Datasheet REG103UA-5, REG103UA-5-2K5, REG103UA-A, REG103UA-A-2K5, REG103FA-A-500 Datasheet (Burr Brown)

®

For most current data sheet and other product

information, visit www.burr-brown.com

500mA Low Dropout Regulator

REG103

REG103

REG103

DMOS

REG103

FEATURES

● NEW DMOS TOPOLOGY:

Ultra Low Dropout Voltage:

115mV typ at 500mA and 3.3V Output

Output capacitor NOT required for stability

● FAST TRANSIENT RESPONSE

●

VERY LOW NOISE:

33µVrms

● HIGH ACCURACY: ±2% max

● HIGH EFFICIENCY:

I

= 1mA at I

GND

Not Enabled: I

= 500mA

OUT

= 0.5µA

GND

● 2.5V, 2.7V, 3.0V, 3.3V, 5.0V AND

ADJUSTABLE OUTPUT VERSIONS

● FOLDBACK CURRENT LIMIT

● THERMAL PROTECTION

● OUTPUT VOLTAGE ERROR INDICATOR

● SMALL SURFACE-MOUNT PACKAGES:

SOT223-5, DDPAK-5, SO-8

APPLICATIONS

● PORTABLE COMMUNICATION DEVICES

● BATTERY-POWERED EQUIPMENT

● PERSONAL DIGITAL ASSISTANTS

● MODEMS

● BAR-CODE SCANNERS

● BACKUP POWER SUPPLIES

(1)

DESCRIPTION

The REG103 is a family of low noise, low dropout
linear regulators with low ground pin current. Its new
DMOS topology provides significant improvement
over previous designs, including low dropout voltage
(only 115mV typ at full load), and better transient
performance. In addition, no output capacitor is re­quired for stability, unlike conventional low dropout
regulators that are difficult to compensate and require
expensive low ESR capacitors greater than 1µF.

Typical ground pin current is only 1mA (at I
500mA) and drops to 0.5µA in “not enabled” mode.
Unlike regulators with PNP pass devices, quiescent
current remains relatively constant over load varia­tions and under dropout conditions.

The REG103 has very low output noise (typically
33µVrms for V

= 3.3V with CNR = 0.01µF),

OUT

making it ideal for use in portable communications
equipment. On-chip trimming results in high output
voltage accuracy. Accuracy is maintained over tem­perature, line, and load variations. Key parameters are
guaranteed over the specified temperature range
(–40°C to +85°C).

The SO-8 version of the REG103 has an Error pin
which provides a “power good” flag indicating the
regulator is in regulation. The REG103 is well pro­tected: internal circuitry provides a current limit which
protects the load from damage. Thermal protection
circuitry keeps the chip from being damaged by exces­sive temperature. In addition to the SO-8 package, the
REG103 is also available in the DDPAK and the
SOT223-5.

OUT

=

Enable

V

IN

+

0.1µF

NR

NR = Noise Reduction

International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: [phone]

Twx: 910-952-1111 • Internet: http://www.burr-brown.com/ • Cable: BBRCORP • Telex: 066-6491 • FAX: [phone] • Immediate Product Info: [phone]

©

2000 Burr-Brown Corporation PDS-1527C Printed in U.S.A. July, 2000

REG103

(Fixed Voltage

Versions)

Gnd

NOTE: (1) SO-8 Package Only. (2) Optional.

V

OUT

+

(2)

C

OUT

V

IN

+

0.1µF

1

Enable

REG103-A

Gnd

(1)

Error

Error

(1)

REG103

R
Adj
R

V

OUT

+

1

2

(2)

C

OUT

®

SPECIFICATIONS

At TJ = +25°C, VIN = V
Boldface limits apply over the specified temperature range, T

OUT

+ 1V (V

= 3.0V for REG103-A), V

OUT

= 2V, I

ENABLE

= –40°C to +85°C.

J

OUT

= 10mA, CNR = 0.01µF, and C

OUT

PARAMETER CONDITION MIN TYP MAX UNITS
OUTPUT VOLTAGE

Output Voltage Range V

REG103-2.5 2.5 V

OUT

REG103-2.7 2.7 V
REG103-3.0 3.0 V
REG103-3.3 3.3 V
REG103-5 5V
REG103-A V

Reference Voltage V
Adjust Pin Current I

Accuracy ±0.5 ±2%

T

= –40°C to +85°C ±2.8 %

J

vs Temperature dV

vs Line and Load

T

= –40°C to +85°CV

J

DC DROPOUT VOLTAGE

For all models except 5V I

(2, 3)

For 5V model I

For all models except 5V I

T

= –40°C to +85°C

J

For 5V models I

T

= –40°C to +85°C

J

VOLTAGE NOISE

f = 10Hz to 100kHz V
Without CNR (all models) CNR = 0, C
With C

(all fixed voltage models) CNR = 0.01µF, C

NR

OUTPUT CURRENT

Current Limit

T

(4)

= –40°C to +85°C 500 1000 mA

J

REF

ADJ

/dT TJ = –40°C to +85°C70ppm/°C

OUT

V

DROP

I

I

= 10mA to 500mA, VIN = (V

OUT

n

CL

= (V

IN

+ 0.9V) to 15V ±3.5 %

OUT

I

= 10mA 3 25 mV

OUT

= 500mA 115 200 mV

OUT

= 500mA 160 250 mV

OUT

= 500mA 230 mV

OUT

= 500mA 280 mV

OUT

+ 0.7V) to 15V

OUT

= 0 30µVrms/V • V

OUT

= 10µF10µVrms/V • V

OUT

REF

550 700 950 mA

RIPPLE REJECTION

f = 120Hz 65 dB

ENABLE CONTROL

V

High (output enabled) V

ENABLE

V

Low (output disabled) –0.2 0.5 V

ENABLE

I

High (output enabled) I

ENABLE

I

Low (output disabled) V

ENABLE

Output Disable Time 50 µs

ENABLE

ENABLE

V

= 2V to VIN, VIN = 2.1V to 6.5

ENABLE

= 0V to 0.5V 2 100 nA

ENABLE

(5)

2V

Output Enable Softstart Time 1.5 ms

ERROR FLAG

Current,
Voltage,

(6)

Logic High (open drain)—Normal Operation
Logic Low—On Error

VIN = V

= V

ERROR

Sinking 500µA 0.2 0.4 V

+ 1V 0.1 10 µA

OUT

THERMAL SHUTDOWN

Junction Temperature

Shutdown 150 °C
Reset from Shutdown 130 °C

GROUND PIN CURRENT

Ground Pin Current I

GND

Enable Pin Low V

INPUT VOLTAGE V
Operating Input Voltage Range

(7)

IN

Specified Input Voltage Range V

T

= –40°C to +85°CV

J

I

= 10mA 0.5 0.7 mA

OUT

I

= 500mA 1 1.3 mA

OUT

≤ 0.5V 0.5 µA

ENABLE

2.1 15 V

> 2.7V V

IN

> 2.9V V

IN

+ 0.7 15 V

OUT

+ 0.9 15 V

OUT

TEMPERATURE RANGE

Specified Range T
Operating Range –55 +125 °C
Storage Range –65 +150 °C

J

–40 +85 °C

Thermal Resistance

DDPAK-5 Surface Mount
SO-8 Surface Mount
SOT223-5 Surface Mount

θ

JC

θ

JA

θ

JC

Junction-to-Case 3 °C/W

Junction-to-Ambient 150 °C/W

Junction-to-Case 15 °C/W

NOTES: (1) The REG103 does not require a minimum output capacitor for stability. However, transient response can be improved with proper capacitor selection. (2) Dropout
voltage is defined as the input voltage minus the output voltage that produces a 2% change in the output voltage from the value at V
for V

less than 2.7V. (4) Current limit is the output current that produces a 10% change in output voltage from VIN = V

OUT

typical performance curve “V
regulates when V
T

= +25°C. See typical performance curve.

J

< V

IN

OUT

ENABLE

+ V

vs I

DROP (MAX)

.” (6) Logic low indicates out of regulation condition by approximately 10%, or thermal shutdown. (7) The REG103 no longer

ENABLE

. In drop-out or when the input voltage is between 2.7V and 2.1V, the impedance from VIN to V

OUT

(1)

= 0.1µF

, unless otherwise noted.

REG103GA
REG103UA
REG103FA

5.5 V

1.295 V

0.2 1 µA

±0.5 ±2.5 %

OUT
OUT

IN

1 100 nA

= V

+ 1V at fixed load. (3) Not applicable

IN

OUT

+ 1V and I

= 10mA. (4) For VIN > 6.5V see

OUT

is typically less than 1Ω at

OUT

µVrms
µVrms

V

®

REG103

2

PIN CONFIGURATIONS

Top View

DDPAK-5

1234

V

GND

O

(1)

NR/Adjust

5

V

IN

Enable

Tab is GND

V

V

NR/Adjust

GND

OUT

OUT

SO-8

1

2

(1)

3

4

8

7

6

5

V

IN

V

IN

Error

Enable

SOT223-5

Tab is GND

12345

GNDV

IN

V

OUT

Enable

NR/Adjust

(1)

(FA Package)

NOTE: (1) For REG103A-A: voltage setting resistor pin.
All other models: noise reduction capacitor pin.

ABSOLUTE MAXIMUM RATINGS

Supply Input Voltage, VIN.......................................................–0.3V to 16V

Enable Input ............................................................................ –0.3V to V

Error Flag Output .....................................................................–0.3V to 6V

Error Flag Current ...............................................................................2mA

Output Short-Circuit Duration ......................................................Indefinite

Operating Temperature Range ....................................... –55°C to +125°C

Storage Temperature Range .......................................... –65°C to +150°C

Junction Temperature ..................................................... –55°C to +150°C

Lead Temperature

NOTE: (1) Stresses above these ratings may cause permanent damage.
Exposure to absolute maximum conditions for extended periods may degrade
device reliability.

(soldering, 3s, SO-8, SOT and DDPAK)

(1)

................ +240°C

(UA Package)

IN

(GA Package)

ELECTROSTATIC
DISCHARGE SENSITIVITY

This integrated circuit can be damaged by ESD. Burr-Brown
recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling
and installation procedures can cause damage.

ESD damage can range from subtle performance degrada­tion to complete device failure. Precision integrated circuits
may be more susceptible to damage because very small
parametric changes could cause the device not to meet its
published specifications.

The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes
no responsibility for the use of this information, and all use of such information shall be entirely at the user's own risk. Prices and specifications are subject to change
without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant
any BURR-BROWN product for use in life support devices and/or systems.

3

REG103

®

PACKAGE/ORDERING INFORMATION

PACKAGE SPECIFIED

PRODUCT PACKAGE NUMBER RANGE MARKING NUMBER

5V Output

REG103FA-5

(2)

DDPAK-5 325 –40°C to +85°C REG103FA-5.0 REG103FA-5 Rails

DRAWING TEMPERATURE PACKAGE ORDERING TRANSPORT

"""""REG103FA-5/500 Tape and Reel

REG103UA-5 SO-8 182 –40°C to +85°C REG103U50 REG103UA-5 Rails

"""""REG103UA-5/2K5 Tape and Reel

REG103GA-5

(2)

SOT223-5 364 –40°C to +85°C R103G50 REG103GA-5 Rails

"""""REG103GA-5/2K5 Tape and Reel

3.3V Output

REG103FA-3.3

(2)

DDPAK-5 325 –40°C to +85°C REG103FA-3.3 REG103FA-3.3 Rails

"""""REG103FA-3.3/500 Tape and Reel

REG103UA-3.3 SO-8 182 –40°C to +85°C REG103UA4 REG103UA-3.3 Rails

"""""REG103UA-3.3/2K5 Tape and Reel

REG103GA-3.3

(2)

SOT223-5 364 –40°C to +85°C R103G33 REG103GA-3.3 Rails

"""""REG103GA-3.3/2K5 Tape and Reel

3.0V Output

REG103FA-3

REG103UA-3

REG103GA-3

(2)

"""""REG103FA-3/500 Tape and Reel

(2)

"""""REG103UA-3/2K5 Tape and Reel

(2)

DDPAK-5 325 –40°C to +85°C REG103FA-3.0 REG103FA-3 Rails

SO-8 182 –40°C to +85°C REG103U30 REG103UA-3 Rails

SOT223-5 364 –40°C to +85°C R103G30 REG103GA-3 Rails

"""""REG103GA-3/2K5 Tape and Reel

2.7V Output

REG103FA-2.7

(2)

DDPAK-5 325 –40°C to +85°C REG103FA-2.7 REG103FA-2.7 Rails

"""""REG103FA-2.7/500 Tape and Reel

REG103UA-2.7 SO-8 182 –40°C to +85°C REG103U27 REG103UA-2.7 Rails

"""""REG103UA-2.7/2K5 Tape and Reel

REG103GA-2.7

(2)

SOT223-5 364 –40°C to +85°C R103G27 REG103GA-2.7 Rails

"""""REG103GA-2.7/2K5 Tape and Reel

2.5V Output

REG103FA-2.5

(2)

DDPAK-5 325 –40°C to +85°C REG103FA-2.5 REG103FA-2.5 Rails

"""""REG103FA-2.5/500 Tape and Reel

REG103UA-2.5 SO-8 182 –40°C to +85°C REG103U25 REG103UA-2.5 Rails

"""""REG103UA-2.5/2K5 Tape and Reel

REG103GA-2.5

(2)

SOT223-5 364 –40°C to +85°C R103G25 REG103GA-2.5 Rails

"""""REG103GA-2.5/2K5 Tape and Reel

Adjustable Output

REG103FA-A

(2)

DDPAK-5 325 –40°C to +85°C REG103FAA REG103FA-A Rails

"""""REG103FA-A/500 Tape and Reel

REG103UA-A SO-8 182 –40°C to +85°C REG103UA REG103UA-A Rails

"""""REG103UA-A/2K5 Tape and Reel

REG103GA-A

(2)

SOT223-5 364 –40°C to +85°C R103GA REG103GA-A Rails

"""""REG103GA-A/2K5 Tape and Reel

NOTES: (1) Models with a slash (/) are available only in Tape and Reel in the quantities indicated (e.g., /2K5 indicates 2500 devices per reel). Ordering 2500 pieces
of “REG103UA-5/2K5” will get a single 2500-piece Tape and Reel. (2) Scheduled availability June, 2000.

(1)

MEDIA

®

REG103

4

TYPICAL PERFORMANCE CURVES

1000 200 300 400 500

180
160
140
120
100

80
60
40
20

0

DC Dropout Voltage (mV)

Output Current (mA)

DC DROPOUT VOLTAGE vs OUTPUT CURRENT

= –55°C
= +25°C
= +125°C

–75 –25–50 250 50 75 100 125

0.5

0.4

0.3

0.2

0.1

0

Output Voltage Change (%)

Temperature (°C)

LINE REGULATION vs TEMPERATURE

(V

IN

= V

OUT

+ 1V to VIN = 15V )

= 10mA
= 100mA

For all models, at TJ = +25°C and V

= 2V, unless otherwise noted.

ENABLE

OUTPUT VOLTAGE CHANGE vs I

(V

= V

IN

OUT

Refered to I

0.5

0

–0.5

–1.0

Output Voltage Change (%)

–1.5

= –55°C
= +25°C
= +125°C

1000 200 300 400 500

OUTPUT VOLTAGE CHANGE vs V

(Output Voltage % Change Refered

to V

0.5

IN

0

+ 1V, Output Voltage % Change

= 10mA at +25°C)

OUT

I

(mA)

OUT

= V

+ 1V at I

OUT

OUT

OUT

IN

= 10mA)

0.1

0.5

OUTPUT VOLTAGE vs TEMPERATURE

(Output Voltage % Change Referred to

I

= 10mA at +25°C)

OUT

–0.5

–1.0

Output Voltage Change (%)

–1.5

0246 108

Input Voltage Above V

DC DROPOUT VOLTAGE vs TEMPERATURE

160

120

80

40

DC Dropout Voltage (mV)

0

–75 –25–50 250 50 75 100 125

Temperature (°C)

OUT

= 10mA
= 100mA
= 500mA

= 10mA
= 100mA
= 500mA

0

–0.5

–1

Output Voltage Change (%)

–1.5

–75 –25–50 250 50 75 100 125

5

= 10mA
= 100mA
= 500mA

Temperature (°C)

®

REG103

TYPICAL PERFORMANCE CURVES (Cont.)

For all models, at TJ = +25°C and V

= 2V, unless otherwise noted.

ENABLE

500mA

10mA

REG103-3.3

V

IN

200mV/div

200mV/div

REG103-Adj.

V

OUT

200mV/div

LOAD TRANSIENT RESPONSE

= 4.3V

C

= 0

OUT

C

= 10µF

OUT

10µs/div

LOAD TRANSIENT RESPONSE

= 3.3V, V

= 4.3V, C

IN

= 0.01µF

FB

LINE TRANSIENT RESPONSE

REG103-3.3

C

= 0

C

OUT

OUT

= 10µF

V

OUT

V

OUT

50mV/div

Load = 100mA

V

OUT

V

OUT

50mV/div

I

OUT

6V

V

IN

5V

50µs/div

LINE TRANSIENT RESPONSE

REG103-Adj.

= 3.3V, C

V

C

= 0

OUT

V

OUT

OUT

50mV/div

= 0.01µF, I

FB

= 100mA

OUT

C

= 0

OUT

V

OUT

C

OUT

200mV/div

500mA

10mA

10µs/div

LOAD REGULATION vs TEMPERATURE

0.5

IN

OUT

+ 1V and 10mA < I

< 500mA)

OUT

(V

= V

0.4

0.3

0.2

0.1

Output Voltage Change (%)

0

–75 –25–50 250 50 10075 125

Temperature (°C)

= 10µF

V

I

OUT

OUT

C

OUT

50mV/div

6V
5V

50µs/div

OUTPUT NOISE DENSITY

10

1

0.1

Noise Density (µV/√Hz)

CNR = 0

= 0

C

OUT

C

= 0.01µF

NR

C

= 10µF

OUT

0.01
10 100 1000 10000 100,000

Frequency (Hz)

= 10µF

V

OUT

V

IN

®

REG103

6

TYPICAL PERFORMANCE CURVES (Cont.)

–75 –50 –25 0 25 50 75 100 125

3

2.5

2

1.5

1

0.5

0

I

GND

(µA)

Temperature (°C)

GROUND PIN CURRENT, NOT ENABLED

vs TEMPERATURE

V

ENABLE

= 0V

–20–40 0 40 80 120–60 20 60 100 140

0.28

0.26

0.24

0.22

0.20

0.18

0.16

0.14

Adjust Pin Current (µA)

Temperature (°C)

I

ADJUST

vs TEMPERATURE

REG103-A

For all models, at TJ = +25°C and V

= 2V, unless otherwise noted.

ENABLE

1.2

GROUND PIN CURRENT vs TEMPERATURE

1.1
1

0.9

(mA)

0.8

GND

I

0.7

0.6

0.5

0.4

–75 –25–50 250 50 75 100 125

Temperature (°C)

1.2

GROUND PIN CURRENT vs I

OUT

1.1
1

0.9

(mA)

0.8

GND

I

0.7

0.6

0.5

0.4

1 10 100 1000

I

(mA)

OUT

= 10mA
= 100mA
= 500mA

730

CURRENT LIMIT vs TEMPERATURE

720
710
700
690
680
670
660

Current Limit (mA)

650
640
630

–75 –50 –25 0 25 50 75 100 125

Temperature (°C)

70

RIPPLE REJECTION vs FREQUENCY

60

50

C

= 10µF

OUT

40

C

Ripple Rejection (dB)

V

= V

OUT

OUT-NOMINAL

V

= 1V

OUT

• 0.90

30

20

10 100 1000 10000 100000

OUT

= 0

Frequency (Hz)

®

7

REG103

TYPICAL PERFORMANCE CURVES (Cont.)

For all models, at TJ = +25°C and V

= 2V, unless otherwise noted.

ENABLE

75

RIPPLE REJECTION vs I

70

V

= 3Vp-p, f = 120Hz

RIPPLE

OUT

65

60

55

50

Ripple Rejection (dB)

45

40

0 100 200 300 400 500

Load Current (mA)

OUTPUT DISABLE TIME

C

= 0

OUT

1V/div

2V

0

10µs/div

V

OUT

V

ENABLE

SOFT START

1V/div

2V

0

250µs/div

45

OUTPUT VOLTAGE DRIFT HISTOGRAM

40
35
30
25
20
15

Percent of Units (%)

10

5
0

40 45 50 55 60 65 70 75 80 85 90

V

Drift (ppm/°C)

OUT

V

OUT

V

ENABLE

®

REG103

60

OUTPUT VOLTAGE ACCURACY HISTOGRAM

50

40

30

20

Percent of Units (%)

10

0

–1 –0.8 –0.6 –0.4 –0.2 0 0.2 0.4 0.6 0.8 1

Error (%)

8

BASIC OPERATION

The REG103 series is a family of LDO (Low Drop-Out)
linear regulators. The family includes five fixed output
versions (2.5V to 5.0V) and an adjustable output version. An
internal DMOS power device provides low dropout regula­tion with near constant ground pin current (largely indepen­dent of load and drop-out conditions) and very fast line and
load transient response. All versions include internal current
limit and thermal shutdown circuitry.

Figure 1 shows the basic circuit connections for the fixed
voltage models. Figure 2 gives the connections for the
adjustable output version (REG103A) and example resistor
values for some commonly used output voltages. Values for
other voltages can be calculated from the equation shown in
Figure 2. The SO-8 package provides two pins each for V
and V
adjacent to the device.

. Both sets of pins MUST be used and connected

OUT

None of the versions require an output capacitor for regula­tor stability. The REG103 will accept any output capacitor
type less than 1µF. For capacitance values larger than 1µF
the effective ESR should be greater than 0.1Ω. This mini­mum ESR value includes parasitics such as printed circuit
board traces, solder joints, and sockets. A minimum 0.1µF
low ESR capacitor connected to the input supply voltage is
recommended.

INTERNAL CURRENT LIMIT

The REG103 internal current limit has a typical value of
700mA. A fold-back feature limits the short-circuit current
to a typical short-circuit value of 40mA. This circuit will
protect the regulator from damage under all load conditions.

IN

A curve of V

3.5

3

2.5

OUT

versus I

is given in Figure 3.

OUT

REG103

Error

C

NR

0.01µF

Optional

V

OUT

C

OUT

Enable

V

IN

0.1µF

In Out

Gnd NR

FIGURE 1. Fixed Voltage Nominal Circuit for REG103.

ErrorEnable

8

V

IN

0.1µF

Pin numbers for SO-8 package.

7

V

OUT

To reduce current through divider, increase resistor
values (see table at right).

As the impedance of the resistor divider increases,
I

(~200nA) may introduce an error.

ADJ

C

improves noise and transient response.

FB

REG103

= (1 + R1/R2) • 1.295V

65

1
2

I

3

4

Gnd

ADJ

R

Adj
R

1

2

C

FB

0.01µF

2

1.5

Output Voltage (V)

1

0.5

0

0 100 200 300 400 500 600 700 800

Output Current (mA)

FIGURE 3. Foldback Current Limit of the REG103-3.3 at

25°C.

EXAMPLE RESISTOR VALUES

(V) R1 (Ω)

V

OUT

1.295 Short Open

2.5 12.1k 13k

3 16.9k 13k

3.3 20k 13k

5 37.4k 13k

NOTE: (1) Resistors are standard 1% values.

(1)

1.21k 1.3k

1.69k 1.3k

2.0k 1.3k

3.74k 1.3k

R2 (Ω)

(1)

C

OUT

Optional

Load

V

OUT

FIGURE 2. Adjustable Voltage Circuit for REG103A.

®

9

REG103

REG103

Error

+5V

10kΩ

Pull-up

3 ENABLE

SO-8 Package

Only

6

Open
Drain

µP

ENABLE

The Enable pin allows the regulator to be turned on and off.
This pin is active high and compatible with standard TTL­CMOS levels. Inputs below 0.5V (max) turn the regulator
off and all circuitry is disabled. Under this condition ground
pin current drops to approximately 0.5µA.

When not used, the enable pin may be connected to VIN.
Internal to the part, the enable pin is connected to an input

resistor-zener diode circuit, as shown in Figure 4, creating a
nonlinear input impedance. The Enable Pin Current versus
Applied Voltage relationship is shown in Figure 5. When the
enable pin is connected to VIN greater than 10V, a series
resistor may be used to limit the current.

ENABLE

175kΩ

V

= 10V

Z

FIGURE 6. ERROR Pin Typical Fault Monitoring Circuit.

OUTPUT NOISE

A precision band-gap reference is used for the internal
reference voltage, V

, for the REG103. This reference is

REF

the dominant noise source within the REG103. It generates
approximately 45µVrms in the 10Hz to 100kHz bandwidth
at the reference output. The regulator control loop gains up
the reference noise, so that the noise voltage of the regulator
is approximately given by:

FIGURE 4. ENABLE Pin Equivalent Input Circuit.

100

10

1

0.1

Enable Current (µA)

0.01

0.001
0 2 4 6 8 10 12 14 16

Enable Voltage

FIGURE 5. Enable Pin Current versus Applied Voltage.

ERROR FLAG

The error indication pin, only available on the SO-8 package
version, provides a fault indication out of regulation condi­tion. During a fault condition, error is pulled low by an open
drain output device. The pin voltage, in the fault state, is
typically less than 0.2V at 500µA.

A fault condition is indicated when the output voltage differs
(either above or below) from the specified value by approxi­mately 10%. Figure 6 shows a typical fault monitoring
application.

®

REG103

V Vrms

=µ

N

Since the value of V

RR

+

12

R

2

is 1.295V, this relationship reduces to:

REF

Vrms

V

N OUT

µ

=

V

Vrms

=µ •45

45

V

•35

V

OUT

V

REF

Connecting a capacitor, CNR, from the Noise Reduction
(NR) pin to ground, can reduce the output noise voltage.
Adding CNR (see Figure 7) forms a low-pass filter for the
voltage reference. For CNR= 10nF, the total noise in the
10Hz to 100kHz bandwidth is reduced by approximately
a factor of 3.5. This noise reduction effect is shown in
Figure 8.

The REG103 adjustable version does not have the noise­reduction pin available, however, the adjust pin is the sum­ming junction of the error amplifier. A capacitor, CFB,
connected from the output to the adjust pin will reduce both
the output noise and the peak error from a load transient.
See Figure 9 for improved output noise performance for two
capacitor combinations.

The REG103 utilizes an internal charge pump to develop an
internal supply voltage sufficient to drive the gate of the
DMOS pass element above VIN. The charge-pump switch­ing noise (nominal switching frequency = 2MHz) is not
measurable at the output of the regulator.

DROP-OUT VOLTAGE

The REG103 uses an N-channel DMOS as the “pass”
element. When the input voltage is within a few hundred
millivolts of the output voltage, the DMOS device behaves
like a resistor. Therefore, for low values of VIN to V

10

OUT

, the

250

200

150

100

50

0

Drop Out Voltage (mV)

0 100 200 300 400 500

I

OUT

(mA)

REG103 –3.3 at 25°C

DC
Transient

V

IN

NR

(fixed output

versions only)

C

NR

(optional)

Enable

FIGURE 7. Block Diagram.

45

V

REF

(1.295V)

Error

Low Noise

Charge Pump

Over Current

Over Temp

Protection

10.0

DMOS
Output

REG103

V

OUT

R

1

Adj

(Adjustable

R

Versions)

2

NOTE: R1 and R2 are internal
on fixed output versions.

35

10Hz - 100kHz)

RMS

Output Noise Voltage

(µV

25

0.001 0.01 0.1 1

FIGURE 8. Output Noise versus Noise Reduction Capacitor.

regulator’s input-to-output resistance is the RdsON of the
DMOS pass element (typically 230mΩ). For static (DC)
loads, the REG103 will typically maintain regulation down
to VIN to V

voltage drop of 115mV at full rated output

OUT

current. In Figure 10, the bottom line (DC dropout) shows
the minimum VIN to V

OUT

drop-out under DC load conditions.
For large step changes in load current, the REG103 requires

a larger voltage drop across it to avoid degraded transient
response. The boundary of this “transient drop-out” region is
shown as the top line in Figure 10. Values of VIN to V
voltage drop above this line insure normal transient re­sponse.

In the transient dropout region between “DC” and “Tran­sient”, transient response recovery time increases. The time
required to recover from a load transient is a function of both
the magnitude and rate of the step change in load current and

C

= 0

OUT

= 10µF

C

OUT

CNR (µF)

voltage drop required to prevent

OUT

1.0

nV/√Hz

C

= 0, CFB = 0

OUT

C

= 0, CFB = 0.01µF

OUT

C

= 10µF, CFB = 0.01µF

0.1

OUT

10010 1000 10000 100000

Frequency

FIGURE 9. Output Noise Density on Adjustable Versions.

FIGURE 10. Transient and DC Dropout.

11

REG103

®

the available “headroom” VIN to V

voltage drop. Under

OUT

worst-case conditions (full-scale load change with VIN to
V

voltage drop close to DC dropout levels), the REG103

OUT

can take several hundred microseconds to re-enter the speci­fied window of regulation.

TRANSIENT RESPONSE

The REG103 response to transient line and load conditions
improves at lower output voltages. The addition of a capaci­tor (nominal value 10nF) from the output pin to ground may
improve the transient response. In the adjustable version, the
addition of a capacitor, CFB (nominal value 10nF), from the
output to the adjust pin will also improve the transient
response.

heat from the device. In those examples where there is
copper on both sides of the PCB, no connection has been
provided between the two sides. The addition of plated
through holes will improve the heat sink effectiveness.

Power dissipation depends on input voltage and load condi­tions. Power dissipation is equal to the product of the
average output current times the voltage across the output
element, VIN to V

PVV I

voltage drop.

OUT

=•(– )

D IN OUT OUT AVG

()

Power dissipation can be minimized by using the lowest
possible input voltage necessary to assure the required
output voltage.

THERMAL PROTECTION

Power dissipated within the REG103 will cause the junction
temperature to rise. The REG103 has thermal shutdown
circuitry that protects the regulator from damage. The ther­mal protection circuitry disables the output when the junc­tion temperature reaches approximately 150°C, allowing the
device to cool. When the junction temperature cools to
approximately 130°C, the output circuitry is again enabled.
Depending on various conditions, the thermal protection
circuit may cycle on and off. This limits the dissipation of
the regulator, but may have an undesirable effect on the load.

Any tendency to activate the thermal protection circuit
indicates excessive power dissipation or an inadequate heat
sink. For reliable operation, junction temperature should be
limited to 125°C, maximum. To estimate the margin of
safety in a complete design (including heat sink), increase
the ambient temperature until the thermal protection is
triggered. Use worst-case loads and signal conditions. For
good reliability, thermal protection should trigger more than
35°C above the maximum expected ambient condition of
your application. This produces a worst-case junction tem­perature of 125°C at the highest expected ambient tempera­ture and worst-case load.

The internal protection circuitry of the REG103 has been
designed to protect against overload conditions. It was not
intended to replace proper heat sinking. Continuously run­ning the REG103 into thermal shutdown will degrade reli­ability.

POWER DISSIPATION

The REG103 is available in three different package configu­rations. The ability to remove heat from the die is different
for each package type and, therefore, presents different
considerations in the printed circuit-board layout. The PCB
area around the device that is free of other components
moves the heat from the device to the ambient air. While it
is difficult-to-impossible to quantify all of the variables in a
thermal design of this type, performance data for several
configurations are shown in Figure 11. In all cases the PCB
copper area is bare copper, free of solder resist mask, and not
solder plated. All examples are for 1-ounce copper. Using
heavier copper will increase the effectiveness in moving the

®

REG103

REGULATOR MOUNTING

The tab of both packages is electrically connected to ground.
For best thermal performance, the tab of the DDPAK sur­face-mount version should be soldered directly to a circuit­board copper area. Increasing the copper area improves heat
dissipation. Figure 12 shows typical thermal resistance from
junction to ambient as a function of the copper area for the
DDPAK.

Although the tabs of the DDPAK and the SOT-223 are
electrically ground, they are not intended to carry any
current. The copper pad that acts as a heat sink should be
isolated from the rest of the circuit to prevent current flow
through the device from the tab to the ground pin. Solder pad
footprint recommendations for the various REG103 devices
are presented in Application Bulletin “Solder Pad Recom­mendations for Surface-Mount Devices” (AB-132), avail­able from the Burr-Brown web site (www.burr-brown.com).

6

5

4

3

2

Power Dissipation (Watts)

1

0

0 25 50 75 100 150125

Ambient Temperature (°C)

CONDITION PACKAGE PCB AREA THETA J-A

1 DDPAK 4in
2 SOT-223 4in
3 DDPAK None 65°C/W
4 SOT-223 0.5in

5 SO-8 None 150°C/W

2

Top Side Only 27°C/W

2

Top Side Only 53°C/W

2

Top Side Only 110°C/W

CONDITIONS

FIGURE 11. Maximum Power Dissipation versus Ambient

Temperature for the Various Packages and
PCB Heat Sink Configurations.

12

#1
#2
#3
#4
#5

THERMAL RESISTANCE vs PCB COPPER AREA

50

40

(°C/W)

JA

30

20

10

Thermal Resistance, θ

0

012345

Copper Area (inches

REG103

Surface Mount Package

1 oz. copper

2

)

FIGURE 12. Thermal Resistance versus PCB Area for the Five Lead DDPAK.

Circuit Board Copper Area

REG103

DDPAK Surface Mount Package

180
160
140

(°C/W)

JA

120

θ

100

Thermal Resistance,

THERMAL RESISTANCE vs PCB COPPER AREA

REG103

Surface Mount Package

1 oz. copper

80
60
40
20

0

012345

Copper Area (inches

2

)

FIGURE 13. Thermal Resistance versus PCB Area for the Five Lead SOT-223.

Circuit Board Copper Area

REG103

SOT-223 Surface Mount Package

13

®

REG103