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PDF ADP2108 Data sheet ( Hoja de datos )
| Número de pieza | ADP2108 | |
| Descripción | Step-Down DC-to-DC Converter | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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Data Sheet
FEATURES
Peak efficiency: 95%
3 MHz fixed frequency operation
Typical quiescent current: 18 μA
Maximum load current: 600 mA
Input voltage: 2.3 V to 5.5 V
Uses tiny multilayer inductors and capacitors
Current mode architecture for fast load and line
transient response
100% duty cycle low dropout mode
Internal synchronous rectifier
Internal compensation
Internal soft start
Current overload protection
Thermal shutdown protection
Shutdown supply current: 0.2 μA
Available in
5-ball WLCSP
5-lead TSOT
Supported by ADIsimPower™ design tool
APPLICATIONS
PDAs and palmtop computers
Wireless handsets
Digital audio, portable media players
Digital cameras, GPS navigation units
Compact, 600 mA, 3 MHz,
Step-Down DC-to-DC Converter
ADP2108
GENERAL DESCRIPTION
The ADP2108 is a high efficiency, low quiescent current step-
down dc-to-dc converter manufactured in two different
packages. The total solution requires only three tiny external
components. It uses a proprietary, high speed current mode,
constant frequency PWM control scheme for excellent stability
and transient response. To ensure the longest battery life in
portable applications, the ADP2108 has a power save mode that
reduces the switching frequency under light load conditions.
The ADP2108 runs on input voltages of 2.3 V to 5.5 V, which
allows for single lithium or lithium polymer cell, multiple alkaline
or NiMH cell, PCMCIA, USB, and other standard power sources.
The maximum load current of 600 mA is achievable across the
input voltage range.
The ADP2108 is available in fixed output voltages of 3.3 V, 3.0 V,
2.5 V, 2.3 V, 1.82 V, 1.8 V, 1.5 V, 1.3 V, 1.2 V, 1.1 V, and 1.0 V. All
versions include an internal power switch and synchronous rect-
ifier for minimal external part count and high efficiency. The
ADP2108 has an internal soft start and is internally compensated.
During logic controlled shutdown, the input is disconnected
from the output and the ADP2108 draws less than 1 μA from
the input source.
Other key features include undervoltage lockout to prevent deep
battery discharge and soft start to prevent input current over-
shoot at startup. The ADP2108 is available in 5-ball WLCSP and
5-lead TSOT packages. The ADP2109 provides the same features
and operations as the ADP2108 and has the additional function
of a discharge switch in the WLCSP package.
TYPICAL APPLICATIONS CIRCUIT
2.3V TO 5.5V
4.7µF
ON
OFF
ADP2108
VIN SW
EN FB
GND
1µH 1.0V TO 3.3V
10µF
Figure 1.
Rev. H
Document Feedback
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.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 ©2008–2014 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
1 page  
Data Sheet
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
ADP2108
BALL A1
INDICATOR
12
VIN GND
A
SW
B
EN FB
C
TOP VIEW
(BALL SIDE DOWN)
Not to Scale
Figure 2. WLCSP Pin Configuration
Table 4. WLCSP Pin Function Descriptions
Pin No. Mnemonic Description
A1 VIN
Power Source Input. VIN is the source of the PFET high-side switch. Bypass VIN to GND with a 2.2 μF or greater
capacitor as close to the ADP2108 as possible.
A2 GND
Ground. Connect all the input and output capacitors to GND.
B SW
Switch Node Output. SW is the drain of the PFET switch and NFET synchronous rectifier.
C1 EN
Enable Input. Drive EN high to turn on the ADP2108. Drive EN low to turn it off and reduce the input current to 0.2 μA.
C2 FB
Feedback Input of the Error Amplifier. Connect FB to the output of the switching regulator.
VIN 1
5 SW
ADP2108
GND 2 TOP VIEW
(Not to Scale)
EN 3
4 FB
Figure 3. TSOT Pin Configuration
Table 5. TSOT Pin Function Descriptions
Pin No. Mnemonic Description
1 VIN
Power Source Input. VIN is the source of the PFET high-side switch. Bypass VIN to GND with a 2.2 μf or greater
capacitor as close to the ADP2108 as possible.
2 GND
Ground. Connect all the input and output capacitors to GND.
3 EN
Enable Input. Drive EN high to turn on the ADP2108. Drive EN low to turn it off and reduce the input current to 0.1 μA.
4 FB
Feedback Input of the Error Amplifier. Connect FB to the output of the switching regulator.
5 SW
Switch Node Output. SW is the drain of the PFET switch and NFET synchronous rectifier.
Rev. H | Page 5 of 20
5 Page 
Data Sheet
ADP2108
THEORY OF OPERATION
FB
GM ERROR
AMP
PWM
COMP
SOFT START
ILIMIT
PSM
COMP
PWM/
PSM
LOW
CONTROL CURRENT
VIN
SW
OSCILLATOR
UNDERVOLTAGE
LOCKOUT
DRIVER
AND
ANTISHOOT-
THROUGH
ADP2108
THERMAL
SHUTDOWN
GND
EN
Figure 29. Functional Block Diagram
The ADP2108 is a step-down dc-to-dc converter that uses a
fixed frequency and high speed current mode architecture. The
high switching frequency allows for a small step-down, dc-to-dc
converter solution.
The ADP2108 operates with an input voltage of 2.3 V to 5.5 V
and regulates an output voltage down to 1.0 V.
CONTROL SCHEME
The ADP2108 operates with a fixed frequency, current mode
PWM control architecture at medium to high loads for high
efficiency, but shifts to a power save mode control scheme at
light loads to lower the regulation power losses. When operating
in fixed frequency PWM mode, the duty cycle of the integrated
switches is adjusted and regulates the output voltage. When
operating in power save mode at light loads, the output voltage
is controlled in a hysteretic manner, with higher VOUT ripple.
During part of this time, the converter is able to stop switching
and enters an idle mode, which improves conversion efficiency.
PWM MODE
In PWM mode, the ADP2108 operates at a fixed frequency of
3 MHz, set by an internal oscillator. At the start of each oscillator
cycle, the PFET switch is turned on, sending a positive voltage
across the inductor. Current in the inductor increases until the
current sense signal crosses the peak inductor current threshold
that turns off the PFET switch and turns on the NFET synchronous
rectifier. This sends a negative voltage across the inductor, causing
the inductor current to decrease. The synchronous rectifier stays
on for the rest of the cycle. The ADP2108 regulates the output
voltage by adjusting the peak inductor current threshold.
POWER SAVE MODE
The ADP2108 smoothly transitions to the power save mode of
operation when the load current decreases below the power
save mode current threshold. When the ADP2108 enters power
save mode, an offset is induced in the PWM regulation level,
which makes the output voltage rise. When the output voltage
reaches a level approximately 1.5% above the PWM regulation
level, PWM operation is turned off. At this point, both power
switches are off, and the ADP2108 enters an idle mode. COUT
discharges until VOUT falls to the PWM regulation voltage, at
which point the device drives the inductor to make VOUT rise
again to the upper threshold. This process is repeated while the
load current is below the power save mode current threshold.
Power Save Mode Current Threshold
The power save mode current threshold is set to 80 mA. The
ADP2108 employs a scheme that enables this current to remain
accurately controlled, independent of VIN and VOUT levels. This
scheme also ensures that there is very little hysteresis between
the power save mode current threshold for entry to and exit from
the power save mode. The power save mode current threshold
is optimized for excellent efficiency over all load currents.
ENABLE/SHUTDOWN
The ADP2108 starts operation with soft start when the EN pin
is toggled from logic low to logic high. Pulling the EN pin low
forces the device into shutdown mode, reducing the shutdown
current below 1 μA.
Rev. H | Page 11 of 20
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet ADP2108.PDF ] | |
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