mA, or ~ 210mA. ƒOSC is the oscillator frequency (1.5Mhz). Figure 8. SP6659 Idle Mode Operation
Date: 07/20/05 SP6659 1.5MHz, 600mA Synchronous Buck Regulator © Copyright 2005 Sipex Corporation THEORY OF OPERATION 200mA), or minimal load regulation (but some transient overshoot), the resistance should be kept below 100mΩ. The DC cur- rent rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation (600mA+105mA). Table 1 lists some typical surface mount inductors that meet target applications for the SP6659. Table 1: Typical Surface Mount Inductors Part # L (µH) Max DCR (mΩ) Rated DC Current (Amps) Size WxLxH (mm) Sumida CR43 1.4 56.2 2.52 4.5x4.0x3.5 2.2 71.2 1.5 3.3 86.2 1.44 4.7 108.7 1.15 Sumida CDRH4D18 1.5 4.7x4.7x2.0 2.2 75 1.32 3.3 110 1.04 4.7 162 0.84 Toko D312C 1.5 120 1.29 3.6x3.6x1.2 2.2 140 1.14 3.3 180 0.98 4.7 240 0.79 SELECTION The input capacitor reduces the surge cur- rent drawn from the input and switching noise from the device. The input capacitor impedance at the switching frequency shall be less than input source impedance to prevent high frequency switching current from passing to the input. A low ESR (Equiva- lent Series Resistance) input capacitor sized for maximum RMS current must be used. Ceramic capacitors with X5R or X7R dielec- trics are highly recommended because of their low ESR and small temperature coeffi- cients. A 4.7µF ceramic capacitor for most applications is sufficient. SELECTION The output capacitor is required to keep the output voltage ripple small and to ensure regulation loop stability. The output capaci- tor must have low impedance at the switch- ing frequency. Ceramic capacitors with X5R or X7R dielectrics are recommended due to their low ESR and high ripple current. The output ripple ∆V OUT is determined by: X {ESR + } (8X ƒOSC X COU T) ∆VOUT ≤ VOUT X (VIN - VOUT ) VIN X L X ƒOSC
Date: 07/20/05 SP6659 1.5MHz, 600mA Synchronous Buck Regulator © Copyright 2005 Sipex Corporation PACKAGE: 5 PIN TSOT23 RESISTANCE Thermal Resistance is specified with approxi- mately 1 square of 1 ounce of copper. L ø1 Gauge Plane VIEW C ø c WITH PLATING BASE METAL b D E E/2 N/221 b e E1/2 N N/2 INDEX AREA (D/2 X E1/2) B-BSection Seating Plane SEE VIEW C B B VIEW A-A SIDE VIEW SEATING PLANE C A SYMBOL MIN NOM MAX A- - 1 . 1 A1 0 - 0.1 A2 0.7 0.9 1 b 0.3 - 0.5 c 0.08 - 0.2 D e E L 0.3 0.45 0.6 ø0 º 4 º8 º ø1 4º 10º 12º Note: Dimensions in (mm)
1.60 BSC
0.60 REF
0.25 BSC
5 Pin TSOT JEDEC MO-193 (AB) Variation
2.90 BSC
0.95 BSC
1.90 BSC
2.80 BSC
Date: 07/20/05 SP6659 1.5MHz, 600mA Synchronous Buck Regulator © Copyright 2005 Sipex Corporation Corporation ANALOG EXCELLENCE Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others. Sipex Corporation Headquarters and Sales Office
233 South Hillview Drive
Milpitas, CA 95035 TEL: (408) 934-7500 FAX: (408) 935-7600 Part Number Operating Temperature Range Package Type /TR = Tape and Reel Pack quantity is 2,500 for TSOT23. Available in lead free packaging. To order add "-L" suffix to part number. Example: SP6659EK1/TR = standard; SP6659EK1-L/TR = lead free