UCC3830-4/-5/-6 5-Bit Microprocessor Power Supply Controller FEATURES DESCRIPTION • 5-Bit Digital-to-Analog Converter (DAC) The UCC3830-4/-5/-6 is a fully integrated single chip solution ideal for powering high performance microprocessors. The chip includes an average current mode PWM controller, has a fully integrated 5-Bit DAC, and includes an on-board precision reference and voltage monitor circuitry. The UCC3830-x converts 5VDC to an adjustable output, ranging from 3.5VDC down to 1.8VDC with 1% DC system accuracy (see Table 1). The UCC3830-x fully supports Intel’s 4-bit Pentium® Pro and 5-bit Pentium® II VID codes. • Supports 4-Bit and 5-Bit Microprocessor VID Codes • Combined DAC/Voltage Monitor and PWM Functions • 1% DAC/Reference • Current Sharing • 100kHz, 200kHz, 400kHz Oscillator Frequency Options • Foldback Current Limiting • Overvoltage and Undervoltage Fault Windows • Undervoltage Lockout The accuracy of the DAC/reference combination is 1%. The overvoltage and undervoltage comparators monitor the system output voltage and indicate when it rises above or falls below its programmed value by more than 8.5%. A second overvoltage protection comparator pulls the current amplifier output voltage low to force zero duty cycle when the system output voltage exceeds its designed value by more than 17.5%. This comparator also terminates the cycle. Undervoltage lockout circuitry assures the correct logic states at the outputs during powerup and powerdown. The gate output can be disabled by bringing the CAO/ENBL pin to below 0.8V. (continued) • 4Ω Totem Pole Output • Chip Disable Function BLOCK DIAGRAM UDG-96188-2 02/99 UCC3830-4/-5/-6 DESCRIPTION (cont.) CONNECTION DIAGRAM The voltage and current amplifiers have a 3MHz gain bandwidth product to satisfy high performance system requirements. The internal current sense amplifier permits the use of a low value current sense resistor, minimizing power loss. The oscillator frequency is fixed internally at 100kHz, 200kHz, or 400kHz, depending upon the option selected. The foldback circuit reduces the converter short circuit current limit to 50% of its nominal value when the converter is short circuited. The gate driver is a 4Ω totem pole output stage capable of driving an external MOSFET. SOIC-20 (Top View) DW Package This device is available in 20-pin dual in-line and surface mount packages. The UCC3830-x is specified for operation from 0°C to 70°C. Pentium® Pro and Pentium® Pro II are registered trademarks of Intel Corporation. ORDERING INFORMATION ABSOLUTE MAXIMUM RATING UCC3830 Input Supply Voltage VIN . . . . . . . . . . . . . . . . . . . . . . . . . . 15V D0, D1, D2, D3, D4, VSENSE, VFB, IS+, IS–, CAM Inputs Maximum Forced Voltage . . . . . . . . . . . . . . . . –0.3V to 5.3V PWRGOOD Output Maximum Voltage. . . . . . . . . . . . . . . . 5.5V COMMAND Ouput Maximum Current . . . . . . Internally Limited Reference Output Current . . . . . . . . . . . . . . . Internally Limited Storage Temperature . . . . . . . . . . . . . . . . . . . –65°C to +150°C Junction Temperature . . . . . . . . . . . . . . . . . . . –55°C to +150°C Lead Temperature (Soldering, 10 sec.) . . . . . . . . . . . . . +300°C – Note: Consult factory for temperature range or package options not shown. Frequency FREQUENCY TABLE 100kHz Currents are positive into negative out of the specified terminal. Pulse is defined as a less than 10% duty cycle with a maximum duration of 500 s. Consult Packaging Section of Databook for thermal limitations and considerations of packages. UCC3830-4 200kHz 400kHz X UCC3830-5 X UCC3830-6 X ELECTRICAL CHARACTERISTICS: Unless otherwise specified, VIN = 12V, VSENSE = 3.5V, VD0 = VD1 = VD2 = VD3 = VD4 = 0V, 0°C < TA < 70°C, TA = TJ. PARAMETER TEST CONDITIONS MIN TYP MAX UNITS 10.5 10.8 V Undervoltage Lockout VIN UVLO Turn-on Threshold VIN UVLO Turn-off Threshold 9.5 10 UVLO Threshold Hysteresis 200 500 700 mV V 7.5 13.5 mA Supply Current lIN D0 through D4 = Open DAC/Reference COMMAND Voltage Accuracy 10.8V < VIN < 13.2V, IVREF = 0mA, 0°C < TA < 70°C –1 1 % D0-D4 Voltage High DX Pin Floating 4 5 5.2 V D0-D4 Input Bias Current DX Pin Tied to GND –100 –70 –20 µA 10 17.5 25 % 20 30 mV –0.5 –0.1 0.5 µA OVP Comparator Trip Point % Over COMMAND Voltage (Note 1), D0 = D1 = D2 = D4 = Open, D3 = GND Hysteresis VSENSE Input Bias Current OV, OVP, UV Combined 2 UCC3830-4/-5/-6 ELECTRICAL CHARACTERISTICS: Unless otherwise specified, VIN = 12V, VSENSE = 3.5V, VD0 = VD1 = VD2 = VD3 = VD4 = 0V, 0°C < TA < 70°C, TA = TJ. PARAMETER TEST CONDITIONS MIN TYP MAX UNITS % Over COMMAND Voltage (Note 1), D0 = D1 = D2 = D4 = Open, D3 = GND 5 8.5 12 % 20 30 mV 470 Ω –8.5 –5 % 20 30 mV –0.02 0.5 µA OV Comparator Trip Point Hysteresis PWRGOOD Equivalent Resistance VSENSE = 2.0V UV Comparator Trip Point % Over COMMAND Voltage (Note 1), D0 = D1 = D2 = D4 = Open, D3 = GND –12 Hysteresis Voltage Error Amplifier Input Bias Current VCM = 3.0V Open Loop Gain 1.5V < VCOMP < 2.5V, D4 = D3 = D2 = D1 = GND, D0 = Open –0.5 Power Supply Rejection Ratio 10.8V < VIN < 15V Output Sourcing Current VVFB = 2V, VCOMMAND = VCOMP = 2.5V Output Sinking Current VVFB = 3V, VCOMMAND = VCOMP = 2.5V 80 dB 85 dB –0.5 0.5 –0.3 1 mA mA Current Sense Amplifier Gain 14.25 Input Resistance Common Mode Rejection Ratio 0V < VCM < 4.5V Power Supply Rejection Ratio 10.8V < VIN < 15V Output Sourcing Current VIS– = 2V, VISOUT = VIS+ = 2.5V Output Sinking Current VIS– = 3V, VISOUT = VIS+ = 2.5V 15.25 3 kΩ 60 dB 80 –0.5 5 V/V dB –0.3 8 mA mA Current Amplifier Input Offset Voltage VCM = 3.0V Input Bias Current VCM = 3.0V –12 12 mV –0.1 µA Open Loop Gain 1V < VCAO/ENBL < 2.5V 80 dB Output Voltage High VCOMP = 3V, VCAM = 2.5V 3.2 V Power Supply Rejection Ratio 10.8V < VIN < 15V 80 Output Sourcing Current VCAM = 2V, VCAO/ENBL = VCOMP = 2.5V –1 Output Sinking Current VCAM = 3V, VCAO/ENBL = VCOMP = 2.5V dB –0.5 mA 3 5 mA Frequency (-4) 85 100 115 kHz Frequency (-5) 170 200 230 kHz Frequency (-6) 340 400 460 kHz Oscillator Frequency Change With Voltage 10.8V < VIN < 15V 1 % Output Section Maximum Duty Cycle 90 95 99 % Output Low Voltage IGATE = –100mA 0.2 V Output High Voltage IGATE = 100mA 11.8 Rise Time CGATE = 3.3nF 20 70 ns Fall Time CGATE = 3.3nF 15 70 ns V Foldback Current Limit Clamp Level Measured at Voltage EA Output; VSENSE = VCOMMAND = 3V 4.28 V VCOMMAND = 3V, VSENSE = 0 3.64 V Note 1: This percentage is measured with respect to the ideal COMMAND voltage programmed by the D0 - D4 pins. 3 UCC3830-4/-5/-6 PIN DESCRIPTIONS CAM (Current Amplifier Inverting Input): The average load current feedback from ISOUT is applied through a resistor to this pin. The current loop compensation network is also connected to this pin (see CAO/ENBL below). respect to GND. Bypass capacitors on the VCC and VREF pins should be connected directly to the ground plane near the GND pin. IS– (Current Sense Amplifier Inverting Input): This pin is the inverting input to the current sense amplifier and is connected to the low side of the average current sense resistor. CAO/ENBL (Current Amplifier Output/Chip Enable): The current loop compensation network is connected between this pin and CAM. The voltage on this pin is the input to the PWM comparator and regulates the output voltage of the system. The GATE output is disabled (held low) unless the voltage on this pin exceeds 1V, allowing the PWM to force zero duty cycle when necessary. The PWM forces maximum duty cycle when the voltage on CAO/ENBL exceeds the oscillator peak voltage (3V). A 3.2V clamp circuit prevents the CAO/ENBL voltage from rising excessively past the oscillator peak voltage for excellent transient response. The user can force this pin below 0.8V externally with an open collector, disabling the GATE drive. IS+ (Current Sense Amplifier Noninverting Input): This pin is the noninverting input to the current sense amplifier and is connected to the high side of the average current sense resistor. ISOUT (Current Sense Amplifier Output): This pin is the output of the current sense amplifier. The voltage on this pin is (COMMAND + GCSA • I • RSENSE), where COMMAND is the voltage on the COMMAND pin, GCSA is the fixed gain of the current sense amplifier, equal to 15, I is the current through the sense resistor, and RSENSE is the value of the average current sensing resistor. COMMAND (Digital-to-Analog Converter Output Voltage): This pin is the output of the 5-bit digital-to-analog converter (DAC) and the noninverting input of the voltage amplifier. The voltage on this pin sets the switching regulator output voltage. This voltage ranges from 1.8V to 3.5V as programmed by the 5-bit DAC according to Table 1. The GATE output is disabled when all 1s or illegal codes are presented at the 5 Bit DAC. The COMMAND source impedance is typically 1.2kΩ and must therefore drive only high impedance inputs if accuracy is to be maintained. Bypass COMMAND with a 0.01µF, low ESR, low ESL capacitor for best circuit noise immunity. PGND (Power Ground): This pin provides a dedicated ground for the output gate driver. The GND and PGND pins should be connected externally using a short printed circuit board trace close to the IC. Decouple VIN to PGND with a low ESR capacitor 0.10µF. PWRGOOD (Undervoltage/Lower Overvoltage Output): This pin is an open drain output which is driven low to reset the microprocessor when VSENSE rises above or falls below its nominal value by 8.5%. The on resistance of the open drain switch will be no higher than 470Ω. The OV and UV comparators’ hysteresis is fixed at 20mV independent of the COMMAND voltage. COMP (Voltage Amplifier Output): The system voltage compensation network is applied between COMP and VFB. VIN (Positive Supply Voltage): This pin supplies power to the chip. Connect VIN to a stable voltage source of at least 10.8V. The GATE and PWRGOOD outputs will be held low until VCC exceeds the upper undervoltage lockout threshold. This pin should be bypassed directly to the GND pin. D0 - D4 (DAC Digital Input Control Codes): These are the DAC digital input control codes, with D0 representing the least significant bit (LSB) and D4, the most significant bit (MSB) as shown in Table 1. A bit is set low by being connected to GND. A bit is set high by floating it, or connecting it to a 5V source. Each control pin is pulled up to approximately 5V by an internal 70µA current source. VFB (Voltage Amplifier Inverting Input): This input is connected to COMP through a feedback network and to the power supply output through a resistor or a divider network. VREF (Voltage Reference Output): This pin provides an accurate 5V reference and is internally short circuit current limited. VREF powers the D/A converter and also provides a threshold voltage for the UVLO comparator. For best reference stability, bypass VREF directly to GND with a low ESR, low ESL capacitor of at least 0.01µF. GATE (PWM Output, MOSFET Driver): This output provides a 4Ω totem pole driver. Use a series resistor between this pin and the gate of the external MOSFET to prevent excessive overshoot. GND (Signal Ground): All voltages are measured with 4 UCC3830-4/-5/-6 PIN DESCRIPTIONS (cont.) VSENSE (Output Voltage Sensing Input): This pin is connected to the system output voltage through a low pass filter. When the voltage on VSENSE rises above or falls below the COMMAND voltage by 8.5%, the PWRGOOD output is driven low to reset the microprocessor. When the voltage on VSENSE rises above the COMMAND voltage by 17.5%, the OVP comparator pulls the current amplifier output voltage below the oscillator valley voltage to force zero duty cycle at the GATE output. This pin is also used by the foldback current limiting circuitry. TYPICAL PERFORMANCE CURVES The curves shown in Figures 1 and 2 depict the typical high gain-bandwidth products for the UCC3830-x Voltage Amplifier, Current Amplifier and Current Sense Ampli- fiers. These high gain-bandwidth devices help achieve an excellent transient response to load and line changes. Figure 1. Open loop gain for UCC3830 voltage and current amplifier. Figure 2. Current sense amplifier gain vs frequency. APPLICATION INFORMATION Short Circuit Current Limit The short circuit current limit, ISC, is set according to: ISC = 1.28V RSENSE • GCSA where RSENSE is the average current sense resistor and GCSA is the current sense amplifier gain. GCSA equals 15. Example: Choose RSENSE to set the short circuit limit at 17A using the UCC3830-5 RSENSE = 1.28V = 0.005Ω. 17A • 15 A lower resistance value may be needed if the AC ripple current in the inductor is more than 20% of the load current. Figure 3. Short circuit foldback reduces stress on circuit components by reducing short circuit current. 5 UCC3830-4/-5/-6 APPLICATION INFORMATION (cont.) UDG-96189 Figure 4. Disabling the UCC3830-x. The UCC3830-x incorporates short circuit current foldback, as shown in Figure 3. When the output of the power supply is short circuited, the output voltage falls. When the output voltage reaches 1/2 of its nominal voltage (COMMAND/2) then the output current is reduced. This feature reduces the amount of current in the MOSFET, diode and capacitors, and insures high reliability. Figure 5. Input capacitors current waveform. Setting the Output Voltage Using the DAC The 5-bit Digital-to-Analog Converter (DAC) is programmed according to Table 1. The COMMAND voltage is always active as long as the UCC3830 VIN pin is above the undervoltage lockout voltage. The output gate drive, GATE, is disabled at certain DAC codes, as shown in Table 1. Disabling the gate drive disables the power supply. Enabling/Disabling the UCC3830-x Gate Drive The CAO/ENBL pin can be used to disable the UCC3830 gate drive by forcing this pin below 0.8V, as shown in Figure 4. Bringing the voltage below the valley of the PWM oscillator ramp will insure a 0% duty cycle, effectively disabling the gate drive. A low noise open collector signal should be used as an Enable/Disable command. Digital Command D4 D3 D2 D1 D0 0 1 1 1 1 0 1 1 1 0 0 1 1 0 1 0 1 1 0 0 0 1 0 1 1 0 1 0 1 0 0 1 0 0 1 0 1 0 0 0 0 0 1 1 1 0 0 1 1 0 0 0 1 0 1 0 0 1 0 0 0 0 0 1 1 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 Operating the 5-Bit Controller with Intel’s 4-Bit Pentium Pro The UCC3830-x 5-Bit Controller is completely backward compatible. When the fifth bit, D4 is left open (4-Bit Processor in circuit), the UCC3830-x acts as a 4-Bit controller with the COMMAND voltage fully compatible with ® Intel’s 4-Bit Pentium Pro family. Command GATEHI/GATELO Voltage Status 1.300 Note 1 1.350 Note 1 1.400 Note 1 1.450 Note 1 1.500 Note 1 1.550 Note 1 1.600 Note 1 1.650 Note 1 1.700 Note 1 1.750 Note 1 1.800 Enabled 1.850 Enabled 1.900 Enabled 1.950 Enabled 2.000 Enabled 2.050 Enabled Digital Command D4 D3 D2 D1 D0 1 1 1 1 1 1 1 1 1 0 1 1 1 0 1 1 1 1 0 0 1 1 0 1 1 1 1 0 1 0 1 1 0 0 1 1 1 0 0 0 1 0 1 1 1 1 0 1 1 0 1 0 1 0 1 1 0 1 0 0 1 0 0 1 1 1 0 0 1 0 1 0 0 0 1 1 0 0 0 0 Table 1. Programming the command voltage for the UCC3830-x. 6 Command GATEHI/GATELO Voltage Status 2.000 Note 1 2.100 Enabled 2.200 Enabled 2.300 Enabled 2.400 Enabled 2.500 Enabled 2.600 Enabled 2.700 Enabled 2.800 Enabled 2.900 Enabled 3.000 Enabled 3.100 Enabled 3.200 Enabled 3.300 Enabled 3.400 Enabled 3.500 Enabled UCC3830-4/-5/-6 APPLICATION INFORMATION (cont.) Figure 6. Load current vs RMS current for input capacitors. Figure 7. Efficiency of UCC3830-5 200kHz demo kit at 2.8V ouput. UDG-96190-1 Figure 8. UCC3830 configured for 4-bit or 5-bit operation. 7 UCC3830-4/-5/-6 APPLICATION INFORMATION (cont.) Choosing the Input Capacitor Figure 6 show the RMS current handled by the total input capacitance in typical VRM circuits delivering 1.8V to 2.8V and powered from 5V. The input capacitors are chosen primarily based on their switching frequency RMS current handling capability and their voltage rating. The input capacitors must handle virtually all of the RMS current at the switching frequency, even if the circuit does not have an input inductor. The switching current in the input capacitors appears as shown in Figure 5. Related Publications U-156 and U-157 are Unitrode Application Notes describing the operation of the UC3886 and the UC3886/ UC3910 together in a Pentium® Pro application. Typical Application The amount of RMS current in an Aluminum Electrolytic capacitor has a strong impact on the reliability and lifetime of the capacitor. Other factors which affect the life of an input capacitor are internal heat rise, external airflow, the amount of time that the circuit operates at maximum current and the operating voltage. The curves in The UCC3830-x is ideal for converting the 5.0V system bus into the required Pentium® Pro bus voltage. The 3.3V system bus can also be converted using the UCC3830-x when the Pentium® Pro requires lower bus voltages. Table I. Parts list. REFERENCE DESIGNATOR DESCRIPTION PACKAGE U1 Unitrode UCC3830DWP-5 DAC/PWM C1 Sanyo 6MV1500GX, 1500µF, 6.3V, Aluminum Electrolytic 10x20mm Radial Can SOIC-20 Wide C2 Sanyo 6MV1500GX, 1500µF, 6.3V, Aluminum Electrolytic 10x20mm Radial Can C3 Sanyo 6MV1500GX, 1500µF, 6.3V, Aluminum Electrolytic 10x20mm Radial Can C4 Sanyo 6MV1500GX, 1500µF, 6.3V, Aluminum Electrolytic 10x20mm Radial Can C5 Sprague/Vishay 595D475X0016A2B, 4.7µF 16V Tantalum SPRAGUE Size A C6 Sanyo 6MV1500GX, 1500µF, 6.3V, Aluminum Electrolytic 10x20mm Radial Can C7 Sanyo 6MV1500GX, 1500µF, 6.3V, Aluminum Electrolytic 10x20mm Radial Can C8 Sanyo 6MV1500GX, 1500µF, 6.3V, Aluminum Electrolytic 10x20mm Radial Can C9 Sanyo 6MV1500GX, 1500µF, 6.3V, Aluminum Electrolytic 10x20mm Radial Can C10 Sanyo 6MV1500GX, 1500µF, 6.3V, Aluminum Electrolytic 10x20mm Radial Can C11 Sprague 593D107X9010D2, 100µF, 6.3V Tantalum C12 0.10µF Ceramic 1206 SMD C13 0.01µF Ceramic 0603 SMD C14 0.01µF Ceramic 0603 SMD C15 0.01µF Ceramic 0603 SMD C16 1000pF Ceramic 0603 SMD C17 0.10µF Ceramic 1206 SMD C18 33pF NPO Ceramic 0603 SMD C19 1500pF Ceramic 0603 SMD C20 82pF NPO Ceramic 0603 SMD C21 0.10µF Ceramic 1206 SMD C22 0.10µF Ceramic 1206 SMD CR1 International Rectifier 32CTQ030 30V, 30A Schottky Diode TO-220AB L1 Micrometals T50-52B, 10 Turns #16AWG, 4.5µH 8 EIA Size D SMD Toroid UCC3830-4/-5/-6 Table I. Parts list. (cont.) REFERENCE DESIGNATOR Q1 DESCRIPTION International Rectifier IRL3103, 30V, 56A PACKAGE TO-220AB R1 Dale/Vishay WSR-2 0.005Ω 1% R2 10Ω, 5%, 1/16 Watt SMD Power Package 0603 SMD R3 8.2kΩ, 5%, 1/16 Watt 0603 SMD R4 6.81kΩ, 1%, 1/16 Watt 0603 SMD R5 3.92kΩ, 1%, 1/16 Watt 0603 SMD R6 261kΩ, 1%, 1/16 Watt 0603 SMD R7 100kΩ, 1%, 1/16 Watt 0603 SMD R8 3.92kΩ, 1%, 1/16 Watt 0603 SMD R9 10.5kΩ, 1%, 1/16 Watt 0603 SMD Q1-HS AAVID 576802 TO-220 Heat Sink TO-220AB CR1-HS AAVID 577002 TO-220 Heat Sink TO-220AB UNITRODE CORPORATION 7 CONTINENTAL BLVD. • MERRIMACK, NH 03054 TEL. (603) 424-2410 • FAX (603) 424-3460 9 IMPORTANT NOTICE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. 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