Freescale Semiconductor Advance Information Document Number: MC34713 Rev. 4.0, 5/2007 5.0 A 1.0 MHz Fully Integrated Single Switch-Mode Power Supply The 34713 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 in different configurations. Its high efficient 5.0 A continuous output current capability combined with its voltage tracking/sequencing ability and tight output regulation, makes it ideal as a single power supply. The 34713 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 mΩ 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 3.6 V • Voltage Tracking Capability in different configurations. • Programmable Switching Frequency Range from 200 kHz to 1.0 MHz with a default of 1.0 MHz • Programmable Soft Start Timing • Over Current Limit and Short Circuit Protection • Thermal Shutdown • Output Overvoltage and Undervoltage Detection • Active Low Power Good Output Signal • Active Low Shutdown Input • Pb-Free Packaging Designated by Suffix Code EP. 34713 SWITCH-MODE POWER SUPPLY EP SUFFIX 98ARL10577D 24-PIN QFN ORDERING INFORMATION Device Temperature Range (TA) Package MC34713EP/R2 -40 to 85°C 24 QFN (3.0V TO 6.0V) VIN 34713 VMASTER VIN VREFIN PGND VDDI FREQ PVIN BOOT SW VOUT INV COMP VIN ILIM VOUT PG GND SD Figure 1. 34713 Simplified Application Diagram * 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. MICROCONTROLLER DSP, FPGA, ASIC INTERNAL BLOCK DIAGRAM INTERNAL BLOCK DIAGRAM SD Internal Voltage Regulator Thermal Monitoring PG System Reset M1 VIN M2 System Control VDDI BOOT ILIMIT Discharge VIN VBOOT Buck Control Logic Oscillator FSW M3 Gate ISENSE Driver Prog Soft Start ISENSE Current Monitoring PWM Comparator + VDDI VDDI VBG M4 PGND Ramp Generator COMP + Bandgap Regulator SW ILIMIT – ILIM Prog Frequency – FREQ PVIN Error Amplifier INV VREFIN VBG Reference Selection M5 GND VOUT Discharge Figure 2. 34713 Simplified Internal Block Diagram 34713 2 Analog Integrated Circuit Device Data Freescale Semiconductor PIN CONNECTIONS VDDI VIN VIN BOOT PVIN PVIN PIN CONNECTIONS 24 23 22 21 20 19 GND 1 18 PVIN FREQ 2 17 SW ILIM 3 16 SW PG 4 15 SW NC 5 14 PGND SD 6 13 PGND 7 8 9 10 11 12 VREFIN NC COMP INV VOUT PGND Transparent Top View Figure 3. 34713 Pin Connections Table 1. 34713 Pin Definitions A functional description of each pin can be found in the Functional Pin Description section beginning on page 9. Pin Number Pin Name Pin Function Formal Name Definition 1 GND Ground Signal Ground 2 FREQ Passive 3 ILIM Input Soft Start 4 PG Output Power Good Active-low (open drain) power-good status reporting pin 5, 8 NC None No Connect No internal connections to these pins. Recommend attaching a 0.1µF capacitor from pin 8 to GND. 6 SD Input Shutdown 7 VREFIN Input Voltage-TrackingReference Input 9 COMP Passive Compensation Buck converter external compensation network pin 10 INV Input Error Amplifier Inverting Input Buck converter error amplifier inverting input pin 11 VOUT Output Output Voltage Discharge FET Discharge FET drain connection (connect to buck converter output capacitors) 12,13,14 PGND Ground Power Ground Ground return for buck converter and discharge FET 15,16,17 SW Power Switching Node Buck converter power switching node 18,19,20 PVIN Supply Power-Circuit Supply Input 21 BOOT Passive Bootstrap 22,23 VIN Supply Logic-Circuit Supply Input 24 VDDI Passive Internal Voltage Regulator Analog signal ground of IC Frequency Adjustment Buck converter switching frequency adjustment pin Soft Start adjustment Shutdown mode input control pin Voltage-Tracking-Reference voltage input Buck converter main supply voltage input Bootstrap switching node (connect to bootstrap capacitor) Logic circuits supply voltage input Internal Vdd Regulator (connect filter capacitor to this pin) 34713 Analog Integrated Circuit Device Data Freescale Semiconductor 3 ELECTRICAL CHARACTERISTICS MAXIMUM RATINGS ELECTRICAL CHARACTERISTICS MAXIMUM RATINGS Table 2. Maximum Ratings All voltages are with respect to ground unless otherwise noted. Exceeding these ratings may cause a malfunction or permanent damage to the device. Ratings Symbol Value Unit VIN -0.3 to 7.0 V High-Side MOSFET Drain Voltage (PVIN) Pin PVIN -0.3 to 7.0 V Switching Node (SW) Pin VSW -0.3 to 7.5 V VBOOT - VSW -0.3 to 7.5 V - -0.3 to 7.0 V - -0.3 to 3.0 V IOUT +5.0 A Human Body Model VESD1 ±2000 V Charge Device Model VESD3 ±750 TA -40 to 85 °C TSTG -65 to +150 °C TPPRT Note 5 °C TJ(MAX) +150 °C PD 2.9 W ELECTRICAL RATINGS Input Supply Voltage (VIN) Pin BOOT Pin (Referenced to SW Pin) PG, VOUT,and SD Pins VDDI, FREQ, ILIM, INV, COMP, and VREFIN Pins Continuous Output Current ESD Voltage (1) (2) THERMAL RATINGS Operating Ambient Temperature (3) Storage Temperature Peak Package Reflow Temperature During Reflow (4) (5) , Maximum Junction Temperature Power Dissipation (TA = 85 °C) (6) Notes 1. Continuous output current capability so long as TJ is ≤ TJ(MAX). 2. 3. 4. 5. 6. ESD1 testing is performed in accordance with the Human Body Model (CZAP = 100 pF, RZAP = 1500 Ω), ESD3 testing is performed in accordance with the Charge Device Model (CDM). The limiting factor is junction temperature, taking into account power dissipation, thermal resistance, and heatsinking. Pin soldering temperature limit is for 10 seconds maximum duration. Not designed for immersion soldering. Exceeding these limits may cause malfunction or permanent damage to the device. Freescale’s Package Reflow capability meets Pb-free requirements for JEDEC standard J-STD-020C. For Peak Package Reflow Temperature and Moisture Sensitivity Levels (MSL), Go to www.freescale.com, 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. Maximum power dissipation at indicated ambient temperature 34713 4 Analog Integrated Circuit Device Data Freescale Semiconductor ELECTRICAL CHARACTERISTICS MAXIMUM RATINGS 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. Ratings Symbol Value Unit Thermal Resistance, Junction to Ambient, Single-Layer Board (1s) (8) RθJA 139 °C/W Thermal Resistance, Junction to Ambient, Four-Layer Board (2s2p) (9) RθJMA 43 °C/W RθJB 22 °C/W THERMAL RESISTANCE (7) Thermal Resistance, Junction to Board (10) Notes 7. The PVIN, SW, and PGND 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 the board. 10. Thermal resistance between the device and the printed circuit board per JEDEC JESD51-8. Board temperature is measured on the top surface of the board near the package. 34713 Analog Integrated Circuit Device Data Freescale Semiconductor 5 ELECTRICAL CHARACTERISTICS STATIC ELECTRICAL CHARACTERISTICS STATIC ELECTRICAL CHARACTERISTICS Table 3. Static Electrical Characteristics Characteristics noted under conditions 3.0 V ≤ VIN ≤ 6.0 V, - 40°C ≤ TA ≤ 85°C, GND = 0 V unless otherwise noted. Typical values noted reflect the approximate parameter means at TA = 25°C under nominal conditions unless otherwise noted. Characteristic Symbol Min Typ Max Unit VIN 3.0 - 6.0 V IIN - - 25 mA IINOFF - - 100 µA VDDI 2.35 2.5 2.65 V VOUT 0.7 - 3.6 V - -1.0 - 1.0 % REGLN -1.0 - 1.0 % REGLD -1.0 - 1.0 % Error Amplifier Common Mode Voltage Range (12), (13) VREF 0.0 - 1.35 V Output Undervoltage Threshold VUVR -1.5 - -8.0 % Output Overvoltage Threshold VOVR 1.5 - 8.0 % Continuous Output Current IOUT - - 5.0 A Over Current Limit ILIM - 6.5 - A VILIM 1.25 - VDDI V ISHORT - 8.5 - A RDS(ON)HS 10 - 45 mΩ RDS(ON)LS 10 - 45 mΩ IC INPUT SUPPLY VOLTAGE (VIN) Input Supply Voltage Operating Range Input DC Supply Current (11) Normal Mode: SD = 1, Unloaded Outputs Input DC Supply Current (11) Shutdown Mode, SD = 0 INTERNAL SUPPLY VOLTAGE OUTPUT (VDDI) Internal Supply Voltage Range BUCK CONVERTER (PVIN, SW, PGND, BOOT, INV, COMP, ILIM) Output Voltage Adjustment Range (12), (13) Output Voltage Accuracy Line Regulation (12), (14) (12) Normal Operation, VIN = 3.0 V to 6.0 V, IOUT = +5.0 A Load Regulation (12) Normal Operation, IOUT = 0.0 A to 5.0 A Soft start Adjusting reference Voltage Range Short Circuit Current Limit High-Side N-CH Power MOSFET (M3) RDS(ON) (12) IOUT = 1.0 A, VBOOT - VSW = 3.3 V Low-Side N-CH Power MOSFET (M4) RDS(ON) (12) IOUT = 1.0 A, VIN = 3.3 V Notes 11. 12. 13. 14. Section “MODES OF OPERATION”, page 12 has a detailed description of the different operating modes of the 34713 Design information only, this parameter is not production tested. The ±1% accuracy is only guaranteed for VEFOUT greater then or equal 0.7V at room tempreature. Overall output accuracy is directly affected by the accuracy of the external feedback network, 1% feedback resistors are recommended 34713 6 Analog Integrated Circuit Device Data Freescale Semiconductor ELECTRICAL CHARACTERISTICS STATIC ELECTRICAL CHARACTERISTICS Table 3. Static Electrical Characteristics Characteristics noted under conditions 3.0 V ≤ VIN ≤ 6.0 V, - 40°C ≤ TA ≤ 85°C, GND = 0 V unless otherwise noted. Typical values noted reflect the approximate parameter means at TA = 25°C under nominal conditions unless otherwise noted. Characteristic M2 RDS(ON) VIN = 3.3 V, M2 is on Symbol Min Typ Max Unit RDS(ON)M2 1.5 - 4.0 Ω IPVIN -10 - 10 µA PVIN Pin Leakage Current Shutdown Mode INV Pin Leakage Current IINV -1.0 - 1.0 µA Thermal Shutdown Threshold (15) TSDFET - 170 - °C Thermal Shutdown Hysteresis (15) TSDHYFET - 25 - °C VFREQ 0.0 - VDDI V VREFIN 0.0 - 1.35 V RTDR(M5) - 50 - Ω VSDHI 2.0 - - V VSDLO - - 0.4 V RSDUP 1.0 - 2.0 MΩ VPGLO - - 0.4 V IPGLKG -1.0 - 1.0 µA OSCILLATOR (FREQ) Oscillator Frequency Adjusting Reference Voltage Range TRACKING (VREFIN, VOUT) VREFIN External Reference Voltage Range (15) VOUT Total Discharge Resistance(15) CONTROL AND SUPERVISORY (SD, PG) SD High Level Input Voltage SD Low Level Input Voltage SD Pin Internal Pull Up Resistor (15) PG Low Level Output Voltage IPG = 3.0 mA PG Pin Leakage Current M1 is off, Pulled up to VIN Notes 15. Design information only, this parameter is not production tested. 34713 Analog Integrated Circuit Device Data Freescale Semiconductor 7 ELECTRICAL CHARACTERISTICS DYNAMIC ELECTRICAL CHARACTERISTICS DYNAMIC ELECTRICAL CHARACTERISTICS Table 4. Dynamic Electrical Characteristics Characteristics noted under conditions 3.0 V ≤ VIN ≤ 6.0 V, - 40°C ≤ TA ≤ 85°C, GND = 0 V unless otherwise noted. Typical values noted reflect the approximate parameter means at TA = 25°C under nominal conditions unless otherwise noted. Characteristic Symbol Min Typ Max Unit tRISE - 14 - ns tFALL - 20 - ns - 3.2 - - 1.6 - 1.82 - 2.13 V - 0.8 - 2.14 - 2.50 V - 0.4 - tLIM - 10 - ms tTIMEOUT 80 - 120 ms tFILTER 5.0 - 25 µs Oscillator Frequency tolerance is ±10% (FREQ = GND) fSW - 1.0 - MHz Oscillator Switching Frequency Range fSW 200 - 1000 KHz PG Reset Delay tPGRESET 8.0 - 12 ms Thermal Shutdown Retry Time-out Period (16) tTIMEOUT 80 - 120 ms BUCK CONVERTER (PVIN, SW, PGND, BOOT) Switching Node (SW) Rise Time (16) (PVIN = 3.3 V, IOUT = 5.0 A) Switching Node (SW) Fall Time (16) (PVIN = 3.3 V, IOUT = 5.0 A) Soft Start Duration (Normal Mode) ILIM= 1.25 - 1.49 V 1.50 - 1.81 V Over Current Limit Timer Over Current Limit Retry Time-out Period Output Undervoltage/Overvoltage Filter Delay Timer tSS ms OSCILLATOR (FREQ) Oscillator Default Switching Frequency CONTROL AND SUPERVISORY (SD, PG) Notes 16. Design information only, this parameter is not production tested. 34713 8 Analog Integrated Circuit Device Data Freescale Semiconductor FUNCTIONAL DESCRIPTION INTRODUCTION FUNCTIONAL DESCRIPTION INTRODUCTION Advanced microprocessor-based systems require compact, efficient, and accurate point-of-load (PoL) power supplies. These PoL supply high current and fast transient response capability while maintaining regulation accuracy. Voltage monitoring (power sequencing) and increased operating frequency are also key features for PoL power supplies. PoL power supplies are non-isolated DC to DC converters that are physically located near their load (on the same printed circuit board) and take their input supply from an intermediate bus. Their close proximity to the load allows for higher efficiency, localized protection, and minimum distribution losses. Their compact design and low component-count also reduces overall system cost. The 34713 is a PoL single-output power supply that embodies an integrated solution that’s both highly costeffective and reliable. It utilizes a voltage-mode synchronous buck switching converter topology with integrated low RDS(ON) (45 mΩ) N-channel power MOSFETs for high- efficiency operation. It provides an output voltage with an accuracy of less than ±2.0 %, capable of supplying up to 5.0 A of continuous current. Its power sequencing/tracking abilities makes it ideal for systems with multiple related supply rails. It has an adjustable switching frequency, thus permitting greater design flexibility and optimization over a wide range of operating conditions, and can operate at up to 1.0 MHz to significantly reduce the external components size and cost. It also features an over-current limit control, and protects against output overvoltage, undervoltage, and overtemperature conditions. It also protects the system from short circuit events and incorporates a power-good output signal to alert the host MCU should a fault occur. Operation can be enabled or disabled by controlling the SD pin, which offers power sequencing capabilities. By monolithically integrating the control and supervisory circuitry along with power-FETs, the 34713 offers a complete, compact, cost-effective, and simple solution to satisfy the PoL needs of today’s systems. FUNCTIONAL PIN DESCRIPTION REFERENCE VOLTAGE INPUT (VREFIN) The 34713 will track the voltage applied at this pin. ERROR AMPLIFIER INVERTING INPUT (INV) Buck converter error amplifier inverting input. Connect the output voltage feedback network to this pin. 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. COMPENSATION INPUT (COMP) Buck converter external compensation network connects to this pin. Use a type III compensation network. INPUT SUPPLY VOLTAGE (VIN) SOFT START ADJUSTMENT INPUT (ILIM) Soft start timing can be adjusted by applying an external voltage between 1.25 and VDDI on this pin. IC power supply input voltage. Input filtering is required for the device to operate properly. POWER GROUND (PGND) SIGNAL GROUND (GND) Analog ground of the IC. Internal analog signals are referenced to this pin voltage. Buck converter and discharge MOSFET power ground. It is the source of the buck converter low-side power MOSFET. SWITCHING NODE (SW) INTERNAL 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. 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 17) between this pin and the SW pin to enhance the gate of the high-side Power MOSFET during switching. 34713 Analog Integrated Circuit Device Data Freescale Semiconductor 9 FUNCTIONAL DESCRIPTION FUNCTIONAL INTERNAL BLOCK DESCRIPTION SHUTDOWN INPUT (SD) POWER GOOD OUTPUT SIGNAL (PG) 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 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., VIN). FUNCTIONAL INTERNAL BLOCK DESCRIPTION Internal Bias Circuits System Control & Logic Oscillator Protection Functions Control & Supervisory Functions Tracking & Sequencing Buck Converter Figure 4. 34713 Block Diagram INTERNAL BIAS CIRCUITS This 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 VDDI voltage that is used to drive the digital/ analog internal circuits. It is equipped with a Power-OnReset (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 LOGIC This block is the brain of the IC where the device processes data and reacts to it. Based on the status of the SD pin, 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. OSCILLATOR This 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 FUNCTIONS This 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 shutdown 34713 10 Analog Integrated Circuit Device Data Freescale Semiconductor FUNCTIONAL DESCRIPTION FUNCTIONAL INTERNAL BLOCK DESCRIPTION threshold, this block will alert the system control for further commands. • Output Overvoltage and Undervoltage Monitoring: This block monitors the buck converter output voltage to ensure it is within regulation boundaries. If not, this block 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: • Shutdown Control Input: An outside host can put the 34713 device into shutdown mode by sending a logic “0” to the SD pin. • Power Good Output Signal PG: The 34713 can communicate to an external host that a fault has occurred 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 SEQUENCING This block allows the output of the 34713 to track the voltage applied at the VREFIN pin in different tracking configurations. This will be discussed in further details later in this document. For power down during a shutdown mode, the 34713 uses internal discharge MOSFET (Figure 2) to discharge the output. The discharge MOSFET is only active during shutdown mode. Using this block along with controlling the SD pin can offer the user power sequencing capabilities by controlling when to turn the 34713 output on or off. BUCK CONVERTER This block provides the main function of the 34713: 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 % to meet today’s requirements. Its output has the ability to track 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 34713 has the ability to supply up to 5.0 A of continuous current, making it suitable for many high current applications. 34713 Analog Integrated Circuit Device Data Freescale Semiconductor 11 FUNCTIONAL DEVICE OPERATION OPERATIONAL MODES FUNCTIONAL DEVICE OPERATION OPERATIONAL MODES VIN < 3.0V SD = 0 Power Off VOUT = OFF VREF = OFF PG = 1 Shutdown VOUT = Discharge VREF = Discharge 3.0V < = VIN < = 6.0V PG = 1 SD = 1 Overvoltage VOUT = ON VREF = ON VOUT > VOV VOUT < VOV Normal VOUT= ON VREF = ON PG = 1 IOUT > = ISHORT PG = 1 PG = 0 tTIMEOUT Expired VOUT > VUV VOUT < VUV Short Circuit VOUT = OFF VREF = OFF tTIMEOUT Expired Undervoltage VOUT= ON VREF = ON PG = 1 TJ < = 145°C & tTIMEOUT Expired Thermal Shutdown VOUT = OFF VREF = OFF Over Current VOUT = OFF VREF = ON IOUT > = ILIM For > = 10ms PG = 1 PG = 1 TJ > = 170°C Figure 5. Operation Modes Diagram MODES OF OPERATION The 34713 has two primary modes of operation: Normal Mode In normal mode, all functions and outputs are fully operational. To be in this mode, the VIN needs to be within its operating range, Shutdown input is high, and no faults are present. This mode consumes the most amount of power. Shutdown Mode In this mode, activated by pulling the SD pin low, the chip is in a shutdown state and the output is disabled and discharged. In this mode, the 34713 consumes the least amount of power since almost all of the internal blocks are disabled. START-UP SEQUENCE When power is first applied, the 34713 checks the status of the SD pin. If the device is in a shutdown mode, no block will power up and the output will not attempt to ramp. Once the SD pin is released to enable the device, the VDDI internal supply voltage and the bias currents are established and the internal VDDI POR signal is also released. The rest of the internal blocks will be enabled and the buck converter switching frequency and soft start values are determined by reading the FREQ and ILIM pins respectively. A soft start cycle is then initiated to ramp up the output of the buck converter. The buck converter error amplifier uses the voltage on the VREFIN pin as its reference voltage until VREFIN is equal to 0.7 V, then the error amplifier defaults to the internal 0.7 V reference voltage. This method helps achieve multiple tracking configurations as will be explained later in this document. Soft start is used to prevent the output voltage from overshooting during startup. At initial startup, the output capacitor is at zero volts; VOUT = 0 V. Therefore, the voltage across the inductor will be PVIN during the capacitor charge phase which will create a very sharp di/dt ramp. Allowing the inductor current to rise too high can result in a large difference between the charging current and the actual load current that can result in an undesired voltage spike once the capacitor is fully charged. The soft start is active each time the IC goes out of standby or shutdown mode, power is recycled, or after a fault retry. After a successful start-up cycle where the device is enabled, no faults have occurred, and the output voltage has reached its regulation point, the 34713 pulls the power good output signal low after a 10 ms reset delay, to indicate to the host that the device is in normal operation. 34713 12 Analog Integrated Circuit Device Data Freescale Semiconductor FUNCTIONAL DEVICE OPERATION PROTECTION AND DIAGNOSTIC FEATURES PROTECTION AND DIAGNOSTIC FEATURES The 34713 monitors the application for several fault conditions to protect the load from overstress. The reaction of the IC to these faults ranges from turning off the outputs to just alerting the host that something is wrong. In the following paragraphs, each fault condition is explained: An overvoltage condition occurs once the output voltage goes higher than the rising overvoltage threshold (VOVR). In this case, the power good output signal is pulled high, alerting the host that a fault is present, but the output will stay active. To avoid erroneous overvoltage conditions, a 20 µs filter is implemented. The buck converter will use its feedback loop to attempt to correct the fault. Once the output voltage falls below the falling overvoltage threshold (VOVF), the fault is cleared and the power good output signal is pulled low, the device is back in normal operation. operation to limit the current, and a 10 ms over current limit timer (tLIM) starts. The converter will stay in this mode of operation until one of the following occurs: • The current is reduced back to the normal level before tLIM expires, and in this case normal operation is regained. • tLIM expires without regaining normal operation, at which point the device turns off the output and the power good output signal is pulled high. At the end of a time-out period of 100 ms (tTIMEOUT), the device will attempt another soft start cycle. • The device reaches the thermal shutdown limit (TSDFET) and turns off the output. The power good output signal is pulled high. • The output current keeps increasing until it reaches the short circuit current limit (ISHORT). See below for more details. Output Undervoltage Short Circuit Current Limit An undervoltage condition occurs once the output voltage falls below the falling undervoltage threshold (VUVF). In this case, the power good output signal is pulled high, alerting the host that a fault is present, but the output will stay active. To avoid erroneous undervoltage conditions, a 20 µs filter is implemented. The buck converter will use its feedback loop to attempt to correct the fault. Once the output voltage rises above the rising undervoltage threshold (VUVR), the fault is cleared and the power good output signal is pulled low, the device is back in normal operation. This block uses the same current detection mechanism as the over current limit detection block. If the load current reaches the ISHORT value, the device reacts by shutting down the output immediately. This is necessary to prevent damage in case of a permanent short circuit. Then, at the end of a time-out period of 100 ms (tTIMEOUT), the device will attempt another soft start cycle. Output Overvoltage Output Over Current This block detects over current in the Power MOSFETs of the buck converter. It is comprised of a sense MOSFET and a comparator. The sense MOSFET acts as a current detecting device by sampling a ratio of the load current. That sample is compared via the comparator with an internal reference to determine if the output is in over current or not. If the peak current in the output inductor reaches the over current limit (ILIM), the converter will start a cycle-by-cycle Thermal Shutdown Thermal limit detection block monitors the temperature of the device and protects against excessive heating. If the temperature reaches the thermal shutdown threshold (TSDFET), the converter output switches off and the power good output signal indicates a fault by pulling high. The device will stay in this state until the temperature has decreased by the hysteresis value and then After a time-out period (TTIMEOUT) of 100 ms, the device will retry automatically and the output will go through a soft start cycle. If successful normal operation is regained, the power good output signal is asserted low to indicate that. 34713 Analog Integrated Circuit Device Data Freescale Semiconductor 13 TYPICAL APPLICATIONS PROTECTION AND DIAGNOSTIC FEATURES TYPICAL APPLICATIONS VIN BOOT VIN BOOT VDDI C15 I/O SIGNALS SW VDDI 0.1uF PVIN 4.7_nopop PVIN J3 ILIM GND VMASTER VOUT R11 10k 3 2 1 R13 10k_nopop FREQ ILIM 19 PVIN 21 22 20 PVIN R12 10k_nopop FREQ R10 10k VIN 24 PVIN 3 2 1 VDDI VIN GND VIN R16 U1 23 C14 0.1uF BOOT J2 1 SGND PVIN 18 2 FREQ SW 17 3 ILIM SW 16 SW SW MC34713 PG PG SW 15 5 N/C GND 14 6 SD GND 13 R7 1k R8 10k GND VOUT GND 12 11 INV COMP 9 10 VIN N/C SD VREFIN SD 7 VMASTER 4 8 VMASTER PGOOD LED PG VREFIN VREFIN C11 VREFIN D1 LED C13 0.1uF 0.1uF R9 10k VOUT LED INV INV COMP C12 0.1uF COMP JUMPERS BUCK CONVERTER VOUT1 VOUT VOUT2 J1 L1 SW 1 VOUT 2 STBY_nopop 1.5uH D2 PVIN VMASTER LED R3 4.7_nopop 1 C6 100uF C7 100uF 2 C8 100uF 1 3 5 7 9 2 4 6 8 10 VREFIN PG SD PMEG2010EA_nopop C9 1nF_nopop 1 CON10A 2 SD COMPENSATION NETWORK PVIN CAPACITORS OPTIONAL nopop VOUT VDDI PVIN ILIM C20 1nF 15k C3 100uF C4 100uF C5 100uF C19 FREQ R6 POT_50K_nopop R5 POT_50K_nopop R14 300 0.02nF R15 C2 1uF R1 20k INV C18 COMP C1 0.1uF VIN CAPACITORS VIN R2 12.7k 1.9nF C17 10uF C16 0.1uF Figure 6. Typical Applications 34713 14 Analog Integrated Circuit Device Data Freescale Semiconductor TYPICAL APPLICATIONS PROTECTION AND DIAGNOSTIC FEATURES COMPONENT SELECTION SWITCHING FREQUENCY SELECTION The switching frequency defaults to a value of 1.0 MHz when the FREQ pin is grounded, and 200 KHz when the FREQ pin is connected to VDDI. Intermediate switching frequencies can be obtained by connecting an external resistor divider to the FREQ pin. The table below shows the resulting switching frequency versus FREQ pin voltage. Table 5. Switching Frequency Adjustment FREQUENCY VOLTAGE APPLIED TO PIN FREQ 200 2.341 – 2.500 253 2.185 - 2.340 307 2.029 - 2.184 360 1.873 - 2.028 413 1.717 – 1.872 466 1.561 – 1.716 520 1.405 - 1.560 573 1.249 - 1.404 627 1.093 - 1.248 680 0.936 - 1.092 733 0.781 - 0.936 787 0.625 - 0.780 840 0.469 - 0.624 893 0.313 - 0.468 947 0.157 - 0.312 1000 0.000 - 0.156 where, Maximum OFF time percentage Switching period. Drain – to – source resistance of FET Winding resistance of Inductor Output current ripple. OUTPUT FILTER CAPACITOR For the output capacitor, the following considerations are more important than the actual capacitance value, the physical size, the ESR and the voltage rating: Transient Response percentage, TR_% Maximum Transient Voltage, TR_v_dip = Vo*TR_% Maximum current step, Inductor Current rise time, where, Figure 7. Resistor Divider for Frequency Adjustment SELECTION OF THE INDUCTOR D_max = Maximum ON time percentage. IO = Rated output current. Vin_min = Minimum input voltage at PVIN As a result, it is possible to calculate Inductor calculation is straight forward, being 34713 Analog Integrated Circuit Device Data Freescale Semiconductor 15 TYPICAL APPLICATIONS PROTECTION AND DIAGNOSTIC FEATURES BOOT Gate Driver FSW In order to find the maximum allowed ESR, CBOOT SW L CO VOUT RS INV PWM Comparitor CS RF + – Ramp Generator RO CX Error Amplifier RB CF COMP + – The effects of the ESR is often neglected by the designers and may present a hidden danger to the ultimate supply stability. Poor quality capacitors have widely disparate ESR value, which can make the closed loop response inconsistent. VREFIN VDDI Bandgap Regulator Reference Selection 34713 R V O = V REF ⎛⎝ ------O- + 1⎞⎠ RB Figure 9. Type III Compensation Network Consider the crossover frequency, FCROSS, of the open loop Io gain at one-sixth of the switching frequency, FSW. Then, Io_step ⇒ Current response dt_I_rise Worst case assumption where RO is a user selected resistor. Knowing the LC frequency, it can be obtained the values of RF and CS: Figure 8. Transient Parameters TYPE III COMPENSATION NETWORK Power supplies are desired to offer accurate and tight regulation output voltages. To accomplish this requires a high DC gain. But with high gain comes the possibility of instability. The purpose of adding compensation to the internal error amplifier is to counteract some of the gains and phases contained in the control-to-output transfer function that could jeopardized the stability of the power supply. The Type III compensation network used for 34713 comprises two poles (one integrator and one high frequency pole to cancel the zero generated from the ESR of the output capacitor) and two zeros to cancel the two poles generated from the LC filter as shown in Figure 9. This gives as a result, & Calculate Rs by placing the Pole 1 at the ESR zero frequency: 34713 16 Analog Integrated Circuit Device Data Freescale Semiconductor TYPICAL APPLICATIONS PROTECTION AND DIAGNOSTIC FEATURES ⇒ Equating the Pole 2 at Crossover Frequency to achieve a faster response and a proper phase margin, node, so it is not ground and it is floating and moving in voltage, so we cannot just apply a voltage directly to the gate of the high side that is referenced to ground, we need a voltage referenced to the SW node. That is why the bootstrap capacitor is needed for. This capacitor charges during the high side off time, since the low side will be on during that time, so the SW node and the bottom of the bootstrap capacitor will be connected to ground and the top of the capacitor will be connected to a voltage source, so the capacitor will charge up to that voltage source (say 5V). Now when the low side MOSFET switches off and the high side MOSFET switches on, the SW nodes rises up to Vin, and the voltage on the boot pin will be Vcap + Vin. So the gate of the high side will have Vcap across it and it will be able to stay enhanced. A 0.1µF capacitor is a good value for this bootstrap element. SOFT START SELECTION Table 6 shows the voltage that should be applied to the terminal ILIM to get the desired configuration of the soft start timing. Table 6. ILIM Table Soft Start (ms) Voltage Applied to ILIM 3.2 1.25 - 1.49 1.6 1.50 - 1.81 BOOTSTRAP CAPACITOR 0.8 1.82 - 2.13 The bootstrap capacitor is needed to supply the gate voltage for the high side MOSFET. This N-Channel MOSFET needs a voltage difference between its gate and source to be able to turn on. The high side MOSFET source is the SW 0.4 2.14 - 2.50 ⇒ 34713 Analog Integrated Circuit Device Data Freescale Semiconductor 17 PACKAGING PACKAGING DIMENSIONS PACKAGING PACKAGING DIMENSIONS EP SUFFIX 24-PIN PLASTIC PACKAGE 98ARL10577D ISSUE B 34713 18 Analog Integrated Circuit Device Data Freescale Semiconductor PACKAGING PACKAGING DIMENSIONS EP SUFFIX 24-PIN PLASTIC PACKAGE 98ARL10577D ISSUE B 34713 Analog Integrated Circuit Device Data Freescale Semiconductor 19 REVISION HISTORY REVISION HISTORY REVISION DATE DESCRIPTION OF CHANGES 1.0 2/2006 • • Pre-release version Implemented Revision History page 2.0 11/2006 • • • Initial release Converted format from Market Assessment to Product Preview Major updates to the data, form, and style 3.0 2/2007 • Major updates to the data, form, and style 5/2007 • • • • • Changed Feature fom 2% to 1%, relabeled to include soft start Changed 34713 Simplified Application Diagram Made change to 34713 Simplified Internal Block Diagram Removed Machine Model in Maximum Ratings Changed Input DC Supply Current (11) Normal mode and Input DC Supply Current (11) Shutdown mode Changed Output Voltage Accuracy (12), (14) Changed Soft start Adjusting reference Voltage Range and Short Circuit Current Limit Changed High-Side N-CH Power MOSFET (M3) RDS(ON) (12) and Low-Side N-CH Power MOSFET (M4) RDS(ON) (12) Changed M2 RDS(ON) and PVIN Pin Leakage Current Changed SD Pin Internal Pull Up Resistor (15) Changed Changed Soft Start Duration (Normal Mode) Changed Over Current Limit Retry Time-out Period and Output Undervoltage/Overvoltage Filter Delay Timer Changed PG Reset Delay and Thermal Shutdown Retry Time-out Period (16) Changed definition for Soft Start Adjustment input (ILIM) Changed drawings in Typical Applications Changed drawing in Type III Compensation Network Changed table for Soft Start Selection Removed PC34713EP/R2 from the ordering information and added MC34713EP/R2 Changed the data sheet status to Advance Information 4.0 • • • • • • • • • • • • • • 34713 20 Analog Integrated Circuit Device Data Freescale Semiconductor How to Reach Us: Home Page: www.freescale.com Web Support: http://www.freescale.com/support USA/Europe or Locations Not Listed: Freescale Semiconductor, Inc. Technical Information Center, EL516 2100 East Elliot Road Tempe, Arizona 85284 +1-800-521-6274 or +1-480-768-2130 www.freescale.com/support Europe, Middle East, and Africa: Freescale Halbleiter Deutschland GmbH Technical Information Center Schatzbogen 7 81829 Muenchen, Germany +44 1296 380 456 (English) +46 8 52200080 (English) +49 89 92103 559 (German) +33 1 69 35 48 48 (French) www.freescale.com/support Japan: Freescale Semiconductor Japan Ltd. Headquarters ARCO Tower 15F 1-8-1, Shimo-Meguro, Meguro-ku, Tokyo 153-0064 Japan 0120 191014 or +81 3 5437 9125 [email protected] Asia/Pacific: Freescale Semiconductor Hong Kong Ltd. Technical Information Center 2 Dai King Street Tai Po Industrial Estate Tai Po, N.T., Hong Kong +800 2666 8080 [email protected] For Literature Requests Only: Freescale Semiconductor Literature Distribution Center P.O. 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