Document number: MC34712Rev. 4.0, 5/2007Freescale Semiconductor Advance Information* This document contains certain information on a new product.Specifications and information herein are subject to change without notice.© Freescale Semiconductor, Inc., 2007. All rights reserved.3.0 A 1.0 MHz Fully Integrated DDR Switch-Mode Power SupplyThe 34712 is a highly integrated, space efficient, low cost, single synchronous buck switching regulator with integrated N-channel power MOSFETs. It is a high performance point-of-load (PoL) power supply with the ability to track an external reference voltage.Its high efficient 3.0 A sink and source capability combined with its voltage tracking/sequencing ability and tight output regulation, makes it ideal to provide the termination voltage (V TT ) for modern data buses such as Double-Data-Rate (DDR) memory buses. It also provides a buffered output reference voltage (V REF ) to the memory chipset The 34712 offers the designer the flexibility of many control,supervisory, and protection functions to allow for easy implementation of complex designs. It is housed in a Pb-Free, thermally enhanced, and space efficient 24-Pin Exposed Pad QFN.Features•45 m Ω Integrated N-Channel Power MOSFETs •Input Voltage Operating Range from 3.0 V to 6.0 V•±1 % Accurate Output Voltage, Ranging from 0.7 V to 1.35 V •±1 % Accurate Buffered Reference Output Voltage•Programmable Switching Frequency Range from 200 kHz to 1.0 MHz with a default of 1.0 MHz•Over Current Limit and Short Circuit Protection •Thermal Shutdown•Output Overvoltage and Undervoltage Detection •Active Low Power Good Output Signal •Active Low Standby and Shutdown Inputs•Pb-Free Packaging Designated by Suffix Code EP.Figure 1. 34712 Simplified Application DiagramSWITCH-MODE POWER SUPPLYEP SUFFIX 98ARL10577D 24-PIN QFN34712ORDERING INFORMATIONDevice Temperature Range (T A )Package MC34712EP/R2-40 to 85°C24 QFNV INMCUPVINVREFINVIN VDDI FREQ GND SDSTBYBOOTSWVOUT INV COMP VREFOUTPGND PGDDR MEMORY CONTROLER34712V DDQDDR MEMORY CHIPSET V INV REFV TTV DDQV DDQMEMORY BUSTERMINATING RESISTORS(3.0V TO 6.0V)INTERNAL BLOCK DIAGRAMINTERNAL BLOCK DIAGRAMFigure 2. 34712 Simplified Internal Block Diagram34712Analog Integrated Circuit Device DataAnalog Integrated Circuit Device Data 34712PIN CONNECTIONSPIN CONNECTIONSFigure 3. 34712 Pin ConnectionsTable 1. 34712 Pin DefinitionsA functional description of each pin can be found in the Functional Pin Description section beginning onpage 10.Pin NumberPin Name Pin Function Formal Name Definition1GND Ground Signal GroundAnalog signal ground of IC2FREQ Passive Frequency Adjustment Buck converter switching frequency adjustment pin3NC None No Connect No internal connections to this pin4PG Output Power Good Active-low (open drain) power-good status reporting pin 5STBY Input Standby Standby mode input control pin 6SDInput Shutdown Shutdown mode input control pin 7VREFIN Input Voltage-Tracking-Reference Input Voltage-Tracking-Reference voltage input8VREFOUTOutput Reference VoltageOutput Buffered output equal to 1/2 of voltage-tracking reference 9COMPPassive Compensation Buck converter external compensation network pin 10INV Input Error Amplifier Inverting Input Buck converter error amplifier inverting input pin11VOUT Output Output Voltage Discharge FET Discharge FET drain connection (connect to buck converter output capacitors)12,13,14PGND Ground Power Ground Ground return for buck converter and discharge FET 15,16,17SW Power Switching Node Buck converter power switching node 18,19,20PVIN Supply Power-Circuit SupplyInputBuck converter main supply voltage input21BOOTPassiveBootstrapBootstrap switching node (connect to bootstrap capacitor)GND FREQ STBY PG NC SDV R E F I NC O M PI N VV O U TP G N DSW P V I NB O O TV I NV D D IV R E F O U TPGND PGNDSW SWPVIN P V I NV I NAnalog Integrated Circuit Device Data34712PIN CONNECTIONS22,23VINSupply Logic-Circuit SupplyInput Logic circuits supply voltage input24VDDIPassiveInternal Voltage RegulatorInternal Vdd Regulator (connect filter capacitor to this pin)Table 1. 34712 Pin Definitions (continued)A functional description of each pin can be found in the Functional Pin Description section beginning on page 10.Pin NumberPin NamePin FunctionFormal Name DefinitionAnalog Integrated Circuit Device Data 34712ELECTRICAL CHARACTERISTICSMAXIMUM RATINGSELECTRICAL CHARACTERISTICSMAXIMUM RATINGSTable 2. Maximum RatingsAll voltages are with respect to ground unless otherwise noted. Exceeding these ratings may cause a malfunction or permanent damage to the device.RatingsSymbolValueUnitELECTRICAL RATINGS Input Supply Voltage (VIN) PinV IN -0.3 to 7.0V High-Side MOSFET Drain Voltage (PVIN) Pin PV IN -0.3 to 7.0V Switching Node (SW) PinV SW -0.3 to 7.5V BOOT Pin (Referenced to SW Pin)V BOOT - V SW-0.3 to 7.5V PG, VOUT, SD, and STBY Pins--0.3 to 7.0V VDDI, FREQ, INV, COMP, VREFIN, and VREFOUT Pins --0.3 to 3.0V Continuous Output Current (1)I OUT±3.0AESD Voltage (2)Human Body Model Device Charge Model (CDM)V ESD1V ESD3±2000±750VTHERMAL RATINGSOperating Ambient Temperature (3)T A -40 to 85°C Storage TemperatureT STG -65 to +150°C Peak Package Reflow Temperature During Reflow (4), (5)T PPRT Note 5°C Maximum Junction Temperature T J(MAX)+150°C Power Dissipation (T A = 85 °C) (6)P D2.9WNotes1.Continuous output current capability so long as T J is ≤ T J(MAX).2.ESD1 testing is performed in accordance with the Human Body Model (C ZAP = 100 pF, R ZAP = 1500 Ω), ESD3 testing is performed inaccordance with the Charge Device Model (CDM).3.The limiting factor is junction temperature, taking into account power dissipation, thermal resistance, and heatsinking.4.Pin soldering temperature limit is for 10 seconds maximum duration. Not designed for immersion soldering. Exceeding these limits maycause malfunction or permanent damage to the device.5.Freescale’s Package Reflow capability meets Pb-free requirements for JEDEC standard J-STD-020C. For Peak Package ReflowTemperature and Moisture Sensitivity Levels (MSL),Go to , search by part number [e.g. remove prefixes/suffixes and enter the core ID to view all orderable parts. (i.e. MC33xxxD enter 33xxx), and review parametrics.6.Maximum power dissipation at indicated ambient temperature.Analog Integrated Circuit Device Data34712ELECTRICAL CHARACTERISTICS MAXIMUM RATINGSTHERMAL RESISTANCE (7)Thermal Resistance, Junction to Ambient, Single-Layer Board (1s) (8)R θJA 139°C/W Thermal Resistance, Junction to Ambient, Four-Layer Board (2s2p) (9)R θJMA 43°C/W Thermal Resistance, Junction to Board (10)R θJB22°C/WNotes7.The PVIN, SW, and GND pins comprise the main heat conduction paths.8.Per SEMI G38-87 and JEDEC JESD51-2 with the single-layer board (JESD51-3) horizontal.9.Per JEDEC JESD51-6 with the board (JESD51-7) horizontal. There are no thermal vias connecting the package to the two planes in theboard.10.Thermal resistance between the device and the printed circuit board per JEDEC JESD51-8. Board temperature is measured on the topsurface of the board near the package.Table 2. Maximum Ratings (continued)All voltages are with respect to ground unless otherwise noted. Exceeding these ratings may cause a malfunction or permanent damage to the device.RatingsSymbolValueUnitAnalog Integrated Circuit Device Data 34712ELECTRICAL CHARACTERISTICSSTATIC ELECTRICAL CHARACTERISTICSSTATIC ELECTRICAL CHARACTERISTICSTable 3. Static Electrical CharacteristicsCharacteristics noted under conditions 3.0 V ≤ V IN ≤ 6.0 V, - 40°C ≤ T A ≤ 85°C, GND = 0 V unless otherwise noted. Typical values noted reflect the approximate parameter means at T A = 25°C under nominal conditions unless otherwise noted.CharacteristicSymbolMinTypMaxUnitIC INPUT SUPPLY VOLTAGE (VIN) Input Supply Voltage Operating Range V IN 3.0- 6.0VInput DC Supply Current (11)Normal Mode: SD = 1 & STBY = 1, Unloaded Outputs I IN --25mAInput DC Supply Current (11)Standby Mode, SD = 1 & STBY = 0I INQ --15mAInput DC Supply Current (11)Shutdown Mode, SD = 0 & STBY = XI INOFF--100µAINTERNAL SUPPLY VOLTAGE OUTPUT (VDDI)Internal Supply Voltage RangeV DDI2.352.52.65VBUCK CONVERTER (PVIN, SW, GND, BOOT, INV, COMP)High-side MOSFET Drain Voltage Range P VIN 2.5- 6.0V Output Voltage Adjustment Range (12)V OUT 0.7- 1.35V Output Voltage Accuracy (12), (13), (14)--1.0- 1.0%Line Regulation (12)Normal Operation, V IN = 3.0 V to 6.0 V, I OUT = ±3.0 A REG LN -1.0- 1.0%Load Regulation (12)Normal Operation, I OUT = -3.0 A to 3.0 AREG LD-1.0- 1.0%Error Amplifier Common Mode Voltage Range (12), (15)V REF0.0- 1.35V Output Undervoltage Threshold V UVR -1.5--8.0%Output Overvoltage Threshold V OVR 1.5-8.0%Continuous Output CurrentI OUT -3.0- 3.0A Over Current Limit, Sinking and Sourcing I LIM - 4.0-A Short Circuit Current Limit (Sourcing and Sinking)I SHORT -6.5-AHigh-Side N-CH Power MOSFET (M3) R DS(ON) (12)I OUT = 1.0 A, V BOOT - V SW = 3.3 VR DS(ON)HS 10-45m ΩLow-Side N-CH Power MOSFET (M4) R DS(ON) (12)I OUT = 1.0 A, V IN = 3.3 V R DS(ON)LS10-45m ΩNotes 11.See section “MODES OF OPERATION”, page 14 has a detailed description of the different operating modes of the 3471212.Design information only, this parameter is not production tested.13.±1% is assured at room temperature.14.Overall output accuracy is directly affected by the accuracy of the external feedback network, 1% feedback resistors are recommended.15.The 1% output voltage regulation is only guaranteed for a common mode voltage range greater than or equal to 0.7V at room temperature.Analog Integrated Circuit Device Data34712ELECTRICAL CHARACTERISTICSSTATIC ELECTRICAL CHARACTERISTICSM2 R DS(ON)(V IN = 3.3 V, M2 is on)R DS(ON)M21.5- 4.0ΩPVIN Pin Leakage Current (Standby and Shutdown Modes)I PVIN -10-10µA INV Pin Leakage Current I INV -1.0- 1.0µA Thermal Shutdown Threshold (16)T SDFET -170-°C Thermal Shutdown Hysteresis (16)T SDHYFET-25-°COSCILLATOR (FREQ)Oscillator Frequency Adjusting Reference Voltage Range V FREQ0.0-V DDIVTRACKING (VREFIN, VREFOUT, VOUT)VREFIN External Reference Voltage Range (16)V REFIN 0.0- 2.7V VREFOUT Buffered Reference Voltage Range V REFOUT0.0- 1.35V VREFOUT Buffered Reference Voltage Accuracy (17)--1.0- 1.0%VREFOUT Buffered Reference Voltage Current Capability I REFOUT 0.0-8.0mA VREFOUT Buffered Reference Voltage Over Current Limit I REFOUTLIM -11-mA VREFOUT Total Discharge Resistance (16)R TDR(M6)-50-ΩVOUT Total Discharge Resistance (16)R TDR(M5)-50-ΩVOUT Pin Leakage Current (Standby Mode, V OUT = 3.6 V)I VOUTLKG-1.0- 1.0µACONTROL AND SUPERVISORY (STBY, SD, PG)STBY High Level Input Voltage V STBYHI 2.0--V STBY Low Level Input Voltage V STBYLO --0.4V STBY Pin Internal Pull Up Resistor R STBYUP 1.0- 2.0M ΩSD High Level Input Voltage V SDHI 2.0--V SD Low Level Input Voltage V SDLO --0.4V SD Pin Internal Pull Up Resistor R SDUP 1.0- 2.0M ΩPG Low Level Output Voltage (I PG = 3.0 mA)V PGLO --0.4VPG Pin Leakage Current (M1 is off, Pulled up to VIN)I PGLKG-1.0- 1.0µANotes16.Design information only, this parameter is not production tested.17.The 1 % accuracy is only guaranteed for V REFOUT greater than or equal to 0.7 V at room temperature.Table 3. Static Electrical CharacteristicsCharacteristics noted under conditions 3.0 V ≤ V IN ≤ 6.0 V, - 40°C ≤ T A ≤ 85°C, GND = 0 V unless otherwise noted. Typical values noted reflect the approximate parameter means at T A = 25°C under nominal conditions unless otherwise noted.CharacteristicSymbol Min Typ Max UnitAnalog Integrated Circuit Device Data 34712ELECTRICAL CHARACTERISTICSDYNAMIC ELECTRICAL CHARACTERISTICSDYNAMIC ELECTRICAL CHARACTERISTICSTable 4. Dynamic Electrical CharacteristicsCharacteristics noted under conditions 3.0 V ≤ V IN ≤ 6.0 V, - 40°C ≤ T A ≤ 85°C, GND = 0 V unless otherwise noted. Typical values noted reflect the approximate parameter means at T A = 25°C under nominal conditions unless otherwise noted.CharacteristicSymbolMinTypMaxUnitBUCK CONVERTER (PVIN, SW, GND, BOOT)Switching Node (SW) Rise Time (19)(P VIN = 3.3 V, I OUT = ±3.0 A)t RISE -14-nsSwitching Node (SW) Fall Time (19)(P VIN = 3.3 V, I OUT = ±3.0 A)t FALL -20-nsSoft Start Duration (Normal Mode)t SS 1.3- 2.6ms Over Current Limit Timert LIM -10-ms Over Current Limit Retry Time-out Periodt TIMEOUT 80-120ms Output Undervoltage/Overvoltage Filter Delay Timer t FILTER5.0-25µsOSCILLATOR (FREQ)Oscillator Default Switching Frequency (18)(FREQ = GND)F SW - 1.0-MHz Oscillator Switching Frequency RangeF SW200-1000kHzCONTROL AND SUPERVISORY (STBY, SD, PG)PG Reset Delayt PGRESET 8.0-12ms Thermal Shutdown Retry Time-out Period (19)t TIMEOUT80-120msNotes18.Oscillator Frequency tolerance is ±10%.19.Design information only, this parameter is not production tested.Analog Integrated Circuit Device Data34712FUNCTIONAL DESCRIPTION INTRODUCTIONFUNCTIONAL DESCRIPTIONINTRODUCTIONIn modern microprocessor/memory applications, address commands and control lines require system level termination to a voltage (V TT ) equal to 1/2 the memory supply voltage (V DDQ ). Having the termination voltage at midpoint, the power supply insures symmetry for switching times. Also, areference voltage (V REF ) that is free of any noise or voltage variations is needed for the DDR SDRAM input receiver, V REF is also equal to 1/2 V DDQ . Varying the V REF voltage will effect the setup and hold time of the memory. To comply with DDR requirements and to obtain best performance, V TT and V REF need to be tightly regulated to track 1/2 V DDQ across voltage, temperature, and noise margins. V TT should track any variations in the DC V REF value (V TT = V REF +/- 40 mV), (See Figure 4) for a DDR system level diagram.The 34712 supplies the V TT and a buffered V REF output. To ensure compliance with DDR specifications, the V DDQ line is applied to the VREFIN pin and divided by 2 internally through a precision resistor divider. This internal voltage is then used as the reference voltage for the V TT output. The same internal voltage is also buffered to give the V REFvoltage at the VREFOUT pin for the application to use without the need for an external resistor divider. The 34712 provides the tight voltage regulation and power sequencing/tracking required along with handling the DDR peak transient current requirements. Buffering the V REF output helps its immunity against noise and load changes.The 34712 utilizes a voltage mode synchronous buck switching converter topology with integrated low R DS(ON) (45 m Ω) N-channel power MOSFETs to provide a V TT voltage with an accuracy of less than ±2.0 %. It has a programmable switching frequency that allows for flexibility and optimization over the operating conditions and can operate at up to1.0 MHz to significantly reduce the external components size and cost. The 34712 can sink and source up to 3.0 A ofcontinuous current. It provides protection against output over current, overvoltage, undervoltage, and overtemperature conditions. It also protects the system from short circuitevents. It incorporates a power-good output signal to alert the host when a fault occurs.For boards that support the Suspend-To-RAM (S3) and the Suspend-To-Disk (S5) states, the 34712 offers the STBY and the SD pins respectively. Pulling any of these pins low, puts the IC in the corresponding state.By integrating the control/supervisory circuitry along with the Power MOSFET switches for the buck converter into a space-efficient package, the 34712 offers a complete, small-size, cost-effective, and simple solution to satisfy the needs of DDR memory applications.Besides DDR memory termination, the 34712 can be used to supply termination for other active buses and graphics card memory. It can be used in Netcom/Telecom applications like servers. It can also be used in desktop motherboards, game consoles, set top boxes, and high end high definition TVs.Figure 4. DDR System Level DiagramFUNCTIONAL PIN DESCRIPTIONREFERENCE VOLTAGE INPUT (VREFIN)The 34712 will track 1/2 the voltage applied at this pin.REFERENCE VOLTAGE OUTPUT (VREFOUT)This is a buffered reference voltage output that is equal to 1/2 V REFIN . It has a 10.0 mA current drive capability. This output is used as the V REF voltage rail and should be filtered against any noise. Connect a 0.1 µF, 6 V low ESR ceramic filter capacitor between this pin and the GND pin andbetween this pin and V DDQ rail. V REFOUT is also used as the reference voltage for the buck converter error amplifier.FREQUENCY ADJUSTMENT INPUT (FREQ)The buck converter switching frequency can be adjusted by connecting this pin to an external resistor divider between VDDI and GND pins. The default switching frequency (FREQ pin connected to ground, GND) is set at 1.0 MHz.SIGNAL GROUND (GND)Analog ground of the IC. Internal analog signals are referenced to this pin voltage.V DDQV DDQV TTV REFBUSDDR Memory Controller DDR Memory Input ReceiverR SR TFUNCTIONAL DESCRIPTION FUNCTIONAL PIN DESCRIPTIONINTERNAL SUPPLY VOLTAGE OUTPUT (VDDI) This is the output of the internal bias voltage regulator. Connect a 1.0 µF, 6 V low ESR ceramic filter capacitor between this pin and the GND pin. Filtering any spikes on this output is essential to the internal circuitry stable operation.OUTPUT VOLTAGE DISCHARGE PATH (VOUT) Output voltage of the Buck Converter is connected to this pin. it only serves as the output discharge path once the SD signal is asserted.ERROR AMPLIFIER INVERTING INPUT (INV) Buck converter error amplifier inverting input. Connect the VTT voltage directly to this pin.COMPENSATION INPUT (COMP)Buck converter external compensation network connects to this pin. Use a type III compensation network.INPUT SUPPLY VOLTAGE (VIN)IC power supply input voltage. Input filtering is required for the device to operate properly.POWER GROUND (PGND)Buck converter and discharge MOSFETs power ground. It is the source of the buck converter low-side power MOSFET. SWITCHING NODE (SW)Buck converter switching node. This pin is connected to the output inductor.POWER INPUT VOLTAGE (PVIN)Buck converter power input voltage. This is the drain of the buck converter high-side power MOSFET. BOOTSTRAP INPUT (BOOT)Bootstrap capacitor input pin. Connect a capacitor (as discussed on page 19) between this pin and the SW pin to enhance the gate of the high-side Power MOSFET during switching.SHUTDOWN INPUT (SD)If this pin is tied to the GND pin, the device will be in Shutdown Mode. If left unconnected or tied to the VIN pin, the device will be in Normal Mode. The pin has an internal pull up of 1.5 MΩ. This input accepts the S5 (Suspend-To-Disk) control signal.STANDBY INPUT (STBY)If this pin is tied to the GND pin, the device will be in Standby Mode. If left unconnected or tied to the VIN pin, the device will be in Normal Mode. The pin has an internal pull up of 1.5 MΩ. This input accepts the S3 (Suspend-To-RAM) control signal.POWER GOOD OUTPUT SIGNAL (PG)This is an active low open drain output that is used to report the status of the device to a host. This output activates after a successful power up sequence and stays active as long as the device is in normal operation and is not experiencing any faults. This output activates after a 10 ms delay and must be pulled up by an external resistor to a supply voltage (e.g.,V IN.).FUNCTIONAL DESCRIPTIONFUNCTIONAL INTERNAL BLOCK DESCRIPTIONFUNCTIONAL INTERNAL BLOCK DESCRIPTIONFigure 5. 34712 Internal Block DiagramINTERNAL BIAS CIRCUITSThis block contains all circuits that provide the necessary supply voltages and bias currents for the internal circuitry. It consists of:•Internal Voltage Supply Regulator: This regulator supplies the V DDI voltage that is used to drive the digital/ analog internal circuits. It is equipped with a Power-On-Reset (POR) circuit that watches for the right regulation levels. External filtering is needed on the VDDI pin. This block will turn off during the shutdown mode.•Internal Bandgap Reference Voltage: This supplies the reference voltage to some of the internal circuitry.•Bias Circuit: This block generates the bias currents necessary to run all of the blocks in the IC. SYSTEM CONTROL AND LOGICThis block is the brain of the IC where the device processes data and reacts to it. Based on the status of the STBY and SD pins, the system control reacts accordingly and orders the device into the right status. It also takes inputs from all of the monitoring/protection circuits and initiates power up or power down commands. It communicates with the buck converter to manage the switching operation and protects it against any faults.OSCILLATORThis block generates the clock cycles necessary to run the IC digital blocks. It also generates the buck converter switching frequency. The switching frequency has a default value of 1.0 MHz and can be programmed by connecting a resistor divider to the FREQ pin, between VDDI and GND pins (See Figure 1).PROTECTION FUNCTIONSThis block contains the following circuits:•Over Current Limit and Short Circuit Detection: This block monitors the output of the buck converter for over current conditions and short circuit events and alerts the system control for further command.•Thermal Limit Detection: This block monitors the temperature of the device for overheating events. If the temperature rises above the thermal shutdownthreshold, this block will alert the system control forfurther commands.•Output Overvoltage and Undervoltage Monitoring: This block monitors the buck converter output voltage toensure it is within regulation boundaries. If not, thisblock alerts the system control for further commands.CONTROL AND SUPERVISORY FUNCTIONS This block is used to interface with an outside host. It contains the following circuits:•Standby Control Input: An outside host can put the 34712 device into standby mode (S3 or Suspend-To-RAM mode) by sending a logic “0” to the STBY pin.•Shutdown Control Input: An outside host can put the 34712 device into shutdown mode (S5 or Suspend-To-Disk mode) by sending a logic “0” to the SD pin.•Power Good Output Signal PG: The 34712 can communicate to an external host that a fault hasInternal Bias System ControlOscillator Circuits& LogicControl &Protection Tracking &SupervisoryFunctionsFunctionsSequencingBuck ConverterFUNCTIONAL DESCRIPTION FUNCTIONAL INTERNAL BLOCK DESCRIPTIONoccurred by releasing the drive on the PG pin high,allowing the signal/pin to be pulled high by the external pull-up resistor.TRACKING AND SEQUENCINGThis block allows the output of the 34712 to track 1/2 the voltage applied at the VREFIN pin. This allows the V REF and V TT voltages to track 1/2 V DDQ and assures that none of them will be higher than V DDQ at any point during normal operating conditions. For power down during a shutdown (S5) mode, the 34712 uses internal discharge MOSFETs (M5 and M6 on Figure 2) to discharge V TT and V REF respectively. These discharge MOSFETs are only active during shutdown mode. Using this block along with controlling the SD and STBY pins can offer the user power sequencing capabilities by controlling when to turn the 34712 outputs on or off.BUCK CONVERTERThis block provides the main function of the 34712: DC to DC conversion from an un-regulated input voltage to a regulated output voltage used by the loads for reliable operation. The buck converter is a high performance, fixed frequency (externally adjustable), synchronous buck PWM voltage-mode control. It drives integrated 45 mΩ N-channel power MOSFETs saving board space and enhancing efficiency. The switching regulator output voltage is adjustable with an accuracy of less than ±2.0 % to meet DDR requirements. Its output has the ability to track 1/2 the voltage applied at the VREFIN pin. The regulator's voltage control loop is compensated using a type III compensation network, with external components to allow for optimizing the loop compensation, for a wide range of operating conditions. A typical Bootstrap circuit with an internal PMOS switch is used to provide the voltage necessary to properly enhance the high-side MOSFET gate.The 34712 is designed to address DDR memory power supplies. The integrated converter has the ability to both sink and source up to 3.0 A of continuous current, making it suitable for bus termination power supplies.FUNCTIONAL DEVICE OPERATIONOPERATIONAL MODESFUNCTIONAL DEVICE OPERATIONOPERATIONAL MODESFigure 6. Operation Modes DiagramMODES OF OPERATIONThe 34712 has three primary modes of operation:Normal ModeIn normal mode, all functions and outputs are fully operational. To be in this mode, the V IN needs to be within its operating range, both Shutdown and Standby inputs are high, and no faults are present. This mode consumes the most amount of power.Standby ModeThis mode is predominantly used in Desktop memory solutions where the DDR supply is desired to be ACPI compliant (Advanced Configuration and Power Interface). When this mode is activated by pulling the STBY pin low, V TT is put in High Z state, I OUT = 0 A, and V REF stays active. This is the S3 state Suspend-To-Ram or Self Refresh mode and it is the lowest DRAM power state. In this mode, the DRAM will preserve the data. While in this mode, the 34712 consumes less power than in the normal mode, because the buck converter and most of the internal blocks are disabled.Shutdown ModeIn this mode, activated by pulling the SD pin low, the chip is in a shutdown state and the outputs are all disabled and discharged. This is the S4/S5 power state or Suspend-To-Disk state, where the DRAM will loose all of its data content (no power supplied to the DRAM). The reason to discharge the V TT and V REF lines is to ensure upon exiting, the Shutdown Mode that V TT and V REF are lower than V DDQ, otherwise V TT can remain floating high, and be higher than V DDQ upon powering up. In this mode, the 34712 consumes the least amount of power since almost all of the internal blocks are disabled.START-UP SEQUENCEWhen power is first applied, the 34712 checks the status of the SD and STBY pins. If the device is in a shutdown mode, no block will power up and the output will not attempt to ramp. If the device is in a standby mode, only the V DDI internal supply voltage and the bias currents are established and no further activities will occur. Once the SD and STBY pins are released to enable the device, the internal V DDI POR signal is also released. The rest of the internal blocks will be enabled。
SPX15873A Low Dropout Voltage RegulatorAdjustable & Fixed Output,Fast Response FEATURES APPLICATIONS• Adjustable Output Down To 1.2V • Powering VGA & Sound Card• Fixed Output Voltages 1.5, 2.5, 3.3, 5.0V • Power PC Supplies• Output Current Of 3A • SMPS Post-Regulator• Low Dropout Voltage 1.1V Typ. • High Efficiency “Green” Computer Systems• Extremely Tight Load And Line Regulation • High Efficiency Linear Power Supplies• Current & Thermal Limiting • Portable Instrumentation• Standard 3-Terminal Low Cost TO-220, TO-263 & TO-252 • Constant Current Regulators• Similar To Industry Standard LT1085/LT1585 • Adjustable Power Supplies• Battery chargerPRODUCT DESCRIPTIONThe SPX1587 is a low power 3A adjustable and fixed voltage regulator that is very easy to use. It requires only 2 external resistors to set the output voltage for adjustable version. The SPX1587 are designed for low voltage applications that offers lower dropout voltage and faster transient response. This device is an excellent choice for use in powering low voltage microprocessor that require a lower dropout, faster transient response to regulate from +2.5V to 3.8V supplies and as a post regulator for switching supplies applications. The SPX1587 features low dropout of a maximum 1.2 volts.The SPX1587 offers over current limit and full protection against reversed input polarity, reversed load insertion, and positive and negative transient voltage. On-Chip trimming adjusts the reference voltage to 1%. The I Q of this device flows into the load, which increases efficiency.The SPX1587 are offered in a 3-pin TO-220, TO-263 & TO-252 packages compatible with other 3 terminal regulators. For a 5A low dropout regulator refer to the SPX1585 data sheet.PIN CONNECTIONSABSOLUTE MAXIMUM RATINGSLead Temp. (Soldering, 10 Seconds)..............................300°C Maximum Input Voltage ......................................10V Storage Temperature Range ............................-65° to +150°C Input to Output Voltage Differential Max...........8.8V Operating Junction Temperature Range......................SPX1587 Control Section.......................... -45°C +125°C SPX1587 Power Transistor.........................-45°C +150°CELECTRICAL CHARACTERISTICS (NOTE 1) at I OUT = 10mA, T A =25°C, unless otherwise specified.PARAMETER CONDITIONS TypSPX1587A Min MaxSPX1587 Min MaxUnits1.5V VersionOutput Voltage (Note 2) SPX1587-1.5V, 0 ≤I OUT ≤3A, 2.75V ≤V IN ≤10V1.5 1.5 1.485 1.470 1.515 1.530 1.470 1.455 1.530 1.545 V2.5V VersionOutput Voltage (Note 2) SPX1587-2.5V, 0 ≤I OUT ≤3A, 4.0V ≤V IN ≤10V2.5 2.5 2.475 2.450 2.525 2.550 2.450 2.425 2.550 2.575 V3.3V VersionOutput Voltage (Note 2) SPX1587-3.3V, 0 ≤I OUT ≤3A, 4.75V ≤V IN ≤10V 3.3 3.3 3.270 3.240 3.330 3.360 3.230 3.201 3.370 3.399 V5.0V VersionOutput Voltage (Note 2) SPX1587-5.0V, 0 ≤I OUT ≤3A, 6.5V ≤V IN ≤10V5.0 5.0 4.95 4.90 5.05 5.10 4.900 4.850 5.100 5.150 VAll Voltage OptionsReference Voltage (V REF )V IN ≤ 7V, P ≤ P MAX1.5V ≤ (V IN -V OUT )≤(V IN -V OUT ) MAX , 10mA ≤I OUT ≤3A1.2501.238 1.2251.263 1.2701.225 1.2121.270 1.288VMin. Load Current (Note 3) 1.5V ≤ (V IN -V OUT )≤ (V IN -V OUT ) MAX 5 10 10 mA Line Regulation (∆V REF (V IN )) 2.75V ≤V IN ≤7V, I OUT =10mA, T J =25°C(Note 3)0.005 0.2 0.2 %V IN ≤7V, I OUT =0mA, T J =25°C(Note 2)0.005 0.2 0.2 %Load Regulation (∆V REF (I OUT ))10mA ≤I OUT ≤3A, (V IN -V OUT )=3V, T J =25°C(Note 3) 0.05 0.3 0.3 %0≤I OUT ≤3A, V IN =7V, T J =25°C(Note 2)0.05 0.3 0.3 %Dropout Voltage ∆V REF =1% I OUT =3AI OUT ≤3A1.1 1.2 1.2 V Current Limit I OUT (MAX ) V IN =7V 1.4V ≤ (V IN - V OUT ) (Note3) 4.0 3.2 3.2 A Long Term Stability T A =125°C, 1000 Hrs. 0.3 (Note 2)1 1 % Thermal Regulation (∆V OUT (Pwr)) T A =25°C, 20 ms pulse0.01 0.020 0.020 %/WTemperature Stability (∆V OUT (T)) 0.25 % Output Noise, RMS 10Hz to 10kHz T A = 25°c0.003%VThermal ResistanceTO-220DD PackageJunction to Tab Junction to Ambient Junction to Tab Junction to Ambient3.0 60 3.0 603.0 60 3.0 60°C/W The Bold specifications apply to the full operating temperature range.Note 1: Changes in output voltage due to heating effects are covered under the specification for thermal regulation. Note 2: Fixed Version Only Note 3: Adjustable Version OnlyAPPLICATION HINTSThe SPX1587 incorporates protection against over-current faults, reversed load insertion, over temperature operation, and positive and negative transient voltage. However, the use of an output capacitor is required in order to improve the stability and the performances.StabilityThe output capacitor is part of the regulator’s frequency compensation system. Either a 22µF aluminum electrolytic capacitor or a 10µF solid tantalum capacitor between the output terminal and ground guarantees stable operation for all operating conditions.However, in order to minimize overshoot and undershoot, and therefore optimize the design, please refer to the section ‘Ripple Rejection’.Ripple RejectionRipple rejection can be improved by adding a capacitor between the ADJ pin and ground as shown in figure 6. When ADJ pin bypassing is used, the value of the output capacitor required increases to its maximum (22µF for an aluminum electrolytic capacitor, or 10µF for a solid tantalum capacitor). If the ADJ pin is not bypass, the value of the output capacitor can be lowered to 10µF for an electrolytic aluminum capacitor or 4.7µF for a solid tantalum capacitor.However the value of the ADJ-bypass capacitor should be chosen with respect to the following equation:C = 1 / (6.28 * F R * R1)Where C = value of the capacitor in Farads (select an equal or larger standard value),F R= ripple frequency in Hz,R1= value of resistor R1 in Ohms.If an ADJ-bypass capacitor is use, the amplitude of the output ripple will be independent of the output voltage. If an ADJ-bypass capacitor is not used, the output ripple will be proportional to the ratio of the output voltage to the reference voltage:M = V OUT / V REFWhere M = multiplier for the ripple seen when the ADJ pinis optimally bypassed.V REF = Reference Voltage Reducing parasitic resistance and inductanceOne solution to minimize parasitic resistance and inductance is to connect in parallel capacitors. This arrangement will improve the transient response of the power supply if your system requires rapidly changing current load condition. Thermal ConsiderationAlthough the SPX1587 offers some limiting circuitry for overload conditions, it is necessary not to exceed the maximum junction temperature, and therefore to be careful about thermal resistance. The heat flow will follow the lowest resistance path, which is the Junction-to-case thermal resistance. In order to insure the best thermal flow of the component, a proper mounting is required. Note that the case of the device is electrically connected to the output. In case the case has to be electrically isolated, a thermally conductive spacer can be used. However do not forget to consider its contribution to thermal resistance.Assuming:V IN = 10V, V OUT = 5V, I OUT = 1.5A, T A = 50°C/W,θHeatsink Case = 6°C/W, θHeatsink Case = 0.5°C/W, θJC = 3°C/W Power dissipation under this conditionP D = (V IN – V OUT) * I OUT = 7.5WJunction TemperatureT J = T A + P D * (θCase - HS+ θHS + θJC)For the Control SectionsT J = 50 + 7.5*(0.5 +6=3) = 121.25°C121.25°C < T J (max) for the Control & Power Sections.In both case reliable operation is insured by adequate junction temperature.Basic Adjustable RegulatorOutput Voltage Consider Figure 2. The resistance R 1 generates a constantcurrent flow, normally the specified load current of 10mA.This current will go through the resistance R 2 to set the overalloutput voltage. The current I ADJ is very small and constant.Therefore its contribution to the overall output voltage is verysmall and can generally be ignored.Load RegulationParasitic line resistance can degrade load regulation. In ordernot to affect the behavior of the regulator, it is best to connectdirectly the R 1 resistance from the resistor divider to the case,and not to the load. For the same reason, it is best to connectthe resistor R 2 to the Negative side of the load.Output VoltageThe fixed voltage LDO voltage regulators are simple to useregulators since the V OUT is preset to the specifications. It is important however, to provide the proper output capacitance for stability and improvement. For most operating conditions a capacitance of 22uF tantalum or 100uF electrolytic will ensure stability and prevent oscillation.Basic Fixed Regulator V IN OUT5V C23.3VTYPICAL APPLICATIONSOUTFig. 5 Typical Adjustable RegulatorFig. 4 3A Current output Regulator VINNote A: VFig. 6 Improving Ripple Rejection V IN*C 1V OUTFig.7 5V Regulator with ShutdownV IN 100µF5VTTL InputNote A: V IN(MIN)= (Intended V OUT) + (V DROPOUT (MAX) )TYPICAL CHARACTERISTICSORDERING INFORMATIONOrdering No. Precision Output Voltage PackagesSPX1587T 2% Adj 3 Lead TO-263SPX1587T-1.5 2% 1.5V 3 Lead TO-263SPX1587T-2.5 2% 2.5V 3 Lead TO-263SPX1587T-3.3 2% 3.3V 3 Lead TO-263SPX1587T-5.0 2% 5.0V 3 Lead TO-263SPX1587AT 1% Adj 3 Lead TO-263SPX1587AT-1.5 1% 1.5V 3 Lead TO-263SPX1587AT-2.5 1% 2.5V 3 Lead TO-263SPX1587AT-3.3 1% 3.3V 3 Lead TO-263SPX1587AT-5.0 1% 5.0V 3 Lead TO-263SPX1587U 2% Adj 3 Lead TO-220SPX1587U-1.5 2% 1.5V 3 Lead TO-220SPX1587U-2.5 2% 2.5V 3 Lead TO-220SPX1587U-3.3 2% 3.3V 3 Lead TO-220SPX1587U-5.0 2% 5.0V 3 Lead TO-220SPX1587AU 1% Adj 3 Lead TO-220SPX1587AU-1.5 1% 1.5V 3 Lead TO-220SPX1587AU-2.5 1% 2.5V 3 Lead TO-220SPX1587AU-3.3 1% 3.3V 3 Lead TO-220SPX1587AU-5.0 1% 5.0V 3 Lead TO-220SPX1587R 2% Adj 3 Lead TO-252SPX1587R-1.5 2% 1.5V 3 Lead TO-252SPX1587R-2.5 2% 2.5V 3 Lead TO-252SPX1587R-3.3 2% 3.3V 3 Lead TO-252SPX1587R-5.0 2% 5.0V 3 Lead TO-252SPX1587AR 1% Adj 3 Lead TO-252SPX1587AR-1.5 1% 1.5V 3 Lead TO-252SPX1587AR-2.5 1% 2.5V 3 Lead TO-252SPX1587AR-3.3 1% 3.3V 3 Lead TO-252SPX1587AR-5.0 1% 5.0V 3 Lead TO-252CorporationSIGNAL PROCESSING EXCELLENCESipex CorporationHeadquarters and Main Offices:22 Linnell CircleBillerica, MA 01821TEL: (978) 667-8700FAX: (978) 670-9001e-mail: sales@233 South Hillview DriveMilpitas, CA 95035TEL: (408) 935-7600FAX: (408) 934-7500Sipex 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 hereing; neither does it convey any license under its patent rights nor the rights of others.。
