Analog Devices ADP3088 c Datasheet

a

SW

DRV

FB

IN

GND

COMP

ADP3088

V

OUT

1.8V

3.3H

10.0k

22.4k

20k

4.7pF

1N5817

IN

GND

10F

0.1F

220pF

V

IN

3.3V

10F

1 MHz, 750 mA Buck Regulator

ADP3088

FEATURES
1 MHz PWM Frequency
Automatic PWM to Power Saving Mode at Light Load
Fully Integrated 1 A Power Switch
3% Output Regulation Accuracy over Temperature,

Line, and Load
100% Duty Cycle Operation
Simple Compensation
Output Voltage: 1.25 V to 10.5 V
Small Inductor and MLC Capacitors
Low Quiescent Current while Pulse Skipping
Thermal Shutdown
Fully Integrated Soft Start
Cycle-by-Cycle Current Limit

APPLICATIONS
PDAs and Palmtop Computers
Notebook Computers
PCMCIA Cards
Bus Products
Portable Instruments

GENERAL DESCRIPTION

The ADP3088 is a high frequency, nonsynchronous PWM

step­down dc-to-dc regulator with an integrated 1 A power switch
in a space-saving MSOP-8 package. It provides high efficiency
and excellent dynamic response and is very simple to use.

The ADP3088’s 1 MHz switching frequency allows for small,
inexpensive external components, and the current mode control
loop is simple to compensate and eases noise filtering. The device
operates in PWM current mode under heavy loads and saves
energy

at lighter loads by switching automatically into power

saving mode. Soft start is integrated completely on-chip, as is

cycle-by-cycle current limit.

the

Capable of operating from 2.5 V to 11 V input, the ADP3088 is
ideal for many applications, including portable, battery-powered
applications where local point-of-use power regulation is
required. Supporting output voltages down to 1.25 V, the
ADP3088 is ideal for generating low voltage rails, providing
the optimal solution in its class for delivering power efficiently,
responsively, and simply with a minimal printed circuit board area.

The device is specified over the industrial temperature range of
–40∞C to +85∞C.

COMP

GND

GND

FUNCTIONAL BLOCK DIAGRAM

IN

IN

CURRENT

SENSE

AMP

PROTECTION

ADP3088

PWM

COMPARATOR

LOGIC

(ILI M, OT)

ERROR

AMP

g

m

+

REF

1.245V

1MHz

S

Q

R

RUN/STOP

COMPARATORS

SOFT START

TIMER

SW

DRV

FB

Figure 1. Typical Application

REV. C

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. 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.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] © 2004 Analog Devices, Inc. All rights reserved.

ADP3088–SPECIFICATIONS

Parameter Symbol Conditions Min Typ Max Unit

SUPPLY

Input Voltage Range V
Ground Current, Operating I

Quiescent Current, Operating I

Shutdown I

Thermal Shutdown Threshold T

OSCILLATOR

Oscillator Frequency f
Minimum Sleep Duty Cycle D
Maximum Duty Cycle D
Wake-Up Hysteresis V

OUTPUT SWITCH

Switch-On Voltage V

Current Limit Threshold I
Leakage Current VIN = 12 V 0.5 mA

ERROR AMPLIFIER

Reference Voltage Accuracy V
Reference Voltage Line FB = COMP, 0.02 %/V

Regulation V

Feedback Input Bias Current I
Sink/Source Current I
Short Circuit Current I

Transconductance gm,

MODULATOR

Transconductance gm,
Control Offset Voltage V
Soft Start Time t
Shutdown Threshold Voltage V
Slope Compensation m

NOTES

1

All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC).

2

For higher efficiency operation, tie the DRV pin to the output for IL < 250 mA and VIN > 3 V.

3

VIN – VSW includes voltage drop across internal current sensor.

Specifications subject to change without notice.

IN

2

GND

Q

SD

SD

SW

PSM

MAX

HYST

3

IO

LIM

REF

FB

COMP

COMP, SD

EA

MOD

PWM, OS

SS

COMP, SD

SC

(VIN = 3.3 V, TA = –40C to +85C, unless otherwise noted.)

DRV = GND 2.5 11 V
VIN = 10 V, IL = 500 mA,
DRV = GND 6 mA
DRV = 2 V 2.5 3.6 mA
No Load 150 250 mA
V

= 0 V 15 40 mA

COMP

160 ∞C

0.75 1 1.25 MHz

IL = 500 mA 14 %

100 %

FB Voltage Drops below V

REF

20 30 40 mV

IL = 500 mA, FB = GND, and 0.25 0.4 V
DRV = GND

1.0 1.2 1.4 A

FB = COMP 1.222 1.245 1.265 V

= 3 V to 12 V

IN

Soft Start Expired –50 +1 +50 nA

35 60 85 mA

V

= 0 V, Activating 20 40 mA

COMP

Shutdown
FB = COMP 480 mA/V

V

COMP

to I

L

1 A/V

0.90 V
250 600 ms

340 750 mV

Effectively Summed to I

SW

0.7 A/ms

1

–2–

REV. C

ADP3088

ABSOLUTE MAXIMUM RATINGS *

Input Supply Voltage . . . . . . . . . . . . . . . . . . . –0.3 V to +12 V

Voltage on Any Pin with Respect to GND . . . –0.3 V to +12 V
(Voltage on Any Pin May Not Exceed V

)

IN

Operating Ambient Temperature Range . . . . –40∞C to +85∞C

Operating Junction Temperature . . . . . . . . . . . . . . . . . . 125∞C

(4-Layer Board) . . . . . . . . . . . . . . . . . . . . . . . . . . 116∞C/W

q

JA

qJA (2-Layer Board) . . . . . . . . . . . . . . . . . . . . . . . . . . 159∞C/W

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

Lead Temperature Range (Soldering 10 sec) . . . . . . . . . 300∞C

Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . . . 215∞C

Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220∞C

*Stresses above those listed under Absolute Maximum Ratings may cause permanent

damage to the device. This is a stress rating only and functional operation of the
device at these or any other conditions above those listed in the operational sections
of this specification is not implied. Exposure to absolute maximum rating conditions
for extended periods may affect device reliability. Only one absolute maximum
rating may be applied at any one time.

ORDERING GUIDE

Temperature Package

Model Range Option Branding

ADP3088ARM-REEL –40∞C to +85∞CMSOP-8 P0A
ADP3088ARM-REEL7 –40∞C to +85∞CMSOP-8 P0A

PIN CONFIGURATION

8

SW

7

DRV

6

GND

5

FB

GND

COMP

1

IN

2

IN

3

4

ADP3088

TOP VIEW

(Not to Scale)

PIN FUNCTION DESCRIPTIONS

Pin No. Mnemonic Function

1, 2 IN Power Supply Input. Both pins must

be connected.

3, 6 GND Ground. Both pins must be

connected.

4 COMP Feedback Loop Compensation and

Shutdown Input. An open drain or
collector used to pull the pin to
ground will shut down the device.

5FB Feedback Voltage Sense Input. This

pin senses the voltage via an external
resistor divider.

7 DRV This pin provides a separate path for

the drive current to be connected to
ground.

8SWSwitching Output.

CAUTION

ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection. Although the
ADP3088 features proprietary ESD protection circuitry, permanent damage may occur on devices
subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended
to avoid performance degradation or loss of functionality.

REV. C

–3–

ADP3088

–Typical Performance Characteristics

100

90

80

70

60

50

40

EFFICIENCY (%)

30

VIN = 5V, CIN = C

20

TA = 25C

10

0

0 500100 200 400300

V

OUT

V

OUT

= 1.5V

OUT

= 10F, L = 10H

LOAD CURRENT (mA)

= 2.5V

V

= 3.3V

OUT

TPC 1. Efficiency vs. Load Current and Output Voltage

100

90

80

70

60

50

40

EFFICIENCY (%)

30

20

10

0

V

OUT

V

= 1.5V

OUT

VIN = 10V, CIN = C

TA = 25C

0 500100 200 400300

= 10F, L = 10H

OUT

LOAD CURRENT (mA)

= 2.5V

V

= 5V

OUT

V

= 3.3V

OUT

TPC 2. Efficiency vs. Load Current and Output Voltage

200.00

180.00

160.00

140.00

120.00

STANDBY QUIESCENT CURRENT (A)

100.00
–40 85–15 10 6035

TEMPERATURE (C)

TPC 4. Standby Quiescent Current vs. Temperature

5.00

4.00

I

= 500mA

3.00

GROUND CURRENT (mA)

2.00

1.00

LOAD

V

= 2V

DRV

–40 85–15 10 6035

TEMPERATURE (C)

TPC 5. Ground Current vs. Temperature

100

IL = 500mA

10

V

= 1.5V, CIN = C

OUT

TA = 25C

1

QUIESCENT CURRENT (mA)

0

01024 86

= 10F, DRV = GND

OUT

IL = 0mA

INPUT VOLTAGE (V)

TPC 3. Quiescent Current vs. Input Voltage

1.2438

1.2433

1.2428

FEEDBACK VOLTAGE (V)

1.2423

1.2418

12

–40 85–15 10 6035

TEMPERATURE (C)

TPC 6. Feedback Voltage vs. Temperature

–4–

REV. C

1.515

12.00

–40 85–15 10 6035

TEMPERATURE (C)

14.00

16.00

18.00

SHUTDOWN SUPPLY CURRENT (A)

20.00

10.00

0.220

–40 85–15 10 6035

TEMPERATURE (C)

0.240

0.260

0.280

SWITCH VOLTAGE (V)

0.300

0.200

I

LOAD

= 500mA

0.400

0.00 1.000.25 0.50 0.75

OUTPUT CURRENT (A)

0.500

0.600

0.900

SWITCH SATURATION VOLTAGE (V)

1.000

0.300

0.700

0.800

0.100

0.200

V

IN

= 2.5V

V

IN

= 5V

V

IN

= 12V

V

IN

= 3.3V

TA = 25C

1.505

ADP3088

1.495

OUTPUT VOLTAGE (V)

1.485
0 500100 200 400300

TPC 7. Load Regulation

1.10

1.05

1.00

FREQUENCY (MHz)

0.95

0.90
–40 85–15 10 6035

VIN = 5V, CIN = C

TA = 25C

OUTPUT CURRENT (mA)

TEMPERATURE (C)

= 10F, L = 10H

OUT

TPC 10. Shutdown Supply Current vs. Temperature

TPC 8. Oscillator Frequency vs. Temperature

1.20

1.15

1.10

CURRENT LIMIT (A)

1.05

REV. C

1.00
–40 85–15 10 6035

TPC 9. Current Limit vs. Temperature

TEMPERATURE (C)

TPC 11. Switch-Sense Resistor Voltage vs. Temperature

TPC 12. Switch Saturation Voltage

vs.

Load

Current and Input Voltage

–5–