ANALOG DEVICES ADP3050 Service Manual

200 kHz, 1 A High Voltage

FEATURES

Wide input voltage range: 3.6 V to 30 V
Adjustable and fixed (3.3 V, 5 V) output options
Integrated 1 A power switch
Uses small surface-mount components
Cycle-by-cycle current limiting
Peak input voltage (100 ms): 60 V
Configurable as a buck, buck-boost, and SEPIC

regulator

Available in 8-lead SOIC package

APPLICATIONS

Industrial power systems
PC peripheral power systems
Preregulator for linear regulators
Distributed power systems
Automotive systems
Battery chargers

Step-Down Switching Regulator

ADP3050

FUNCTIONAL BLOCK DIAGRAM

SD

GND

6

7

AND CURRENT LIMIT

4

FB

BIAS

3

2.50V

REGULATOR

FREQUENCY

FOLDBACK

+

1.2V

g

m

200kHz

OSCILLATOR

CMP

5

COMP

Figure 1.

CURRENT SENSE

AMPLIFIER

CURRENT

LIMIT

SQ

R

ADP3050

DRIVER

IN

8

BOOST

2

1

SWITCH

00125-001

GENERAL DESCRIPTION

The ADP3050 is a current mode monolithic buck (step down)
PWM switching regulator that contains a high current 1 A power
switch and all control, logic, and protection functions. It uses a
unique compensation scheme allowing the use of any type of
output capacitor (tantalum, ceramic, electrolytic, OS-CON).
Unlike some buck regulators, the design is not restricted to using
a specific type of output capacitor or ESR value.

A special boosted drive stage is used to saturate the NPN power
switch, providing a system efficiency higher than conventional
bipolar buck switchers. Further efficiency improvements are
obtained by using the low voltage regulated output to provide
the internal operating current of the device. A high switching
frequency allows the use of small external surface-mount compo­nents. A wide variety of standard off-the-shelf devices can be
used, providing a great deal of design flexibility. A complete
regulator design requires only a few external components.

Rev. B

Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.

The ADP3050 includes a shutdown input that places the device
in a low power mode, reducing the total supply current to under
20 µA. Internal protection features include thermal shutdown
circuitry and a cycle-by-cycle current limit for the power switch
to provide complete device protection under fault conditions.

The ADP3050 provides excellent line and load regulation,
maintaining typically less than ±3% output voltage accuracy
over temperature and under all input voltage and output
current conditions.

The ADP3050 is specified over the industrial temperature range
of −40°C to +85°C and is available in a thermally enhanced 8-lead
(not Pb-free only) SOIC package and a standard 8-lead (Pb-free
only) RoHS-compliant SOIC package.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] ©2008 Analog Devices, Inc. All rights reserved.

ADP3050

TABLE OF CONTENTS

Features .............................................................................................. 1

Applications ....................................................................................... 1 

Functional Block Diagram .............................................................. 1

General Description ......................................................................... 1

Revision History ............................................................................... 2

Specifications ..................................................................................... 3

Absolute Maximum Ratings ............................................................ 4

ESD Caution .................................................................................. 4

Pin Configuration and Function Descriptions ............................. 5

Typical Performance Characteristics ............................................. 6

Theory of Operation ...................................................................... 10

Setting the Output Voltage ........................................................ 10

Applications Information .............................................................. 11

Inductor Selection ...................................................................... 11

Output Capacitor Selection ....................................................... 12

Catch Diode Selection ............................................................... 14

Input Capacitor Selection .......................................................... 14

Discontinous Mode Ringing ..................................................... 15

Setting the Output Voltage ........................................................ 15

Frequency Compensation ......................................................... 15

Current Limit/Frequency Foldback ......................................... 16

Bias Pin Connection .................................................................. 16

Boosted Drive Stage ................................................................... 16

Start-Up/Minimum Input Voltage ........................................... 16

Thermal Considerations ............................................................ 16

Board Layout Guidelines ............................................................... 18

Typical Applications ................................................................... 18

Inverting (Buck Boost) Regulator ............................................ 19

Outline Dimensions ....................................................................... 21

Ordering Guide .......................................................................... 21

REVISION HISTORY

3/08—Rev. A to Rev. B

Updated Format .................................................................. Universal

Changes to General Description Section ...................................... 1

Changes to Figure 3 and Figure 5 ................................................... 6

Changes to Table 2 ............................................................................ 4

Deleted Table 4 ................................................................................ 14

Changes to Table 5 .......................................................................... 15

Deleted Table 8 ................................................................................ 15

Deleted Table 7 ................................................................................ 16

Deleted Table 9 ................................................................................ 16

Changes to Boosted Drive Stage Section and Thermal

Considerations Sections ............................................................ 19

Changes to Figure 27 ...................................................................... 20

Changes to Ordering Guide .......................................................... 23

Rev. B | Page 2 of 24

ADP3050

SPECIFICATIONS

VIN = 10 V, TA = −40°C to +85°C, unless otherwise noted.

Table 1.

Parameter1 Symbol Conditions Min Typ Max Unit

FEEDBACK

Feedback Voltage VFB Over line and temperature

ADP3050 1.16 1.20 1.24 V
ADP3050-3.3 3.20 3.30 3.40 V

ADP3050-5 4.85 5.00 5.15 V
Line Regulation VIN = 10 V to 30 V, no load 0.005 %/V
Load Regulation I

ADP3050AR-3.3, ADP3050AR-5 −0.5 +0.1 +0.5 %/A

Input Bias Current IFB ADP3050AR only 0.65 2 μA

ERROR AMPLIFIER

Transconductance
Voltage Gain

2

2

A

gm 1250 μMho

300 V/V

VOL

Output Current

ADP3050 COMP = 1.0 V, FB = 1.1 V to 1.3 V ±115 μA

ADP3050-3.3 COMP = 1.0 V, FB = 3.0 V to 3.6 V ±120 μA

ADP3050-5 COMP = 1.0 V, FB = 4.5 V to 5.5 V ±135 μA

OSCILLATOR

Oscillator Frequency3 f
Minimum Duty Cycle D
Maximum Duty Cycle D

170 200 240 kHz

OSC

10 %

MIN

90 %

MAX

SWITCH

Average Output Current Limit

4

I

CL(AVG)

ADP3050 BOOST = 15 V, FB = 1.1 V 1.0 1.25 1.5 A

ADP3050-3.3 BOOST = 15 V, FB = 3.0 V 1.0 1.25 1.5 A

ADP3050-5 BOOST = 15 V, FB = 4.5 V 1.0 1.25 1.5 A
Peak Switch Current Limit5 I

1.5 1.7 2.1 A

CL(PEAK)

Saturation Voltage BOOST = 15 V, I
Leakage Current 50 nA

SHUTDOWN

Input Voltage Low 0.4 V

Input Voltage High 2.0 V

SUPPLY

Input Voltage Range
Minimum BIAS Voltage V
Minimum BOOST Voltage V

6

VIN 3.6 30 V

3.0 V

BIAS

3.0 V

BOOST

IN Supply Current IQ

Normal Mode BIAS = 5.0 V 0.7 1.5 mA

Shutdown Mode
BIAS Supply Current I
BOOST Supply Current I

BIAS = 5.0 V 4.0 6.0 mA

BIAS

BOOST = 15 V, ISW = 0.5 A 18 mA

BOOST

BOOST = 15 V, ISW = 1.0 A 20 40 mA

1

All limits at temperature extremes are guaranteed via correlation using standard statistical quality control (SQC).

2

Transconductance and voltage gain measurements refer to the internal amplifier without the voltage divider. To calculate the transconductance and gain of the fixed

voltage parts, divide the values shown by FB/1.20.

3

The switching frequency is reduced when the feedback pin is lower than 0.8 × FB.

4

See Figure 24 for typical application circuit.

5

Switch current limit is measured with no diode, no inductor, and no output capacitor.

6

Minimum input voltage is not measured directly, but is guaranteed by other tests. The actual minimum input voltage needed to keep the output in regulation

depends on output voltage and load current.

= 100 mA to 1 A, ADP3050AR only −1.0 +0.1 +1.0 %/A

LOAD

= 1 A 0.65 0.95 V

LOAD

= 0 V, VIN ≤ 30 V

SD

15 40 μA

Rev. B | Page 3 of 24

ADP3050

ABSOLUTE MAXIMUM RATINGS

Table 2.

Parameter Rating

IN Voltage

Continuous −0.3 V to +40 V
Peak (<100 ms) −0.3 V to +60 V

BOOST Voltage

Continuous −0.3 V to +45 V

Peak (<100 ms) −0.3 V to +65 V
SD, BIAS Voltage
FB Voltage −0.3 V to +8 V
COMP Voltage −0.3 V to IN + 0.3 V
SWITCH Voltage −0.3 V to IN + 0.3 V
Operating Ambient Temperature Range −40°C to +85°C
Operating Junction Temperature Range −40°C to +125°C
Storage Temperature Range −65°C to +150°C
θJA (4-Layer PCB)1 60.6°C/W
θJA (4-Layer PCB)2 87.5°C/W
Lead Temperature (Soldering, 60 sec) 300°C

1

Applied to all models that are not Pb-free.

2

Applied to all Pb-free models.

−0.3 V to IN + 0.3 V

Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.

ESD CAUTION

Rev. B | Page 4 of 24

ADP3050

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

SWITCH

1

FB

ADP3050

2

3

TOP VIEW

(Not to Scale)

4

BOOST

BIAS

Figure 2. Pin Configuration

Table 3. Pin Function Descriptions

Pin No. Mnemonic Description

1 SWITCH

2 BOOST

Switch Node. This pin is the emitter of the internal NPN power switch. The voltage at this pin switches between

and approximately −0.5 V.

V

IN

Boost Pin. This pin is used to provide a boosted voltage (higher than V
switch. With the higher drive voltage, the power switch can be saturated, greatly reducing the switch power
losses.

3 BIAS

Bias Input Pin. Connect this pin to the regulated output voltage to maximize system efficiency. When this pin is
above 2.7 V, most of the ADP3050 operating current is taken from the output instead of the input supply. Leave
unconnected if not used.

4 FB

Feedback Pin. This feedback pin senses the regulated output voltage. Connect this pin directly to the output
(fixed output versions).

5 COMP

Compensation Node. This pin is used to compensate the regulator with an external resistor and capacitor. This
pin is also used to override the control loop. However, the voltage on this pin should not exceed 2 V, because
the pin is internally clamped to ensure a fast transient response. Use a pull-up resistor if this pin is to be pulled
higher than 2 V.

6

SD

Shutdown Pin. Use this pin to turn the device on and off. If this feature is not needed, tie this pin directly to IN.

7 GND Ground Pin. Connect this pin to local ground plane.
8 IN

Power Input. Connect this pin to the input supply voltage. An input bypass capacitor must be placed close to
this pin to ensure proper regulator operation.

8

7

6

5

IN

GND

SD

COMP

00125-002

) for the drive stage of the NPN power

IN

Rev. B | Page 5 of 24

ADP3050

TYPICAL PERFORMANCE CHARACTERISTICS

5.0
VIN = 10V, NO L OAD

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

QUIESCENT O PERATING CURRENT (mA)

0.5

INTO BIAS PIN

INTO IN PIN

0

–45 –35

–25 –15 –5 5 15 25 35 45 55 65 75 85

TEMPERATURE ( °C)

Figure 3. Quiescent Operating Current vs. Temperature

25

20

15

10

2.0
VIN = 10V

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

AVERAGE OUTP UT CURRENT (A)

0.2

0

00125-003

–45 –35 –25 –15 –5 5 15 25 35 45 55 65 75 85

TEMPERATURE (° C)

00125-006

Figure 6. Average Output Current Limit vs. Temperature

25

VIN = 10V

20

15

10

5

SHUTDOWN QUI ESCENT CURRENT (µA)

0

5 10152025

SUPPLY VOLTAGE (V)

Figure 4. Shutdown Quiescent Current vs. Supply Voltage

10

BIAS TIED T O V

8

6

4

2

QUIESCENT O PERATING CURRENT (mA)

0

OUT

V

= 3.3V

OUT

SUPPLY VOLTAGE (V)

V

= 5V

OUT

Figure 5. Quiescent Operating Current vs. Supply Voltage

BOOST CURRENT (mA)

5

300

00125-004

0

0

0.1 0.2

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
LOAD CURRENT (A)

00125-007

Figure 7. Boost Current vs. Load Current

100

90

80

70

60

50

40

EFFICIE NCY (%)

30

20

10

300 5 10 15 20 25

00125-005

0

0 200 400 600 800

L = 33µH
C

= 22µF

IN

C

= 100µF

OUT

VIN = 6V

VIN = 24V

= 12V

V

IN

V

= 18V

IN

OUTPUT CURRENT (mA)

VIN = 30V

k1

00125-008

Figure 8. 5 V Output Efficiency

Rev. B | Page 6 of 24

ADP3050

100

90

80

70

60

50

40

EFFICIENCY (%)

30

20

10

0

VIN = 12V

L = 33µH
C

= 22µF

IN

= 100µF

C

OUT

V

= 5V

IN

VIN = 24V

VIN = 18V

OUTPUT CURRENT (mA)

V

= 30V

N

Figure 9. 3.3 V Output Efficiency

0.5

VIN = 10V

0.4
I

= 1A

LOAD

0.3

0.2

0.1

0

–0.1

–0.2

–0.3

OUTPUT VO LTAGE CHANGE (%)

–0.4

–0.5

–45 –35 –25 –15 –5 5 15 25 35 45 55 65 75 85

TEMPERATURE ( °C)

Figure 10. Output Voltage Change vs. Temperature

0.6
V

= 5V

OUT

0.4

0.2

= 1A

I

0

0.2

OUTPUT VO LTAGE CHANGE (%)

0.4

0.6

0

LOAD

= 100mA

I

LOAD

10 20 30

INPUT VOLTAGE (V)

Figure 11. 5 V Output Voltage Change vs. Input Voltage

0.6
V

= 3.3V

OUT

0.4

0.2

I

= 100mA

0

0.2

OUTPUT VO LTAGE CHANGE (%)

0.4

1k0 200 400 600 800

00125-009

0.6

0

LOAD

= 1A

I

LOAD

10 20 30

INPUT VOLTAGE (V)

00125-012

Figure 12. 3.3 V Output Voltage Change vs. Input Voltage

8

7

V

= 5V

6

5

4

MINIMUM INPUT VOLTAGE (V)

3

2

0

00125-010

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1. 0

OUT

V

= 3.3V

OUT

LOAD CURRENT (A)

00125-013

Figure 13. Minimum Input Voltage vs. Load Current

0

–0.02

–0.04

–0.06

–0.08

–0.10

–0.12

–0.14

OUTPUT VO LTAGE CHANGE (%)

–0.16

–0.18

00125-011

VIN = 10V

0

0.10.20.30.40.50.60.70.80.91.0
LOAD CURRENT(A)

0125-014

Figure 14. Load Regulation

Rev. B | Page 7 of 24

ADP3050

A

A

0.8

0.7

0.6

VIN = 10V

VSW = 5V/DIV

0.5

0.4

0.3

0.2

SWITCH SATURATION VOLTAGE (V)

0.1

0

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
LOAD CURRENT (A)

Figure 15. Switch Saturation Voltage vs. Load Current

210

VIN = 10V

208

I

= 250µA

LOAD

206

204

202

200

198

196

194

SWITCHING FREQUENCY (kHz)

192

190

–45 –35 –25 –15 –5 5 15 25 35 45 55 65 75 85

AMBIENT TEM PERATURE (°C)

Figure 16. Switching Frequency vs. Temperature

0V

= 500mA/DIV

I

L

VIN = 10V
V

= 5V

OUT

I

= 800mA

0

00125-015

LOAD

L = 33µH
C

= 22µF

IN

C

= 100µF

OUT

TIME (1µs/DIV)

00125-018

Figure 18. Continuous Conduction Mode Waveforms

VSW = 5V/DIV

0V

I

= 500mA/DIV

L

VIN = 10V

= 5V

V

OUT

= 100mA

I

LOAD

L = 33µH

= 22µF

C

IN

= 100µF

C

OUT

0

0125-016

TIME (1µs/DIV)

00125-019

Figure 19. Discontinuous Conduction Mode Waveforms

250

200

150

100

SWITCHING FREQUENCY (kHz)

50

0

0

VIN = 10V
COMP = 0.4V

NORMALIZE D FEEDBACK VOLTAGE (V)

Figure 17. Frequency Foldback

1.00.2 0.4 0.6 0.8

00125-017

Rev. B | Page 8 of 24

V

= 200mV/DIV

5V

1A

0A

OUT

I

LOAD

VIN = 10V

= 5V

V

OUT

= 100mA TO 1A SW ITCHED

I

LOAD

L = 33µH

= 22µF

C

IN

= 100µF

C

OUT

TIME (400µ s/DIV)

00125-020

Figure 20. Transient Response