UC3886D

application INFO available UC2886 UC3886 Average Current Mode PWM Controller IC FEATURES DESCRIPTION • 10.3V - 20V Operating Range The UC3886 family of PWM controller ICs is designed for DC-to-DC converters with average current mode control. It is designed for use in conjunction with the UC3910 4-bit DAC and Voltage Monitor. The UC3886 drives an external N-channel MOSFET and can be used to power the Intel Pentium® Pro and other high-end microprocessors. • Low Offset Voltage Amplifier • High Bandwidth Current and Voltage Amplifiers • Low Offset Current Sense Amplifier • Undervoltage Lockout • Trimmed 5 Volt Reference • Externally Programmable Oscillator Charge Current • 1.5A Peak Totem Pole Output • Available in 16-pin DIL or SOIC Packages BLOCK DIAGRAM The UC3886 in conjunction with the UC3910 converts 5VDC to an adjustable output ranging from 2.0V to 3.5V in 100mV steps with 35mV DC system accuracy. The oscillator is programmed by the user’s selection of an external resistor and capacitor, and is designed for 300kHz typical operation. The voltage and current amplifiers have 3.5MHz 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. It has inputs and outputs accessible to allow user-selection of gain-setting resistors, and is internally compensated for a gain of 5 and above. The command voltage input is buffered and provided for use as the reference for the current sense amplifier. The output of the voltage amplifier (input to the current amplifier) is clamped to 1 volt above the command voltage to serve as a current limit. The gate output can be disabled by bringing the CAO/ENBL pin to below 0.8 volts. UDG-95098-2 SLUS231 - JUNE 1998 UC2886 UC3886 CONNECTION DIAGRAM ABSOLUTE MAXIMUM RATINGS Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20V Output Current CAM, COMMAND, VSENSE, ISN, ISP . . . . . . . . . . . . . ± 1A Analog Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3V to 7V Storage Temperature . . . . . . . . . . . . . . . . . . . –65°C to +150°C Junction Temperature . . . . . . . . . . . . . . . . . . . –55°C to +150°C Lead Temperatue (Soldering, 10 sec.) . . . . . . . . . . . . . +300°C DIL-16, SOIC-16 (Top View) N or D Packages Currents are positive into, negative out of the specified terminal. Consult Packaging Section of Databook for thermal limitations and considerations of packages. ELECTRICAL CHARACTERISTICS Unless otherwise specified, VCC = 12V, VCOMMAND = 3.0V, CT = 1nF, RT = 10k, TA = TJ = 0°C < TA < 70°C for the UC3886. (Note: –25°C < TA < 85°C for the UC2886, PARAMETER TEST CONDITIONS MIN TYP MAX UNITS 10 15 mA 5 mA Overall Supply Current VCC = 11V, Gate Open VCC = 9.3V Undervoltage Lockout Start Threshold 9.7 10.3 10.8 V 0.25 0.4 V VCM = 3.0V (UC3886) 4 mV VCM = 3.0V (UC2886) 15 mV UVLO Hysteresis Voltage Error Amplifier Input Offset Voltage Input Bias Current VCM = 3.0V Input Offset Current VCM = 3.0V (UC3886) VCM = 3.0V (UC2886) −2 µA 0.01 µA 0.1 µA 2.5V < VCOMP < 3.5V 60 85 dB Common-Mode Rejection Ratio 2V < VCOMP < 4V 60 85 dB Power Supply Rejection Ratio 11V < VCC < 15V 60 85 dB ICOMP = –100µA (UC3886) 3.95 4 4.05 V ICOMP = –100µA (UC2886) 3.9 4.1 V 2.7 Open Loop Gain Output High Voltage (Clamp) Output Low Voltage (Clamp) ICOMP = 100µA 1.9 Output Sink Current VCOMP = 3.7V 0.9 V Output Source Current VCOMP = 2.8V –0.15 −0.25 mA Gain-Bandwidth Product F = 100kHz 2 3.5 MHz 4.9 5 mA 5.0V Reference Output Voltage IVREF = 1.0mA Total Variation Line, Load, Temperature Line Regulation 11V < VCC < 15V Load Regulation 0 < IVREF < 2mA Short Circuit Current 4.825 –10 2 5.1 V 5.175 V 10 mV 15 mV −40 mA UC2886 UC3886 ELECTRICAL CHARACTERISTICS Unless otherwise specified, VCC = 12V, VCOMMAND = 3.0V, CT = 1nF, RT = 10k, TA = TJ = 0°C < TA < 70°C for the UC3886. (Note: –25°C < TA < 85°C for the UC2886, PARAMETER TEST CONDITIONS MIN TYP IBUF = ± 500µA (UC3886) 0.98 1 IBUF = ± 500µA (UC2886) 0.95 MAX UNITS Input Buffer Gain 1.02 V/V 1.05 V/V VCM = 3.0V (UC3886) 2 mV VCM = 3.0V (UC2886) 6 mV Current-Sense Amplifier Input Offset Voltage Input Bias Current VCM = 3.0V -1 µA Input Offset Current VCM = 3.0V 0.2 µA Open Loop Gain 2V < VISO < 6V 60 85 dB CMRR 0V < VCM < 4.5V 60 85 dB PSRR 11V < VCC < 15V 60 85 dB Output High Voltage IISO = –100µA 5 Output Low Voltage IISO = 1mA Output Source Current VISO = 2V Gain-Bandwidth Product F = 100kHz V 1 −0.2 2 V mA 3.5 MHz Current Amplifier Input Offset Voltage Input Bias Current VCM = 3.0V (UC3886) 13 mV VCM = 3.0V (UC2886) 18 mV VCM = 3.0V 1 µA Open Loop Gain 1V < VCAO < 3V 60 85 dB CMRR 1.5V < VCM < 4.5V 60 85 dB PSRR 11V < VCC < 15V 60 85 Output High Voltage ICAO = –100µA 3 Output Low Voltage ICAO = 100µA Output Source Current VCAO =1V Gain-Bandwidth Product F = 100kHz dB 3.3 1 V V −0.1 –0.25 mA 2 3.5 MHz RT = 10k, CT = 1nF (UC3886) 90 100 RT = 10k, CT = 1nF (UC2886) 85 Oscillator Frequency Frequency Change With Voltage 110 kHz 115 kHz 1 % 1 1.2 V 1.6 1.8 2.0 V 1.6 2.2 V 9 10.3 11V > VCC > 15V CT Peak Voltage 2.6 CT Valley Voltage CT Peak-to-Peak Voltage 2.8 V Output Section Output Low Voltage IGATE = 200mA Output High Voltage IGATE = –200mA Output Low Voltage V 5V < VCC < 9V, IGATE = 10mA 0.5 V VCAO < 0.8V, IGATE = 10mA 0.5 V 150 ns Rise/Fall Time CL = 1nF Maximum Duty Cycle (UC3886) 90 % (UC2886) 85 % 3 UC2886 UC3886 PIN DESCRIPTIONS GATE: (PWM Output) The output is a 1A totem pole driver. Use a series resistor of at least 5 to prevent interaction between the gate impedance and the output driver that might cause excessive overshoot. BUF: (Buffer Output) The voltage on COMMAND pin is buffered and presented to the user here. This voltage is used to provide the operating bias point for the current sense amplifier by connecting a resistor between BUF and ISP. Decouple BUF with 0.01µF or greater to SGND. CAM: (Current Amplifier Minus Input) The average load current feedback from ISO is typically applied through a resistor here. ISN: (Current Sense Amplifier Inverting Input) A resistor to the low side of the average current sense resistor and a resistor to ISO are applied to this pin to make a differential sensing amplifier. CAO/ENBL: (Current Amplifier Output/Chip Enable) The current loop compensation network is connected between CAO/ENBL and CAM, the inverting input of the current amplifier. The voltage at CAO/ENBL 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 at this pin exceeds 1.0 volts, allowing the PWM to force zero duty cycle when necessary. The user can force this pin below 0.8 volts externally with an open collector, disabling the GATE drive. ISO: (Current Sense Amplifier Output) A feedback resistor to ISN is connected here to make a differential sensing amplifier. The voltage at this pin is equal to (VBUF + A • IAVG • RSENSE) where A is the user determined gain of the differential amplifier, IAVG is the average load current of the system, and RSENSE is the average current sensing resistor. For stability, A must be greater than 5. Set A such that A • ISC • RSENSE = 1.0V where ISC is the user-determined short circuit current limit. COMMAND: (Voltage Amplifier Non-Inverting Input) This input to the voltage amplifier is connected to a command voltage, such as the output of a DAC. This voltage sets the switching regulator output voltage. ISP: (Current Sense Amplifier Non-Inverting Input) A resistor to the high side of the average current sense resistor and a resistor to BUF are connected to this pin to make a differential sensing amplifier. COMP: (Compensation, Voltage Amplifier Output) The system voltage compensation network is applied between COMP and VSENSE. The voltage at COMP is clamped to prevent it from going more than 1V above the COMMAND voltage. This is used to provide an accurate average current limit. The voltage on COMP is also clamped to 0.7V below the voltage on COMMAND. This is done to avoid applying a full charge to capacitors in the compensation network during transients, allowing quick recovery time and little overshoot. PGND: (Power Ground) The PWM output current returns to ground through this pin. This is separated from SGND to avoid on-chip ground noise generated by the output current. CT: (Oscillator Timing Capacitor) A capacitor from CT to SGND along with the resistor on RT, sets the PWM frequency and maximum duty cycle according to these formulas: VCC: (Positive Supply Voltage) This pin supplies power to the chip and to the gate drive output. Decouple to PGND and separately to SGND for best noise immunity. The reference (VREF), GATE output, oscillator, and amplifiers are disabled until VCC exceeds 10.3V. DMAX = 1 – RT: (Oscillator Charging Current) This pin is held at 2V. Resistor RT from this pin to SGND sets the oscillator charging current. Use 5k < RT < 100k. SGND: (Signal Ground) For better noise immunity, signal ground is provided at this pin. 2 .0 V RT • 4 .0 mA VREF: (Voltage Reference Output) An accurate 5V reference as provided at this pin. The output can deliver 2mA to external circuitry, and is internally short circuit current limited. VREF is disabled if VCC is below UVLO. Bypass 5V REF to SGND with an 0.01µF or larger capacitor for best stability. where DMAX is the maximum operating duty cycle, and RT is in ohms. FOSC = 2 .0 V • ( ( 4 .0 mA • RT ) – 2 .0 V ) CT • 1.8 V • RT 2 • 4 .0 mA VSENSE: (Voltage Sense Input) This input is connected to COMP through a feedback network and to the power supply output through a resistor or a divider network. where FOSC is the UC3886 oscillator switching frequency in Hz, RT is in ohms, and CT is in farads. 4 UC2886 UC3886 APPLICATION INFORMATION 1.00 OSCILLATOR 0.98 The UC3886 oscillator is a saw tooth. The rising edge is governed by a current controlled by RT flowing into the capacitor CT. The falling edge of the sawtooth sets the dead time for the output. Selection of RT should be done first, based on desired maximum duty cycle. CT can then be chosen based on the desired frequency, FS, and the value of RT. The design equations are: DMAX DMAX 0.96 0.94 0.92 0.90 2 .0 V =1 – RT • 4 .0 mA FOSC = 0.88 0 2 .0 V • ( ( 4 .0 mA • RT ) – 2 .0 V ) 20 40 60 80 100 120 RT (kΩ) CT • 1.8 V • RT 2 • 4 .0 mA Figure 2. Programming Maximum Duty Cycle with RT FSWITCH (kHz) 1000 100pF 100 220pF 470pF UDG-96022 1nF 10 0 Figure 1. Oscillator 20 Configuring the Current Sense Amplifier RT = 5k 0.500 RT = 100k 0.400 TD (us) R2 • R1 The Current Sense Amplifier gain, GCSA, must be programmed to be greater than or equal to 5.0 (14dB), as this amplifier is not stable with gain below 5.0. The Current Sense Amplifier gain is limited on the high side by its Gain-Bandwidth product of 2.5MHz. Therefore GCSA must be programmed between and 100 0.600 The Current Sense Amplifier gain, GCSA, is given by the ratio of R2/R1. The output of the Current Sense Amplifier at the ISO pin is given by GCSA_MIN = 5.0 80 Figure 3. Programming Switching Frequency with CT The UC3886 Current Sense Amplifier is used to amplify a differential current sense signal across a low value current sense resistor, RSENSE. This amplifier must be set up as a differential amplifier as shown. VISO = VBUF + V SENSE 40 60 RT (kΩ) 0.300 0.200 0.100 0.000 100 GCSA_MAX = 2.5MHz/FSWITCH 300 500 700 CT (pF) Figure 4. Deadtime vs. CT and RT 5 900 1100 UC2886 UC3886 APPLICATION INFORMATION (cont.) Enabling/Disabling the UC3886 Gate Drive The CAO/ENBL pin can be used to Disable the UC3886 gate drive by forcing this pin below 0.8V, as shown. 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. UDG-96024 UDG-96023 Figure 6. Enabling/Disabling the UC3886 Figure 5. Configuring the Current Sense Amplifier TYPICAL APPLICATIONS UDG-96025 Figure 7. The UC3886 Configured in a Buck Regulator 6 UC2886 UC3886 TYPICAL APPLICATIONS (cont.) UDG-96021 Figure 8. UC3886 Configured with the UC3910 for a Pentium® Pro DC/DC Converter UNITRODE CORPORATION 7 CONTINENTAL BLVD. • MERRIMACK, NH 03054 TEL. (603) 424-2410 FAX (603) 424-3460 7 PACKAGE OPTION ADDENDUM www.ti.com 17-May-2014 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty UC2886D LIFEBUY SOIC D 16 UC2886DG4 LIFEBUY SOIC D 16 UC3886D LIFEBUY SOIC D 16 UC3886DG4 LIFEBUY SOIC D 16 UC3886DTR LIFEBUY SOIC D 16 UC3886N LIFEBUY PDIP N 16 UC3886NG4 LIFEBUY PDIP N 16 Eco Plan Lead/Ball Finish MSL Peak Temp (2) (6) (3) 40 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR -40 to 85 TBD Call TI Call TI -40 to 85 40 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR 0 to 70 TBD Call TI Call TI 0 to 70 25 Op Temp (°C) Device Marking (4/5) TBD Call TI Call TI 0 to 70 Green (RoHS & no Sb/Br) CU NIPDAU N / A for Pkg Type 0 to 70 TBD Call TI Call TI 0 to 70 UC2886D UC3886D UC3886N (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation of the previous line and the two combined represent the entire Device Marking for that device. Addendum-Page 1 Samples PACKAGE OPTION ADDENDUM www.ti.com 17-May-2014 (6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish value exceeds the maximum column width. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis. Addendum-Page 2 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All semiconductor products (also referred to herein as “components”) are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI’s terms and conditions of sale of semiconductor products. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by applicable law, testing of all parameters of each component is not necessarily performed. TI assumes no liability for applications assistance or the design of Buyers’ products. Buyers are responsible for their products and applications using TI components. To minimize the risks associated with Buyers’ products and applications, Buyers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right relating to any combination, machine, or process in which TI components or services are used. Information published by TI regarding third-party products or services does not constitute a license to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional restrictions. Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or service voids all express and any implied warranties for the associated TI component or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. Buyer acknowledges and agrees that it is solely responsible for compliance with all legal, regulatory and safety-related requirements concerning its products, and any use of TI components in its applications, notwithstanding any applications-related information or support that may be provided by TI. Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which anticipate dangerous consequences of failures, monitor failures and their consequences, lessen the likelihood of failures that might cause harm and take appropriate remedial actions. Buyer will fully indemnify TI and its representatives against any damages arising out of the use of any TI components in safety-critical applications. In some cases, TI components may be promoted specifically to facilitate safety-related applications. With such components, TI’s goal is to help enable customers to design and create their own end-product solutions that meet applicable functional safety standards and requirements. Nonetheless, such components are subject to these terms. No TI components are authorized for use in FDA Class III (or similar life-critical medical equipment) unless authorized officers of the parties have executed a special agreement specifically governing such use. Only those TI components which TI has specifically designated as military grade or “enhanced plastic” are designed and intended for use in military/aerospace applications or environments. Buyer acknowledges and agrees that any military or aerospace use of TI components which have not been so designated is solely at the Buyer's risk, and that Buyer is solely responsible for compliance with all legal and regulatory requirements in connection with such use. TI has specifically designated certain components as meeting ISO/TS16949 requirements, mainly for automotive use. In any case of use of non-designated products, TI will not be responsible for any failure to meet ISO/TS16949. Products Applications Audio www.ti.com/audio Automotive and Transportation www.ti.com/automotive Amplifiers amplifier.ti.com Communications and Telecom www.ti.com/communications Data Converters dataconverter.ti.com Computers and Peripherals www.ti.com/computers DLP® Products www.dlp.com Consumer Electronics www.ti.com/consumer-apps DSP dsp.ti.com Energy and Lighting www.ti.com/energy Clocks and Timers www.ti.com/clocks Industrial www.ti.com/industrial Interface interface.ti.com Medical www.ti.com/medical Logic logic.ti.com Security www.ti.com/security Power Mgmt power.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defense Microcontrollers microcontroller.ti.com Video and Imaging www.ti.com/video RFID www.ti-rfid.com OMAP Applications Processors www.ti.com/omap TI E2E Community e2e.ti.com Wireless Connectivity www.ti.com/wirelessconnectivity Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265 Copyright © 2014, Texas Instruments Incorporated