UCC283-3/-5/-ADJ UCC383-3/-5/-ADJ Low Dropout 3 Ampere Linear Regulator Family FEATURES DESCRIPTION • Precision Positive Series Pass The UCC283-3/-5/-ADJ family of positive linear series pass regulators are tailored Voltage Regulation for low drop out applications where low quiescent power is important. Fabricated with a BiCMOS technology ideally suited for low input to output differential applica• 0.45V Dropout at 3A tions, the UCC283-5 will pass 3A while requiring only 0.45V of typical input voltage • 50mV Dropout at 10mA headroom (guaranteed 0.6V dropout). These regulators include reverse voltage sensing that prevents current in the reverse direction. Quiescent current is always • Quiescent Current Under less than 650µA. These devices have been internally compensated in such a man650µA Irrespective of Load ner that the need for a minimum output capacitor has been eliminated. • Adjustable (5 Lead) Output UCC283-3 and UCC283-5 versions are in 3 lead packages and have preset outputs Voltage Version at 3.3V and 5.0V respectively. The output voltage is regulated to 1.5% at room tem• Fixed (3 Lead) Versions for perature. The UCC283-ADJ version, in a 5 lead package, regulates the output volt3.3V and 5V Outputs age programmed by an external resistor ratio. • Logic Shutdown Capability • Short Circuit Power Limit of 3% •VIN • ISHORT • Low VOUT to VIN Reverse Leakage • Thermal Shutdown Short circuit current is internally limited. The device responds to a sustained overcurrent condition by turning off after a TON delay. The device then stays off for a period, TOFF, that is 32 times the TON delay. The device then begins pulsing on and off at the TON/(TON+TOFF) duty cycle of 3%. This drastically reduces the power dissipation during short circuit and means heat sinks need only accommodate normal operation. On the 3 leaded versions of the device TON is fixed at 750µs, on the adjustable 5 leaded versions an external capacitor sets the on time — the off time is always 32 times TON. The external timing control pin, CT, on the five leaded versions also serves as a shutdown input when pulled low. Internal power dissipation is further controlled with thermal overload protection circuitry. Thermal shutdown occurs if the junction temperature exceeds 165°C. The chip will remain off until the temperature has dropped 20°C. The UCC283 series is specified for operation over the industrial range of −40°C to +85°C, and the UCC383 series is specified from 0°C to +70°C. These devices are available in 3 and 5 pin TO-220 and TO-263 power packages. BLOCK DIAGRAM UDG-98133 SLUS215 - OCTOBER 1998 UCC283-3/-5/-ADJ UCC383-3/-5/-ADJ CONNECTION DIAGRAMS ABSOLUTE MAXIMUM RATINGS VIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9V CT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . −0.3 to 3V ADJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . −0.3 to 9V Storage Temperature . . . . . . . . . . . . . . . . . . . −65°C to +150°C Junction Temperature . . . . . . . . . . . . . . . . . . . −55°C to +150°C Lead Temperature (Soldering, 10 sec.) . . . . . . . . . . . . . +300°C TO-263-3 (Front View) TD Package TO-263-5 (Front View) TD Package Currents are positive into, negative out of the specified terminal. Consult Packaging Section of Databook for thermal limitations and considerations of packages. All voltages are referenced to GND. See Note 1 TO-220-3 (Front View) T Package TO-220-5 (Front View) T Package See Note 1 See Note 1 Note 1: Tab = GND ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications hold for TA = 0°C to 70°C for the UCC383-X series, −40°C to +85°C for the UCC283-X, VVIN = VVOUT + 1.5V, IOUT = 10mA, CIN = 10µF, COUT = 22µF. For the 283-ADJ, VVIN = 6.5V, CT = 750pF, TJ = TA. PARAMETER TEST CONDITIONS MIN TYP MAX UNITS TJ = 25°C 4.925 5 5.075 V Over Temperature 4.875 5.125 V UCC283-5 Fixed 5V, 3A Family Output Voltage Line Regulation VVIN = 5.15V to 9V 2 10 mV Load Regulation IOUT = 10mA to 3A 10 20 mV Dropout Voltage, VDROPOUT = VVIN − VVOUT IOUT = 3A, VOUT = 4.85V 0.4 0.6 V IOUT = 1.5A, VOUT = 4.85V 0.2 0.45 V IOUT = 10mA, VOUT = 4.85V Peak Current Limit VVOUT = 0V Overcurrent Threshold Current Limit Duty Cycle VVOUT = 0V Overcurrent Time Out, TON VVOUT = 0V Quiescent Current No load Reverse Leakage Current 0V < VVIN < VVOUT, VVOUT ≤ 5.1V, at VVOUT UVLO VIN where VOUT passes current 2 50 150 mV 4 5 6.5 A 3 4 5.5 A 3 5 % 400 750 1400 µs 400 650 µA 0 75 mA 2.8 3 V 2.6 UCC283-3/-5/-ADJ UCC383-3/-5/-ADJ ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications hold for TA = 0°C to 70°C for the UCC383-X series, −40°C to +85°C for the UCC283-X, VVIN = VVOUT + 1.5V, IOUT = 10mA, CIN = 10µF, COUT = 22µF. For the 283-ADJ, VVIN = 6.5V, CT = 750pF, TJ = TA. PARAMETER TEST CONDITIONS MIN TYP MAX UNITS TJ = 25°C 3.25 3.3 3.35 V Over Temperature 3.22 3.38 V UCC283-3 Fixed 3.3V, 3A Family Output Voltage Line Regulation VVIN = 3.45V to 9V 2 7 mV Load Regulation IOUT = 10mA to 3A 7 15 mV Dropout Voltage, VDROPOUT = VVIN - VVOUT IOUT = 3A, VOUT = 3.15V 0.5 1 V IOUT = 1.5A, VOUT = 3.15V 0.25 0.6 V IOUT = 10mA, VOUT = 3.15V Peak Current Limit VVOUT = 0V Overcurrent Threshold Current Limit Duty Cycle 50 150 mV 4 5 6.5 A 3 4 5.5 A 3 5 % VVOUT = 0V 750 1400 µs 400 650 µA 0 75 mA 2.6 2.8 3 V TJ = 25°C 1.23 1.25 1.27 V Over Temperature 1.22 1.28 V Overcurrent Time Out, TON VVOUT = 0V Quiescent Current No load 400 Reverse Leakage Current 0V < VVIN < VVOUT, VVOUT ≤ 3.35V, at VVOUT UVLO VIN where VOUT passes current UCC283-ADJ Adjustable Output, 3A Family Regulating Voltage at ADJ Pin Line Regulation, at ADJ Input VVIN = VVOUT + 150mV to 9V 1 3 mV Load Regulation, at ADJ Input IOUT = 10mA to 3A 2 5 mV Dropout Voltage, VDROPOUT = VIN − VOUT VVIN > 4V, IOUT = 3A 0.4 0.6 V VVIN > 3V, IOUT = 1.5A 0.2 0.45 V 50 150 mV Peak Current Limit VVIN > 3V, IOUT = 10mA VVOUT = 0V, VIN = 6.5V 4 5 6.5 A Overcurrent Threshold VVIN = 6.5V 3 4 5.5 A 3 5 Current Limit Duty Cycle VVOUT = 0V Overcurrent Time Out, TON VVOUT = 0V, CT = 1500pF Reverse Leakage Current 0V < VVIN < VVOUT, VVOUT ≤ 9V, at VVOUT Bias current at ADJ Input Quiescent Current No load Shutdown Threshold At CT Input Quiescent Current in Shutdown VVIN = 10V UVLO VIN where VOUT passes current 3 % µs 750 0 100 mA 100 250 nA 400 650 µA 0.25 0.45 V 40 75 µA 2.6 2.8 3 V UCC283-3/-5/-ADJ UCC383-3/-5/-ADJ PIN DESCRIPTIONS GND: Reference ground. ADJ: Adjust pin for the UCC283-ADJ version only. Feedback pin for the linear regulator. Program the output voltage with R1 connected from ADJ to GND and R2 connected from VOUT to ADJ. Output voltage is given by: VOUT = VIN: Input voltage, This pin must be bypassed with a low ESL/ESR 1µF or larger capacitor to GND. VIN can range from (VOUT + VDROPOUT) to 9V. If VIN is reduced to zero while VOUT is held high, the reverse leakage from VOUT to VIN is less than 75µA. 1. 25V · (R1+ R 2) R1 CT: Short circuit timing capacitor and shutdown input for the UCC283-ADJ version. Pulling CT below 0.25V turns off the regulator and places it in a low quiescent current mode. A timing capacitor, C, from CT to GND programs the duration of the pulsed short circuit on-time. On-time, TON, is approximately given by: TON = 500k · C. VOUT: Regulated output voltage. A bypass capacitor is not required at VOUT, but may be desired for good transient response. The bypass capacitor must not exceed a maximum value in order to insure the regulator can start. ORDERING INFORMATION Table I. Package Information Temperature Range Package Output Voltage 2: –40°C to +85°C T: TO-220 3: 3.3V 3: 0°C to +70°C TD: TO-263 5: 5V ADJ: Adjustable APPLICATION INFORMATION large, the output voltage will not come into regulation during the initial TON period and the UCC383 will enter pulsed mode operation. The peak current limit, TON period, and load characteristics determine the maximum value of output capacitor that can be charged. For a constant current load the maximum output capacitance is given as follows: Overview The UCC383 family of low dropout linear (LDO) regulators provide a regulated output voltage for applications with up to 3A of load current. The regulators feature a low dropout voltage and short circuit protection, making their use ideal for demanding high current applications requiring fault protection. T COUT (max) = (ICL - I LOAD ) · ON Farads VOUT Short Circuit Protection The UCC383 provides unique short circuit protection circuitry that reduces power dissipation during a fault. When an overload situation is detected, the device enters a pulsed mode of operation at 3% duty cycle reducing the heat sink requirements during a fault. The UCC383 has two current thresholds that determine its behavior during a fault as shown in Figure 1.When the regulator current exceeds the overcurrent threshold for a period longer than TON, the UCC383 shuts off for a period (TOFF) which is 32 times TON. During an overload, the regulator actively limits the maximum current to the peak current limit value. The peak current limit is nominally 1 Amp greater than the overcurrent threshold. The regulator will continue in pulsed mode until the fault is cleared as illustrated in Figure 1. (1) For worst case calculations the minimum values of on time (TON) and peak current limit (ICL) should be used. The adjustable version allows the TON time to be adjusted with a capacitor on the CT pin: TON ( ADJ ) = 500, 000 · C ( m Farad ) microseconds (2) TON ( m sec) = 500, 000 · C ( m Farads ) For a resistive load (RLOAD) the maximum output capacitor can be estimated from: COUT (max) = Short Circuit Protection A capacitive load on the regulator’s output will appear as a short circuit during start-up. If the capacitance is too 4 TON (sec) æ ç ç 1 RLOAD · lnç VOUT ç1ICL · RLOAD è ö ÷ ÷ ÷ ÷ ø Farads (3) UCC283-3/-5/-ADJ UCC383-3/-5/-ADJ APPLICATION INFORMATION (cont.) Figure 1. UCC383 Short Circuit Timing versions of the part, as well as the adjustable version programmed to 3.0V. Dropout Performance Referring to the Block Diagram, the dropout voltage of the UCC383 is equal to the minimum voltage drop (VIN to VOUT) across the N-Channel MOSFET. The dropout voltage is dependent on operating conditions such as load current, input and load voltages, as well as temperature. The UCC383 achieves a low RDS(ON) through the use of an internal charge-pump (VPUMP) that drives the MOSFET gate. Figure 2 depicts typical dropout voltages versus load current for the 3.3V and 5V Vout = 3V Vout = 3.3V Figure 3. depicts the typical dropout performance of the adjustable version with various output voltages and load currents. Operating temperatures also effect the RDS(ON) and dropout voltage of the UCC383. Figure 4. graphs the typical dropout for the 3.3V and 5V versions with a 3A load over temperature. Vout = 5V Iout = 1A Iout = 1.5A Iout = 3A 0.8 0.5 0.7 VIN – VOUT(V) VIN – VOUT (V) 0.4 0.3 0.2 0.6 0.5 0.4 0.3 0.2 0.1 0.1 0 0 1 1.5 2 2.5 3 3 Iout (A) Figure 2. UCC383 Typical Dropout vs. Load Current 3.5 4 VOUT (V) 4.5 5 Figure 3. Typical Dropout Voltage vs. IOUT and VVOUT 5 UCC283-3/-5/-ADJ UCC383-3/-5/-ADJ Thermal Design Voltage Programming and Shutdown Feature for Adjustable Version The Packing Information section of the data book contains reference material for the thermal ratings of various packages. The section also includes an excellent article Thermal Characteristics of Surface Mount Packages, that is the basis of the following discussion. A typical application circuit based on the UCC383 adjustable version is shown in Figure 5. The output voltage is externally programmed through a resistive divider at the ADJ pin. æ R2 ö ÷ volts VOUT = 1. 25 ·ç1+ è R1ø Thermal design for the UCC383 includes two modes of operation, normal and pulsed mode. In normal operation, the linear regulator and heat sink must dissipate power equal to the maximum forward voltage drop multiplied by the maximum load current. Assuming a constant current load, the expected heat rise at the regulator’s junction can be calculated as follows: (4) The maximum programmed output voltage is constrained by the 9V absolute rating of the IC (this includes the charge pump voltage) and its ability to enhance the NChannel MOSFET. Unless the load current is below the 3A rating of the device, output voltages above 7V are not recommended. The minimum output voltage can be programmed down to 1.25V, however, the input voltage must always be greater than the UVLO of the part. TRISE ( q ) = PDISS · (q jc + q ca ) °C (5) Where theta, (θ) is thermal resistance and PDISS is the power dissipated. The thermal resistance of both the TO-220 and TO-263 packages (junction to case) is 3 degrees Celsius per Watt. In order to prevent the regulator from going into thermal shutdown, the case to ambient theta must keep the junction temperature below 150°C. If the LDO is mounted on a 5 square inch pad of 1 ounce copper, for example, the thermal resistance from junction to ambient becomes 60 degrees Celsius per Watt. If a lower thermal resistance is required by the application, the device heat sinking would need to be improved. The adjustable version includes a shutdown feature, limiting quiescent current to 40uA typical. The UCC383 is shutdown by pulling the CT pin to below 0.25V. As shown in Figure 4, a small logic level MOSFET or BJT transistor in parallel with the timing capacitor can be driven with a digital signal, putting the device in shutdown. If the CT pin is not pulled low, the IC will internally pull up on the pin enabling the regulator. The CT pin should not be forced high, as this will interfere with the short circuit protection feature. Selection of the timing capacitor is explained in Short Circuit Protection. The adjustable version can be used in applications requiring remote voltage sensing (i.e. monitoring a voltage other than or not directly tied to the VOUT pin). This is possible since the inverting input of the voltage amplifier (see Block Diagram) is brought out to the ADJ pin. Vout = 3.3v Vout = 5v 0.5 IDD CURRENT(mAMPS) VIN – VOUT (mv) 0.6 0.5 0.4 0.3 0.4 0.3 0.2 0.1 0 0.2 -40 10 0 60 1 2 3 LOAD CURRENT (AMPS) TEMPERATURE (°C) Figure 4. Typical dropout voltage vs. case temperature with a 3A load Figure 5. Typical application for the 5 pin adjustable version. 6 UCC283-3/-5/-ADJ UCC383-3/-5/-ADJ When the UCC383 regulator is in pulsed mode due to an overload or short circuit in the application, the maximum average power dissipation is calculated as follows: Ripple Rejection Even though the UCC383 family of linear regulators are not optimized for fast transient applications (Refer to UC182 Fast LDO Linear Regulator), they do offer significant power supply rejection at lower frequencies. Figure 6 depicts ripple rejection performance in a typical application. The performance can be improved with additional filtering. TON (6) PPULSE _ AVE = (VIN – VOUT ) · ICL · Watts 33 ·TON As seen in equation 6, the average power during a fault is reduced dramatically by the duty cycle, allowing the heat sink to be sized for normal operation. Although the peak power in the regulator during the TON period can be significant, the thermal mass of the package will generally keep the junction temperature from rising unless the TON period is increased to tens of milliseconds. Figure 6. Typical supply current vs. load current. UDG-94093 Figure 7. Ripple rejection vs. frequency. UNITRODE CORPORATION 7 CONTINENTAL BLVD. • MERRIMACK, NH 03054 TEL. (603) 424-2410 FAX (603) 424-3460 7 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. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. 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