www.fairchildsemi.com FAN5059 High Performance Programmable Synchronous DC-DC Controller for Multi-Voltage Platforms Features Applications • Programmable output for Vcore from 1.3V to 3.5V using an integrated 5-bit DAC • Controls adjustable linears for Vagp (selectable 1.5V/3.3V), Vclock (2.5V), and Vtt (1.5V) or Vnorthbridge (1.8V) • Meets VRM specification with as few as 5 capacitors • Meets 1.550V +40/-70mV over initial tolerance, temperature and transients • • • • • • • • • • • Remote sense Programmable Active Droop™ (Voltage Positioning) Drives N-Channel MOSFETs Overcurrent protection using MOSFET sensing 85% efficiency typical at full load Integrated Power Good and Enable/Soft Start functions 24 pin SOIC package Power supply for Pentium® III Camino Platform Power supply for Pentium III Whitney Platform VRM for Pentium III processor Programmable multi-output power supply Description The FAN5059 is a synchronous mode DC-DC controller IC which provides a highly accurate, programmable set of output voltages for multi-voltage platforms such as the Intel Camino, and provides a complete solution for the Intel Whitney and other high-performance processors. The FAN5059 features remote voltage sensing, independently adjustable current limit, and a proprietary Programmable Active Droop™ for optimal converter transient response. The FAN5059 uses a 5-bit D/A converter to program the output voltage from 1.3V to 3.5V. The FAN5059 uses a high level of integration to deliver load Block Diagram +5V VCCA 21 +3.3V 9 +1.5V + - RD PWRGD, OCL 10 VCCP 11 19 + REF OCL + - REF +12V PWRGD, OCL 12 +2.5V + OSC RS 20 24 VCCP 1 HIDRV + 15 14 + - V + Digital Control + 2 VCC 23 LODRV PWRGD, OCL 13 +5V 18 22 3.3/1.5V GNDP 5-Bit DAC 8 7 65 4 VID0 VID2 VID4 VID1 VID3 1.24V Reference Power Good 3 GNDA 17 PWRGD 16 ENABLE/SS Pentium is a registered trademark of Intel Corporation. Programmable Active Droop is a trademark of Fairchild Semiconductor. Rev. 1.0.0 FAN5059 PRODUCT SPECIFICATION currents in excess of 16A from a 5V source with minimal external circuitry. Synchronous-mode operation offers optimum efficiency over the entire specified output voltage range. An on-board precision low TC reference achieves tight tolerance voltage regulation without expensive external components, while Programmable Active Droop™ permits exact tailoring of voltage for the most demanding load transients. The FAN5059 includes linear regulator controllers for Vtt termination (1.5V), Vclock (2.5V), and Vnorthbridge (1.8V) or Vagp (selectable 1.5V/3.3V), each adjustable with an external divider. The FAN5059 also offers integrated functions including Power Good, Output Enable/Soft Start and current limiting, and is available in a 24 pin SOIC package. Pin Assignments HIDRV SW GNDA VID4 VID3 VID2 VID1 VID0 VTTGATE VTTFB VCKGATE VCKFB 1 2 3 4 5 6 7 8 9 10 11 12 FAN5059 24 23 22 21 20 19 18 17 16 15 14 13 VCCP LODRV GNDP VCCA VFB DROOP ILIM PWRGD SS/ENABLE TYPEDET VAGPGATE VAGPFB Pin Definitions Pin Number Pin Name 2 Pin Function Description 1 HIDRV High Side FET Driver. Connect this pin through a resistor to the gate of an N-channel MOSFET. The trace from this pin to the MOSFET gate should be <0.5". 2 SW High side Driver Source and Low side Driver Drain Switching Node. Together with DROOP and ILIM pins allows FET sensing for Vcc current. 3 GNDA Analog Ground. Return path for low power analog circuitry. This pin should be connected to a low impedance system ground plane to minimize ground loops. 4-8 VID0-4 Voltage Identification Code Inputs. These open collector/TTL compatible inputs will program the output voltage over the ranges specified in Table 2. Pull-up resistors are internal to the controller. 9 VTTGATE Gate Driver for VTT Transistor. For 1.5V output. 10 VTTFB Voltage Feedback for VTT. 11 VCKGATE Gate Driver for VCK Transistor. For 2.5V output. 12 VCKFB Voltage Feedback for VCK. 13 VAGPFB Voltage Feedback for VAGP. 14 VAGPGATE Gate Driver for VAGP Transistor. For 3.3/1.5V output. 15 TYPEDET Type Detect. Sets 3.3V or 1.5V for AGP. 16 ENABLE/SS Output Enable. A logic LOW on this pin will disable all outputs. An internal current source allows for open collector control. This pin also doubles as soft start for all outputs. 17 PWRGD Power Good Flag. An open collector output that will be logic LOW if any output voltage is more than ±12% outside of the nominal output voltage setpoint. 18 ILIM Vcc Current Feedback. Pin 18 is used in conjunction with pin 2 as the input for the Vcc current feedback control loop. Layout of these traces is critical to system performance. See Application Information for details. 19 DROOP Droop set. Use this pin to set magnitude of active droop. 20 VFB Vcc Voltage Feedback. Pin 20 is used as the input for the Vcc voltage feedback control loop. See Application Information for details regarding correct layout. 21 VCCA Analog VCC. Connect to system 5V supply and decouple with a 0.1µF ceramic capacitor. 22 GNDP Power Ground. Return pin for high currents flowing in pin 24 (VCCP). 23 LODRV Vcc Low Side FET Driver. Connect this pin through a resistor to the gate of an N-channel MOSFET for synchronous operation. The trace from this pin to the MOSFET gate should be <0.5". 24 VCCP Power VCC. For all FET drivers. Connect to system 12V supply through a 33Ω, and decouple with a 1µF ceramic capacitor. REV. 1.0.0 7/13/00 PRODUCT SPECIFICATION FAN5059 Absolute Maximum Ratings Supply Voltage VCCA to GND 13.5V Supply Voltage VCCP to GND 15V Voltage Identification Code Inputs, VID0-VID4 VCCA All Other Pins 13.5V Junction Temperature, TJ 150°C Storage Temperature -65 to 150°C Lead Soldering Temperature, 10 seconds 300°C Thermal Resistance Junction-to-ambient, ΘJA1 75°C/W Note: 1. Component mounted on demo board in free air. Recommended Operating Conditions Parameter Conditions Min. Typ. Max. Units Supply Voltage VCCA 4.5 5 5.25 V Input Logic HIGH 2.0 0.8 V 70 °C 13.2 V V Input Logic LOW Ambient Operating Temperature 0 Output Driver Supply, VCCP 10.8 12 Electrical Specifications (VCCA = 5V, VCCP = 12V, VOUT = 2.0V, and TA = +25°C using circuit in Figure 1 unless otherwise noted.) The • denotes specifications which apply over the full operating temperature range. Parameter Conditions Min. Typ. Max. Units 3.5 V VCC Regulator Output Voltage See Table 1 • 1.3 Output Current 18 A Initial Voltage Setpoint ILOAD = 0.8A,VOUT = 2.400V VOUT = 2.000V VOUT = 1.550V Output Temperature Drift TA = 0 to 70°C,VOUT = 2.000V VOUT = 1.550V • • +8 +6 mV mV Line Regulation VIN = 4.75V to 5.25V • -4 mV/V Internal Droop Impedance ILOAD = 0.8A to 12.5A 2.397 2.000 1.550 13.0 Maximum Droop 2.424 2.020 1.565 14.4 2.454 2.040 1.580 15.8 60 V V V KΩ mV Output Ripple 20MHz BW, ILOAD = 18A Total Output Variation, Steady State1 VOUT = 2.000V VOUT = 1.550V3 • • 1.940 1.480 2.070 1.590 V Total Output Variation, Transient2 ILOAD = 0.8A to 18A, VOUT = 2.000V VOUT = 1.550V3 • • 1.900 1.480 2.100 1.590 V • 45 60 µA Short Circuit Detect Current 11 50 mVpk Efficiency ILOAD = 18A, VOUT = 2.0V 85 % Output Driver Rise & Fall Time See Figure 3 50 nsec Output Driver Deadtime See Figure 3 50 nsec REV. 1.0.0 7/13/00 3 FAN5059 PRODUCT SPECIFICATION Electrical Specifications (Continued) (VCCA = 5V, VCCP = 12V, VOUT = 2.0V, and TA = +25°C using circuit in Figure 1 unless otherwise noted.) The • denotes specifications which apply over the full operating temperature range. Parameter Conditions Min. Duty Cycle Typ. 0 Max. Units 100 % 5V UVLO • 3.74 4 4.26 V 12V UVLO • 7.65 8.5 9.35 V Soft Start Current • 5 10 17 µA • 1.455 1.5 1.545 V VTT Linear Regulator Output Voltage ILOAD ≤ 2A Under Voltage Trip Level Over Current 80 %VO VCLK Linear Regulator Output Voltage ILOAD ≤ 2A Under Voltage Trip Level Over Current • 2.375 2.5 2.625 80 V %VO VAGP Linear Regulator Output Voltage ILOAD ≤ 2A, TYPEDET=0V • 1.425 1.5 1.575 V Output Voltage ILOAD ≤ 2A, TYPEDET=OPEN • 3.135 3.3 3.465 V Under Voltage Trip Level Over Current 80 %VO Common Functions Oscillator Frequency PWRGD Threshold Logic HIGH, All Outputs Logic LOW, Any Output Linear Regulator Under Voltage Over Current Delay Time • 255 • • 88 84 310 30 345 kHz 112 116 %VOUT µsec Notes: 1. Steady State Voltage Regulation includes Initial Voltage Setpoint, Droop, Output Ripple and Output Temperature Drift and is measured at the converter’s VFB sense point. 2. As measured at the converter’s VFB sense point. For motherboard applications, the PCB layout should exhibit no more than 0.5mΩ trace resistance between the converter’s output capacitors and the CPU. Remote sensing should be used for optimal performance. 3. Using the VFB pin for remote sensing of the converter’s output at the load, the converter will be in compliance with Intel’s VRM 8.4 specification of +50, –80mV. If Intel specifications on maximum plane resistance from the converter’s output capacitors to the CPU are met, the specification of +40, –70mV at the capacitors will also be met. 4 REV. 1.0.0 7/13/00 PRODUCT SPECIFICATION FAN5059 Table 1. Output Voltage Programming Codes VID4 VID3 VID2 VID1 VID0 Nominal VOUT 0 1 1 1 1 1.30V 0 1 1 1 0 1.35V 0 1 1 0 1 1.40V 0 1 1 0 0 1.45V 0 1 0 1 1 1.50V 0 1 0 1 0 1.55V 0 1 0 0 1 1.60V 0 1 0 0 0 1.65V 0 0 1 1 1 1.70V 0 0 1 1 0 1.75V 0 0 1 0 1 1.80V 0 0 1 0 0 1.85V 0 0 0 1 1 1.90V 0 0 0 1 0 1.95V 0 0 0 0 1 2.00V 0 0 0 0 0 2.05V 1 1 1 1 1 2.0V 1 1 1 1 0 2.1V 1 1 1 0 1 2.2V 1 1 1 0 0 2.3V 1 1 0 1 1 2.4V 1 1 0 1 0 2.5V 1 1 0 0 1 2.6V 1 1 0 0 0 2.7V 1 0 1 1 1 2.8V 1 0 1 1 0 2.9V 1 0 1 0 1 3.0V 1 0 1 0 0 3.1V 1 0 0 1 1 3.2V 1 0 0 1 0 3.3V 1 0 0 0 1 3.4V 1 0 0 0 0 3.5V Note: 1. 0 = processor pin is tied to GND. 1 = processor pin is open. REV. 1.0.0 7/13/00 5 FAN5059 PRODUCT SPECIFICATION Typical Operating Characteristics (VCCA = 5V, VCCP = 12V, and TA = +25°C using circuits in Figure 1, unless otherwise noted.) Droop, VCPU = 2.0V, RD = 8K Ω VCPU Efficiency vs. Output Current 2.04 2.03 VOUT = 2.000V 86 84 82 80 2.02 2.01 2.00 VOUT = 1.550V VOUT (V) Efficiency (%) 88 78 76 74 1.99 1.98 1.97 1.96 72 70 1.95 1.94 68 66 64 0 3 6 9 12 15 18 Output Current (A) 0 3 6 9 12 Output Current (A) 15 18 CPU Output Voltage vs. Output Current 3.5 3.0 VOUT (V) 2.5 2.0 1.5 1.0 0.5 0 0 5 10 15 20 25 Output Current (A) Output Programming, VID4 = 1 2.1 3.5 1.9 3.0 1.7 2.5 VCPU(V) VCPU(V) Output Programming, VID4 = 0 1.5 1.3 1.5 1.1 1.0 1.30 1.40 1.50 1.60 1.70 DAC Setpoint 6 2.0 1.80 1.90 2.00 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2. 3.3 3.4 3.5 DAC Setpoint REV. 1.0.0 7/13/00 PRODUCT SPECIFICATION FAN5059 Typical Operating Characteristics (continued) Transient Response, 12.5A to 0.5A VCPU (50mV/div) VCPU (20mV/div) Output Ripple, 2.0V @ 18A 1.590V 1.550V 1.480V Time (100µs/div) Time (1µs/div) Switching Waveforms, 18A Load VCPU (50mV/div) 5V/div Transient Response, 0.5A to 12.5A HIDRV pin 1.550V 5V/div 1.590V LODRV pin 1.480V Time (1µs/div) Time (100µs/div) Output Startup from Enable VCPU (1V/div) VIN (2V/div) VCPU (1V/div) ENABLE (2V/div) Output Startup, System Power-up Time (10ms/div) REV. 1.0.0 7/13/00 Time (10ms/div) 7 FAN5059 PRODUCT SPECIFICATION Typical Operating Characteristics (continued) Linear Regulator Noise AC COUPLED VOUT (10mV/div) 2.042 2.040 VCPU (V) 2.038 2.036 2.034 2.030 2.028 2.026 0 25 70 100 Time (100µs/div) Temperature (°C) Application Circuit L1 (Optional) +5V CIN* C1 R6 R7 R5 C2 R2 Q1 L2 1 2 3 VO COUT* Q2 R3 D1 3.3V IN Q3 C10 C11 1.5V† Q4 VID4 VID3 VID2 VID1 VID0 4 5 6 7 8 9 10 11 12 R1 24 23 22 U1 FAN5059 21 20 19 18 17 16 15 14 +12V C5 C3 VCC R4 PWRGD ENABLE/SS TYPEDET 13 C7 C8 C6 C4 Q5 3.3/1.5V (AGP)† 2.5V† C9 C12 * Refer to Appendix for values of CIN, COUT, R5 and R7. † Adjustable with an external divider. Figure 1. Typical Application Circuit (Worst Case Analyzed! See Appendix for Details) 8 REV. 1.0.0 7/13/00 PRODUCT SPECIFICATION FAN5059 Table 2. FAN5059 Application Bill of Materials (Components based on Worst Case Analysis—See Appendix for Details) Reference Manufacturer Part # Quantity Description Requirements/Comments C1 AVX TAJB475M010R5 1 4.7µF, 10V Capacitor C2, C5 Panasonic ECU-V1C105ZFX 2 1µF, 16V Capacitor C3-4,C6 Panasonic ECU-V1H104ZFX 3 100nF, 50V Capacitor C7-9 Sanyo 6MV1000FA 3 1000µF, 6.3V Electrolytic C10-12 Any 3 22µF, 6.3V Capacitor Low ESR CIN Sanyo 10MV1200GX * 1200µF, 10V Electrolytic IRMS = 2A COUT Sanyo 6MV1500GX * 1500µF, 6.3V Electrolytic ESR ≤ 44mΩ D1 Motorola MBRD835L 1 8A Schottky Diode L1 Any Optional 2.5µH, 8A Inductor DCR ~ 10mΩ See Note 1. L2 Any 1 1.3µH, 20A Inductor DCR ~ 2mΩ Q1 Fairchild FDB6030L 1 N-Channel MOSFET RDS(ON) = 20mΩ @ VGS = 4.5V See Note 2. Q2 Fairchild FDB7030BL 1 N-Channel MOSFET RDS(ON) = 10mΩ @ VGS = 4.5V See Note 2. Q3-5 Fairchild FDB4030L 3 N-Channel MOSFET R1 Any 1 33Ω R2-3 Any 2 4.7Ω R4 Any 1 10KΩ R5 Any 1 * R6 Any 1 10Ω R7 Any 1 * U1 Fairchild FAN5059M 1 DC/DC Controller Notes: 1. Inductor L1 is recommended to isolate the 5V input supply from noise generated by the MOSFET switching, and to comply with Intel dI/dt requirements. L1 may be omitted if desired. 2. For 17.4A designs using the TO-220 MOSFETs, heatsinks with thermal resistance ΘSA < 20°C/W should be used. For designs using the TO-263 MOSFETs, adequate copper area should be used. For details and a spreadsheet on MOSFET selections, refer to Applications Bulletins AB-8 and AB-15. *Refer to Appendix for values. REV. 1.0.0 7/13/00 9 FAN5059 PRODUCT SPECIFICATION L1 (Optional) +5V CIN* C1 R6 R7 R5 C2 R8 R2 Q1 L2 1 2 3 VO COUT* Q2 R3 D1 3.3V IN Q3 C10 C11 1.5V† Q4 VID4 VID3 VID2 VID1 VID0 4 5 6 7 8 9 10 11 12 R1 24 23 22 U1 FAN5059 21 20 19 18 17 16 15 14 +12V C5 C3 VCC R4 PWRGD ENABLE/SS TYPEDET 13 C7 C8 C6 C4 Q5 3.3/1.5V (AGP)† 2.5V† C12 C9 *Refer to Table 4 for values of COUT and CIN. † Adjustable with an external divider. Figure 2. Application Circuit for Coppermine/Camino Motherboards (Typical Design) 10 REV. 1.0.0 7/13/00 PRODUCT SPECIFICATION FAN5059 Table 3. FAN5059 Application Bill of Materials for Intel Coppermine/Camino Motherboards (Typical Design) Reference Manufacturer Part # C1 AVX TAJB475M010R5 Quantity 1 4.7µF, 10V Capacitor Description C2, C5 Panasonic ECU-V1C105ZFX 2 1µF, 16V Capacitor C3-4,C6 Panasonic ECU-V1H104ZFX 3 100nF, 50V Capacitor C7-9 Sanyo 6MV1000FA 3 1000µF, 6.3V Electrolytic C10-12 Any 3 22µF, 6.3V Capacitor Low ESR CIN Sanyo 10MV1200GX 3 1200µF, 10V Electrolytic IRMS = 2A COUT Sanyo 6MV1500GX 12 1500µF, 6.3V Electrolytic ESR ≤ 44mΩ D1 Motorola MBRD835L 1 8A Schottky Diode L1 Any Optional 2.5µH, 5A Inductor DCR ~ 10mΩ See Note 1. L2 Any 1 1.3µH, 15A Inductor DCR ~ 3mΩ Q1 Fairchild FDB6030L 1 N-Channel MOSFET RDS(ON) = 20mΩ @ VGS = 4.5V See Note 2. Q2 Fairchild FDB7030BL 1 N-Channel MOSFET RDS(ON) = 10mΩ @ VGS = 4.5V See Note 2. Q3-5 Fairchild FDB4030L 3 N-Channel MOSFET R1 Any 1 33Ω R2-3 Any 2 4.7Ω R4 Any 1 10KΩ R5, R7 Any 2 6.24KΩ R6 Any 1 10Ω R8 N/A 1 3.0mΩ U1 Fairchild FAN5059M 1 DC/DC Controller Requirements/Comments PCB Trace Resistor Notes: 1. Inductor L1 is recommended to isolate the 5V input supply from noise generated by the MOSFET switching, and to comply with Intel dI/dt requirements. L1 may be omitted if desired. 2. For 12.5A designs using the TO-220 MOSFETs, heatsinks with thermal resistance ΘSA < 20°C/W should be used. For designs using the TO-263 MOSFETs, adequate copper area should be used. For details and a spreadsheet on MOSFET selections, refer to Applications Bulletins AB-8 and AB-15. REV. 1.0.0 7/13/00 11 FAN5059 PRODUCT SPECIFICATION Test Parameters High Current Output Drivers tR tF 5V 2V HIDRV to SW 5V 2V t DT 2V tDT 2V LODRV Figure 3. Ouput Drive Timing Diagram The FAN5059 contains two identical high current output drivers that utilize high speed bipolar transistors in a push-pull configuration. The drivers’ power and ground are separated from the chip’s power and ground for switching noise immunity. The power supply pin, VCCP, is supplied from an external 12V source through a series 33Ω resistor. The resulting voltage is sufficient to provide the gate to source drive to the external MOSFETs required in order to achieve a low RDS,ON. Internal Voltage Reference The FAN5059 is a programmable synchronous DC-DC controller IC. When designed around the appropriate external components, the FAN5059 can be configured to deliver more than 16A of output current, as appropriate for the Katmai and Coppermine and other processors. The FAN5059 functions as a fixed frequency PWM step down regulator. The reference included in the FAN5059 is a precision bandgap voltage reference. Its internal resistors are precisely trimmed to provide a near zero temperature coefficient (TC). Based on the reference is the output from an integrated 5-bit DAC. The DAC monitors the 5 voltage identification pins, VID0-4. When the VID4 pin is at logic HIGH, the DAC scales the reference voltage from 2.0V to 3.5V in 100mV increments. When VID4 is pulled LOW, the DAC scales the reference from 1.30V to 2.05V in 50mV increments. All VID codes are available, including those below 1.80V. Main Control Loop Power Good (PWRGD) Refer to the FAN5059 Block Diagram on page 1. The FAN5059 implements “summing mode control”, which is different from both classical voltage-mode and current-mode control. It provides superior performance to either by allowing a large converter bandwidth over a wide range of output loads. The FAN5059 Power Good function is designed in accordance with the Pentium II and III DC-DC converter specifications and provides a continuous voltage monitor on the VFB pin. The circuit compares the VFB signal to the VREF voltage and outputs an active-low interrupt signal to the CPU should the power supply voltage deviate more than ±16% of its nominal setpoint. Power Good outputs an open collector high when the output voltage is within ±12% of its nominal setpoint. The Power Good flag provides no other control function to the FAN5059. Application Information The FAN5059 Controller The control loop of the regulator contains two main sections: the analog control block and the digital control block. The analog section consists of signal conditioning amplifiers feeding into a comparator which provides the input to the digital control block. The signal conditioning section accepts input from the DROOP (current feedback) and VFB (voltage feedback) pins and sets up two controlling signal paths. The first, the voltage control path, amplifies the difference between the VFB signal and the reference voltage from the DAC and presents the output to one of the summing amplifier inputs. The second, current control path, takes the difference between the DROOP and SW pins when the high-side MOSFET is on, reproducing the voltage across the MOSFET and thus the input current; it presents the resulting signal to another input of the summing amplifier. These two signals are then summed together. This output is then presented to a comparator looking at the oscillator ramp, which provides the main PWM control signal to the digital control block. The digital control block takes the analog comparator input and the main clock signal from the oscillator to provide the appropriate pulses to the HIDRV and LODRV output pins. These two outputs control the external power MOSFETs. There is an additional comparator in the analog control section whose function is to set the point at which the FAN5059 current limit comparator disables the output drive signals to the external power MOSFETs. 12 Output Enable/Soft Start (ENABLE/SS) The FAN5059 will accept an open collector/TTL signal for controlling the output voltage. The low state disables the output voltage. When disabled, the PWRGD output is in the low state. Even if an enable is not required in the circuit, this pin should have attached a capacitor (typically 100nF) to softstart the switching. A larger value may occasionally be required if the converter has a very large capacitor at its output. Over-Voltage Protection The FAN5059 constantly monitors the output voltage for protection against over-voltage conditions. If the voltage at the VFB pin exceeds the selected program voltage, an over-voltage condition is assumed and the FAN5059 disables the output drive signal to the external high-side MOSFET. The DCDC converter returns to normal operation after the output voltage returns to normal levels. Oscillator The FAN5059 oscillator section uses a fixed frequency of operation of 300KHz. REV. 1.0.0 7/13/00 PRODUCT SPECIFICATION FAN5059 Design Considerations and Component Selection Additional information on design and component selection may be found in Fairchild’s Application Note 57. MOSFET Selection This application requires N-channel Logic Level Enhancement Mode Field Effect Transistors. Desired characteristics are as follows: • Low Static Drain-Source On-Resistance, RDS,ON < 20mΩ (lower is better) • Low gate drive voltage, VGS = 4.5V rated Some margin should be maintained away from both Lmin and Lmax. Adding margin by increasing L almost always adds expense since all the variables are predetermined by system performance except for CO, which must be increased to increase L. Adding margin by decreasing L can be done by purchasing capacitors with lower ESR. The FAN5059 provides significant cost savings for the newer CPU systems that typically run at high supply current. FAN5059 Short Circuit Current Characteristics The FAN5059 protects against output short circuit on the core supply by turning off both the high-side and low-side MOSFETs and resetting softstart. The short circuit limit is set with the RS resistor, as given by the formula • Power package with low Thermal Resistance • Drain-Source voltage rating > 15V. RS = The on-resistance (RDS,ON) is the primary parameter for MOSFET selection. The on-resistance determines the power dissipation within the MOSFET and therefore significantly affects the efficiency of the DC-DC Converter. For details and a spreadsheet on MOSFET selection, refer to Applications Bulletin AB-8. Inductor Selection Choosing the value of the inductor is a tradeoff between allowable ripple voltage and required transient response. The system designer can choose any value within the allowed minimum to maximum range in order to either minimize ripple or maximize transient performance. The first order equation (close approximation) for minimum inductance is: Lmin = (Vin – Vout) x Vout Vin f ESR x ISC *RDS, on IDetect with IDetect ≈ 50µA, ISC is the desired current limit, and RDS,on the high-side MOSFET’s on resistance. Remember to make the RS large enough to include the effects of initial tolerance and temperature variation on the MOSFET’s RDS,on. Alternately, use of a sense resistor in series with the source of the MOSFET eliminates this source of inaccuracy in the current limit. The value of RS should be less than 8.3KΩ. If a greater value is necessary, a lower RDS,on MOSFET should be used instead. As an example, Figure 4 shows the typical characteristic of the DC-DC converter circuit with an FDB6030L high-side MOSFET (RDS = 20mΩ maximum at 25°C * 1.25 at 75°C = 25mΩ) and a 8.2KΩ RS. Vripple CPU Output Voltage vs. Output Current The first order equation for maximum allowed inductance is: 3.5 3.0 2.5 VOUT (V) where: Vin = Input Power Supply Vout = Output Voltage f = DC/DC converter switching frequency ESR = Equivalent series resistance of all output capacitors in parallel Vripple = Maximum peak to peak output ripple voltage budget. 2.0 1.5 1.0 0.5 0 Lmax = 2CO (Vin – Vout) Dm Vtb Ipp2 where: Co = The total output capacitance Ipp = Maximum to minimum load transient current Vtb = The output voltage tolerance budget allocated to load transient Dm = Maximum duty cycle for the DC/DC converter (usually 95%). REV. 1.0.0 7/13/00 0 5 10 15 20 25 Figure 4. FAN5059 Short Circuit Characteristic The converter exhibits a normal load regulation characteristic until the voltage across the MOSFET exceeds the internal short circuit threshold of 50µA * 8.2KΩ = 410mV, which occurs at 410mV/25mΩ = 16.4A. (Note that this current limit level can be as high as 410mV/15mΩ = 27A, if the MOSFET has typical RDS,on rather than maximum, and is at 25°C). 13 FAN5059 At this point, the internal comparator trips and signals the controller to discharge the softstart capacitor. This causes a drastic reduction in the output voltage as the load regulation collapses into the short circuit control mode. With a 40mΩ output short, the voltage is reduced to 16.4A * 40mΩ = 650mV. The output voltage does not return to its nominal value until the output current is reduced to a value within the safe operating ranges for the DC-DC converter. If any of the linear regulator outputs are loaded heavily enough that their output voltage drops below 80% of nominal for >30µsec, all FAN5059 outputs, including the switcher, are shut off and remain off until power is recycled. PRODUCT SPECIFICATION It is necessary to have some low ESR aluminum electrolytic capacitors at the input to the converter. These capacitors deliver current when the high side MOSFET switches on. Figure 5 shows 3 x 1000µF, but the exact number required will vary with the speed and type of the processor. For the top speed Katmai and Coppermine, the capacitors should be rated to take 9A and 6A of ripple current respectively. Capacitor ripple current rating is a function of temperature, and so the manufacturer should be contacted to find out the ripple current rating at the expected operational temperature. For details on the design of an input filter, refer to Applications Bulletin AB-15. 2.5µH Schottky Diode Selection The application circuit of Figure 1 shows a Schottky diode, D1, which is used as a free-wheeling diode to assure that the body-diode in Q2 does not conduct when the upper MOSFET is turning off and the lower MOSFET is turning on. It is undesirable for this diode to conduct because its high forward voltage drop and long reverse recovery time degrades efficiency, and so the Schottky provides a shunt path for the current. Since this time duration is very short, the selection criterion for the diode is that the forward voltage of the Schottky at the output current should be less than the forward voltage of the MOSFET’s body diode. Output Filter Capacitors The output bulk capacitors of a converter help determine its output ripple voltage and its transient response. It has already been seen in the section on selecting an inductor that the ESR helps set the minimum inductance, and the capacitance value helps set the maximum inductance. For most converters, however, the number of capacitors required is determined by the transient response and the output ripple voltage, and these are determined by the ESR and not the capacitance value. That is, in order to achieve the necessary ESR to meet the transient and ripple requirements, the capacitance value required is already very large. The most commonly used choice for output bulk capacitors is aluminum electrolytics, because of their low cost and low ESR. The only type of aluminum capacitor used should be those that have an ESR rated at 100kHz. Consult Application Bulletin AB-14 for detailed information on output capacitor selection. Vin 5V 1000µF, 10V Electrolytic 0.1µF Figure 5. Input Filter Programmable Active Droop™ The FAN5059 includes Programmable Active Droop™: as the output current increases, the output voltage drops, and the amount of this drop is user adjustable. This is done in order to allow maximum headroom for transient response of the converter. The current is typically sensed by measuring the voltage across the RDS,on of the high-side MOSFET during its on time, as shown in Figure 1. To program the amount of droop, use the formula RD 14.4KΩ *Imax *Rsense VDroop *18 where Imax is the current at which the droop occurs, and Rsense is the resistance of the current sensor, either the source resistor or the high-side MOSFET’s on-resistance. For example, to get 30mV of droop with a maximum output current of 12.5A and a 10mΩ sense resistor, use RD = 14.4KΩ * 12.5A * 10mΩ/ (30mV * 18) = 3.33KΩ. Further details on use of the Programmable Active Droop™ may be found in Applications Bulletin AB-24. Remote Sense The output capacitance should also include a number of small value ceramic capacitors placed as close as possible to the processor; 0.1µF and 0.01µF are recommended values. Input Filter The DC-DC converter design may include an input inductor between the system +5V supply and the converter input as shown in Figure 5. This inductor serves to isolate the +5V supply from the noise in the switching portion of the DC-DC converter, and to limit the inrush current into the input capacitors during power up. A value of 2.5µH is recommended. 14 The FAN5059 offers remote sense of the output voltage to minimize the output capacitor requirements of the converter. It is highly recommended that the remote sense pin, Pin 20, be tied directly to the processor power pins, so that the effects of power plane impedance are eliminated. Further details on use of the remote sense feature of the FAN5059 may be found in Applications Bulletin AB-24. REV. 1.0.0 7/13/00 PRODUCT SPECIFICATION FAN5059 Adjusting the Linear Regulators’ Output Voltages Any or all of the linear regulators’ outputs may be adjusted high to compensate for voltage drop along traces, as shown in Figure 6. VGATE VOUT R VFB 10KΩ Figure 6. Adjusting the Output Voltage of the Linear Regulator The resistor value should be chosen as R = 10KΩ* Vout Vnom –1 For example, to get the VTT voltage to be 1.55V instead of 1.50V, use R = 10KΩ * [(1.55/1.50) – 1] = 333Ω. Using the FAN5059 for Vnorthbridge = 1.8V In some motherboards, Intel requires that the AGP power can not be greater than 2.2V while the chipset voltage (Vnorthbridge = 1.8V) is less than 1.0V. The FAN5059 can accomplish this by using the VTT regulator to generate Vnorthbridge. Use the circuit in Figure 6 with R = 2KΩ. Since the linear regulators on the FAN5059 all rise proportionally to one another, when Vnorthbridge = 1.0V, Vagp = 1.8V, meeting the Intel requirement. • Place the 0.1µF decoupling capacitors as close to the FAN5059 pins as possible. Extra lead length on these reduces their ability to suppress noise. • Each VCC and GND pin should have its own via to the appropriate plane. This helps provide isolation between pins. • Place the MOSFETs, inductor, and Schottky as close together as possible for the same reasons as in the first bullet above. Place the input bulk capacitors as close to the drains of the high side MOSFETs as possible. In addition, placement of a 0.1µF decoupling cap right on the drain of each high side MOSFET helps to suppress some of the high frequency switching noise on the input of the DC-DC converter. • Place the output bulk capacitors as close to the CPU as possible to optimize their ability to supply instantaneous current to the load in the event of a current transient. Additional space between the output capacitors and the CPU will allow the parasitic resistance of the board traces to degrade the DC-DC converter’s performance under severe load transient conditions, causing higher voltage deviation. For more detailed information regarding capacitor placement, refer to Application Bulletin AB-5. • A PC Board Layout Checklist is available from Fairchild Applications. Ask for Application Bulletin AB-11. Additional Information For additional information contact Fairchild Semiconductor at http://www.fairchildsemi.com/cf/tsg.htm or contact an authorized representative in your area. PCB Layout Guidelines • Placement of the MOSFETs relative to the FAN5059 is critical. Place the MOSFETs such that the trace length of the HIDRV and LODRV pins of the FAN5059 to the FET gates is minimized. A long lead length on these pins will cause high amounts of ringing due to the inductance of the trace and the gate capacitance of the FET. This noise radiates throughout the board, and, because it is switching at such a high voltage and frequency, it is very difficult to suppress. • In general, all of the noisy switching lines should be kept away from the quiet analog section of the FAN5059. That is, traces that connect to pins 1, 2, 23, and 24 (HIDRV, SW, LODRV and VCCP) should be kept far away from the traces that connect to pins 3, 20 and 21. REV. 1.0.0 7/13/00 15 FAN5059 PRODUCT SPECIFICATION The value of R7 must be ≤ 8.3KΩ. If a greater value is calculated, RD must be reduced. Appendix Worst-Case Formulae for the Calculation of Cin, Cout , R5, R7 and Roffset (Circuits similar to Figure 1 only) The following formulae design the FAN5059 for worst-case operation, including initial tolerance and temperature dependence of all of the IC parameters (initial setpoint, reference tolerance and tempco, internal droop impedance, current sensor gain), the initial tolerance and temperature dependence of the MOSFET, and the ESR of the capacitors. The following information must be provided: Number of capacitors needed for Cout = the greater of: ESR * IO X = VT- + VS+ – .024 * Vnom or VS+, the value of the positive static voltage limit; ESR * IO Y= |VS-|, the absolute value of the negative static voltage limit; 14400 * IO * RD VT+ – VS+ + 18 * R5 * 1.1 VT+, the value of the positive transient voltage limit; |VT-|, the absolute value of the negative transient voltage limit; Vin, the input voltage (typically 5V); Example: Suppose that the static limits are +89mV/-79mV, transient limits are ±134mV, current I is 14.2A, and the nominal voltage is 2.000V, using MOSFET current sensing. We have VS+ = 0.089, |VS-| = 0.079, VT+ = |VT-| = 0.134, IO = 14.2, Vnom = 2.000, and ∆RD = 1.67. We calculate: Irms, the ripple current rating of the input capacitors, per cap (2A for the Sanyo parts shown in this datasheet); Since Y > X, we choose Y, and round up to find we need 7 capacitors for COUT. RD, the resistance of the current sensor (usually the MOSFET); A detailed explanation of this calculation may be found in Applications Bulletin AB-24. IO, the maximum output current; Vnom, the nominal output voltage; ∆RD, the tolerance of the current sensor (usually about 67% for MOSFET sensing, including temperature); and ESR, the ESR of the output capacitors, per cap (44mΩ for the Sanyo parts shown in this datasheet). 2.000 14.2 * 5 – 2.000 2 5 = 3.47 ⇒ 4 caps Cin = 2 IO * Vnom – Vin 2 Vnom Vin Roffset = 0.089 – .024 * 2.000 *1000 = 20.3Ω 1.01 * 2.000 Cin = Irms R7 = Roffset = VS+ – .024 * Vnom 14.2 * 0.010 * (1 + 0.67) = 5.25KΩ 45 * 10-6 * 1KΩ 1.01 * Vnom R5 = 14400 * 14.2 * 0.020 * (1 + 0.67) * 1.1 = 3.48KΩ 18 * (0.089 + 0.079 – .024 * 2.000) R7 = IO* RD * (1 + ∆RD) 45 * 10-6 14400 * IO* RD * (1 + ∆RD) *1.1 R5 = 18 * (VS+ + VS- – .024 * Vnom) 16 X= 0.044 * 14.2 = 3.57 0.134 + 0.089 – .024 * 2.00 0.044 * 14.2 = 6.14 Y = 0.134 – 0.089 + 14400 * 14.2 * 0.020 18 * 3640 * 1.1 REV. 1.0.0 7/13/00 PRODUCT SPECIFICATION FAN5059 Mechanical Dimensions 24 Lead SOIC Inches Symbol Notes: Millimeters Notes Min. Max. Min. Max. A A1 B C D .093 .004 .013 .009 .599 .104 .012 2.35 0.10 0.33 0.23 15.20 2.65 0.30 E e H h L N α ccc .290 .299 .050 BSC .394 .419 7.36 7.60 1.27 BSC 10.00 10.65 .010 .016 0.25 0.40 .020 .013 .614 .020 .050 24 2. "D" and "E" do not include mold flash. Mold flash or protrusions shall not exceed .010 inch (0.25mm). 3. "L" is the length of terminal for soldering to a substrate. 0.51 0.32 15.60 4. Terminal numbers are shown for reference only. 5 2 2 0.51 1.27 0° 8° 0° 8° .004 — 0.10 24 5. "C" dimension does not include solder finish thickness. 6. Symbol "N" is the maximum number of terminals. 3 6 24 — 1. Dimensioning and tolerancing per ANSI Y14.5M-1982. 13 E 1 H 12 h x 45° D C A1 A e B SEATING PLANE –C– α L LEAD COPLANARITY ccc C REV. 1.0.0 7/13/00 17 FAN5059 PRODUCT SPECIFICATION Ordering Information Product Number Package FAN5059M 24 pin SOIC DISCLAIMER FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS. LIFE SUPPORT POLICY FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, or (c) whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. www.fairchildsemi.com 7/13/00 0.0m 012 Stock#DS30005058 2000 Fairchild Semiconductor Corporation