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ADP123 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer ADP123
Beschreibung (ADP122 / ADP123) CMOS Linear Regulator
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 20 Seiten
ADP123 Datasheet, Funktion
5.5 V Input, 300 mA, Low Quiescent
Current, CMOS Linear Regulator
ADP122/ADP123
FEATURES
Input voltage supply range: 2.3 V to 5.5 V
300 mA maximum output current
Fixed and adjustable output voltage versions
Very low dropout voltage: 85 mV at 300 mA load
Low quiescent current: 45 μA at no load
Low shutdown current: <1 μA
Initial accuracy: ±1% accuracy
Up to 31 fixed-output voltage options available from
1.75 V to 3.3 V
Adjustable-output voltage range
0.8 V to 5.0 V (ADP123)
Excellent PSRR performance: 60 dB at 100 kHz
Excellent load/line transient response
Optimized for small 1.0 μF ceramic capacitors
Current limit and thermal overload protection
Logic controlled enable
Compact, 5-lead TSOT package
APPLICATIONS
Digital camera and audio devices
Portable and battery-powered equipment
Automatic meter reading (AMR) meters
GPS and location management units
Medical instrumentation
Point-of-sale equipment
GENERAL DESCRIPTION
www.DaTthaeShAeDetP41U2.c2o/AmDP123 are low quiescent current, low dropout
linear regulators. They are designed to operate from an input
voltage between 2.3 V and 5.5 V and to provide up to 300 mA of
output current. The low 85 mV dropout voltage at a 300 mA load
improves efficiency and allows operation over a wide input
voltage range.
The low 170 μA of quiescent current at full load makes the ADP122
ideal for battery-operated portable equipment.
The ADP122 is capable of 31 fixed output voltages from 1.75 V
to 3.3 V. The ADP123 is the adjustable version of the device and
allows the output voltage to be set between 0.8 V and 5.0 V by
an external voltage divider.
TYPICAL APPLICATION CIRCUIT
VIN = 2.3V TO 5.5V
CIN
1µF
1 VIN VOUT 5
ADP122
2 GND
VOUT = 1.8V
COUT
1µF
ON
OFF
3 EN
NC 4
Figure 1. ADP122 with Fixed Output Voltage
VIN = 2.3V TO 5.5V
CIN
1µF
1 VIN VOUT 5
ADP123
2 GND
VOUT = 0.5V(1 + R1/R2)
COUT
1µF
R1
ON
OFF
3 EN
ADJ 4
R2
Figure 2. ADP 123 with Adjustable Output Voltage
The ADP122/ADP123 are specifically designed for stable operation
with tiny 1 μF ceramic input and output capacitors to meet the
requirements of high performance, space constrained applications.
The ADP122/ADP123 have an internal soft start that gives a
constant start-up time of 350 μs. Short-circuit protection and
thermal overload protection circuits prevent damage in adverse
conditions. The ADP122/ADP123 are available in a tiny, 5-lead
TSOT package for the smallest footprint solution to meet a
variety of portable applications.
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.
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 Analog Devices, Inc. All rights reserved.






ADP123 Datasheet, Funktion
ADP122/ADP123
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
VIN 1
5 VOUT
ADP122
GND 2 TOP VIEW
(Not to Scale)
EN 3
4 NC
NC = NO CONNECT
Figure 3. ADP122 Fixed Output Pin Configuration
VIN 1
5 VOUT
ADP123
GND 2 TOP VIEW
(Not to Scale)
EN 3
4 ADJ
Figure 4. ADP123 Adjustable Output Pin Configuration
Table 5. Pin Function Descriptions
Pin No.
ADP122 ADP123 Mnemonic Description
1 1 VIN
Regulator Input Supply. Bypass VIN to GND with a capacitor of at least 1 μF.
2
2
GND
Ground.
3 3 EN
Enable Input. Drive EN high to turn on the regulator; drive EN low to turn off the regulator. For
automatic startup, connect EN to VIN.
N/A 4 ADJ Output Voltage Adjust Input. Connect the midpoint of an external divider from VOUT to GND to this
pin to set the output voltage.
4 N/A NC
Not Connected Internally.
5
5
VOUT
Regulated Output Voltage. Bypass VOUT to GND with a capacitor of at least 1 μF.
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Rev. 0 | Page 6 of 20

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ADP123 pdf, datenblatt
ADP122/ADP123
APPLICATIONS INFORMATION
CAPACITOR SELECTION
Output Capacitor
The ADP122/ADP123 are designed for operation with small,
space-saving ceramic capacitors, but these devices can function
with most commonly used capacitors as long as care is taken to
ensure an appropriate effective series resistance (ESR) value. The
ESR of the output capacitor affects the stability of the LDO control
loop. A minimum of 0.70 μF capacitance with an ESR of 1 Ω or
less is recommended to ensure stability of the ADP122/ADP123.
The transient response to changes in load current is also affected by
the output capacitance. Using a larger value of output capacitance
improves the transient response of the ADP122/ADP123 to
dynamic changes in load current. Figure 28 and Figure 29 show
the transient responses for output capacitance values of 1 μF and
4.7 μF, respectively.
IOUT
1mA TO 300mA LOAD STEP
1
Input and Output Capacitor Properties
Any good quality ceramic capacitors can be used with the ADP122/
ADP123, as long as the capacitor meets the minimum capacitance
and maximum ESR requirements. Ceramic capacitors are manu-
factured with a variety of dielectrics, each with different behavior
over temperature and applied voltage. Capacitors must have an
adequate dielectric to ensure the minimum capacitance over the
necessary temperature range and dc bias conditions. Using an
X5R or X7R dielectric with a voltage rating of 6.3 V or 10 V is
recommended. However, using Y5V and Z5U dielectrics is not
recommended for any LDO, due to their poor temperature and
dc bias characteristics.
Figure 30 depicts the capacitance vs. capacitor voltage bias charac-
teristics of a 0603, 1 μF, 6.3 V X5R capacitor. The voltage stability of
a capacitor is strongly influenced by the capacitor size and the
voltage rating. In general, a capacitor in a larger package or of a
higher voltage rating exhibits better stability. The temperature
variation of the X5R dielectric is about ±15% over the −40°C to
+85°C temperature range and is not a function of package or
voltage rating.
1.10
2
VOUT
1.05
1.00
VIN = 3.7V
VOUT = 3.3V
CH1
200mA
B
W
CH2
50.0mV
B
W
M 400ns
A
CH1
T 14.80%
196mA
Figure 28. Output Transient Response, COUT = 1 μF
0.95
0.90
0.85
0.80
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IOUT
1mA TO 300mA LOAD STEP
1
2
VOUT
VIN = 3.7V
VOUT = 3.3V
CH1
200mA
B
W
CH2 20.0mV
M 400ns
A CH1
196mA
T 15.00%
Figure 29. Output Transient Response, COUT = 4.7 μF
Input Bypass Capacitor
Connecting a 1 μF capacitor from VIN to GND reduces the circuit
sensitivity to the printed circuit board (PCB) layout, especially
when a long input trace or high source impedance is encountered.
If greater than 1 μF of output capacitance is required, the input
capacitor should be increased to match it.
0.75
0.70
01234567
BIAS VOLTAGE (V)
Figure 30. Capacitance vs. Capacitor Voltage Bias Characteristics
Equation 1 can be used to determine the worst-case capacitance,
accounting for capacitor variation over temperature, component
tolerance, and voltage.
CEFF = C × (1 − TEMPCO) × (1 − TOL)
(1)
where:
CEFF is the effective capacitance at the operating voltage.
TEMPCO is the worst-case capacitor temperature coefficient.
TOL is the worst-case component tolerance.
In this example, the worst-case temperature coefficient (TEMPCO)
over −40°C to +85°C is assumed to be 15% for an X5R dielectric.
The tolerance of the capacitor (TOL) is assumed to be 10%, and
C is 0.96 μF at 4.2 V from the graph in Figure 30.
Substituting these values in Equation 1 yields
CEFF = 0.96 μF × (1 − 0.15) × (1 − 0.1) = 0.734 μF
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