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PDF ADP1611 Data sheet ( Hoja de datos )
| Número de pieza | ADP1611 | |
| Descripción | 1.2 MHz Step-Up DC-to-DC Switching Converter | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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FEATURES
Fully integrated 1.2 A , 0.23 Ω power switch
Pin-selectable 700 kHz or 1.2 MHz PWM frequency
90% efficiency
Adjustable output voltage up to 20 V
3% output regulation accuracy
Adjustable soft start
Input undervoltage lockout
MSOP 8-lead package
APPLICATIONS
TFT LC bias supplies
Portable applications
Industrial/instrumentation equipment
20 V,1.2 MHz Step-Up
DC-to-DC Switching Converter
ADP1611
GENERAL DESCRIPTION
The ADP1611 is a step-up dc-to-dc switching converter with an
integrated 1.2 A, 0.23 Ω power switch capable of providing an
output voltage as high as 20 V. With a package height of less
than 1.1 mm, the ADP1611 is optimal for space-constrained
applications such as portable devices or thin film transistor
(TFT) liquid crystal displays (LCDs).
The ADP1611 operates in pulse-width modulation (PWM)
current mode with up to 90% efficiency. Adjustable soft start
prevents inrush currents at startup. The pin-selectable switching
frequency and PWM current-mode architecture allow excellent
transient response, easy noise filtering, and the use of small,
cost-saving external inductors and capacitors.
The ADP1611 is offered in the Pb-free 8-lead MSOP and
operates over the temperature range of −40°C to +85°C.
FB 2
RT 7
FUNCTIONAL BLOCK DIAGRAM
REF
COMP
1
ERROR
AMP
gm
IN
6
BIAS
ADP1611
RAMP
GEN
OSC
F/F
RQ
S
COMPARATOR
DRIVER
5 SW
SS 8
SD 3
SOFT START
CURRENT-
SENSE
AMPLIFIER
4
GND
Figure 1.
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: 781.326.8703 © 2005 Analog Devices, Inc. All rights reserved.
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PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
ADP1611
COMP 1
FB 2
SD 3
GND 4
ADP1611
TOP VIEW
(Not to Scale)
8 SS
7 RT
6 IN
5 SW
Figure 3. Pin Configuration
Table 3. Pin Function Descriptions
Pin No. Mnemonic Description
1
COMP
Compensation Input. Connect a series resistor-capacitor network from COMP to GND to compensate the
regulator.
2 FB
Output Voltage Feedback Input. Connect a resistive voltage divider from the output voltage to FB to set the
regulator output voltage.
3 SD
Shutdown Input. Drive SD low to shut down the regulator; drive SD high to turn it on.
4 GND Ground.
5 SW
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.
6 IN
Main Power Supply Input. IN powers the ADP1611 internal circuitry. Connect IN to the input source voltage.
Bypass IN to GND with a 10 µF or greater capacitor as close to the ADP1611 as possible.
7 RT
Frequency Setting Input. RT controls the switching frequency. Connect RT to GND to program the oscillator to
700 kHz, or connect RT to IN to program it to 1.2 MHz.
8 SS
Soft-Start Timing Capacitor Input. A capacitor from SS to GND brings up the output slowly at power-up.
Rev. 0 | Page 5 of 20
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ADP1611
Table 4. Inductor Manufacturers
Vendor
Part
Sumida
CMD4D11-2R2MC
847-956-0666
CMD4D11-4R7MC
www.sumida.com
CDRH4D28-100
CDRH5D18-220
CR43-4R7
CR43-100
Coilcraft 847-639-6400 DS1608-472
www.coilcraft.com
DS1608-103
Toko 847-297-0070
D52LC-4R7M
www.tokoam.com
D52LC-100M
L (µH)
2.2
4.7
10
22
4.7
10
4.7
10
4.7
10
Using the duty cycle and switching frequency, fSW, determine
the on time by the following equation:
tON = D
f SW
(4)
The inductor ripple current (∆IL) in steady state is
∆ IL = VIN × tON
L
Solving for the inductance value, L,
(5)
L = VIN ×tON
∆IL
(6)
Make sure 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 duty cycles greater than 50%, which occur with input
voltages greater 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 LMIN
L > LMIN
=
VOUT −VIN
1.8 A × f SW
(7)
CHOOSING THE INPUT AND OUTPUT CAPACITORS
The ADP1611 requires input and output bypass capacitors to
supply transient currents while maintaining constant input and
output voltage. Use a low equivalent series resistance (ESR)
input capacitor, 10 µF or greater, to prevent noise at the
ADP1611 input. Place the capacitor between IN and GND as
close to the ADP1611 as possible. Ceramic capacitors are
preferred because of their low ESR characteristics. Alternatively,
use a high value, medium ESR capacitor in parallel with a 0.1 µF
low ESR capacitor as close to the ADP1611 as possible.
Max DC Current
0.95
0.75
1.00
0.80
1.15
1.04
1.40
1.00
1.14
0.76
Max DCR (mΩ)
116
216
128
290
109
182
60
75
87
150
Height (mm)
1.2
1.2
3.0
2.0
3.5
3.5
2.9
2.9
2.0
2.0
The output capacitor maintains the output voltage and supplies
current to the load while the ADP1611 switch is on. The value
and characteristics of the output capacitor greatly affect the
output voltage ripple and stability of the regulator. Use a low
ESR output capacitor; ceramic dielectric capacitors are
preferred.
For very low ESR capacitors, such as ceramic capacitors, the
ripple current due to the capacitance is calculated as follows.
Because the capacitor discharges during the on time, tON, the
charge removed from the capacitor, QC, is the load current
multiplied by the on time. Therefore, the output voltage ripple
(∆VOUT) is
∆VOUT
= QC
COUT
=
I L × tON
COUT
(8)
where:
COUT is the output capacitance.
IL is the average inductor current.
tON
=
D
f SW
and D = VOUT −VIN
VOUT
Choose the output capacitor based on the following equation:
COUT
≥
I L × (VOUT − VIN )
f SW ×VOUT × ∆VOUT
(9)
Table 5. Capacitor Manufacturers
Vendor
Phone No.
AVX 408-573-4150
Murata
714-852-2001
Sanyo
408-749-9714
Taiyo–Yuden 408-573-4150
Web Address
www.avxcorp.com
www.murata.com
www.sanyovideo.com
www.t-yuden.com
Rev. 0 | Page 11 of 20
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| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet ADP1611.PDF ] | |
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