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UC182-1,-2,-3,-ADJ UC282-1,-2,-3,-ADJ UC382-1,-2,-3,-ADJ
Fast LDO Linear Regulator
FEATURES
* Fast Transient Response * 10mA to 3A Load Current * Short Circuit Protection * Maximum Dropout of 450mV at 3A Load Current * Separate Bias and VIN Pins * Available in Adjustable or Fixed Output Voltages * 5 Pin Package allows Kelvin Sensing of Load Voltage * Reverse Current Protection DESCRIPTION The UC382 is a low dropout linear regulator providing a quick response to fast load changes. Combined with its precision on-board reference, the UC382 excels at driving GTL and BTL buses. Due to its fast response to load transients, the total capacitance required to decouple the regulator's output can be significantly decreased when compared to standard LDO linear regulators. Dropout voltage (VIN to VOUT) is only 450mV maximum at 100C and 350mV typical at 3A load. The on-board bandgap reference is stable with temperature and scaled for a 1.200V input to the internal power amplifier. The UC382 is available in fixed output voltages of 1.5V, 2.1V, or 2.5V. The output voltage of the adjustable version can be set with two external resistors. If the external resistors are omitted, the output voltage defaults to 1.2V.
BLOCK DIAGRAM
UDG-96037-1
SLUS317 - JANUARY 1999
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UC182-1,-2,-3,-ADJ UC282-1,-2,-3,-ADJ UC382-1,-2,-3,-ADJ ABSOLUTE MAXIMUM RATINGS
VB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13V VIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7.5V Output Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . +1.2V to 6.0V Storage Temperature . . . . . . . . . . . . . . . . . . . -65C to +150C Junction Temperature . . . . . . . . . . . . . . . . . . . -55C to +150C Lead Temperature (Soldering, 10 sec.) . . . . . . . . . . . . . +300C
ORDERING INFORMATION
Currents are positive into, negative out of the specified terminal. Consult Packaging Section of Databook for thermal limitations and considerations of packages.
Temperature Range Package Output Voltage 1: -55C to +125C T: TO-220 1: 1.5V 2: -25C to +100C TD: TO-263 2: 2.1V 3: 0C to +100C 3: 2.5V ADJ: 1.2V or Adjustable
CONNECTION DIAGRAMS
5-Pin TO-220 (Top View) T Package 5-Pin TO-263 (Top View) TD Package
Note: Tab tied to Pin 3.
Note: Tab tied to Pin 3.
ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these parameters apply for TA = -55C to 125C for the UC182-X series, -25C to +100C for the UC282-X series and 0C to +100C for the UC382-X, VB = 5V; VIN = 3.3V, VOUT = 2.5V for the UC382-ADJ, TA = TJ.
PARAMETERS UC382-3 Fixed 2.5V, 3A Family Output Voltage (IVOUT = 100mA) Load Regulation VIN PSSR VB PSSR VIN Dropout Voltage = VIN-VOUT IVOUT = 3A, TJ = 25C IVOUT = 3A, UC382-3 IVOUT = 3A, UC282-3 and UC182-3 VB Dropout = VB-VOUT IVOUT = 3A, UC382-3 IVOUT = 3A, UC282-3 IVOUT = 3A, UC182-3 Short Circuit Current Limit VB Current VIN Current UC382-2 Fixed 2.1V, 3A Family Output Voltage (IVOUT = 100mA) Load Regulation VIN PSSR UC382-2 UC282-2 and UC182-2 IVOUT = 10mA to 3A 80 2.079 2.058 2.100 2.100 0.5 100 2.121 2.121 4 V V mV dB IVOUT = 10mA IVOUT = 3A IVOUT = 3A 2.94 3.3 6 18 2.97 UC382-3 UC282-3 and UC182-3 IVOUT = 10mA to 3A 80 50 2.475 2.450 2.500 2.500 0.5 100 60 350 350 350 1.8 1.8 1.8 425 450 500 2.10 2.20 2.35 4.5 9 60 2.525 2.525 4 V V mV dB dB mV mV mV V V V A mA mA A TEST CONDITIONS MIN TYP MAX UNITS
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UC182-1,-2,-3,-ADJ UC282-1,-2,-3,-ADJ UC382-1,-2,-3,-ADJ ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these parameters apply for TA = -55C to 125C for the UC182-X series, -25C to +100C for the UC282-X series and 0C to +100C for the UC382-X, VB = 5V; VIN = 3.3V, VOUT = 2.5V for the UC382-ADJ, TA = TJ.
PARAMETERS UC382-2 Fixed 2.1V, 3A Family (cont.) VB PSSR VIN Dropout Voltage = VIN-VOUT IVOUT = 3A, TJ = 25C IVOUT = 3A, UC382-2 IVOUT = 3A, UC282-2 and UC182-2 VB Dropout = VB-VOUT IVOUT = 3A, UC382-2 IVOUT = 3A, UC282-2 IVOUT = 3A, UC182-2 Short Circuit Current Limit VB Current VIN Current UC382-1 Fixed 1.5V, 3A Family Output Voltage (IVOUT = 100mA) Load Regulation VIN PSSR VB PSSR VIN Dropout Voltage = VIN-VOUT IVOUT = 3A, TJ = 25C IVOUT = 3A, UC282-1 IVOUT = 3A, UC282-2 and UC182-1 VB Dropout = VB-VOUT IVOUT = 3A, UC382-1 IVOUT = 3A, UC282-1 IVOUT = 3A, UC182-1 Short Circuit Current Limit VB Current VIN Current UC382-ADJ Adjustable, 3A Family ADJ Voltage (IVOUT = 100 mA) Load Regulation VIN PSSR VB PSSR VIN Dropout Voltage = VIN-VOUT UC382-ADJ UC282-ADJ and UC182-ADJ IVOUT = 10mA to 3A VOUT Programmed for 2.5V VOUT Programmed for 2.5V IVOUT = 3A, TJ = 25C IVOUT = 3A, UC382-ADJ IVOUT = 3A, UC282-ADJ and UC182-ADJ VB Dropout = VB-VOUT Short Circuit Current Limit VB Current VIN Current IVOUT = 10mA IVOUT = 3A IVOUT = 3A 2.94 IVOUT = 3A, UC382-ADJ IVOUT = 3A, UC282-ADJ 3.3 6 18 2.97 80 50 1.188 1.176 1.200 1.200 0.5 100 60 350 350 350 1.8 1.8 425 450 500 2.10 2.20 4.5 9 60 1.212 1.212 4 V V mV dB dB mV mV mV V V A mA mA A IVOUT = 10mA IVOUT = 3A IVOUT = 3A 2.94 3.3 6 18 2.97 UC382-1 UC282-1 and UC182-1 IVOUT = 10mA to 3A 80 55 1.485 1.500 1.470 1.500 0.5 100 65 350 350 350 1.8 1.8 1.8 425 450 500 2.10 2.20 2.35 4.5 9 60 1.515 1.515 4 V V mV dB dB mV mV mV V V V A mA mA A IVOUT = 10mA IVOUT = 3A IVOUT = 3A 2.94 3.3 6 18 2.97 52 62 350 350 350 1.8 1.8 1.8 425 450 500 2.10 2.20 2.35 4.5 9 60 dB mV mV mV V V V A mA mA A TEST CONDITIONS MIN TYP MAX UNITS
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UC182-1,-2,-3,-ADJ UC282-1,-2,-3,-ADJ UC382-1,-2,-3,-ADJ PIN DESCRIPTIONS
ADJ: In the adjustable version, the user programs the output voltage with two external resistors. The resistors should be 0.1% for high accuracy. The output amplifier is configured as a non-inverting operational amplifier. The resistors should meet the criteria of R3 || R4 < 100. Connect ADJ to VOUT for an output voltage of 1.2V. Note that the point at which the feedback network is connected to the output is the Kelvin sense point. GND: For accurate results, the GND pin should be referenced to the load ground. VB: Supplies power to all circuits of the regulator except the collector of the output power transistor. The 2V headroom from VB to VOUT allows the use of a Darlington output stage for inherently low output impedance and fast response. (Dropout is derated for junction temperatures below 0C.) VIN: Supplies the current to the collector of the output power transistor only. The dropout (VIN-VOUT) is under 100mV for light loads; maximum dropout is 450mV at 3A for TJ = 0C to +110C. (Dropout is derated for junction temperatures over 110C.) At full load, the majority of the VB current is going to the load. VOUT: This pin should be connected to the load via a low impedance path. Avoid connectors which add significant inductance and resistance. Note that even though a Kelvin sense is available through a 5 pin package, care must be taken since voltage drops along wire traces add to the dropout voltage.
1.9
400
1.8
VDROPOUT (mV)
VDROPOUT (V)
300
1.7
200
1.6 0 1 IL (A) 2 3
100 100mA
1A IL
2A
3A
Figure 1. Typical Dropout (VB - VOUT), TJ = 27C
Figure 2. Typical Dropout (VIN - VOUT), TJ = 27C
APPLICATION INFORMATION
The UC382 is easy to use. The adjustable version requires two 0.1% resistors to set the output voltage. The fixed versions of the UC382 require no external resistors. All versions of the UC382 require decoupling capacitors on the input and output. In a typical application, VB and VIN are driven from switching power supplies which may have large filter capacitors at their outputs. If the UC382 is further than 12 inches from the power supply, it is recommended to add local decoupling as close as possible to the linear regulator. Decouple the output of the UC382 with at least 100F of high quality tantalum or Sanyo OSCON capacitors close to the VOUT pin for maximum stability. Many applications involving ultra fast GTL or BTL applications require additional capacitance close to the load. The exact amount will vary according to speed and magnitude of the load transients and the tolerance allowed for transients on VOUT. When specifying the decoupling capacitors, the series resistance of the capacitor bank is an important factor in its ability to filter load transients. The UC382 allows for Kelvin sensing the voltage at the load. This improves regulation performance and eliminates the voltage drops due to wire trace resistance. This voltage drop must be added to the headroom (VIN to VOUT and VB to VOUT). The dropout of 450mV is measured at the pins and does not include additional drops due to trace resistance. The minimum load current is 10mA. Two or more UC382's may be used in parallel. While stable, this arrangement does degrade the transient response. 4
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UC182-1,-2,-3,-ADJ UC282-1,-2,-3,-ADJ UC382-1,-2,-3,-ADJ APPLICATION INFORMATION (cont.)
Figure 3. Open Loop Gain (100F Output Capacitance, 1A Load).
Figure 4. Open Loop Phase (100F Output Capacitance, 1A Load).
60 50 40
dB
30 20 10 0 100
1k
10k
100k
1M
10M
FREQUENCY (Hz)
Figure 5. PSRR (VB) 2.5V Out.
UDG-96038
Figure 6. Transient test circuit.
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UC182-1,-2,-3,-ADJ UC282-1,-2,-3,-ADJ UC382-1,-2,-3,-ADJ APPLICATION INFORMATION (cont.)
VO 10mV/DIV
IL 1A/DIV
2s/DIV
Figure 7. 10mA to 3A/s load transient response.
UDG-96039
UDG-96040
Figure 8. Typical UC382-ADJ application
Figure 9. Typical UC382-1, -2, or -3 application
UNITRODE CORPORATION 7 CONTINENTAL BLVD. * MERRIMACK, NH 03054 TEL. (603) 424-2410 FAX (603) 424-3460
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