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PDF ADP2109 Data sheet ( Hoja de datos )
| Número de pieza | ADP2109 | |
| Descripción | Step-Down Converter | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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Data Sheet
Compact 600 mA, 3 MHz, Step-Down
Converter with Output Discharge
ADP2109
FEATURES
Peak efficiency: 95%
Discharge switch function
Fixed frequency operation: 3 MHz
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
5-ball WLCSP
Supported by ADIsimPower™ design tool
APPLICATIONS
PDAs and palmtop computers
Wireless handsets
Digital audio, portable media players
Digital cameras, GPS navigation units
GENERAL DESCRIPTION
The ADP2109 is a high efficiency, low quiescent current step-
down dc-to-dc converter with an internal discharge switch that
allows automatic discharge of the output capacitor in an ultra-
small 5-ball WLCSP package.
The total solution requires only three tiny external components.
It uses a proprietary high speed current mode and constant
frequency pulse-width modulation (PWM) control scheme for
excellent stability, and transient response. To ensure the longest
battery life in portable applications, the ADP2109 has a power
save mode that reduces the switching frequency under light
load conditions.
The ADP2109 runs on input voltages of 2.3 V to 5.5 V, which
allow for single lithium or lithium polymer cell, multiple alkaline
or NiMH cells, PCMCIA, USB, and other standard power
sources. The maximum load current of 600 mA is achievable
across the input voltage range.
The ADP2109 is available in fixed output voltages of 1.8 V, 1.5 V,
1.2 V, and 1.0 V. All versions include an internal power switch
and synchronous rectifier for minimal external part count and
high efficiency. The ADP2109 has an internal soft start and internal
compensation. During logic-controlled shutdown, the input is
disconnected from the output and the ADP2109 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 overshoot
at startup. The ADP2109 is available in a 5-ball WLCSP.
A similar converter, the ADP2108, provides the same features
and operations as the ADP2109 without the discharge switch
and is available in both WLCSP and TSOT packages with
additional output voltages.
TYPICAL APPLICATIONS CIRCUIT
2.3V TO 5.5V
4.7µF
VIN
1µH 1.0V TO 1.8V
SW
10µF
ADP2109
ON
OFF
EN FB
GND
Figure 1.
Rev. B
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibilityisassumedbyAnalogDevices for itsuse,nor foranyinfringementsofpatentsor 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
www.analog.com
Fax: 781.461.3113 ©2009–2012 Analog Devices, Inc. All rights reserved.
Free Datasheet http://www.datasheet4u.com/
1 page  
Data Sheet
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
ADP2109
BALL A1
INDICATOR
12
VIN GND
A
SW
B
EN FB
C
TOP VIEW
(BALL SIDE DOWN)
Not to Scale
Figure 2. Pin Configuration
Table 5. 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 ADP2109 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 ADP2109. Drive EN low to turn it off and reduce the input current to 0.1 μA.
C2 FB
Feedback Input of the Error Amplifier. Connect FB to the output of the switching regulator.
Rev. B | Page 5 of 16
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5 Page 
Data Sheet
ENABLE/SHUTDOWN
The ADP2109 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.
DISCHARGE SWITCH
The ADP2109 has an integrated resistor of typically 150 Ω, as
shown in Figure 27, to discharge the output capacitor when the
EN pin goes low or when the device goes into under-voltage
lock out or thermal shutdown. The time to discharge is typically
200 µs.
FB
Figure 27. Internal Discharge Switch on Feedback
SHORT-CIRCUIT PROTECTION
The ADP2109 includes frequency foldback to prevent output
current runaway on a hard short. When the voltage at the feed-
back pin falls below half of the target output voltage, indicating
the possibility of a hard short at the output, the switching fre-
quency is reduced to half of the internal oscillator frequency.
The reduction in the switching frequency allows more time
for the inductor to discharge, preventing a runaway of output
current.
UNDERVOLTAGE LOCKOUT
To protect against battery discharge, undervoltage lockout
circuitry is integrated on the ADP2109. If the input voltage
drops below the 2.15 V undervoltage lockout (UVLO) thre-
shold, the ADP2109 shuts down and both the power switch
and synchronous rectifier turn off. When the voltage rises
above the UVLO threshold, the soft start period is initiated,
and the part is enabled.
THERMAL PROTECTION
In the event the ADP2109 junction temperatures rise above 150°C,
the thermal shutdown circuit turns off the converter. Extreme
junction temperatures can be the result of high current opera-
tion, poor circuit board design, and/or high ambient temperature.
A 20°C hysteresis is included so that when thermal shutdown
occurs, the ADP2109 does not return to operation until the
on-chip temperature drops below 130°C. When coming out
of thermal shutdown, soft start is initiated.
ADP2109
SOFT START
The ADP2109 has an internal soft start function that ramps
the output voltage in a controlled manner upon startup, thereby
limiting the inrush current. This prevents possible input voltage
drops when a battery or a high impedance power source is
connected to the input of the converter.
After the EN pin is driven high, internal circuits start to power
up. The time required to settle after the EN pin is driven high is
called the power-up time. After the internal circuits are powered
up, the soft start ramp is initiated and the output capacitor is
charged linearly until the output voltage is in regulation. The
time required for the output voltage to ramp is called the soft
start time.
Start-up time in the ADP2109 is the measure of when the output
is in regulation after the EN pin is driven high. Start-up time
consists of the power-up time and soft start time.
CURRENT LIMIT
The ADP2109 has protection circuitry to limit the amount of
positive current flowing through the PFET switch and through
the synchronous rectifier. The positive current limit on the
power switch limits the amount of current that can flow from
the input to the output. The negative current limit prevents the
inductor current from reversing direction and flowing out of
the load.
100% DUTY OPERATION
With a drop in VIN, or an increase in ILOAD, the ADP2109
reaches the limit where, even with the PFET switch on 100%
of the time, VOUT drops below the desired output voltage. At
this limit, the ADP2109 smoothly transitions to a mode where
the PFET switch stays on 100% of the time. When the input
conditions change again and the required duty cycle falls,
the ADP2109 immediately restarts PWM regulation without
allowing overshoot on VOUT.
Rev. B | Page 11 of 16
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11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet ADP2109.PDF ] | |
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