650 kHz/1.3 MHz, 4 A, Step-Up, PWM, DC-to-DC Switching Converter ADP1614 Data Sheet

650 kHz/1.3 MHz, 4 A, Step-Up, PWM, DC-to-DC Switching Converter ADP1614 Data Sheet

Data Sheet

FEATURES

Adjustable and fixed current-limit options

Adjustable up to 4 A

Fixed 3 A

2.5 V to 5.5 V input voltage range

650 kHz or 1.3 MHz fixed frequency option

Adjustable output voltage, up to 20 V

Adjustable soft start

Undervoltage lockout

Thermal shutdown

3 mm × 3 mm, 10-lead LFCSP

Supported by ADIsimPower design tool

APPLICATIONS

TFT LCD bias supplies

Portable applications

Industrial/instrumentation equipment

GENERAL DESCRIPTION

The ADP1614 is a step-up, dc-to-dc switching converter with an integrated power switch capable of providing an output voltage as high as 20 V. The ADP1614 is available with a pin-adjustable current limit that is set via an external resistor with the boost switching frequency fixed to either 650 kHz or 1.3 MHz.

Alternatively, the ADP1614 is also available with fixed 3 A current limit and a pin-selectable frequency. With a package height of 0.8 mm, the ADP1614 is optimal for space constrained applications, such as portable devices or thin film transistor

(TFT) liquid crystal displays (LCDs).

The ADP1614 operates in current-mode pulse-width modulation

(PWM) with up to 94% efficiency. Adjustable soft start prevents inrush currents when the part is enabled. The PWM current-mode architecture allows excellent transient response, easy noise filtering, and the use of small, cost-saving external inductors and capacitors.

Other key features include undervoltage lockout (UVLO), thermal shutdown (TSD), and logic controlled enable.

The ADP1614 is available in a Pb-free, 10-lead lead frame chip scale package (LFCSP).

650 kHz/1.3 MHz, 4 A, Step-Up,

PWM, DC-to-DC Switching Converter

ADP1614

V

IN

C

IN

R

CL

TYPICAL APPLICATIONS CIRCUITS

L1

OFF

ON

8 VIN

ADP1614

ADJUSTABLE

CURRENT

LIMIT

SW 6

SW 7

3 EN

FB 2

9 CLRES

C

SS

10

SS

GND GND

4 5

COMP

EP

11

1

Figure 1. Step-Up Regulator Configuration for Adjustable Current-Limit Options

L1

V

IN

C

IN

8 VIN

ADP1614

FIXED

CURRENT

LIMIT

SW 6

ON

SW 7

OFF 3

EN

FB 2

1.3MHz

9

650kHz

(DEFAULT)

C

SS

FREQ

10 SS

GND GND

4 5

COMP

EP

11

1

D1

R

COMP

C

COMP

D1

R

COMP

C

COMP

R1

R2

R1

R2

V

OUT

C

OUT

V

OUT

C

OUT

Figure 2. Step-Up Regulator Configuration for Fixed Current-Limit Options

Rev. B Document Feedback

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Tel: 781.329.4700 ©2012–2014 Analog Devices, Inc. All rights reserved.

Technical Support www.analog.com

ADP1614

TABLE OF CONTENTS

Features .............................................................................................. 1

Applications ....................................................................................... 1

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

Typical Applications Circuits .......................................................... 1

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

Specifications ..................................................................................... 3

Absolute Maximum Ratings ............................................................ 5

Thermal Resistance ...................................................................... 5

ESD Caution .................................................................................. 5

Pin Configuration and Function Descriptions ............................. 6

Typical Performance Characteristics ............................................. 7

Theory of Operation ...................................................................... 12

Current-Mode PWM Operation .............................................. 13

Adjustable Current Limit .......................................................... 13

Frequency Selection ................................................................... 13

REVISION HISTORY

11/14—Rev. A to Rev. B

Changes to Ordering Guide .......................................................... 18

6/13—Rev. 0 to Rev. A

Changes to Features Section, General Description Section, and

Figure 1 .............................................................................................. 1

Added Figure 2; Renumbered Sequentially .................................. 1

Changes to Table 1 ............................................................................ 3

Added FREQ Pin to Table 2 ............................................................ 5

Changes to Pin 9 ............................................................................... 6

Added Figure 26 and Figure 27..................................................... 10

Added Figure 28 to Figure 31 ........................................................ 11

Changes to Theory of Operation Section and Figure 32 ........... 12

Changes to Adjustable Current Limit Section and Frequency

Selection Section ............................................................................. 13

Changes to Figure 35 and Figure 36 Captions ............................ 17

Updated Outline Dimensions ....................................................... 18

Changes to Ordering Guide .......................................................... 18

6/12—Revision 0: Initial Version

Data Sheet

Soft Start ...................................................................................... 13

Thermal Shutdown (TSD) ........................................................ 13

Undervoltage Lockout (UVLO) ............................................... 13

Shutdown Mode ......................................................................... 13

Applications Information .............................................................. 14

ADIsimPower Design Tool ....................................................... 14

Setting the Output Voltage ........................................................ 14

Inductor Selection ...................................................................... 14

Choosing the Input and Output Capacitors ........................... 15

Diode Selection ........................................................................... 15

Loop Compensation .................................................................. 15

Soft Start Capacitor .................................................................... 16

PCB Layout Guidelines .................................................................. 17

Outline Dimensions ....................................................................... 18

Ordering Guide .......................................................................... 18

Rev. B | Page 2 of 18

Data Sheet ADP1614

SPECIFICATIONS

V

IN

= 3.6 V, unless otherwise noted. Minimum and maximum values are guaranteed for T

J

= −40°C to +125°C. Typical values specified are at T

J

= 25°C. All limits at temperature extremes are guaranteed by correlation and characterization using standard statistical quality control (SQC), unless otherwise noted.

Table 1.

Parameter

SUPPLY

Input Voltage

Quiescent Current

Shutdown

Nonswitching State

Switching State 1

UNDERVOLTAGE LOCKOUT (UVLO)

Undervoltage Lockout Threshold

OUTPUT

Output Voltage 2

Load Regulation

V

OUT

REFERENCE

Feedback Voltage

Line Regulation

ERROR AMPLIFIER

V

FB

Transconductance

Voltage Gain

FB Pin Bias Current

SWITCH (SW)

G

MEA

A

V

On Resistance

Adjustable Peak Current Limit 3

Maximum Adjustable Peak

Current Limit 2

R

DSON

Fixed Peak Current Limit

SW Pin Leakage Current

CLRES VOLTAGE 4

OSCILLATOR

SOFT START (SS)

SS Pin Voltage

Oscillator Frequency

Maximum Duty Cycle

3

EN/FREQ LOGIC THRESHOLD

Input Voltage Low

Input Voltage High

EN Pin Leakage Current

FREQ Pin Leakage Current

Charging Current f

I

I

Symbol Test Conditions/Comments

V

IN

I

QSHDN

I

Q

I

QSW f f

V

EN

V

FB

SW

SW

= 0 V, V

SW

= 1.3 V, V

= GND

SW

= GND, f

= 1.3 MHz, V

= 650 kHz, V

SW

SW

SW

= 1.3 MHz and 650 kHz

= GND, no load

= GND, no load

V

V

EN

SS

V

SW

D

IL

IH

SS

MAX

V

V

V

V

IN

IN

rising

falling

OUT

IN

= 10 V, I

ΔI = 4 µA

V

FB

= 1.245 V

LOAD

= 1 mA to 1 A

= 2.5 V to 5.5 V

I

SW

= 1.0 A

R

CL

= 154 kΩ, duty cycle = 70%

R

CL

= 61.9 kΩ, V

IN

= 3.6 V, V

OUT

= 15 V

Min

2.5

2.0

V

IN

Typ

0.25 1.5 µA

700 1100 µA

5.5

3

2.33

2.20

0.005

Max

5.5

7

4.5

2.5

20

Unit

V mA mA

1.2250 1.2445 1.2650 V

0.02 0.2 %/V

0.95

150

80

1

50

1.30

4

50

100

1.65

µA/V dB nA mΩ

A

A

ADP1614ACPZ-R7 only, duty cycle = 70%

V

SW

= 20 V

ADP1614ACPZ-650-R7 and ADP1614ACPZ-1.3-R7

I

CLRES

= 5 µA

I

CLRES

= 20 µA

ADP1614ACPZ-1.3-R7 and ADP1614ACPZ-R7 , V

FREQ

≥ 1.6 V 1.1

ADP1614ACPZ-650-R7 and ADP1614ACPZ-R7 , V

FREQ

≤ 0.3 V 500

COMP = open, V

FB

= 1 V, f

SW

= 1.3 MHz and 650 kHz 88

FREQ pin is ADP1614ACPZ-R7 only

V

IN

= 2.5 V to 5.5 V

V

V

V

IN

EN

= 2.5 V to 5.5 V

= 3.6 V

FREQ

= 3.6 V, V

FB

= 1.3 V

1.6

2.50 3.10 3.60

0.1 10

1.225 1.27 1.315 V

1.18 1.22 1.25 V

A

µA

1.3

650

92

1.4

720

0.3

V

V

SS

FB

= 0 V

= 1.3 V

3.4

1.17

3.4 7

0.005 1

5.5 7

1.23 1.29

µA

V

MHz kHz

%

V

V

µA

µA

V

V

V mV/mA

Rev. B | Page 3 of 18

ADP1614 Data Sheet

Parameter Symbol Test Conditions/Comments Min Typ Max Unit

THERMAL SHUTDOWN

Thermal Shutdown Threshold 150 °C

Thermal Shutdown Hysteresis 20 °C

1 This parameter specifies the average current when the device switches internally with the SW pins (Pin 6 and Pin 7) grounded.

2

Guaranteed by design.

3

Current limit is a function of duty cycle. For the adjustable current limit versions, it is also a function of the resistor on the CLRES pin. See Figure 10 through Figure 13.

4 The CLRES pin cannot be controlled with a current source. An equivalent resistance should be used.

Rev. B | Page 4 of 18

Data Sheet

ABSOLUTE MAXIMUM RATINGS

Table 2.

Parameter Rating

VIN, EN, FB, FREQ to GND

CLRES to GND

COMP to GND

SS to GND

−0.3 V to +6 V

−0.3 V to VIN

1.0 V to 1.6 V

−0.3 V to +1.3 V

SW to GND 21 V

Operating Junction Temperature Range −40°C to +125°C

Storage Temperature Range

Soldering Conditions

−65°C to +150°C

JEDEC J-STD-020

Stresses at or above those listed under Absolute Maximum

Ratings may cause permanent damage to the product. This is a stress rating only; functional operation of the product at these or any other conditions above those indicated in the operational section of this specification is not implied. Operation beyond the maximum operating conditions for extended periods may affect product reliability.

Absolute maximum ratings apply individually only, not in combination.

ADP1614

THERMAL RESISTANCE

The junction-to-ambient thermal resistance (θ

JA

) of the package is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages. The θ

JA

is highly dependent on the application and board layout. In applications where high maximum power dissipation exists, attention to thermal board design is required. The value of θ

JA

may vary, depending on the printed circuit board (PCB) material, layout, and environmental conditions.

The boundary conditions for the thermal resistance of the

ADP1614 are modeled under natural convection cooling at

25°C ambient temperature, JESD 51-9, and 1 W power input on a

4-layer board.

Table 3. Thermal Resistance 1

Package Type

10-Lead LFCSP

θ

JA

47

1 Thermal numbers per JEDEC standard JESD 51-9.

ESD CAUTION

θ

JC

7.22

Unit

°C/W

Rev. B | Page 5 of 18

ADP1614

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

Data Sheet

COMP 1

FB 2

EN 3

GND 4

GND 5

ADP1614

TOP VIEW

(Not to Scale)

10 SS

9 CLRES/FREQ

8 VIN

7 SW

6 SW

NOTES

1. THE EXPOSED PAD IS NOT ELECTRICALLY

CONNECTED; CONNECT THIS PAD TO A GROUND

PLANE FOR BETTER HEAT DISTRIBUTION.

Figure 3. Pin Configuration

Table 4. Pin Function Descriptions

Pin No. Mnemonic

1 COMP

2 FB

Description

Compensation Input. Connect a series resistor-capacitor network from COMP to GND to compensate the regulator.

Output Voltage Feedback Input. Connect a resistive voltage divider from the output voltage to FB to set the regulator output voltage.

3

4, 5

6, 7

EN

GND

SW

Enable Input. Drive EN low to shut down the regulator; drive EN high to turn on the regulator.

Ground.

Switching Output. Connect the power inductor from the input voltage to SW and connect the external rectifier from SW to the output voltage to complete the step-up converter.

8 VIN Main Power Supply Input. VIN powers the ADP1614 internal circuitry. Connect VIN to the input source voltage.

Bypass VIN to GND with a 10 μF or greater capacitor as close to the ADP1614 as possible.

10 SS

11 EP

Frequency Setting Input (FREQ). Connect FREQ to GND to program the oscillator to 650 kHz, or connect FREQ to

VIN to program it to 1.3 MHz. Do not leave this pin floating.

Soft Start. A capacitor connected from SS to GND brings up the output slowly at power-up and reduces inrush current.

Exposed Die Attach Pad. The exposed pad is not electrically connected; connect this pad to a ground plane for better heat distribution.

Rev. B | Page 6 of 18

Data Sheet

TYPICAL PERFORMANCE CHARACTERISTICS

100

ADP1614ACPZ-650-R7

90

80

70

60

50

40

30

20

10

0

1

V

IN

= 3.6V

f

SW

R

CL

= 650kHz

= 71.5kΩ

10

V

OUT

= 5V

V

OUT

= 10V

V

OUT

= 15V

100

LOAD CURRENT (mA)

1k 10k

Figure 4. Efficiency vs. Load Current, V

IN

= 3.6 V, f

SW

= 650 kHz

50

40

30

100

90

V

IN

= 3.6V

f

SW

R

CL

= 1.3MHz

= 71.5kΩ

80

70

60

20

10

0

1

ADP1614ACPZ-1.3-R7

10 100

LOAD CURRENT (mA)

1k

V

OUT

= 5V

V

OUT

= 10V

V

OUT

= 15V

10k

Figure 5. Efficiency vs. Load Current, V

IN

= 3.6 V, f

SW

= 1.3 MHz

50

40

30

100

90

V

IN

= 5V f

SW

R

CL

= 650kHz

= 71.5kΩ

80

70

60

20

10

0

1

ADP1614ACPZ-650-R7

10 100

LOAD CURRENT (mA)

1k

V

OUT

= 10V

V

OUT

= 15V

V

OUT

= 20V

10k

Figure 6. Efficiency vs. Load Current, V

IN

= 5 V, f

SW

= 650 kHz

ADP1614

60

50

40

100

90

V

IN

= 5V f

SW

R

CL

= 1.3MHz

= 71.5kΩ

80

70

30

20

10

0

1

ADP1614ACPZ-1.3-R7

10 100

LOAD CURRENT (mA)

1k

V

OUT

= 10V

V

OUT

= 15V

V

OUT

= 20V

10k

Figure 7. Efficiency vs. Load Current, V

IN

= 5 V, f

SW

= 1.3 MHz

4.0

3.5

3.0

2.5

2.0

V

IN

= 4.5V

ADP1614ACPZ-650-R7

ADP1614ACPZ-1.3-R7

1.5

V

IN

= 3.5V

1.0

V

IN

= 2.5V

0.5

0

60

V

OUT

= 5V

75 90 105 120 135 150

R

CL

(kΩ)

Figure 8. Typical Maximum Continuous Output Current vs. R

CL

, V

OUT

= 5 V

1.4

ADP1614ACPZ-650-R7

ADP1614ACPZ-1.3-R7

1.2

1.0

V

IN

= 5.5V

0.8

V

IN

= 4.5V

0.6

V

IN

= 3.5V

0.4

V

IN

= 2.5V

0.2

0

60

V

OUT

= 15V

75 90 105 120 135 150

R

CL

(kΩ)

Figure 9. Typical Maximum Continuous Output Current vs. R

CL

, V

OUT

= 15 V

Rev. B | Page 7 of 18

ADP1614

4.0

V

IN

= 4.5V

ADP1614ACPZ-650-R7

ADP1614ACPZ-1.3-R7

3.5

V

IN

= 2.5V

3.0

2.5

2.0

V

IN

= 3.5V

1.5

1.0

60

V

OUT

= 5V

75 90 105

R

CL

(kΩ)

120 135

Figure 10. Peak Current Limit of Switch vs. R

CL

, V

OUT

= 5 V

150

3.90

3.85

ADP1614ACPZ-650-R7

ADP1614ACPZ-1.3-R7

3.80

3.75

T

A

= +85°C

3.70

T

A

= +25°C

3.65

3.60

2.5

V

OUT

R

CL

= 5V

= 71.5k

3.0

T

A

= –40°C

3.5

4.0

4.5

INPUT VOLTAGE (V)

Figure 11. Peak Current Limit of Switch vs. V

IN

over Temperature, V

OUT

= 5 V

4.0

3.5

V

IN

= 2.5V

3.0

2.5

V

IN

= 4.5V

V

IN

= 5.5V

2.0

V

IN

= 3.5V

ADP1614ACPZ-650-R7

ADP1614ACPZ-1.3-R7

1.5

1.0

60

V

OUT

= 15V

75 90 105

R

CL

(kΩ)

120 135

Figure 12. Peak Current Limit of Switch vs. R

CL

, V

OUT

= 15 V

150

Data Sheet

3.60

3.55

3.50

3.45

T

A

= –40°C

3.40

3.35

3.30

3.25

T

A

= +85°C

T

A

= +25°C

ADP1614ACPZ-650-R7

ADP1614ACPZ-1.3-R7

3.20

3.15

2.5

V

OUT

R

CL

= 15V

= 71.5k

3.0

3.5

4.0

4.5

4.0

5.5

INPUT VOLTAGE (V)

Figure 13. Peak Current Limit of Switch vs. V

IN

over Temperature, V

OUT

= 15 V

80

70

60

T

A

= +125°C

I

SW

= 1A

50

T

A

= +25°C

40

T

A

= –40°C

30

2.5

3.0

3.5

4.0

4.5

INPUT VOLTAGE (V)

5.0

Figure 14. Switch On Resistance vs. Input Voltage

5.5

94.5

94.0

93.5

93.0

92.5

92.0

T

A

= +25°C

T

A

= +125°C

T

A

= –40°C

91.5

91.0

2.5

3.0

3.5

4.0

4.5

INPUT VOLTAGE (V)

5.0

Figure 15. Maximum Duty Cycle vs. Input Voltage

5.5

Rev. B | Page 8 of 18

Data Sheet

700

680

660

640

620

600

780

760

740

720

T

A

= +125°C

T

A

= +25°C

T

A

= –40°C

580

2.5

3.0

3.5

4.0

4.5

INPUT VOLTAGE (V)

5.0

5.5

Figure 16. Nonswitching Quiescent Current vs. Input Voltage

4.5

f

SW

= 650kHz

4.0

3.5

T

A

= +125°C

T

A

= +25°C

T

A

= –40°C

3.0

2.5

2.0

2.5

3.0

3.5

4.0

4.5

INPUT VOLTAGE (V)

5.0

5.5

Figure 17. Switching Quiescent Current vs. Input Voltage, f

SW

= 650 kHz

5

4

7

6

9 f

SW

= 1.3MHz

8

T

A

= +25°C

T

A

= +125°C

T

A

= –40°C

3

2.5

3.0

3.5

4.0

4.5

INPUT VOLTAGE (V)

5.0

5.5

Figure 18. Switching Quiescent Current vs. Input Voltage, f

SW

= 1.3 MHz

Rev. B | Page 9 of 18

ADP1614

4

3

2

1

7

6

5

T

A

= +125°C

T

A

= +25°C

T

A

= –40°C

0

0 0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

EN PIN VOLTAGE (V)

Figure 19. EN Pin Current vs. EN Pin Voltage

6.0

5.8

5.6

5.4

5.2

V

IN

= 2.5V

V

IN

= 5.5V

V

IN

= 3.6V

5.0

4.8

–40 –10 20 50

TEMPERATURE (°C)

80

Figure 20. SS Pin Current vs. Temperature

110

4

3

1

2

V

IN

= 3.6V

V

OUT

= 15V

I

LOAD

= 60Ω

C f

SS

SW

= 68nF

= 1.3MHz

OUTPUT VOLTAGE (5V/DIV)

SWITCH VOLTAGE (10V/DIV)

INDUCTOR CURRENT (500mA/DIV)

EN PIN VOLTAGE (5V/DIV)

TIME (4ms/DIV)

Figure 21. Startup, C

SS

= 68 nF

ADP1614

V

IN

= 3.6V

V

OUT

= 5V f

SW

= 650kHz

L = 4.7µH

OUTPUT VOLTAGE (100mV/DIV)

AC-COUPLED

1

LOAD CURRENT (50mA/DIV)

3

1

TIME (200µs/DIV)

Figure 22. 50 mA to 150 mA Load Transient,

V

IN

= 3.6 V, V

OUT

= 5 V, f

SW

= 650 kHz

V

IN

= 3.6V

V f

OUT

SW

= 5V

= 1.3MHz

L = 4.7µH

OUTPUT VOLTAGE (100mV/DIV)

AC-COUPLED

3

LOAD CURRENT (50mA/DIV)

TIME (200µs/DIV)

Figure 23. 50 mA to 150 mA Load Transient,

V

IN

= 3.6 V, V

OUT

= 5 V, f

SW

= 1.3 MHz

1

V

IN

= 5V

V f

OUT

SW

= 15V

= 650kHz

L = 15µH

OUTPUT VOLTAGE (100mV/DIV)

AC-COUPLED

3

LOAD CURRENT (50mA/DIV)

TIME (200µs/DIV)

Figure 24. 50 mA to 150 mA Load Transient,

V

IN

= 5 V, V

OUT

= 15 V, f

SW

= 650 kHz

1

V

IN

= 5V

V

OUT

= 15V f

SW

= 1.3MHz

L = 10µH

OUTPUT VOLTAGE (200mV/DIV)

AC-COUPLED

Data Sheet

LOAD CURRENT (50mA/DIV)

3

TIME (200µs/DIV)

Figure 25. 50 mA to 150 mA Load Transient,

V

IN

= 5 V, V

OUT

= 15 V, f

SW

= 1.3 MHz

70

60

50

40

30

20

10

100

90

80

V

IN f

= 5V

SW

= 650kHz

ADP1614ACPZ-R7

V

OUT

V

OUT

= 8V

= 12V

0

1m 10m 100m

LOAD CURRENT (A)

1 10

Figure 26. Efficiency vs. Load Current, V

IN

= 5 V, f

SW

= 650 kHz

60

50

40

30

20

10

100

90

80

70

V

IN f

= 5V

SW

= 1.3MHz

ADP1614ACPZ-R7

V

OUT

V

OUT

= 8V

= 12V

0

1m 10m 100m

LOAD CURRENT (A)

1 10

Figure 27. Efficiency vs. Load Current, V

IN

= 5 V, f

SW

= 1.3 MHz

Rev. B | Page 10 of 18

Data Sheet

1.7

ADP1614ACPZ-R7

1.5

1.3

1.1

0.9

0.7

0.5

V

OUT

= 8V

V

OUT

= 12V

0.3

2.5

3.0

3.5

4.0

4.5

INPUT VOLTAGE (V)

5.0

5.5

Figure 28. Typical Maximum Continuous Output Current vs. V

IN

3.30

3.25

3.20

3.15

3.10

3.05

3.00

2.95

T

A

= –40°C

T

A

= +25°C

T

A

= +85°C

2.90

2.85

V

OUT

= 12V

ADP1614ACPZ-R7

2.80

2.5

3.0

3.5

4.0

4.5

5.0

5.5

INPUT VOLTAGE (V)

Figure 29. Peak Current Limit of Switch vs. V

IN

over Temperature, V

OUT

= 12 V

ADP1614

1.26

1.24

1.22

1.20

660

650

640

630

620

610

600

590

T

A

= –40°C

T

A

= +25°C

T

A

= +125°C f

SW

= 650kHz

580

2.5

3.0

3.5

4.0

4.5

INPUT VOLTAGE (V)

5.0

Figure 30. Frequency vs. Input Voltage, f

SW

= 650 kHz

5.5

1.30

f

SW

= 1.3MHz

1.28

T

A

= –40°C

T

A

= +25°C

T

A

= +125°C

1.18

1.16

2.5

3.0

3.5

4.0

4.5

INPUT VOLTAGE (V)

5.0

Figure 31. Frequency vs. Input Voltage, f

SW

= 1.3 MHz

5.5

Rev. B | Page 11 of 18

ADP1614

THEORY OF OPERATION

The ADP1614 current-mode, step-up switching converter boosts a 2.5 V to 5.5 V input voltage to an output voltage as high as 20 V. The internal switch allows a high output current, and the 650 kHz/1.3 MHz switching frequency allows the use of

V

IN

L1

tiny external components. The switch current is monitored on a pulse-by-pulse basis to limit the current to the value set by the

R

CL

resistor on the CLRES pin on the adjustable current-limit version or to 3 A typical on the fixed current-limit version.

ADP1614ACPZ-R7

1.3MHz

650kHz

9

FREQ

C

IN

VIN

8

VIN

D

COMPARATOR

V

OUT

PWM

COMPARATOR

R1

FB

2

ERROR

AMPLIFIER

R2

R

COMP

C

COMP

C

SS

COMP

1

SS

10

V

BG

V

SS

5.5µA

SOFT

START

UVLO

COMPARATOR

V

IN

UVLO

REF

TSD

COMPARATOR

T

SENSE

T

REF

D

REF

OSCILLATOR

RESET

+

BG

+

S

R

Q

5.5µA

DRIVER

BAND GAP

A

CURRENT

SENSING

AGND

1.1MΩ

ADP1614

N1

CLRES

R

CL

9

OFF

ADP1614ACPZ-650-R7

AND

ADP1614ACPZ-1.3-R7

3

EN

ON

AGND

11

EP

4

GND

5

GND

6

SW

7

SW

NOTES

1. THE PORTIONS IN THE DASHED BOXES DISPLAY THE TWO POSSIBLE FUNCTIONALITIES OF PIN 9 ON THE ADP1614.

Figure 32. Block Diagram with Step-Up Regulator Application Circuit

D1

C

OUT

Data Sheet

V

OUT

Rev. B | Page 12 of 18

Data Sheet

CURRENT-MODE PWM OPERATION

The ADP1614 utilizes a current-mode PWM control scheme to regulate the output voltage over all load conditions. The output voltage is monitored at FB through a resistive voltage divider. The voltage at FB is compared with the internal 1.245 V reference by the internal transconductance error amplifier to create an error voltage at COMP. The current of the switch is internally measured and added to the stabilizing ramp. The resulting sum is compared with the error voltage at COMP to control the PWM modulator.

This current-mode regulation system allows fast transient response while maintaining a stable output voltage. By selecting the proper resistor-capacitor network from COMP to GND, the regulator response is optimized for a wide range of input voltages, output voltages, and load conditions.

ADJUSTABLE CURRENT LIMIT

A key feature of the ADP1614ACPZ-650-R7 and

ADP1614ACPZ-1.3-R7 is a pin-adjustable peak current limit of

up to 4 A (see Figure 10 to Figure 13 and Figure 33). This adjustable

current limit allows the other external components to be selected specifically for the application. The current limit is set via an external resistor connected from Pin 9 (CLRES) to ground. For the ADP1614ACPZ-R7 , the current limit is fixed at 3 A.

4.0

V

IN

= 3.5V

3.5

2.0

1.5

3.0

2.5

V

OUT

= 5V

V

OUT

= 15V

1.0

60 75 90 105

R

CL

(kΩ)

120 135

Figure 33. Peak Current Limit of Switch vs. R

CL

150

FREQUENCY SELECTION

The adjustable current-limit versions of the ADP1614 are internally programmed to operate at either 650 kHz or 1.3 MHz.

Operation of the ADP1614 at 650 kHz ( ADP1614ACPZ-650-R7 ) optimizes the efficiency of the device, whereas operation of the

ADP1614 at 1.3 MHz ( ADP1614ACPZ-1.3-R7 ) enables the device to be used with smaller external components. For the fixed current-limit version ( ADP1614ACP-R7 ), the frequency is pin selectable via the FREQ Pin (Pin 9). Connect FREQ to

GND for 650 kHz operation or connect FREQ to VIN for

1.3 MHz operation. Do not leave the FREQ pin floating.

ADP1614

SOFT START

To prevent input inrush current to the converter when the part is enabled, connect a capacitor from SS to GND to set the soft start period. After the ADP1614 is turned on, SS sources 5 µA

(typical) to the soft start capacitor (C

SS

) until it reaches 1.23 V at startup. As the soft start capacitor charges, it limits the peak current allowed by the part. By slowly charging the soft start capacitor, the input current ramps slowly to prevent it from overshooting excessively at startup. When the ADP1614 is disabled, the SS pin is internally shorted to GND to discharge the soft start capacitor.

THERMAL SHUTDOWN (TSD)

The ADP1614 includes TSD protection. If the die temperature exceeds 150°C (typical), TSD turns off the NMOS power device, significantly reducing power dissipation in the device and preventing output voltage regulation. The NMOS power device remains off until the die temperature is reduced to 130°C (typical).

The soft start capacitor is discharged during TSD to ensure low output voltage overshoot and inrush currents when regulation resumes.

UNDERVOLTAGE LOCKOUT (UVLO)

If the input voltage is below the UVLO threshold, the ADP1614 automatically turns off the power switch and places the part into a low power consumption mode. This prevents potentially erratic operation at low input voltages and prevents the power device from turning on when the control circuitry cannot operate it. The UVLO levels have ~100 mV of hysteresis to ensure glitch-free startup.

SHUTDOWN MODE

The EN pin turns the ADP1614 regulator on or off. Drive EN low to shut down the regulator and reduce the input current to

0.25 µA (typical). Drive EN high to turn on the regulator.

When the converter is in shutdown mode (EN ≤ 0.3 V), there is a dc path from the input to the output through the inductor and output rectifier. This causes the output voltage to remain slightly below the input voltage by the forward voltage of the rectifier, preventing the output voltage from dropping to ground when the regulator is shut down.

Regardless of the state of the EN pin, when a voltage is applied to the VIN pin, a large current spike occurs due to the nonisolated path through the inductor and diode between V

IN

and V

OUT

. The high current is a result of the output capacitor charging. The peak value is dependent on the inductor, output capacitor, and any load active on the output of the regulator.

Rev. B | Page 13 of 18

ADP1614

APPLICATIONS INFORMATION

ADIsimPOWER DESIGN TOOL

The ADP1614 is supported by the ADIsimPower ™ design toolset.

ADIsimPower is a collection of tools that produce complete power designs that are optimized for a specific design goal. The tools enable the user to generate a full schematic and bill of materials and to calculate performance in minutes. ADIsimPower can optimize designs for cost, area, efficiency, and parts count while taking into consideration the operating conditions and limitations of the IC and the external components. For more information about the ADIsimPower design tools, visit www.analog.com/ADIsimPower . The toolset is available from this website, and users can request an unpopulated board.

SETTING THE OUTPUT VOLTAGE

The ADP1614 features an adjustable output voltage range of V

IN to 20 V. The output voltage is set by the resistor voltage divider,

R1 and R2 (see Figure 32), from the output voltage (V

OUT

) to the

1.245 V feedback input at FB. Use the following equation to determine the output voltage:

V

OUT

= 1.245 × (1 + R1/R2)

Choose R1 based on the following equation:

(1)

R1

=

R2

×

V

OUT

1

1 .

245

.

245

(2)

INDUCTOR SELECTION

The inductor is an essential part of the step-up switching converter. It stores energy during the on time of the power switch and transfers that energy to the output through the output rectifier during the off time. To balance the trade-offs between small inductor current ripple and efficiency, inductance values in the range of 4.7 µH to 22 µH are recommended. In general, lower inductance values have higher saturation current and lower series resistance for a given physical size. However, lower inductance values result in higher peak current, which can lead to reduced efficiency and greater input and/or output ripple and noise. A peak-to-peak inductor ripple current close to 30% of the maximum dc input current typically yields an optimal compromise.

For determining the inductor ripple current in continuous operation, the input (V

IN

) and output (V

OUT

) voltages determine the switch duty cycle (D) as follows:

D

=

V

OUT

V

OUT

V

IN

(3)

Data Sheet

The duty cycle and switching frequency (f

SW

) can be used to determine the on time:

t

ON

=

D f

SW

(4)

The inductor ripple current (∆I

L

) in steady state is calculated by

I

L

=

V

IN

×

L t

ON

(5)

Solve for the inductance value (L) as follows:

L

=

V

IN

×

I

L t

ON

(6)

Ensure that the peak inductor current (the maximum input current plus half the inductor ripple current) is below the rated saturation current of the inductor. Likewise, make sure that the maximum rated rms current of the inductor is greater than the maximum dc input current to the regulator.

For continuous current-mode (CCM) duty cycles greater than

50% that occur with input voltages less than one-half the output voltage, slope compensation is required to maintain stability of the current-mode regulator. For stable current-mode operation, ensure that the selected inductance is equal to or greater than the minimum calculated inductance, L

MIN

, for the application parameters in the following equation:

L

>

L

MIN

=

(

V

OUT

8

×

2

×

f

SW

V

IN

) (7)

Inductors smaller than the 4.7 µH to 22 µH recommended range can be used as long as Equation 7 is satisfied for the given application. For input/output combinations that approach the

90% maximum duty cycle, doubling the inductor is recommended

to ensure stable operation. Table 5 suggests a series of inductors

for use with the ADP1614 .

Table 5. Suggested Inductors

Manufacturer Part Series

Coilcraft

TOKO Inc.

XAL40xx, XAL50xx, XAL6060, DO3316P

FDV06xx, DG6045C, FDSD0630, DEM8045C,

FDVE1040

Würth Elektronik WE-HCI, WE-TPC, WE-PD, WE-PD2, WE -PDF

Vishay Dale IHLP-2020, IHLP-2525, IHLP-3232, IHLP-4040

TDK Components SPM6530, VLP8040, VLF10040, VLF10045

Taiyo Yuden NRS8030, NRS8040

Rev. B | Page 14 of 18

Data Sheet

CHOOSING THE INPUT AND OUTPUT CAPACITORS

The ADP1614 requires input and output bypass capacitors to supply transient currents while maintaining constant input and output voltages. Use low equivalent series resistance (ESR) capacitors of 10 µF or greater to prevent noise at the ADP1614 input. Place the capacitor between VIN and GND, as close as possible to the ADP1614 . Ceramic capacitors are preferable because of their low ESR characteristics. Alternatively, use a high value, medium ESR capacitor in parallel with a 0.1 µF low

ESR capacitor, placed as close as possible to the ADP1614 .

The output capacitor maintains the output voltage and supplies current to the load while the ADP1614 switch is on. The value and characteristics of the output capacitor greatly affect the output voltage ripple and stability of the regulator. A low ESR ceramic dielectric capacitor is preferable. The output voltage ripple (∆V

OUT

) is calculated as follows:

V

OUT

=

Q

C

C

OUT

=

I

OUT

×

t

ON

C

OUT

C

OUT

f

I

OUT

SW

×

×

V

(

V

OUT

OUT

×

V

IN

V

OUT

)

(8)

I

where:

Q

C

is the charge removed from the capacitor.

C

OUT

is the output capacitance.

OUT

is the output load current.

t

ON

is the on time of the switch.

The on time of the switch is determined as follows:

t

ON

=

D f

SW

(9)

The input (V

IN

) and output (V

OUT

) voltages determine the switch duty cycle (D) as follows:

D

=

V

OUT

V

OUT

V

IN

(10)

Choose the output capacitor based on the following equation:

(11)

Multilayer ceramic capacitors are recommended for this application.

DIODE SELECTION

The output rectifier conducts the inductor current to the output capacitor and load while the switch is off. For high efficiency, minimize the forward voltage drop of the diode. For this reason, using Schottky rectifiers is recommended. However, for high voltage, high temperature applications, where the Schottky rectifier reverse leakage current becomes significant and can degrade efficiency, use an ultrafast junction diode.

Many diode manufacturers derate the current capability of the diode as a function of the duty cycle. Verify that the output

ADP1614

diode is rated to handle the average output load current with the minimum duty cycle. The minimum duty cycle in CCM of the ADP1614 is

D

MIN

=

V

OUT

V

IN

(

MAX

)

V

OUT

(12) where V

IN(MAX)

is the maximum input voltage.

The following are suggested Schottky diode manufacturers:

• ON Semiconductor

• Diodes, Inc.

• Toshiba

• ROHM Semiconductor

LOOP COMPENSATION

The ADP1614 uses external components to compensate the regulator loop, allowing optimization of the loop dynamics for a given application.

The step-up converter produces an undesirable right-half plane zero in the regulation feedback loop. This requires compensating the regulator such that the crossover frequency occurs well below the frequency of the right-half plane zero. The right-half plane zero is determined by the following equation:

F

Z

(

RHP

)

=



V

IN

V

OUT



2

×

R

2

π

LOAD

×

L

where:

F

Z

(RHP) is the right-half plane zero.

R

LOAD

is the equivalent load resistance or the output voltage divided by the load current.

To stabilize the regulator, ensure that the regulator crossover frequency is less than or equal to one-fifth of the right-half plane zero.

The regulator loop gain is

(13)

A

VL

=

V

FB

V

OUT

×

V

IN

V

OUT

×

G

MEA

×

R

OUT

Z

COMP

×

G

CS

×

Z

OUT

where:

A

VL

is the loop gain.

V

FB

is the feedback regulation voltage, 1.245 V.

V

OUT

is the regulated output voltage.

V

IN

is the input voltage.

G

MEA

is the error amplifier transconductance gain.

R

OUT

= 67 MΩ.

Z

COMP

is the impedance of the series RC network from COMP to GND.

G

CS

is the current sense transconductance gain (the inductor current divided by the voltage at COMP), which is internally set by the ADP1614 .

Z

OUT

is the impedance of the load in parallel with the output capacitor.

(14)

Rev. B | Page 15 of 18

ADP1614

To determine the crossover frequency, it is important to note that at the crossover frequency the compensation impedance (Z

COMP

) is dominated by a resistor, and the output impedance (Z

OUT

) is dominated by the impedance of an output capacitor. Therefore, when solving for the crossover frequency, the equation (by definition of the crossover frequency) is simplified to

A

VL

2

π ×

=

f

C

V

FB

V

OUT

1

×

×

C

OUT

V

IN

V

OUT

=

1

×

G

MEA

×

R

COMP

×

G

CS

×

(15) where:

R

COMP

is the compensation resistor.

f

C

is the crossover frequency.

Solve for R

COMP

as follows:

R

COMP

=

2

π ×

V

FB f

C

×

×

V

IN

C

OUT

×

G

×

(

MEA

V

OUT

×

G

)

CS

2 where:

V

FB

= 1.245 V.

G

MEA

G

CS

= 150 µA/V.

= 7 A/V.

Therefore,

(16)

R

COMP

=

4806

×

f

C

×

C

OUT

×

(

V

OUT

)

2

V

IN

(17)

After the compensation resistor is known, set the zero formed by the compensation capacitor and resistor to one-fourth of the crossover frequency, or

C

COMP

=

π ×

f

C

2

×

R

COMP

(18) where C

COMP

is the compensation capacitor.

ERROR

AMPLIFIER

FB 2 g m

COMP

1

V

BG

R

COMP

C2

C

COMP

Figure 34. Compensation Components

Data Sheet

Capacitor C2 is chosen to cancel the zero introduced by the ESR of the output capacitor.

Solve for C2 as follows:

C2

=

ESR

×

C

OUT

R

COMP

(19)

If a low ESR, ceramic output capacitor is used for C

OUT

, C2 is optional. For optimal transient performance, R

COMP

and C

COMP might need to be adjusted by observing the load transient response of the ADP1614 . For most applications, the compensation resistor should be within the range of 1 kΩ to 100 kΩ, and the compensation capacitor should be within the range of 100 pF to

10 nF.

SOFT START CAPACITOR

Upon startup (EN ≥ 1.6 V) or fault recovery, the voltage at SS ramps up slowly by charging the soft start capacitor (C

SS

) with an internal 5.5 µA current source (I

SS

). As the soft start capacitor charges, it limits the peak current allowed by the part to prevent excessive overshoot at startup. Use the following equation to determine the necessary value of the soft start capacitor (C

SS

) for a specific overshoot and start-up time when the part is at the current limit with maximum load:

C

SS

=

I

SS

t

V

SS

where:

I

SS

= 5.5 μA (typical).

Δt is the start-up time at the current limit.

V

SS

= 1.23 V (typical).

(20)

If the applied load does not place the part at the current limit, the value of C

SS

can be reduced. A 68 nF soft start capacitor results in negligible input current overshoot at startup and, therefore, is suitable for most applications. If an unusually large output capacitor is used, a longer soft start period is required to prevent input inrush current.

However, if fast startup is required, the soft start capacitor can be reduced or removed, which allows the ADP1614 to start quickly but with greater peak switch current.

Rev. B | Page 16 of 18

Data Sheet

PCB LAYOUT GUIDELINES

For high efficiency, good regulation, and stability, a well designed

PCB layout is required.

Use the following guidelines when designing PCBs (see Figure 32

for a block diagram and Figure 3 for a pin configuration).

• Keep the low ESR input capacitor (C

IN

), which is labeled as

C4 in Figure 35, close to VIN and GND. This minimizes

noise injected into the part from board parasitic inductance.

• Keep the high current path from C

IN

through the L1 inductor to SW and GND as short as possible.

• Keep the high current path from VIN through the inductor

(L1), the rectifier (D1), and the output capacitor (C

OUT

),

which is labeled as C7 in Figure 35, as short as possible.

• Keep high current traces as short and as wide as possible.

• Place the feedback resistors as close to FB as possible to prevent noise pickup. Connect the ground of the feedback network directly to an AGND plane that makes a Kelvin connection to the GND pin.

• Place the compensation components as close as possible to

COMP. Connect the ground of the compensation network directly to an AGND plane that makes a Kelvin connection to the GND pin.

• Connect the soft start capacitor (C

SS

), which is labeled as

C1 in Figure 35, as close as possible to the device. Connect

the ground of the soft start capacitor to an AGND plane that makes a Kelvin connection to the GND pin.

• Connect the current-limit set resistor (R

CL

), which is labeled as

R4 in Figure 35, as close as possible to the device. Connect

the ground of the CL resistor to an AGND plane that makes a

Kelvin connection to the GND pin.

• The PCB must be properly designed to conduct the heat away from the package. This is achieved by adding thermal vias to the PCB, which provide a thermal path to the inner or bottom layers. Thermal vias should be placed on the PCB underneath the exposed pad of the LFCSP and in the GND plane around the ADP1614 package to improve thermal performance of the package.

Avoid routing high impedance traces from the compensation and feedback resistors near any node connected to SW or near the inductor to prevent radiated noise injection.

ADP1614

Figure 35. ADP1614 Recommended Top Layer Layout for the Adjustable

Current-Limit Boost Application

Figure 36. ADP1614 Recommended Bottom Layer Layout for the Adjustable

Current-Limit Boost Application

Rev. B | Page 17 of 18

ADP1614

OUTLINE DIMENSIONS

Data Sheet

3.10

3.00 SQ

2.90

2.48

2.38

2.23

10

0.50 BSC

6

PIN 1 INDEX

AREA

0.80

0.75

0.70

SEATING

PLANE

TOP VIEW

EXPOSED

PAD

1.74

1.64

1.49

0.50

0.40

0.30

5

0.05 MAX

0.02 NOM

COPLANARITY

0.08

0.20 REF

BOTTOM VIEW

1

0.20 MIN

PIN 1

INDICATOR

(R 0.15)

FOR PROPER CONNECTION OF

THE EXPOSED PAD, REFER TO

THE PIN CONFIGURATION AND

FUNCTION DESCRIPTIONS

SECTION OF THIS DATA SHEET.

0.30

0.25

0.20

Figure 37. 10-Lead Lead Frame Chip Scale Package [LFCSP_WD]

3 mm × 3 mm Body, Very Very Thin, Dual Lead

(CP-10-9)

Dimensions shown in millimeters

ORDERING GUIDE

Model 1

Temperature

Range

Switching

Frequency

ADP1614ACPZ-1.3-R7 −40°C to +125°C 1.3 MHz

Current Limit Package Description

Adjustable up to 4 A 10-Lead LFCSP_WD

ADP1614ACPZ-650-R7 −40°C to +125°C 650 kHz

ADP1614ACPZ-R7

Adjustable up to 4 A

−40°C to +125°C Pin selectable Fixed 3 A

10-Lead LFCSP_WD

10-Lead LFCSP_WD

ADP1614-1.3-EVALZ 1.3 MHz

ADP1614-650-EVALZ 650 kHz

Adjustable up to 4 A Evaluation Board, 15 V Output

Voltage Configuration

Adjustable up to 4 A Evaluation Board, 5 V Output

Voltage Configuration

1 Z = RoHS Compliant Part.

Package

Option Branding

CP-10-9 LM4

CP-10-9 LM5

CP-10-9 LNG

©2012–2014 Analog Devices, Inc. All rights reserved. Trademarks and

registered trademarks are the property of their respective owners.

D10293-0-11/14(B)

Rev. B | Page 18 of 18

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