MIC5167 1MHz, 6A, Integrated Switch, High-Efficiency, Synchronous Buck DDR Memory Terminator General Description The MIC5167 is a high-efficiency, 6A, integrated switch, synchronous regulator designed for use as a double data rate (DDR) or quad data rate (QDR) terminator. The MIC5167 is optimized for highest efficiency, achieving more than 94% efficiency while still switching at 1MHz over a broad range. The device works with a small 0.4µH inductor and 300µF output capacitor. The MIC5167 offers a simple, low-cost, JEDEC-compliant solution for terminating high-speed, low-voltage, digital buses (i.e. DDR, DDR2, DDR3, DDR3L, DDR3UL, DDR4, SCSI, GTL, SSTL, HSTL, LV-TTL, LV-PECL, and LV_ECL) with a Power-Good (PG) output. The output voltage is controlled externally by input to the VDDQ pin. The output voltage is one-half the voltage applied to the VDDQ pin. The output voltage can be adjusted down to 0.6V to address low-voltage power needs. The MIC5167 will source 6A and sink up to 6A. A window comparator monitors the output voltage and controls the PG output. If the output voltage is outside ±15% limit of VREF the PG is driven low. ® The MIC5167 is available in a 24-pin 4mm x 4mm MLF with a junction operating range from –40°C to +125°C. Data sheets and support documentation can be found on Micrel’s web site at: www.micrel.com. Features • • • • • • • • • • • • • Input voltage range: 2.6V to 5.5V VTT voltage adjustable down to 0.35V Output load current up to ±6A Power-Good (PG) fault flag Efficiency > 94% across a broad load range Ultra-fast transient response Easy RC compensation 100% maximum duty cycle Fully-integrated MOSFET switches Micropower shutdown Thermal-shutdown and current-limit protection 24-pin 4mm x 4mm MLF® –40°C to +125°C junction temperature range Applications • Double data rate (DDR) or quad data rate (QDR) memory terminator • High power density point-of-load conversion • Servers and routers • DVD recorders / Blu-ray players • Computing peripherals • Base stations • FPGAs, DSP, and low-voltage ASIC power ____________________________________________________________________________________________________________ Typical Application MIC5167 ±6A Synchronous Buck DDR Terminator Ramp Control is a trademark of Micrel, Inc. MLF and MicroLeadFrame are registered trademarks of Amkor Technology, Inc. Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com January 2012 M9999-012312-B Micrel, Inc. MIC5167 Ordering Information Part Number Voltage MIC5167YML Adjustable Junction Temperature Range –40°C to +125°C Package 24-Pin 4x4 MLF Lead Finish ® Pb-Free Note: ® MLF is a GREEN RoHS-compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free. Pin Configuration 24-Pin 4mm x 4mm MLF® (ML) Pin Description Pin Number Pin Name 1, 6, 13, 18 PVIN Description Power Supply Voltage (Input): The PVIN pins are the input supply to the internal P-Channel Power MOSFET. A 22µF ceramic is recommended for bypassing at each PVIN pin. The SVIN pin must be connected to the PVIN pin. 2 EN/DLY Enable/Delay (Input): This pin is internally fed with a 1µA current source from SVIN. A delayed turn on is implemented by adding a capacitor to this pin. The delay is proportional to the capacitor value. The internal circuits are held off until EN/DLY reaches the enable threshold of 1.24V. This pin is pulled low when the input voltage is lower than the UVLO threshold. 3 VDDQ VDDQ (Input): VDDQ is connected to an internal precession divider which provides the reference voltage (VREF). 4 VREF VTT Reference (Output): This output provides an output of the internal reference voltage VDDQ/2. Connect a 100pF capacitor to ground at this pin. 5 PG PG (Output): This is an open drain output that indicates when the output voltage is within ±15% of its nominal voltage. The PG flag is asserted without delay when the enable is set low or when the output goes outside ±15% the window threshold. 14 FB Feedback (Input): Input to the error amplifier. 15 COMP Compensation pin (Input): The MIC5167 uses an internal compensation network containing a fixed-frequency zero (phase lead response) and pole (phase lag response) which allows the external compensation network to be much simplified for stability. The addition of a single capacitor and resistor to the COMP pin will add the necessary pole and zero for voltage mode loop stability using low value, low-ESR ceramic capacitors. 16 SGND Signal Ground: Internal signal ground for all low power circuits. January 2012 2 M9999-012312-B Micrel, Inc. MIC5167 Pin Description (Continued) Pin Number Pin Name 17 SVIN Signal Power Supply Voltage (Input): This pin is connected externally to the PVIN pin. A 22µF ceramic capacitor from the SVIN pin to SGND must be placed next to the IC. 7, 12, 19, 24 PGND Power Ground: Internal ground connection to the source of the internal N-Channel MOSFETs. 8, 9, 10, 11, 20, 21, 22, 23 SW EP GND January 2012 Description Switch (Output): This is the connection to the drain of the internal P-Channel MOSFET and drain of the N-Channel MOSFET. This is a high-frequency, high-power connection; therefore traces should be kept as short and as wide as practical. Exposed Pad (Power): Must be connected to a GND plane for full output power to be realized. 3 M9999-012312-B Micrel, Inc. MIC5167 Absolute Maximum Ratings(1,2) Operating Ratings(3) PVIN to PGND.................................................... –0.3V to 6V SVIN to PGND..................................................–0.3V to PVIN VDDQ to PGND .................................................–0.3V to PVIN VSW to PGND...................................................–0.3V to PVIN VEN/DLY to PGND ..............................................–0.3V to PVIN VPG to PGND ...................................................–0.3V to PVIN PGND to SGND ............................................. –0.3V to 0.3V Junction Temperature ................................................ 150°C Storage Temperature Range ....................–65°C to +150°C Lead Temperature (soldering, 10s)............................ 260°C Supply Voltage (PVIN,SVIN) .............................. 2.6V to 5.5V Supply Voltage (VDDQ) .......................................0.7V to PVIN Power-Good (PG) Voltage (VPG)..........................0V to PVIN Enable Input (VEN/DLY)...........................................0V to PVIN Junction Temperature (TJ) ..................–40°C ≤ TJ ≤ +125°C Package Thermal Resistance 4mm x 4mm MLF®-24 (θJC)................................14°C/W 4mm x 4mm MLF®-24 (θJA)................................40°C/W Electrical Characteristics(4) SVIN = PVIN = VEN/DLY = 3.3V, VFB = VTT = 0.6V, TA = 25°C, unless noted. Bold values indicate –40°C< TJ < +125°C. Parameter Condition Min. Typ. Max. Units 5.5 V 2.5 2.6 V 280 0.85 5 1.3 10 mV mA µA 0.6 0.612 V Power Input Supply Input Voltage Range (PVIN) Undervoltage Lockout (UVLO) Trip Level UVLO Hysteresis Quiescent Supply Current Shutdown Current VTT Output VTT Output Voltage Load Regulation Line Regulation FB Pin Bias Current Enable Control EN/DLY Threshold Voltage EN Hysteresis EN/DLY Source Current Oscillator Switching Frequency Maximum Duty Cycle Short-Current Protection Sourcing Current Limit Internal FETs 2.6 PVIN Rising 2.4 VFB = 0.9V (not switching) VEN/DLY = 0V VDDQ =1.2V 0.588 VFB =0.6V, IOUT = -6A to +6A VFB = 0.6V; VIN = 2.6 to 5.5V, ILOAD= 100mA VFB = 0.6V 0.4 0.2 10 1.14 % % nA 1.24 20 1.0 1.34 VEN/DLY = 0.5V; VIN = 2.9V and VIN = 5.5V 0.7 IOUT = 0A VFB ≤ 0.5V 0.8 100 1.0 1.2 MHz % VFB = 0.5V 6.5 9 14 A 1.3 Top-MOSFET RDS(ON) VFB = 0.5V, ISW = 1A 30 Bottom-MOSFET RDS(ON) VFB = 0.9V, ISW = -1A 25 SW Leakage Current PVIN = 5.5V, VSW = 5.5V, VEN = 0V 60 VIN Leakage Current PVIN = 5.5V, VSW = 0V, VEN = 0V 25 January 2012 V mV µA 4 mΩ mΩ µA M9999-012312-B Micrel, Inc. MIC5167 Electrical Characteristics(4) (Continued) SVIN = PVIN = VEN/DLY = 3.3V, VFB = VTT = 0.6V, TA = 25°C, unless noted. Bold values indicate –40°C< TJ < +125°C. Parameter Condition Min. Typ. Max. Threshold % of VTT from VREF ±10 ±15 ±20 Units Power-Good (PG) PG Window Hysteresis PG Output Low Voltage PG Leakage Current Thermal Protection Over-Temperature Shutdown Over-Temperature Shutdown Hysteresis 2.5 IPG = 5mA (sinking), VFB = 0.4V; VEN = VIN 130 mV 1.0 VPG = 5.5V; VFB = 0.625V 2.0 TJ Rising % % μA 160 °C 20 °C Notes: 1. Exceeding the absolute maximum rating may damage the device. 2. Devices are ESD sensitive. Handling precautions recommended. 3. The device is not guaranteed to function outside its operating rating. 4. Specification for packaged product only. January 2012 5 M9999-012312-B Micrel, Inc. MIC5167 Typical Characteristics 20 16 12 8 VTT = 0.6V IOUT = 0A SWITCHING 4 0 3.0 16 0.505 12 8 3.5 4.0 4.5 5.0 0.495 4 VTT = 0.9V IOUT = 0A 0.490 5.5 2.5 3.0 3.5 4.0 4.5 5.0 2.5 5.5 3.0 3.5 4.0 4.5 5.0 INPUT VOLTAGE (V) INPUT VOLTAGE (V) Load Regulation vs. Input Voltage Current Limit vs. Input Voltage VTT/VDDQ Tracking Ratio vs. VDDQ 0.510 20 5.5 VIN = 5.0V VTT = 0.6V CURRENT LIMIT (A) IOUT = 0A to 6A 0.6% 0.4% 0.2% IOUT = 0A 0.505 15 VTT/VDDQ (%) 0.8% 10 5 0.500 0.495 VTT = 0.6V 0.0% 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 0.490 2.5 3.0 Switching Frequency vs. Input Voltage 4.0 4.5 5.0 5.5 1000 950 900 VTT = 0.6V IOUT = 0A 800 3.5 4.0 4.5 INPUT VOLTAGE (V) January 2012 1.0 5.0 5.5 1.2 1.4 1.6 1.8 Power Good Window/VTT Ratio vs. Input Voltage 120% 5 VEN/DLY = 0V 4 3 2 1 110% 100% 90% 80% 70% VTT = 0.6V 60% 0 3.0 0.8 VDDQ (V) VPG WINDOW/VTT (%) ENABLE INPUT CURRENT (µA) 1050 2.5 0.6 Enable Input Current vs. Input Voltage 1100 850 3.5 INPUT VOLTAGE (V) INPUT VOLTAGE (V) SWITCHING FREQUENCY (kHz) 0.500 INPUT VOLTAGE (V) 1.0% TOTAL REGULATION (%) 0.510 0 2.5 VTT/VDDQ Tracking Ratio vs. Input Voltage VEN/DLY = 0V VTT/VDDQ SHUTDOWN CURRENT (µA) 20 SUPPLY CURRENT (mA) VIN Shutdown Current vs. Input Voltage VIN Operating Supply Current vs. Input Voltage 2.5 3.0 3.5 4.0 4.5 INPUT VOLTAGE (V) 6 5.0 5.5 2.5 3.0 3.5 4.0 4.5 5.0 5.5 INPUT VOLTAGE (V) M9999-012312-B Micrel, Inc. MIC5167 Typical Characteristics (Continued) VIN Operating Supply Current vs. Temperature 20 10 VIN = 3.3V VTT = 0.9V 5 IOUT = 0A VDDQ = 1.8V SWITCHING 0 IOUT = 0A VEN/DLY = 0V 12 8 4 10 40 70 100 130 -20 10 40 1.0% LOAD REGULATION (%) VTT = 0.9V IOUT = 0A 0.500 0.495 0.490 70 100 130 -50 10 40 70 100 -0.5% ENABLE INPUT CURRENT (µA) 1000 950 900 VIN = 3.3V VTT = 0.9V IOUT = 0A 800 -20 10 40 70 100 -20 10 40 70 TEMPERATURE (°C) January 2012 IOUT = 0A 0.3% 0.2% 0.1% -50 130 -20 100 130 10 40 70 100 130 TEMPERATURE (°C) Current Limit vs. Temperature 5 20 VIN = 3.3V 4 VEN/DLY = 0V VTT = 0.9V 3 2 1 15 10 5 VIN = 3.3V VTT = 0.9V 0 0 -50 130 VTT = 0.9V Enable Input Current vs. Temperature Switching Frequency vs. Temperature 850 0.4% TEMPERATURE (°C) 1050 100 0.0% -50 TEMPERATURE (°C) 1100 70 VIN = 2.6V to 5.5V IOUT = 0A to 6A 0.0% 130 40 0.5% V IN = 3.3V V TT = 0.9V 0.5% 10 Line Regulation vs. Temperature CURRENT LIMIT (A) -20 -20 TEMPERATURE (°C) -1.0% -50 1.8 Load Regulation vs. Temperature VIN = 3.3V 0.505 Falling TEMPERATURE (°C) VTT/VDDQ Tracking Ratio vs. Temperature 0.510 2.2 1.0 -50 LINE REGULATION (%) -20 2.6 1.4 TEMPERATURE (°C) VTT/VDDQ (%) Rising VIN = 3.3V 16 0 -50 SWITCHING FREQUENCY (kHz) 3.0 VIN THRESHOLD (V) SHUTDOWN CURRENT (uA) SUPPLY CURRENT (mA) 15 VIN UVLO Threshold vs. Temperature VIN Shutdown Current vs. Temperature -50 -20 10 40 70 TEMPERATURE (°C) 7 100 130 -50 -20 10 40 70 100 130 TEMPERATURE (°C) M9999-012312-B Micrel, Inc. MIC5167 Typical Characteristics (Continued) Efficiency vs. Output Current 3.3V IN 90 EFFICIENCY (%) VTT LOAD REGULATION (mV) 10 5.0VIN 85 80 75 VTT = 0.9V VDDQ = 1.8V 1100 0 -10 -20 VIN = 5.0V -30 VTT = 0.6V VDDQ = 1.2V -40 70 0 1 95 2 3 4 5 -6 6 -4 -2 0 2 4 OUTPUT CURRENT (A) OUTPUT CURRENT (A) Efficiency (VIN = 3.3V) vs. Output Current Efficiency (VIN = 5.0V) vs. Output Current 6 1050 1000 950 900 VIN = 5.0V VTT = 0.9V 850 VDDQ = 1.8V 800 0 1 2 3 4 5 OUTPUT CURRENT (A) 95 90 90 VTT 1.8V 1.6V 1.4V 1.2V 85 80 1.0V 0.9V 0.8V VIN = 3.3V 75 EFFICIENCY (%) EFFICIENCY (%) Switching Frequency vs. Output Current SWITCHING FREQUENCY (kHz) 95 VTT Load Regulation vs. Output Current VTT 1.8V 1.6V 1.4V 1.2V 1.0V 0.9V 0.8V 85 80 VIN = 5.0V 75 0.6V 0.6V 70 70 0 1 2 3 4 5 6 OUTPUT CURRENT (A) January 2012 7 8 0 1 2 3 4 5 6 7 8 OUTPUT CURRENT (A) 8 M9999-012312-B 6 Micrel, Inc. MIC5167 Functional Characteristics January 2012 9 M9999-012312-B Micrel, Inc. MIC5167 Functional Diagram Figure 1. MIC5167 Block Diagram January 2012 10 M9999-012312-B Micrel, Inc. MIC5167 Since the voltage across the resistance is VDDQ/2, the power dissipated is one-quarter the power of a termination voltage of VDDQ. The memory bits are not usually all at a logic high or logic low at the same time so the VTT supply is usually not sinking or sourcing much current. Application Information DDR memory requires two power supplies, one for the memory chip, referred to as VDDQ and the other for a termination supply VTT, which is one-half VDDQ. With memory speeds in excess of 300MHz, the memory system bus must be treated as transmission lines. To maintain good signal integrity the memory bus must be terminated to minimize signal reflections. Figure 2 shows the simplified termination circuit. Each control, address and data lines have these termination resistors RS and RT connected to them. VDDQ 1.8V + VDDQ VTT VTT is regulated to VREF. Due to high speed signaling, the load current seen by VTT is constantly changing. To maintain adequate transient response, large OS-CON and ceramics are recommended on VTT. The proper combination and placement of the OS-CON and ceramic capacitors is important to reduce both ESR and ESL such that high-current and high-speed transients do not exceed the dynamic voltage tolerance requirement of VTT. The larger OS-CON capacitors provide bulk charge storage while the smaller ceramic capacitors provide current during the fast edges of the bus transition. Using several smaller ceramic capacitors distributed near the termination resistors is important to reduce the effects of PCB trace inductance. When VTT is sinking current, the external power supply that powers the MIC5167 (PVIN) must be able to sink current-to-ground; otherwise, the supply voltage will start to increase. It is crucial that this external power supply must also be able to source and sink current. VDDQ DDR MEMORY CHIP SET RS + RT VDDQ RS - RT VREF + MIC5167 VDDQ VIN 5.0V 22µF x4 PVIN SVIN PGND FB VDDQ The VDDQ input on the MIC5167 is used to create the internal reference voltage for VTT. The reference voltage is generated from an internal resistor divider network of two 60kΩ resistors, generating a reference voltage VREF that is VDDQ/2. The VDDQ input should be Kelvin connected as close as possible to the memory supply voltage. Since the reference is simply VDDQ/2, any perturbations on VDDQ will also appear at half the amplitude on the reference. For this reason, both ceramics and low-ESR bulk capacitors such as OS-CON are recommended on the VDDQ supply. This will aid in performance by improving the source impedance over a wide frequency range. 0.4µH VTT/0.9V SW 100µF x3 EP SGND VREF 100pF Figure 2. DDR Memory Termination Circuit Bus termination provides a means to increase signaling speed while maintaining good signal integrity. The termination network consists of a series resistor (RS) and a terminating resistor (RT). Values of RS range between 10Ω to 30Ω with a typical of 22Ω, while RT ranges from 22Ω to 28Ω with a typical value of 25Ω. VTT will dynamically sink and source current to maintain a termination voltage under all conditions. This method of bus termination reduces common mode noise, settling time, voltage swings, EMI/RFI and improves slew rates. VDDQ powers all the memory IC’s, memory drivers and receivers for all the memory bits in the DDR memory system. When the driver is logic low VTT sources current. When the driver is logic high VTT sinks current. The MIC5167 regulates VTT to VDDQ/2 during sourcing or sinking current. The power dissipated in RS (bus resistance) and RT (termination resistance) is VTT squared divided by their respective resistance. January 2012 Feedback The feedback (FB) pin provides the path for the error amplifier to regulate VTT. The FB input must also be Kelvin connected to the VTT bypass capacitors. If the FB input is connected to close to the MIC5167, the IR drop of the PCB trace can cause the VTT voltage at the memory chip to be too low. Placing the MIC5167 as close as possible to the DDR memory will improve the load regulation performance. 11 M9999-012312-B Micrel, Inc. MIC5167 VREF can also be manipulated for different applications. A separate voltage source can be used to externally set the reference point, bypassing the divider network. Also, external resistor to VREF divider network can be added to shift the reference point up or down. PWM The MIC5167 is a voltage mode, Pulse Width Modulation (PWM) controller. By controlling the ratio of on-to-off time, or duty cycle, a regulated DC output voltage is achieved. As load or supply voltage changes, so does the duty cycle to maintain a constant output voltage. In cases where the input supply runs into a dropout condition, the MIC5167 will run at 100% duty cycle. The MIC5167 provides constant switching at 1MHz with synchronous internal MOSFETs. The internal MOSFETs include a high-side P-Channel MOSFET from the input supply to the switch pin and an N-Channel MOSFET from the switch pin-to-ground. Since the low-side NChannel MOSFET provides the current during the off cycle, very low power is dissipated during the off period. PWM control provides fixed frequency operation. By maintaining a constant switching frequency, predictable fundamental and harmonic frequencies are achieved. Other methods of regulation, such as burst and skip modes, have frequency spectrums that change with load that can interfere with sensitive communication equipment. The feedback trace is a noise sensitive input and should be routed away from the switch node. A 0.1μF capacitor placed next to the IC can help filter any high frequency noise that may cause VTT errors. Enable/Delay Pin The internal circuits are held off until EN/DLY input reaches the enable threshold of 1.24V. A 1µA current source out of the IC is used to charge the delay capacitor. The delay time is simply the time it takes 1µA to charge CEN/DLY to 1.25V. Therefore: t EN / DLY = 1.24 × CEN / DLY 1× 10 6 The enable/delay pin is pulled low when the input voltage is lower than the UVLO threshold, ensuring that the delay start up voltage starts at zero. Power-Good (PG) The power-good output provides a under and over voltage fault flag. The PG output remains high as long as VTT is within ±15% range of VREF and goes low if output moves beyond this range. VREF A minimum capacitor value of 100pF from VREF-toground is required to remove high-frequency signals reflected from the source (see Figure 3). Large capacitance values (>1500pF) should be avoided. Values greater than 1500pF slow down VREF and detract from the reference voltage’s ability to track VDDQ during high-speed load transients. Component selection Input Capacitor A 22µF X5R or X7R dielectrics ceramic capacitor is recommended on each of the PVIN pins for bypassing. Y5V dielectrics capacitor should not be used. Aside from losing most of their capacitance over temperature, they also become resistive at high frequencies. This reduces their ability to filter out high frequency noise. Output Capacitor The MIC5167 was designed specifically for the use of ceramic output capacitors. The 300µF can be increased to improve transient performance. Since the MIC5167 uses voltage mode control, the control loop is affected by the 180-deg phase shift generated by the complex pole created by the inductor and output capacitor. For this reason, do not use excessively large output capacitors. The output capacitor requires either an X7R or X5R dielectric. Y5V and Z5U dielectric capacitors, aside from the undesirable effect of their wide variation in capacitance over temperature, become resistive at high frequencies. Using Y5V or Z5U capacitors can cause instability in the MIC5167. Figure 3. VREF Follows VDDQ January 2012 12 M9999-012312-B Micrel, Inc. MIC5167 Reduced current draw from a battery increases the devices operating time, critical in hand held devices. There are mainly two loss terms in switching converters: static losses and switching losses. Static losses are simply the power losses due to VI or I2R. For example, power is dissipated in the high-side switch during the on cycle. Power loss is equal to the high-side MOSFET RDS(ON) multiplied by the RMS Switch Current squared (ISW2). During the off-cycle, the low-side N-Channel MOSFET conducts, also dissipating power. Similarly, the inductor’s DCR and capacitor’s ESR also contribute to the I2R losses. Device operating current also reduces efficiency by the product of the quiescent (operating) current and the supply voltage. The current required to drive the gates on and off at a constant 1MHz frequency and the switching transitions make up the switching losses. Figure 4 shows an efficiency curve. The portion, from 0A to 1A, efficiency losses are dominated by quiescent current losses, gate drive, transition and core losses. In this case, lower supply voltages yield greater efficiency in that they require less current to drive the MOSFETs and have reduced input power consumption. Inductor Selection Inductor selection will be determined by the following (not necessarily in the order of importance): • Inductance • Rated current value • Size requirements • DC resistance (DCR) The MIC5167 is designed for use with a 0.4µH to 4.7µH inductor. Maximum current ratings of the inductor are generally given in two methods: permissible DC current and saturation current. Permissible DC current can be rated either for a 40°C temperature rise or a 10% loss in inductance. Ensure the inductor selected can handle the maximum operating current. When saturation current is specified, make sure that there is enough margin that the peak current will not saturate the inductor. The ripple current can add as much as 1.2A to the output current level. The RMS rating should be chosen to be equal or greater than the Current Limit of the MIC5167 to prevent overheating in a fault condition. For best electrical performance, the inductor should be placed very close to the SW nodes of the IC. For this reason, the heat of the inductor is somewhat coupled to the IC, so it offers some level of protection if the inductor gets too hot. It is important to test all operating limits before settling on the final inductor choice. The size requirements refer to the area and height requirements that are necessary to fit a particular design. Please refer to the inductor dimensions on their datasheet. DC resistance is also important. While DCR is inversely proportional to size, DCR can represent a significant efficiency loss. Refer to the “Efficiency Considerations” below for a more detailed description. Efficiency 95 EFFICIENCY (%) 90 VIN = 3.3V VTT = 1.8 70 0 1 2 3 4 5 6 OUTPUT CURRENT (A) Figure 4. Efficiency Curve The region, 1A to 6A, efficiency loss is dominated by MOSFET RDS(ON) and inductor DC losses. Higher input supply voltages will increase the Gate-to-Source voltage on the internal MOSFETs, thereby reducing the internal RDS(ON). This improves efficiency by decreasing DC losses in the device. All but the inductor losses are inherent to the device. In which case, inductor selection becomes increasingly critical in efficiency calculations. As the inductors are reduced in size, the DC resistance (DCR) can become quite significant. The DCR losses can be calculated as follows: ⎞ ⎟⎟ × 100 ⎠ Maintaining high efficiency serves two purposes. It decreases power dissipation in the power supply, reducing the need for heat sinks and thermal design considerations and it decreases consumption of current for battery powered applications. January 2012 80 75 Efficiency Considerations Efficiency is defined as the amount of useful output power, divided by the amount of power consumed. ⎛V ×I Efficiency % = ⎜⎜ OUT OUT ⎝ VIN × IIN 85 LPD = IOUT2 × DCR 13 M9999-012312-B Micrel, Inc. MIC5167 From that, the loss in efficiency due to inductor resistance can be calculated as follows: ⎡ ⎛ VOUT × IOUT Efficiency Loss = ⎢1− ⎜⎜ ⎣⎢ ⎝ (VOUT × IOUT ) + L PD The circuit in Figure 5 describes the operation of the current limit circuit. Since the actual RDS(ON) of the PChannel MOSFET varies part-to-part, over temperature and with input voltage, simple IR voltage detection is not employed. Instead, a smaller copy of the Power MOSFET (Reference FET) is fed with a constant current which is a directly proportional to the factory set current limit. This sets the current limit as a current ratio and thus, is not dependant upon the RDS(ON) value. Current limit is set to nominal value. Variations in the scale factor K between the Power PFET and the reference PFET used to generate the limit threshold account for a relatively small inaccuracy. ⎞⎤ ⎟⎥ × 100 ⎟ ⎠⎦⎥ Efficiency loss due to DCR is minimal at light loads and gains significance as the load is increased. Inductor selection becomes a trade-off between efficiency and size in this case. Alternatively, under lighter loads, the ripple current due to the inductance becomes a significant factor. When light load efficiencies become more critical, a larger inductor value maybe desired. Larger inductances reduce the peakto-peak inductor ripple current, which minimize losses. Compensation The MIC5167 has a combination of internal and external stability compensation to simplify the circuit for small, high efficiency designs. In such designs, voltage mode conversion is often the optimum solution. Voltage mode is achieved by creating an internal 1MHz ramp signal and using the output of the error amplifier to modulate the pulse width of the switch node, thereby maintaining output voltage regulation. With a typical gain bandwidth of 100-200kHz, the MIC5167 is capable of extremely fast transient responses. The MIC5167 is designed to be stable with a typical application using a 1µH inductor and a 100µF ceramic (X5R) output capacitor. These values can be varied dependant upon the tradeoff between size, cost and efficiency, keeping the LC natural frequency 1 ) ideally less than 26kHz to ensure ( 2× π× L C stability can be achieved. The minimum recommended inductor value is 0.4µH and minimum recommended output capacitor value is 100µF. The tradeoff between changing these values is that with a larger inductor, there is a reduced peak-to-peak current which yields a greater efficiency at lighter loads. A larger output capacitor will improve transient response by providing a larger hold up reservoir of energy to the output. PVIN HSD CONTROL LOGIC CLOCK LSD I LIMIT/K PGND Figure 5. Current-Limit Detail Thermal Considerations The MIC5167 is packaged in a MLF® 4mm x 4mm, a package that has excellent thermal performance. This maximizes heat transfer from the junction to the exposed pad (ePAD) which connects to the ground plane. The size of the ground plane attached to the exposed pad determines the overall thermal resistance from the junction to the ambient air surrounding the printed circuit board. Sequencing and Tracking The MIC5167 provides PG and EN/DLY pins to provide sequencing and turn on delay capability for connecting multiple voltage regulators together. Current Limit The MIC5167 is protected against overload in two stages. The first is to limit the current in the P-channel switch; the second is over temperature shutdown. Current is limited by measuring the current through the high-side MOSFET during its power stroke and immediately switching off the driver when the preset limit is exceeded. January 2012 SW PVIN Enable/DLY Pin The Enable pin contains a trimmed, 1µA current source which can be used with a capacitor to implement a fixed desired delay in some sequenced power systems. The threshold level for power on is 1.24V with a hysteresis of 20mV. 14 M9999-012312-B Micrel, Inc. MIC5167 Sequencing Examples Sequencing and turn on delay of the MIC5167 can be easily implemented using the PG and EN/DLY pins. The following diagrams illustrate turn on sequencing and turn on sequencing with delay. Figure 6. VTT Turn-On with Delay January 2012 Figure 7. VTT Turn-On without Delay 15 M9999-012312-B Micrel, Inc. MIC5167 PCB Layout Guidelines Inductor Warning!!! To minimize EMI and output noise, follow these layout recommendations. PCB Layout is critical to achieve reliable, stable and efficient performance. A ground plane is required to control EMI and minimize the inductance in power, signal and return paths. The following guidelines should be followed to insure proper operation of the MIC5167 converter. • Keep the inductor connection to the switch node (SW) short. • Do not route any digital lines underneath or close to the inductor. • Keep the switch node (SW) away from the feedback (FB) pin. • To minimize noise, place a ground plane underneath the inductor. • The inductor can be placed on the opposite side of the PCB with respect to the IC. It does not matter whether the IC or inductor is on the top or bottom as long as there is enough air flow to keep the power components within their temperature limits. The input and output capacitors must be placed on the same side of the board as the IC. Output Capacitor IC • The 22µF ceramic capacitor, which is connected to the SVIN pin, must be located right at the IC. The SVIN pin is very noise sensitive and placement of the capacitor is very critical. Use wide traces to connect to the SVIN and SGND pins. • The signal ground pin (SGND) must be connected directly to the ground planes. Do not route the SGND pin to the PGND Pad on the top layer. • Place the IC close to the point-of-load (POL). • Use fat traces to route the input and output power lines. • Signal and power grounds should be kept separate and connected at only one location. Input Capacitor • A 22µF X5R or X7R dielectrics ceramic capacitor is recommended on each of the PVIN pins for bypassing. • Place the input capacitors on the same side of the board and as close to the IC as possible. • Keep both the PVIN pin and PGND connections short. • Place several vias to the ground plane close to the input capacitor ground terminal. • Use either X7R or X5R dielectric input capacitors. Do not use Y5V or Z5U type capacitors. • Do not replace the ceramic input capacitor with any other type of capacitor. Any type of capacitor can be placed in parallel with the input capacitor. • If a Tantalum input capacitor is placed in parallel with the input capacitor, it must be recommended for switching regulator applications and the operating voltage must be derated by 50%. • In “Hot-Plug” applications, a Tantalum or Electrolytic bypass capacitor must be used to limit the overvoltage spike seen on the input supply with power is suddenly applied. January 2012 16 • Use a wide trace to connect the output capacitor ground terminal to the input capacitor ground terminal. • Phase margin will change as the output capacitor value and ESR changes. Contact the factory if the output capacitor is different from what is shown in the BOM. • The feedback divider network must be place close to the IC with the bottom of R2 connected to SGND. • The feedback trace should be separate from the power trace and connected as close as possible to the output capacitor. Sensing a long high current load trace can degrade the DC load regulation. M9999-012312-B Micrel, Inc. MIC5167 January 2012 20 SW PGND 24 21 SW PGND 19 22 SW PGND 12 7 PGND SW 23 Evaluation Board Schematic 17 M9999-012312-B Micrel, Inc. MIC5167 Bill of Materials Item C1, C2, C3, C4, C5 Part Number Manufacturer C2012X5R0J226M TDK 08056D226MAT AVX Description Qty. 22µF/6.3V Ceramic Capacitor, X5R, 0805 5 GRM21BR60J226ME39L Murata VJ0603A102KXA Vishay 1000pF/50V Ceramic Capacitor, COG, 0603 GRM188R71H102KA01D Murata 1000pF/50V Ceramic Capacitor, X7R, 0603 C1608C0G1H102J TDK 1000pF/50V Ceramic Capacitor, COG, 0603 C7 C1608C0G1H104K TDK 0.1µF/50V Ceramic Capacitor, X7R, 0603 1 C8 C0603X5R1H101M TDK 100pF/50V Ceramic Capacitor, X5R, 0603 1 C9 C1005COG1H470J TDK 47pF/50V Ceramic Capacitor, COG, 0402 1 C10, C11, C12 JMK316BJ107ML-T Taiyo Yuden 100µF/6.3V Ceramic Capacitor, X5R, 1206 3 CIN B41125A3477M000 Epcos 470µF/10V Electrolytic Capacitor, 8x10 1 C6 Coiltronics 1 L1 HCP0704-0R4-R 0.4µH, 12A, size 6.8x6.8x4.2mm 1 R1, R3 CRCW060310K0FKEA Vishay Dale 10.0kΩ Resistor, 0603, 1% 2 R2 CRCW06031K00FKEA Vishay Dale 1.00kΩ Resistor, 0603, 1% 1 Q1 CMDPM7002A Central Semiconductor Signal MOSFET, SOT-23-6 1 U1 MIC5167YML Micrel, Inc. Integrated 6A DDR Regulator 1 Notes: 1. TDK: www.tdk.com 2. AVX: www.avx.com 3. Murata: www.murata.com 4. Vishay: www.vishay.com 5. BC Components: www.bccomponents.com 6. Coiltronics: www.coiltronics.com 7. Central Semiconductor: www.centralsemi.com 8. Micrel, Inc.: www.micrel.com January 2012 18 M9999-012312-B Micrel, Inc. MIC5167 PCB Layout Recommendations MIC5167 Evaluation Board Top Silk MIC5167 Evaluation Board Top Layer January 2012 19 M9999-012312-B Micrel, Inc. MIC5167 PCB Layout Recommendations (Continued) MIC5167 Evaluation Board Mid-Layer 1 (Ground Plane) MIC5167 Evaluation Board Mid-Layer 2 January 2012 20 M9999-012312-B Micrel, Inc. MIC5167 PCB Layout Recommendations (Continued) MIC5167 Evaluation Board Bottom Layer January 2012 21 M9999-012312-B Micrel, Inc. MIC5167 Package Information 24-Pin 4mm x 4mm MLF® (ML) January 2012 22 M9999-012312-B Micrel, Inc. MIC5167 Recommended Land Pattern 24-Pin 4mm x 4mm MLF® Land Pattern MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry, specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2012 Micrel, Incorporated. January 2012 23 M9999-012312-B