AD ADP1614ACPZ-650-R7 650 khz/1.3 mhz, 4 a, step-up Datasheet

FEATURES
Adjustable current limit, up to 4 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
TYPICAL APPLICATIONS CIRCUIT
L1
ADP1614
VIN
8
VIN
3
EN
ON
OFF
D1
VOUT
SW 6
SW 7
CIN
R1
FB 2
9
10
RCL
CSS
CLRES
R2
COMP
SS
GND GND EP
4
5
11
1
RCOMP
CCOMP
COUT
10293-001
Data Sheet
650 kHz/1.3 MHz, 4 A, Step-Up,
PWM, DC-to-DC Switching Converter
ADP1614
Figure 1. Step-Up Regulator Configuration
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 pinadjustable current limit that is set via an external resistor. The
boost switching frequency is fixed to either 650 kHz or 1.3 MHz.
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).
Rev. 0
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.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2012 Analog Devices, Inc. All rights reserved.
ADP1614
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
Soft Start ...................................................................................... 11
Applications ....................................................................................... 1
Thermal Shutdown (TSD) ........................................................ 11
General Description ......................................................................... 1
Undervoltage Lockout (UVLO) ............................................... 11
Typical Applications Circuit............................................................ 1
Shutdown Mode ......................................................................... 11
Revision History ............................................................................... 2
Applications Information .............................................................. 12
Specifications..................................................................................... 3
ADIsimPower Design Tool ....................................................... 12
Absolute Maximum Ratings ............................................................ 4
Setting the Output Voltage ........................................................ 12
Thermal Resistance ...................................................................... 4
Inductor Selection ...................................................................... 12
ESD Caution .................................................................................. 4
Choosing the Input and Output Capacitors ........................... 13
Pin Configuration and Function Descriptions ............................. 5
Diode Selection ........................................................................... 13
Typical Performance Characteristics ............................................. 6
Loop Compensation .................................................................. 13
Theory of Operation ...................................................................... 10
Soft Start Capacitor .................................................................... 14
Current-Mode PWM Operation .............................................. 11
PCB Layout Guidelines .................................................................. 15
Adjustable Current Limit .......................................................... 11
Outline Dimensions ....................................................................... 16
Frequency Selection ................................................................... 11
Ordering Guide .......................................................................... 16
REVISION HISTORY
6/12—Revision 0: Initial Version
Rev. 0 | Page 2 of 16
Data Sheet
ADP1614
SPECIFICATIONS
VIN = 3.6 V, unless otherwise noted. Minimum and maximum values are guaranteed for TJ = −40°C to +125°C. Typical values specified
are at TJ = 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
Symbol
Enable Pin Bias Current
UNDERVOLTAGE LOCKOUT (UVLO)
Undervoltage Lockout Threshold
IEN
OUTPUT
Output Voltage
Load Regulation
REFERENCE
Feedback Voltage
Line Regulation
ERROR AMPLIFIER
Transconductance
Voltage Gain
FB Pin Bias Current
SWITCH (SW)
On Resistance
Leakage Current
Peak Current Limit 2
Maximum Peak Current Limit 3
CLRES VOLTAGE 4
OSCILLATOR
Oscillator Frequency
Maximum Duty Cycle
EN LOGIC THRESHOLD
Input Voltage Low
Input Voltage High
SOFT START (SS)
Charging Current
Pin Voltage
Test Conditions/Comments
VIN
IQSHDN
IQ
IQSW
Min
VEN = 0 V
VFB = 1.3 V, fSW = 1.3 MHz and 650 kHz
fSW = 1.3 MHz, no load
fSW = 650 kHz, no load
VEN = 3.6 V
VOUT
2.0
VFB
DMAX
−1.6%
ΔI = 4 µA
V
0.25
700
5.5
3
3.4
1.5
1100
7
4.5
7
µA
µA
mA
mA
µA
2.33
2.20
2.5
V
V
20
V
mV/mA
+1.6%
0.2
V
%/V
50
µA/V
dB
nA
1.245
0.02
VFB = 1.245 V
150
80
1
ISW = 1.0 A
VSW = 20 V
RCL = 154 kΩ, duty cycle = 70%
RCL = 61.9 kΩ, VIN = 3.6 V, VOUT = 15 V
ICLRES = 5 µA
ICLRES = 20 µA
100
10
1.65
1.225
1.18
50
0.1
1.3
4
1.27
1.22
1.1
500
88
1.3
650
92
1.4
720
MHz
kHz
%
0.3
V
V
7
1.29
µA
V
ADP1614ACPZ-1.3-R7
ADP1614ACPZ-650-R7
COMP = open, VFB = 1 V, fSW = 1.3 MHz and 650 kHz
VIN = 2.5 V to 5.5 V
VIL
VIH
ISS
VSS
5.5
0.005
VIN = 2.5 V to 5.5 V
fSW
Unit
VIN
VOUT = 10 V, ILOAD = 1 mA to 1 A
RDSON
Max
2.5
VIN rising
VIN falling
GMEA
AV
Typ
0.95
1.315
1.25
1.6
VSS = 0 V
VFB = 1.3 V
THERMAL SHUTDOWN
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
3.4
1.17
5.5
1.23
150
20
mΩ
µA
A
A
V
V
°C
°C
This parameter specifies the average current when the device switches internally with the SW pins (Pin 6 and Pin 7) floating.
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 9 through Figure 12.
Guaranteed by design.
4
The CLRES pin cannot be controlled with a current source. An equivalent resistance should be used.
1
2
3
Rev. 0 | Page 3 of 16
ADP1614
Data Sheet
ABSOLUTE MAXIMUM RATINGS
THERMAL RESISTANCE
Table 2.
Parameter
VIN, EN, FB to GND
CLRES to GND
COMP to GND
SS to GND
SW to GND
Operating Junction Temperature Range
Storage Temperature Range
Soldering Conditions
Rating
−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
21 V
−40°C to +125°C
−65°C to +150°C
JEDEC J-STD-020
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.
Absolute maximum ratings apply individually only, not in
combination.
The junction-to-ambient thermal resistance (θJA) of the package
is specified for the worst-case conditions, that is, a device soldered
in a circuit board for surface-mount packages. The θJA 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 θJA 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 Resistance1
Package Type
10-Lead LFCSP
1
θJA
47
Thermal numbers per JEDEC standard JESD 51-9.
ESD CAUTION
Rev. 0 | Page 4 of 16
θJC
7.22
Unit
°C/W
Data Sheet
ADP1614
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
COMP 1
ADP1614
9
CLRES
EN 3
TOP VIEW
(Not to Scale)
8
VIN
GND 4
7
SW
GND 5
6
SW
NOTES
1. THE EXPOSED PAD IS NOT ELECTRICALLY
CONNECTED; CONNECT THIS PAD TO A GROUND
PLANE FOR BETTER HEAT DISTRIBUTION.
10293-002
10 SS
FB 2
Figure 2. Pin Configuration
Table 4. Pin Function Descriptions
Pin No.
1
2
Mnemonic
COMP
FB
3
4, 5
6, 7
EN
GND
SW
8
VIN
9
10
CLRES
SS
11
EP
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.
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.
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.
Connect a resistor to GND to set the peak inductor current.
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. 0 | Page 5 of 16
ADP1614
Data Sheet
100
100
90
90
80
80
70
70
EFFICIENCY (%)
60
50
40
30
50
40
20
1
10
100
1k
10k
LOAD CURRENT (mA)
0
10293-003
0
VOUT = 10V
VOUT = 15V
VOUT = 20V
10
1
10
100
1k
10k
LOAD CURRENT (mA)
Figure 3. Efficiency vs. Load Current, VIN = 3.6 V, fSW = 650 kHz
10293-006
VOUT = 5V
VOUT = 10V
VOUT = 15V
VIN = 3.6V
fSW = 650kHz
RCL = 71.5kΩ
10
Figure 6. Efficiency vs. Load Current, VIN = 5 V, fSW = 1.3 MHz
100
4.0
VIN = 3.6V
fSW = 1.3MHz
RCL = 71.5kΩ
3.5
MAXIMUM OUTPUT CURRENT (A)
80
70
60
50
40
30
20
VOUT = 5V
VOUT = 10V
VOUT = 15V
0
1
10
100
1k
10k
LOAD CURRENT (mA)
VIN = 4.5V
2.5
2.0
VIN = 3.5V
1.5
1.0
VIN = 2.5V
0.5
VOUT = 5V
0
60
75
10293-004
10
3.0
Figure 4. Efficiency vs. Load Current, VIN = 3.6 V, fSW = 1.3 MHz
90
105
120
135
150
RCL (kΩ)
10293-100
90
EFFICIENCY (%)
60
30
20
Figure 7. Typical Maximum Continuous Output Current vs. RCL, VOUT = 5 V
100
1.4
VIN = 5V
fSW = 650kHz
RCL = 71.5kΩ
1.2
MAXIMUM OUTPUT CURRENT (A)
90
80
70
60
50
40
30
20
VOUT = 10V
VOUT = 15V
VOUT = 20V
10
0
1
10
100
1k
10k
LOAD CURRENT (mA)
Figure 5. Efficiency vs. Load Current, VIN = 5 V, fSW = 650 kHz
1.0
VIN = 5.5V
0.8
VIN = 4.5V
0.6
VIN = 3.5V
0.4
0.2
VOUT = 15V
0
60
75
10293-005
EFFICIENCY (%)
VIN = 5V
fSW = 1.3MHz
RCL = 71.5kΩ
VIN = 2.5V
90
105
RCL (kΩ)
120
135
150
10293-101
EFFICIENCY (%)
TYPICAL PERFORMANCE CHARACTERISTICS
Figure 8. Typical Maximum Continuous Output Current vs. RCL, VOUT = 15 V
Rev. 0 | Page 6 of 16
Data Sheet
ADP1614
3.60
4.0
VIN = 4.5V
3.55
TA = –40°C
3.5
3.50
TA = +25°C
CURRENT LIMIT (A)
CURRENT LIMIT (A)
VIN = 2.5V
3.0
2.5
VIN = 3.5V
2.0
3.45
3.40
TA = +85°C
3.35
3.30
3.25
3.20 V
OUT = 15V
RCL = 71.5kΩ
3.15
2.5
3.0
90
105
120
135
150
RCL (kΩ)
4.5
4.0
80
3.90
SWITCH ON RESISTANCE (mΩ)
3.85
CURRENT LIMIT (A)
4.0
3.80
TA = +85°C
3.75
3.70
TA = +25°C
3.65
70
TA = +125°C
60
50
TA = +25°C
40
3.0
3.5
4.0
TA = –40°C
4.5
INPUT VOLTAGE (V)
30
2.5
10293-102
3.60
2.5
ISW = 1A
TA = –40°C
VOUT = 5V
RCL = 71.5kΩ
5.5
INPUT VOLTAGE (V)
Figure 12. Peak Current Limit of Switch vs. VIN over Temperature, VOUT = 15 V
Figure 9. Peak Current Limit of Switch vs. RCL, VOUT = 5 V
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
Figure 10. Peak Current Limit of Switch vs. VIN over Temperature, VOUT = 5 V
Figure 13. Switch On Resistance vs. Input Voltage
4.0
94.5
94.0
3.5
TA = +125°C
MAXIMUM DUTY CYCLE (%)
VIN = 2.5V
3.0
VIN = 3.5V
VIN = 4.5V
2.5
VIN = 5.5V
2.0
1.5
VOUT = 15V
1.0
60
75
93.5
93.0
TA = –40°C
TA = +25°C
92.5
92.0
91.5
90
105
120
135
RCL (kΩ)
150
10293-105
CURRENT LIMIT (A)
3.5
10293-008
75
91.0
2.5
3.0
3.5
4.0
4.5
5.0
INPUT VOLTAGE (V)
Figure 14. Maximum Duty Cycle vs. Input Voltage
Figure 11. Peak Current Limit of Switch vs. RCL, VOUT = 15 V
Rev. 0 | Page 7 of 16
5.5
10293-015
1.0
60
10293-104
VOUT = 5V
10293-103
1.5
ADP1614
Data Sheet
7
760
6
740
TA = +125°C
700
680
TA = +25°C
660
5
EN PIN CURRENT (µA)
720
640
TA = +125°C
4
3
TA = –40°C
2
TA = –40°C
TA = +25°C
620
1
580
2.5
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
0
0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Figure 18. EN Pin Current vs. EN Pin Voltage
6.0
VIN = 2.5V
5.8
4.0
3.5
TA = +25°C
VIN = 5.5V
SS PIN CURRENT (µA)
TA = +125°C
TA = –40°C
3.0
5.6
VIN = 3.6V
5.4
5.2
2.5
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
4.8
–40
20
50
80
110
TEMPERATURE (°C)
Figure 16. Switching Quiescent Current vs. Input Voltage, fSW = 650 kHz
9
–10
10293-017
5.0
10293-011
Figure 19. SS Pin Current vs. Temperature
VIN = 3.6V
VOUT = 15V
ILOAD = 60Ω
CSS = 68nF
fSW = 1.3MHz
fSW = 1.3MHz
8
OUTPUT VOLTAGE (5V/DIV)
SWITCH VOLTAGE (10V/DIV)
7
TA = +125°C
1
2
6
TA = –40°C
TA = +25°C
INDUCTOR CURRENT (500mA/DIV)
5
4
4
3
3.0
3.5
4.0
4.5
INPUT VOLTAGE (V)
5.0
5.5
10293-012
3
2.5
EN PIN VOLTAGE (5V/DIV)
Figure 17. Switching Quiescent Current vs. Input Voltage, fSW = 1.3 MHz
Rev. 0 | Page 8 of 16
TIME (4ms/DIV)
Figure 20. Startup, CSS = 68 nF
10293-106
SWITCHING QUIESCENT CURRENT (mA)
1.5
fSW = 650kHz
2.0
2.5
SWITCHING QUIESCENT CURRENT (mA)
1.0
EN PIN VOLTAGE (V)
Figure 15. Nonswitching Quiescent Current vs. Input Voltage
4.5
0.5
10293-016
600
10293-009
NONSWITCHING QUIESCENT CURRENT (µA)
780
Data Sheet
ADP1614
VIN = 5V
VOUT = 15V
OUTPUT VOLTAGE (100mV/DIV)
AC-COUPLED
fSW = 650kHz
L = 15µH
VIN = 3.6V
VOUT = 5V
OUTPUT VOLTAGE (100mV/DIV)
fSW = 650kHz
AC-COUPLED
L = 4.7µH
1
1
LOAD CURRENT (50mA/DIV)
LOAD CURRENT (50mA/DIV)
10293-020
TIME (200µs/DIV)
TIME (200µs/DIV)
Figure 21. 50 mA to 150 mA Load Transient,
VIN = 3.6 V, VOUT = 5 V, fSW = 650 kHz
10293-022
3
3
Figure 23. 50 mA to 150 mA Load Transient,
VIN = 5 V, VOUT = 15 V, fSW = 650 kHz
VIN = 5V
VOUT = 15V
OUTPUT VOLTAGE (200mV/DIV)
AC-COUPLED
fSW = 1.3MHz
L = 10µH
VIN = 3.6V
VOUT = 5V
OUTPUT VOLTAGE (100mV/DIV)
fSW = 1.3MHz
AC-COUPLED
L = 4.7µH
1
1
LOAD CURRENT (50mA/DIV)
LOAD CURRENT (50mA/DIV)
TIME (200µs/DIV)
TIME (200µs/DIV)
Figure 22. 50 mA to 150 mA Load Transient,
VIN = 3.6 V, VOUT = 5 V, fSW = 1.3 MHz
Figure 24. 50 mA to 150 mA Load Transient,
VIN = 5 V, VOUT = 15 V, fSW = 1.3 MHz
Rev. 0 | Page 9 of 16
10293-023
3
10293-021
3
ADP1614
Data Sheet
THEORY OF OPERATION
tiny external components. The switch current is monitored on a
pulse-by-pulse basis to limit the current to the value set by the
RCL resistor on the CLRES pin.
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
L1
VIN
CIN
VIN
8
+
VIN
D
COMPARATOR
VOUT
R1
ERROR
AMPLIFIER
FB
PWM
COMPARATOR
CURRENT
SENSING
COUT
S
Q
UVLOREF
VSS
N1
R
TSD
COMPARATOR
5.5µA
10
VOUT
DRIVER
VIN
RCOMP
SS
SW
D1
DREF
UVLO
COMPARATOR
1
CCOMP
7
SW
OSCILLATOR
VBG
COMP
6
+
2
R2
A
TSENSE
SOFT
START
TREF
RESET
BG
BAND GAP
CSS
AGND
1.1MΩ
ADP1614
AGND
3
11
EN
4
EP
5
GND
GND
10293-024
CLRES
RCL
9
>1.6V
<0.3V
Figure 25. Block Diagram with Step-Up Regulator Application Circuit
Rev. 0 | Page 10 of 16
Data Sheet
ADP1614
CURRENT-MODE PWM OPERATION
SOFT START
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.
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 (CSS) 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.
ADJUSTABLE CURRENT LIMIT
A key feature of the ADP1614 is a pin-adjustable peak current
limit of up to 4 A (see Figure 9 to Figure 12 and Figure 26). 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.
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)
4.0
VIN = 3.5V
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.
3.5
CURRENT LIMIT (A)
THERMAL SHUTDOWN (TSD)
3.0
VOUT = 5V
2.5
VOUT = 15V
2.0
SHUTDOWN MODE
1.0
60
75
90
105
120
135
RCL (kΩ)
150
10293-007
1.5
Figure 26. Peak Current Limit of Switch vs. RCL
FREQUENCY SELECTION
The ADP1614 is 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 (ADP1614ACPZ1.3-R7) enables the device to be used with smaller external
components.
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 VIN and VOUT. 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. 0 | Page 11 of 16
ADP1614
Data Sheet
APPLICATIONS INFORMATION
ADIsimPower DESIGN TOOL
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SETTING THE OUTPUT VOLTAGE
The ADP1614 features an adjustable output voltage range of VIN
to 20 V. The output voltage is set by the resistor voltage divider,
R1 and R2 (see Figure 25), from the output voltage (VOUT) to the
1.245 V feedback input at FB. Use the following equation to
determine the output voltage:
VOUT = 1.245 × (1 + R1/R2)
(1)
Choose R1 based on the following equation:
− 1.245 
V
R1 = R2 ×  OUT

1.245


(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 (VIN) and output (VOUT) voltages determine
the switch duty cycle (D) as follows:
D=
VOUT − VIN
VOUT
(3)
The duty cycle and switching frequency (fSW) can be used to
determine the on time:
t ON =
D
f SW
(4)
The inductor ripple current (∆IL) in steady state is calculated by
∆I L =
VIN × t ON
L
(5)
Solve for the inductance value (L) as follows:
L=
VIN × t ON
(6)
∆I L
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, LMIN, for the application
parameters in the following equation:
L > LMIN =
(VOUT − 2 × VIN )
8 × f SW
(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
Coilcraft
TOKO Inc.
Würth Elektronik
Vishay Dale
TDK Components
Taiyo Yuden
Rev. 0 | Page 12 of 16
Part Series
XAL40xx, XAL50xx, XAL6060, DO3316P
FDV06xx, DG6045C, FDSD0630, DEM8045C,
FDVE1040
WE-HCI, WE-TPC, WE-PD, WE-PD2, WE -PDF
IHLP-2020, IHLP-2525, IHLP-3232, IHLP-4040
SPM6530, VLP8040, VLF10040, VLF10045
NRS8030, NRS8040
Data Sheet
ADP1614
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 (∆VOUT) is calculated as follows:
∆VOUT =
QC
I
×t
= OUT ON
C OUT
C OUT
(8)
where:
QC is the charge removed from the capacitor.
COUT is the output capacitance.
IOUT is the output load current.
tON is the on time of the switch.
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 =
D
f SW
(9)
(10)
Choose the output capacitor based on the following equation:
C OUT ≥
I OUT × (VOUT − VIN )
f SW × VOUT × ∆VOUT
•
•
•
•
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:
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
2
 R LOAD
 ×
 2π × L

(13)
where:
FZ(RHP) is the right-half plane zero.
RLOAD 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
(11)
Multilayer ceramic capacitors are recommended for this
application.
(12)
The following are suggested Schottky diode manufacturers:
 V
FZ (RHP ) =  IN
 VOUT
The input (VIN) and output (VOUT) voltages determine the
switch duty cycle (D) as follows:
V
− VIN
D = OUT
VOUT
VOUT
where VIN(MAX) is the maximum input voltage.
The on time of the switch is determined as follows:
t ON =
VOUT − VIN ( MAX )
AVL =
V
VFB
× IN × G MEA × ROUT Z COMP × GCS × Z OUT (14)
VOUT VOUT
where:
AVL is the loop gain.
VFB is the feedback regulation voltage, 1.245 V.
VOUT is the regulated output voltage.
VIN is the input voltage.
GMEA is the error amplifier transconductance gain.
ROUT = 67 MΩ.
ZCOMP is the impedance of the series RC network from COMP
to GND.
GCS is the current sense transconductance gain (the inductor
current divided by the voltage at COMP), which is internally
set by the ADP1614.
ZOUT is the impedance of the load in parallel with the output
capacitor.
Rev. 0 | Page 13 of 16
ADP1614
Data Sheet
To determine the crossover frequency, it is important to note that
at the crossover frequency the compensation impedance (ZCOMP)
is dominated by a resistor, and the output impedance (ZOUT) 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
V
VFB
× IN × G MEA × RCOMP × GCS ×
VOUT VOUT
1
=1
2π × f C × C OUT
AVL =
(15)
where:
RCOMP is the compensation resistor.
fC is the crossover frequency.
Solve for C2 as follows:
C2 =
ESR × C OUT
RCOMP
2π × f C × C OUT × (VOUT ) 2
(16)
VFB × VIN × G MEA × GCS
where:
VFB = 1.245 V.
GMEA = 150 µA/V.
GCS = 7 A/V.
If a low ESR, ceramic output capacitor is used for COUT, C2 is
optional. For optimal transient performance, RCOMP and CCOMP
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.
Upon startup (EN ≥ 1.6 V) or fault recovery, the voltage at SS
ramps up slowly by charging the soft start capacitor (CSS) with
an internal 5.5 µA current source (ISS). 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 (CSS) for a specific overshoot and start-up time when
the part is at the current limit with maximum load:
C SS = I SS
Therefore,
RCOMP =
4806 × f C × C OUT × (VOUT ) 2
VIN
(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
2
=
π × f C × RCOMP
(18)
where CCOMP is the compensation capacitor.
ERROR
AMPLIFIER
gm
VBG
1
RCOMP
(20)
where:
ISS = 5.5 μA (typical).
Δt is the start-up time at the current limit.
VSS = 1.23 V (typical).
If the applied load does not place the part at the current limit,
the value of CSS 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.
10293-026
C2
CCOMP
∆t
VSS
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.
COMP
FB 2
(19)
SOFT START CAPACITOR
Solve for RCOMP as follows:
RCOMP =
Capacitor C2 is chosen to cancel the zero introduced by the ESR
of the output capacitor.
Figure 27. Compensation Components
Rev. 0 | Page 14 of 16
Data Sheet
ADP1614
PCB LAYOUT GUIDELINES
For high efficiency, good regulation, and stability, a well designed
PCB layout is required.
•
•
•
•
•
•
•
•
Keep the low ESR input capacitor (CIN), which is labeled as
C4 in Figure 28, close to VIN and GND. This minimizes
noise injected into the part from board parasitic inductance.
Keep the high current path from CIN 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 (COUT),
which is labeled as C7 in Figure 28, 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 (CSS), which is labeled as
C1 in Figure 28, 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 (RCL), which is
labeled as R4 in Figure 28, 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.
Figure 28. ADP1614 Recommended Top Layer Layout for Boost Application
10293-028
•
10293-027
Use the following guidelines when designing PCBs (see Figure 25
for a block diagram and Figure 2 for a pin configuration).
Figure 29. ADP1614 Recommended Bottom Layer Layout for Boost Application
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.
Rev. 0 | Page 15 of 16
ADP1614
Data Sheet
OUTLINE DIMENSIONS
2.48
2.38
2.23
3.10
3.00 SQ
2.90
0.50 BSC
6
0.50
0.40
0.30
5
TOP VIEW
0.80
0.75
0.70
SEATING
PLANE
10
1.74
1.64
1.49
EXPOSED
PAD
0.05 MAX
0.02 NOM
0.30
0.25
0.20
1
BOTTOM VIEW
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.
0.20 REF
121009-A
PIN 1 INDEX
AREA
Figure 30. 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
ADP1614ACPZ-1.3-R7
ADP1614ACPZ-650-R7
ADP1614-1.3-EVALZ
ADP1614-650-EVALZ
1
Temperature
Range
−40°C to +125°C
−40°C to +125°C
Switching
Frequency
1.3 MHz
650 kHz
1.3 MHz
650 kHz
Package Description
10-Lead Lead Frame Chip Scale Package [LFCSP_WD]
10-Lead Lead Frame Chip Scale Package [LFCSP_WD]
Evaluation Board, 15 V Output Voltage Configuration
Evaluation Board, 5 V Output Voltage Configuration
Z = RoHS Compliant Part.
©2012 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D10293-0-6/12(0)
Rev. 0 | Page 16 of 16
Package
Option
CP-10-9
CP-10-9
Branding
LM4
LM5