UNITRODE UC182-1, UC182-2, UC182-3, UC282-1, UC282-2 Technical data

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Fast LDO Linear Regulator

UC182-1,-2,-3,-ADJ
UC282-1,-2,-3,-ADJ
UC382-1,-2,-3,-ADJ

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

BLOCK DIAGRAM

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 100°C 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.

SLUS317 - JANUARY 1999

UDG-96037-1

ABSOLUTE MAXIMUM RATINGS

VB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13V

VIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7.5V

Output Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . +1.2V to 6.0V

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. Consult Packaging Section of Databook for thermal limita­tions and considerations of packages.

CONNECTION DIAGRAMS

UC182-1,-2,-3,-ADJ
UC282-1,-2,-3,-ADJ
UC382-1,-2,-3,-ADJ

ORDERING INFORMATION

Temperature Range Package Output Voltage

1: –55°C to +125°C T: TO-220 1: 1.5V
2: –25°C to +100°C TD: TO-263 2: 2.1V
3: 0°C to +100°C 3: 2.5V

ADJ: 1.2V or Adjustable

5-Pin TO-220 (Top View)
T Package

Note: Tab tied to Pin 3.

5-Pin TO-263 (Top View)
TD Package

Note: Tab tied to Pin 3.

ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these parameters apply for TA = –55°C to 125°C for the

UC182-X series, –25°C to +100°C for the UC282-X series and 0°C to +100°C for the UC382-X, VB = 5V; VIN = 3.3V, VOUT =

2.5V for the UC382-ADJ, TA = TJ.

PARAMETERS TEST CONDITIONS MIN TYP MAX UNITS

UC382-3 Fixed 2.5V, 3A Family

Output Voltage (I

Load Regulation I
VIN PSSR 80 100 dB
VB PSSR 50 60 dB
VIN Dropout Voltage = VIN–VOUT I

VB Dropout = VB–VOUT I

Short Circuit Current Limit 3.3 4.5 A
VB Current I

VIN Current I

UC382-2 Fixed 2.1V, 3A Family

Output Voltage (IVOUT = 100mA) UC382-2 2.079 2.100 2.121 V

Load Regulation I
VIN PSSR 80 100 dB

VOUT = 100mA) UC382-3 2.475 2.500 2.525 V

UC282-3 and UC182-3 2.450 2.500 2.525 V

VOUT = 10mA to 3A 0.5 4 mV

VOUT = 3A, TJ = 25°C 350 425 mV
VOUT = 3A, UC382-3 350 450 mV

I

VOUT = 3A, UC282-3 and UC182-3 350 500 mV

I

VOUT = 3A, UC382-3 1.8 2.10 V
VOUT = 3A, UC282-3 1.8 2.20 V

I

VOUT = 3A, UC182-3 1.8 2.35 V

I

VOUT = 10mA 6 9 mA
VOUT = 3A 18 60 mA

I

VOUT = 3A 2.94 2.97 A

UC282-2 and UC182-2 2.058 2.100 2.121 V

VOUT = 10mA to 3A 0.5 4 mV

2

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 = –55°C to 125°C for the

UC182-X series, –25°C to +100°C for the UC282-X series and 0°C to +100°C for the UC382-X, VB = 5V; VIN = 3.3V, VOUT =

2.5V for the UC382-ADJ, TA = TJ.

PARAMETERS TEST CONDITIONS MIN TYP MAX UNITS

UC382-2 Fixed 2.1V, 3A Family (cont.)

VB PSSR 52 62 dB
VIN Dropout Voltage = VIN–VOUT IVOUT = 3A, TJ = 25°C 350 425 mV

VOUT = 3A, UC382-2 350 450 mV

I

VOUT = 3A, UC282-2 and UC182-2 350 500 mV

I

VB Dropout = VB–VOUT I

VOUT = 3A, UC382-2 1.8 2.10 V
VOUT = 3A, UC282-2 1.8 2.20 V

I

VOUT = 3A, UC182-2 1.8 2.35 V

I
Short Circuit Current Limit 3.3 4.5 A
VB Current I

VIN Current I

VOUT = 10mA 6 9 mA
VOUT = 3A 18 60 mA

I

VOUT = 3A 2.94 2.97 A

UC382-1 Fixed 1.5V, 3A Family

Output Voltage (IVOUT = 100mA) UC382-1 1.485 1.500 1.515 V

UC282-1 and UC182-1 1.470 1.500 1.515 V
Load Regulation I

VOUT = 10mA to 3A 0.5 4 mV

VIN PSSR 80 100 dB
VB PSSR 55 65 dB
VIN Dropout Voltage = VIN–VOUT I

VB Dropout = VB–VOUT I

VOUT = 3A, TJ = 25°C 350 425 mV
VOUT = 3A, UC282-1 350 450 mV

I

VOUT = 3A, UC282-2 and UC182-1 350 500 mV

I

VOUT = 3A, UC382-1 1.8 2.10 V
VOUT = 3A, UC282-1 1.8 2.20 V

I

VOUT = 3A, UC182-1 1.8 2.35 V

I
Short Circuit Current Limit 3.3 4.5 A
VB Current I

VIN Current I

VOUT = 10mA 6 9 mA
VOUT = 3A 18 60 mA

I

VOUT = 3A 2.94 2.97 A

UC382-ADJ Adjustable, 3A Family

ADJ Voltage (IVOUT = 100 mA) UC382-ADJ 1.188 1.200 1.212 V

UC282-ADJ and UC182-ADJ 1.176 1.200 1.212 V
Load Regulation I

VOUT = 10mA to 3A 0.5 4 mV

VIN PSSR VOUT Programmed for 2.5V 80 100 dB
VB PSSR VOUT Programmed for 2.5V 50 60 dB
VIN Dropout Voltage = VIN–VOUT I

VB Dropout = VB–VOUT I

VOUT = 3A, TJ = 25°C 350 425 mV
VOUT = 3A, UC382-ADJ 350 450 mV

I

VOUT = 3A, UC282-ADJ and UC182-ADJ 350 500 mV

I

VOUT = 3A, UC382-ADJ 1.8 2.10 V
VOUT = 3A, UC282-ADJ 1.8 2.20 V

I
Short Circuit Current Limit 3.3 4.5 A
VB Current I

VIN Current I

VOUT = 10mA 6 9 mA
VOUT = 3A 18 60 mA

I

VOUT = 3A 2.94 2.97 A

3

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 < 100Ω.
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

UC182-1,-2,-3,-ADJ
UC282-1,-2,-3,-ADJ
UC382-1,-2,-3,-ADJ

impedance and fast response. (Dropout is derated for
junction temperatures below 0°C.)

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 T

J = 0°C to +110°C. (Dropout is derated for junction

temperatures over 110°C.) 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 througha5pin
package, care must be taken since voltage drops along
wire traces add to the dropout voltage.

1.9

1.8

(V)

DROPOUT

1.7

V

1.6
0123

I

L(A)

Figure 1. Typical Dropout (VB- V

), TJ= 27°C

OUT

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 100µFof
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

400

300

(mV)

DROPOUT

200

V

100

100mA

1A 2A

L

I

Figure 2. Typical Dropout (VIN- V

), TJ= 27°C

OUT

3A

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

APPLICATION INFORMATION (cont.)

UC182-1,-2,-3,-ADJ
UC282-1,-2,-3,-ADJ
UC382-1,-2,-3,-ADJ

Figure 3. Open Loop Gain (100µF Output
Capacitance, 1A Load).

60

50

40

30

dB

20

10

0

100 1k 10k 100k 1M 10M

Figure 5. PSRR (VB) 2.5V Out.

Figure 4. Open Loop Phase (100µF Output
Capacitance, 1A Load).

FREQUENCY (Hz)

Figure 6. Transient test circuit.

UDG-96038

5

APPLICATION INFORMATION (cont.)

∆V

O

10mV/DIV

I

L

1A/DIV

UC182-1,-2,-3,-ADJ
UC282-1,-2,-3,-ADJ
UC382-1,-2,-3,-ADJ

Figure 7. 10mA to 3A/µs load transient response.

UDG-96039

Figure 8. Typical UC382-ADJ application

2 s/DIVµ

UDG-96040

Figure 9. Typical UC382-1, -2, or -3 application

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