UCC2920 UCC3920 PRELIMINARY –3V to –15V Hot Swap Power Manager FEATURES • Integrated 0.1Ω Power MOSFET • –3V to –15V Operation • Programmable Electronic Circuit Breaker • Digital Programmable Current Limit from 0A to 3A • Programmable Maximum Output Current from 0A to 4A • Programmable On Time • Fixed 2% Fault Duty Cycle • Thermal Shutdown • Fault Output Indicator • Power SOIC Package DESCRIPTION The UCC3920 Low RDSon Hot Swap Power Manager provides complete power management, hot swap capability, and circuit breaker functions. The only component needed to operate the device, other than supply bypassing, is the fault timing capacitor, CT. All control and housekeeping functions are integrated and externally programmable. These include the fault current level, maximum output sourcing current, maximum fault time, and start up delay. In the event of a constant fault, the internal fixed 2% duty cycle ratio limits the average output power. The internal 3 bit DAC allows programming of the fault level current from 0mA to 500mA with 250mA resolution, and from 500mA to 3A with 500mA resolution. The IMAX control pin sets the maximum sourcing current to 1A above the fault level when driven low, and to a full 4A when driven high for applications which require fast output charging. When the output current is below the fault level, the output MOSFET is switched on with a nominal resistance of 0.1Ω. When the output current exceeds the fault level or the maximum sourcing level, the output remains on, but the fault timer starts charging CT. Once CT charges to a preset threshold, the switch is turned off, and remains off for 50 times the programmed fault time. When the output current reaches the maximum sourcing level, the MOSFET transitions form a switch to a constant current source, regulating the output current at a constant level. Other features include an Open Drain Fault Output Indicator, Thermal Shutdown, Undervoltage Lockout, –3V to –15V operation, and a low thermal resistance Small Outline Power Package. All level shifting is done internally, which means that the DAC, IMAX and Shutdown Inputs can be driven form the logic supply. The fault output is also referenced to the logic GND, so this can easily interface back to the logic supply. BLOCK DIAGRAM UDG-96235-1 4/97 UCC2920 UCC3920 ABSOLUTE MAXIMUM RATINGS CONNECTION DIAGRAM Input Supply Voltage (VDD). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7V (VSS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –15V Maximum Differential Suppy (VDD - VSS). . . . . . . . . . . . . . 18V Maximum Supply Shunt Current . . . . . . . . . . . . . . . . . . . 20mA Fault Output Sink Current. . . . . . . . . . . . . . . . . . . . . . . . . 20mA Fault Output Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7V Output Current (DC) . . . . . . . . . . . . . . . . . . . . Internally Limited TTL Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to 7V Storage Temperature . . . . . . . . . . . . . . . . . . . −65°C to +150°C Junction Temperature . . . . . . . . . . . . . . . . . . –55°C to +150°C Lead Temperature (Soldering, 10 sec.) . . . . . . . . . . . . . +300°C Currents are positive into, negative out of the specified terminal. Pulsed is defined as a less than 10% duty cycle with a maximum duration of 500µS. Consult Packaging Section of Databook for thermal limitations and considerations of packages. DIL-16, SOIC-16 (Top View) N, DP Package Note: Do Not Connect to GND. * Heat sink connection points electronically connected to Vss. For N Package, pins 4, 12, and 13 are N/C. ELECTRICAL CHARACTERISTICS Unless otherwise stated, these specificaiton apply for TA = 0°C to 70°C for the UCC3920 and TA = –40°C to 85°C for the UCC2920, TA = TJ. PARAMETER TEST CONDITIONS MIN TYP MAX UNITS 3 5 5.5 V –13.2 –12 –3 V VSS Supply Current 0.5 2 mA VDD Supply Current 0.5 2 mA 0.5 2 mA 18 20 V Supply Section Voltage Input Range - VDD Minimum < VDD < Maximum (Note 3) Voltage Input Range - VSS Minimum < VSS < Maximum Sleep Mode Current Shutdown = 0.2V Shunt Clamp Voltage - (VDD - VSS) I = 2mA to 10mA, Note 3 16.2 Output Section Voltage Drop Short Circuit Response IOUT = 1A 0.1 0.2 V IOUT = 2A 0.2 0.4 V IOUT = 3A 0.3 0.6 V IOUT = 1A, VSS = –3V 0.1 0.2 V IOUT = 2A, VSS = –3V 0.2 0.4 V IOUT = 3A, VSS = –3V 0.3 0.6 V Note 1 20 Code = 000 0 µS DAC Section Trip Current Maximum Output Current 20 µA Code = 001 0.1 0.25 0.45 A Code = 010 0.25 0.5 0.75 A Code = 011 0.75 1 1.25 A Code = 100 1.25 1.5 1.75 A Code = 101 1.7 2 2.3 A Code = 110 2.1 2.5 2.9 A Code = 111 2.5 Code = 000, IMAX = 0.4V Code = 011, IMAX = 0.4V 1 3 3.5 A 0 20 µA 2 3 A Code = 101, IMAX = 0.4V 2 3 4 A Code = 111, IMAX = 0.4V 2.8 4 5.2 A 3 4 5.2 A IMAX = 2.4V, All Codes 2 UCC2920 UCC3920 ELECTRICAL CHARACTERISTICS (cont.) Unless otherwise stated, these specificaiton apply for TA = 0°C to 70°C for the UCC3920 and TA = –40°C to 85°C for the UCC2920, TA = TJ. PARAMETER TEST CONDITIONS MIN TYP MAX UNITS Fault Section CT Charge Current VCT = 1V, Note 2 –50 –36 –22 µA CT Discharge Current VCT = 1V, Note 2 0.36 0.6 1 µA Output Duty Cycle VOUT = 0V 1 2 4 % CT Fault Threshold Note 2 1.25 1.5 1.75 V CT Reset Threshold Note 2 0.25 0.5 0.75 V 1.1 1.5 1.9 V Shutdown Section Shutdown Threshold Shutdown Hysterisis 50 mV Open Drain Fault Output 1 µA IOUT = 2mA 0.4 V IOUT = 10mA 0.9 V High Level Output Current Low Level Output Voltage Logic Input DC Characteristics Input Voltage High 2 V Input Voltage Low Input High Current VIH = 2.4V Input Low Current VIL = 0.4V 3 0.8 V 10 µA 1 µA Note 1: Guaranteed by design. Not 100% tested in production. Note 2: Voltages measured with respect to VSS. Note 3: An external resistor in series with VDD could be used to limit the current to 10mA if an input voltage higher than 15V is desired. PIN DESCRIPTIONS BO - B2: These pins provide a digital input to the DAC. They can be used to provide a digital soft start, adaptive current limiting, or be strapped for static applications. current will always be 1A above the programmed trip level, and with a logic high the linear current will always be a constant 4A for applications which require fast charging of load capacitance. CT: A capacitor connected to CT sets the maximum fault time. The maximum must be more than the time to charge external load capacitance. The maximum fault time is defined as TFAULT = 28 • 103 • CT. Once the fault time is reached the output will shutdown for a time given by: TSD = 1.67 • 106 • CT, this equates to a 2% duty cycle. SHTDWN: When this pin is brought down low the IC is put into a sleep mode. VDD: Positive input voltage to the circuit breaker. The input voltage range is 3V to 5.5V. If the total voltage excursion, VDD - VSS could be 15V or greater, VDD should have an external limiting resistor in series with it. FAULT: Open drain output which, pulls low, from VDD to GND, upon any condition which causes the output to open: Fault, Thermal Shutdown, or Shutdown. VSS: The input voltage to the circuit breaker. The recommended voltage range is –3.3V to –15V. GND: Reference return for VDD and VSS (VIN). This serves as the reference point for digital signals. VOUT: Output voltage for the circuit breaker. When switched the output voltage will be approximately VIN + 0.1Ω • IOUT. IMAX: When this pin is at a logic low the linear output 3 UCC2920 UCC3920 TYPICAL APPLICATION UDG-96236-1 Note 1: Most applications will require a capacitor mounted between VOUT and GND at the IC pins to cancel out stray inductance. UDG-96237 Estimating Maximum Load Capacitance For a worst-case constant-current load of value just less than the trip limit; COUT(max) can be estimated from: For power management applications, the rate at which the total output capacitance can be charged depends on the maximum output current available and the nature of the load. For a constant-current current-limited circuit, the output will rise if the load asks for less than the maximum available short-circuit current. 28 • 103 • CT COUT(max) ≈ (IMAX − ILOAD) • VOUT Where VOUT is the output voltage. For a resistive load of value RI, the value of COUT(max) can be estimated from: To guarantee duty-cycle recovery of the current-limited power manager from a short-circuited load condition, there is a maximum total output capacitance which can be charged for a given unit ON time (Fault time). The design value of ON or Fault time can be adjusted by changing the timing capacitor CT. 28 • 103 • CT COUT(max) ≈ 1 RL • ln 1 − VOUT IMAX • RL 4 UCC2920 UCC3920 UCC3920 ON TIME CONTROL CIRCUITRY UDG-96238-1 The overcurrent comparator senses both the DAC output and a representation of the output current. When the output current exceeds the programmed level the timing capacitor CT charges with 36µA of current. If the fault occurs for the time it takes for CT to charge up to 1.5V, the fault latch is set and the output switch is opened. The output remains opened until CT dis- charges to 0.5V with a 0.6µA current source. Once the 0.5V is reached the output is enabled and will either appear as a switch, if the fault is removed, or a current source if the fault remains. If the over current condition is still present then CT will begin charging, starting the cycle over, resulting in approximately a 2% duty cycle. UCC3920 TYPICAL PERFORMANCE IFAULT Response Shutdown to VOUT Delay (VOUT Turning On) 5 UCC2920 UCC3920 UCC3920 TYPICAL PERFORMANCE (cont.) Shutdown to Fault and VOUT Delay (VOUT Turning Off) Hot Swap of VOUT SAFETY RECOMMENDATION Hot Swap of VSS (Input) Although the UCC3920 is designed to provide system protection for all fault conditions, all integrated circuits can ultimately fail short. For this reason, if the UCC3920 is intended for use in safety critical applications where UL or some other safety rating is required, a redundant safety device such as a fuse should be placed in series with the device. The UCC3920 will prevent the fuse from blowing for virtually all fault conditions, increasing system reliability and reducing maintenance cost, in addition to providing the hot swap benefits of the device. UNITRODE CORPORATION 7 CONTINENTAL BLVD. • MERRIMACK, NH 03054 TEL. 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