AD ADP3303AR-2.7 High accuracy anycap 200 ma low dropout linear regulator Datasheet

a
High Accuracy anyCAP™
200 mA Low Dropout Linear Regulator
ADP3303
FEATURES
High Accuracy Over Line and Load ⴞ0.8% @ at +25ⴗC,
ⴞ1.4% Over Temperature
Ultralow Dropout Voltage: 180 mV (Typ) @ 200 mA
Requires Only CO = 0.47 ␮F for Stability
anyCAP = Stable with All Types of Capacitors
(Including MLCC)
3.2 V to 12 V Supply Range
Current and Thermal Limiting
Low Noise
Dropout Detector
Low Shutdown Current: < 1 ␮A
Thermally Enhanced SO-8 Package
Excellent Line and Load Regulation Performance
APPLICATIONS
Cellular Telephones
Notebook, Palmtop Computers
Battery Powered Systems
Portable Instruments
Post Regulator for Switching Supplies
Bar Code Scanners
FUNCTIONAL BLOCK DIAGRAM
ADP3303
Q1
IN
THERMAL
PROTECTION
ERR
OUT
R1
CC
DRIVER
Q2
gm
SD
R2
BANDGAP
REF
GND
NR 3
ADP3303-5.0
VIN
7
8
IN
OUT
1
VOUT = +5V
2
330kV
C1
0.47mF
ERR 6
SD
GND
5
4
EOUT
C2
0.47mF
ON
OFF
GENERAL DESCRIPTION
The ADP3303 is a member of the ADP330x family of precision low dropout anyCAP voltage regulators. The ADP3303
stands out from the conventional LDOs with a novel architecture, an enhanced process and a new package. Its patented
design requires only a 0.47 µF output capacitor for stability.
This device is insensitive to capacitor Equivalent Series Resistance (ESR) and is stable with any good quality capacitor, including ceramic types (MLCC) for space restricted applications.
The ADP3303 achieves exceptional accuracy of ± 0.8% at room
temperature and ± 1.4% overall accuracy over temperature, line
and load regulations. The dropout voltage of the ADP3303 is
only 180 mV (typical) at 200 mA.
In addition to the new architecture and process, ADI’s new
proprietary thermally enhanced package (Thermal Coastline)
can handle 1 W of power dissipation without external heatsink
or large copper surface on the PC board. This keeps PC board
real estate to a minimum and makes the ADP3303 very attractive for use in portable equipment.
SD
Figure 1. Typical Application Circuit
It features an error flag that signals when the device is about to
lose regulation or when the short circuit or thermal overload
protection is activated. Other features include shutdown and
optional noise reduction capabilities. The ADP330x anyCAP
LDO family offers a wide range of output voltages and output
current levels:
ADP3300 (50 mA, SOT-23)
ADP3301 (100 mA)
ADP3302 (100 mA, Dual Output)
ADP3307 (100 mA, SOT-23-6)
ADP3308 (50 mA, SOT-23-5)
ADP3309 (100 mA, SOT-23-5)
The ADP3303 operates with a wide input voltage range from
3.2 V to 12 V and delivers a load current in excess of 200 mA.
anyCAP is a trademark of Analog Devices Inc.
REV. A
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 1998
T = –20ⴗC to +85ⴗC, V = 7 V, C = 0.47 ␮F, C
ADP3303-xx–SPECIFICATIONS (@otherwise
noted)
A
IN
OUT = 0.47 ␮F, unless
IN
1
Parameter
Symbol
Conditions
Min
OUTPUT VOLTAGE
ACCURACY
VOUT
VIN = VOUTNOM +0.5 V to 12 V
IL = 0.1 mA to 200 mA
TA = +25°C
VIN = VOUTNOM +0.5 V to 12 V
IL = 0.1 mA to 200 mA
Typ
Max
Units
–0.8
+0.8
%
–1.4
+1.4
%
∆VO
∆VIN
VIN = VOUTNOM +0.5 V to 12 V
TA = +25°C
0.01
mV/V
∆VO
∆IL
IL = 0.1 mA to 200 mA
TA = +25°C
0.013
mV/mA
GROUND CURRENT
IGND
IL = 200 mA
IL = 0.1 mA
1.5
0.25
4
0.4
mA
mA
GROUND CURRENT
IN DROPOUT
IGND
VIN = 2.5 V
IL = 0.1 mA
1.12
2.5
mA
DROPOUT VOLTAGE
VDROP
VOUT = 98% of VOUTNOM
IL = 200 mA
IL = 10 mA
IL = 1 mA
0.18
0.02
0.003
0.4
0.07
0.03
V
V
V
0.3
V
V
1
22
µA
µA
1
µA
5
µA
LINE REGULATION
LOAD REGULATION
SHUTDOWN THRESHOLD
VTHSD
ON
OFF
2.0
SHUTDOWN PIN
INPUT CURRENT
ISDIN
0 < VSD < 5 V
5 ≤ VSD ≤ 12 V @ VIN = 12 V
GROUND CURRENT IN
SHUTDOWN MODE
IQ
VSD = 0, VIN = 12 V
TA = +25°C
VSD = 0, VIN = 12 V
TA = +85°C
IOSD
TA = +25°C @ VIN = 12 V
TA = +85°C @ VIN = 12 V
2.5
4
µA
µA
ERROR PIN OUTPUT
LEAKAGE
IEL
VEO = 5 V
13
µA
ERROR PIN OUTPUT
“LOW” VOLTAGE
VEOL
ISINK = 400 µA
0.15
0.3
V
PEAK LOAD CURRENT
ILDPK
VIN = VOUTNOM + 1 V
300
mA
OUTPUT NOISE
@ 5 V OUTPUT
VNOISE
f = 10 Hz–100 kHz
CNR = 0
CNR = 10 nF, CL = 10 µF
100
30
µV rms
µV rms
OUTPUT CURRENT IN
SHUTDOWN MODE
NOTES
1
Ambient temperature of +85°C corresponds to a typical junction temperature of +125°C under typical full load test conditions.
Specifications subject to change without notice.
–2–
REV. A
ADP3303
ABSOLUTE MAXIMUM RATINGS*
PIN FUNCTION DESCRIPTIONS
Input Supply Voltage . . . . . . . . . . . . . . . . . . . –0.3 V to +16 V
Shutdown Input Voltage . . . . . . . . . . . . . . . . –0.3 V to +16 V
Error Flag Output Voltage . . . . . . . . . . . . . . . –0.3 V to +16 V
Noise Bypass Pin Voltage . . . . . . . . . . . . . . . . –0.3 V to +5 V
Power Dissipation . . . . . . . . . . . . . . . . . . . Internally Limited
Operating Ambient Temperature Range . . . . –20°C to +85°C
Operating Junction Temperature Range . . . –20°C to +125°C
θJA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96°C/W
θJC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55°C/W
Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C
Lead Temperature Range (Soldering 10 sec) . . . . . . . +300°C
Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . +215°C
Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . +220°C
Pin
Mnemonic
Function
1&2
OUT
Output of the Regulator. Bypass to
ground with a 0.47 µF or larger
capacitor. Pins 1 and 2 must be connected together for proper operation.
3
NR
Noise Reduction Pin. Used for reduction of the output noise. (See text for
details.) No connection if not used.
4
GND
Ground Pin.
5
SD
Active Low Shutdown Pin. Connect to
ground to disable the regulator output.
When shutdown is not used, this pin
should be connected to the input pin.
6
ERR
Open Collector Output. Goes low to
indicate that the output is about to go
out of regulation.
7&8
IN
Regulator Input. Pins 7 and 8 must
be connected together for proper
operation.
*This is a stress rating only; operation beyond these limits can cause the device to
be permanently damaged.
ORDERING GUIDE
Model
Output
Voltage
Package
Option*
ADP3303AR-2.7
ADP3303AR-3
ADP3303AR-3.2
ADP3303AR-3.3
ADP3303AR-5
2.7 V
3.0 V
3.2 V
3.3 V
5.0 V
SO-8
SO-8
SO-8
SO-8
SO-8
PIN CONFIGURATION
Contact the factory for the availability of other output voltage options.
*SO = Small Outline.
OUT 2
Other Members of anyCAP Family 1
Model
Output
Current
Package
Options2
Comments
ADP3300
ADP3301
ADP3302
ADP3307
ADP3308
ADP3309
50 mA
100 mA
100 mA
100 mA
50 mA
100 mA
SOT-23-6
SO-8
SO-8
SOT-23-6
SOT-23-5
SOT-23-5
High Accuracy
High Accuracy
Dual Output
Small Size
Improved LP2980
Improved MIC5205
8 IN
OUT 1
ADP3303
7 IN
TOP VIEW
6 ERR
(Not to Scale)
5 SD
GND 4
NR 3
NOTES
1
See individual data sheets for detailed ordering information.
2
SO = Small Outline, SOT = Surface Mount.
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection.
Although the ADP3303 features proprietary ESD protection circuitry, permanent damage may
occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD
precautions are recommended to avoid performance degradation or loss of functionality.
REV. A
–3–
WARNING!
ESD SENSITIVE DEVICE
ADP3303 –Typical Performance Characteristics
IL = 0mA
3.3005
VIN = 7V
VOUT = 3.2V
3.2995
IL = 100mA
3.2990
3.2985
IL = 200mA
3.2980
3.2000
3.1995
3.1990
3.1985
3.1980
3.2975
3.2970
3.3 4
3.1975
5
6 7 8 9 10 11 12 13 14 15 16
INPUT VOLTAGE – Volts
Figure 2. Line Regulation: Output
Voltage vs. Supply Voltage
VOUT = 3.3V
IL = 0mA
1.0
GROUND CURRENT – mA
VOUT = 3.3V
OUTPUT VOLTAGE – Volts
3.3000
OUTPUT VOLTAGE – Volts
3.2005
IL = 10mA
0
20 40
0.2
1400
0.1
0.6
0.4
0.2
0
0
60 80 100 120 140 160 180 200
OUTPUT LOAD – mA
Figure 3. Output Voltage vs. Load
Current
1600
0.8
2
4
6
8
10
12
INPUT VOLTAGE – Volts
14
16
Figure 4. Quiescent Current vs.
Supply Voltage
2500
1000
800
IL = 0 TO 200mA
600
0.0
IL = 0mA
–0.1
–0.2
–0.3
400
200
0
20 40 60 80 100 120 140 160 180 200
OUTPUT LOAD – mA
Figure 5. Quiescent Current vs. Load
Current
2000
IL = 200mA
1500
1000
500
IL = 0mA
–0.4
–45 –25 –5
15
35
55
75
0
–25
95 115 135
–5
TEMPERATURE – ⴗC
Figure 6. Output Voltage Variation
% vs. Temperature
15
35
55
75
95
TEMPERATURE – ⴗC
8.0
VIN
VOUT = 3.3V
140
120
100
80
60
40
20
7.0
4
3
2
RL = 16.5⍀
1
0
0
0
20 40
60 80 100 120 140 160 180 200
OUTPUT LOAD – mA
Figure 8. Dropout Voltage vs. Output
Current
INPUT-OUTPUT VOLTAGE – Volts
INPUT-OUTPUT VOLTAGE – Volts
160
115 135
Figure 7. Quiescent Current vs.
Temperature
5
180
INPUT-OUTPUT VOLTAGE – mV
GROUND CURRENT – ␮A
1200
OUTPUT VOLTAGE – %
GROUND CURRENT – mA
VIN = 7V
0
1
2
4
3
2
3
INPUT VOLTAGE – Volts
1
Figure 9. Power-Up/Power-Down
–4–
0
6.0
5.0
4.0
VOUT
3.0
VSD = VIN OR 3V
2.0
CL = 0.47mF
RL = 16.5V
VOUT = 3.3V
1.0
0
0
20
40 60
80 100 120 140 160 180 200
TIME – ms
Figure 10. Power-Up Transient
REV. A
ADP3303
5.02
3.310
5.02
VOUT = 5V
5.01
5.00
5.00
3.305
Volts
5.01
4.99
4.99
25⍀, 0.47␮F LOAD
Volts
4.98
3.295
3.290
VIN
7.5
7.0
20 40
60 80 100 120 140 160 180 200
TIME – ␮s
Figure 11. Line Transient Response
I(VOUT)
200
10
7.0
0
CL = 0.47␮F
4.98
VIN
7.5
5k⍀, 0.47␮F LOAD
VOUT
3.300
mA
Volts
VOUT = 3.3V
VOUT = 5V
0
40
0
80 120 160 200 240 280 320 360 400
TIME – ␮s
Figure 12. Line Transient Response
200
400
600
TIME – ␮s
800
1000
Figure 13. Load Transient for 10 mA
to 200 mA Pulse
3.310
VOUT = 3.3V
3.3V
3.5
Volts
VOUT
0
3
400
2
3.3V
VOUT
CL = 10␮F
300
IOUT
mA
3.290
I(VOUT)
mA
200
Volts
CL = 10␮F, RL = 16.5⍀
3.295
10
200
400
600
TIME – ␮s
800
0
100
5
3
0
1000
Figure 14. Load Transient for
10 mA to 200 mA Pulse
RIPPLE REJECTION – dB
2
VOUT
1
0
5
REV. A
5
–20
–30
a. 0.47␮F, RL = 33k⍀
b. 0.47␮F, RL = 16.5⍀
c. 10␮F, RL = 33k⍀
d. 10␮F, RL = 16.5⍀
VOUT = 3.3V
b
–40
d
–50
–60
–70
a
b d
c
–80
–90
VSD
Figure 17. Turn Off
4
0
–10
3
10
15
TIME – ␮s
2
3
TIME – sec
20
SD
0
40
Figure 15. Short Circuit Current
C = 0.47␮F
R = 16.5⍀ ON 3.3V OUTPUT
5
1
0
4
0
CL = 10␮F, RL = 3.3k⍀
1
200
0
0
Volts
CL = 0.47␮F, RL = 3.3k⍀
4
25
–100
10
a c
100
1k
10k 100k
FREQUENCY – Hz
1M
10M
Figure 18. Power Supply Ripple
Rejection
–5–
80
120
TIME – ␮s
160
200
Figure 16. Turn On
VOLTAGE NOISE SPECTRAL DENSITY – ␮V/ Hz
Volts
VOUT
3.300
0
VIN = 7V
VIN = 7V
3.305
10
0.47␮F BYPASS
PIN 7, 8 TO PIN 3
VOUT = 5V, CL = 0.47␮F,
IL = 1mA, CNR = 0
1
VOUT = 3.3V, CL = 0.47␮F,
IL = 1mA, CNR = 0
0.1
0.01
100
VOUT = 2.7-5.0V, CL = 10␮F,
IL = 1mA, CNR = 10nF
1k
10k
FREQUENCY – Hz
100k
Figure 19. Output Noise Density
ADP3303
This is no longer true with the ADP3303 anyCAP LDO. It can
be used with virtually any capacitor, with no constraint on the
minimum ESR. The innovative design allows the circuit to be
stable with just a small 0.47 µF capacitor on the output. Additional advantages of the pole splitting scheme include superior line
noise rejection and very high regulator gain, which leads to excellent line and load regulation. An impressive ±1.4% accuracy is
guaranteed over line, load and temperature.
THEORY OF OPERATION
The new anyCAP LDO ADP3303 uses a single control loop for
regulation and reference functions. The output voltage is sensed
by a resistive voltage divider consisting of R1 and R2, which is
varied to provide the available output voltage options. Feedback
is taken from this network by way of a series diode (D1) and a
second resistor divider (R3 and R4) to the input of an amplifier.
Additional features of the circuit include current limit, thermal
shutdown and noise reduction. Compared to standard solutions
that give warning after the output has lost regulation, the
ADP3303 provides improved system performance by enabling the
ERR Pin to give warning before the device loses regulation.
OUT
IN
Q1
NONINVERTING
WIDEBAND
DRIVER
COMPENSATION
R1
CAPACITOR
ATTENUATION
(VBANDGAP/VOUT)
gm
PTAT
VOS
R4
R3
D1
(a)
PTAT
CURRENT
R2
As the chip’s temperature rises above 165°C, the circuit activates a soft thermal shutdown, indicated by a signal low on the
ERR Pin, to reduce the current to a safe level.
RLOAD
CLOAD
ADP3303
To reduce the noise gain of the loop, the node of the main divider network (a) is made available at the noise reduction (NR)
pin, which can be bypassed with a small capacitor (10 nF–100 nF).
GND
Figure 20. Functional Block Diagram
APPLICATION INFORMATION
Capacitor Selection
A very high gain error amplifier is used to control this loop. The
amplifier is constructed in such a way that at equilibrium it
produces a large, temperature proportional input “offset voltage”
that is repeatable and very well controlled. The temperatureproportional offset voltage is combined with the complementary
diode voltage to form a “virtual bandgap” voltage, implicit in
the network, although it never appears explicitly in the circuit.
Ultimately, this patented design makes it possible to control the
loop with only one amplifier. This technique also improves the
noise characteristics of the amplifier by providing more flexibility on the tradeoff of noise sources that leads to a low noise
design.
Output Capacitors: as with any micropower device, output
transient response is a function of the output capacitance. The
ADP3303 is stable with a wide range of capacitor values, types
and ESR. A capacitor as low as 0.47 µF is all that is needed for
stability; larger capacitors can be used if high output current
surges are anticipated. The ADP3303 is stable with extremely
low ESR capacitors (ESR ≈ 0), such as Multilayer Ceramic
Capacitors (MLCC) or OSCON.
Input Bypass Capacitor: an input bypass capacitor is not
required; for applications where the input source is high impedance or far from the input pins, a bypass capacitor is recommended. Connecting a 0.47 µF capacitor from the input pins to
ground reduces the circuit’s sensitivity to PC board layout. If a
larger value output capacitor is used, then a larger value input
capacitor is also recommended.
The R1, R2 divider is chosen in the same ratio as the bandgap
voltage to the output voltage. Although the R1, R2 resistor
divider is loaded by the diode D1, and a second divider consisting of R3 and R4, the values are chosen to produce a temperature stable output. This unique arrangement specifically corrects
for the loading of the divider so that the error resulting from
base current loading in conventional circuits is avoided.
Noise Reduction
A noise reduction capacitor (CNR) can be used to further reduce
the noise by 6 dB–10 dB (Figure 21). Low leakage capacitors in
the 10 nF–100 nF range provide the best performance. Since
the noise reduction pin (NR) is internally connected to a high
impedance node, any connection to this node should be carefully
done to avoid noise pickup from external sources. The pad
connected to this pin should be as small as possible. Long PC
board traces are not recommended.
The patented amplifier controls a new and unique noninverting
driver that drives the pass transistor, Q1. The use of this special
noninverting driver enables the frequency compensation to
include the load capacitor in a pole splitting arrangement to
achieve reduced sensitivity to the value, type and ESR of the
load capacitance.
Most LDOs place strict requirements on the range of ESR values for the output capacitor because they are difficult to stabilize due to the uncertainty of load capacitance and resistance.
Moreover, the ESR value, required to keep conventional LDOs
stable, changes depending on load and temperature. These ESR
limitations make designing with LDOs more difficult because
of their unclear specifications and extreme variations over
temperature.
NR 3
ADP3303-5.0
7
VIN
C1 +
1mF
1
IN
OUT
8
SD
5
2
ERR 6
GND
CNR
10nF
VOUT = 5V
R1
+
330kV
EOUT
C2
10mF
4
ON
OFF
SD
Figure 21. Noise Reduction Circuit
–6–
REV. A
ADP3303
Thermal Overload Protection
The ADP3303 is protected against damage due to excessive
power dissipation by its thermal overload protection circuit,
which limits the die temperature to a maximum of 165°C.
Under extreme conditions (i.e., high ambient temperature and
power dissipation), where die temperature starts to rise above
165°C, the output current is reduced until the die temperature
has dropped to a safe level. The output current is restored when
the die temperature is reduced.
It is not recommended to use solder mask or silkscreen on the
PCB traces adjacent to the ADP3303’s pins since it will increase
the junction to ambient thermal resistance of the package.
COPPER
LEAD-FRAME
Current and thermal limit protections are intended to protect
the device against accidental overload conditions. For normal
operation, device power dissipation should be externally limited
so that junction temperatures will not exceed 125°C.
1
8
2
7
COPPER PADDLE
3
6
4
5
Calculating Junction Temperature
Device power dissipation is calculated as follows:
PD = (VIN – VOUT) ILOAD + (VIN) IGND
Where ILOAD and IGND are load current and ground current, VIN
and VOUT are input and output voltages, respectively.
Assuming ILOAD = 200 mA, IGND = 2 mA, VIN = 7 V and
VOUT = 5.0 V, device power dissipation is:
PD = (7 V – 5 V ) 200 mA + (7 V ) 2 mA = 414 mW
The proprietary package used in ADP3303 has a thermal
resistance of 96°C/W, significantly lower than a standard 8-lead
SOIC package at 170°C/W.
Junction temperature above ambient temperature will be approximately equal to:
0.414 W × 96°C/W = 39.7°C
To limit the maximum junction temperature to 125°C, maximum ambient temperature must be lower than:
TAMAX = 125°C – 40°C = 85°C
Printed Circuit Board Layout Consideration
All surface mount packages rely on the traces of the PC board to
conduct heat away from the package.
In standard packages, the dominant component of the heat
resistance path is the plastic between the die attach pad and the
individual leads. In typical thermally enhanced packages, one or
more of the leads are fused to the die attach pad, significantly
decreasing this component. To make the improvement meaningful, however, a significant copper area on the PCB must be
attached to these fused pins.
Figure 22. Thermal Coastline
Error Flag Dropout Detector
The ADP3303 will maintain its output voltage over a wide
range of load, input voltage and temperature conditions. If, for
example, the output is about to lose regulation by reducing the
supply voltage below the combined regulated output and dropout voltages, the ERR flag will be activated. The ERR output is
an open collector, which will be driven low.
Once set, the ERR flag’s hysteresis will keep the output low
until a small margin of operating range is restored either by
raising the supply voltage or reducing the load.
Shutdown Mode
Applying a TTL high signal to the shutdown (SD) pin, or tying
it to the input pin, will turn the output ON. Pulling SD down to
0.3 V or below, or tying it to ground, will turn the output OFF.
In shutdown mode, quiescent current is reduced to much less
than 1 µA.
APPLICATION CIRCUITS
Crossover Switch
The circuit in Figure 23 shows that two ADP3303s can be used
to form a mixed supply voltage system. The output switches
between two different levels selected by an external digital input.
Output voltages can be any combination of voltages from the
Ordering Guide.
The patented thermal coastline lead frame design of the
ADP3303 (Figure 22) uniformly minimizes the value of the
dominant portion of the thermal resistance. It ensures that heat
is conducted away by all pins of the package. This yields a very
low, 96°C/W, thermal resistance for an SO-8 package, without
any special board layout requirements, relying on the normal
traces connected to the leads. The thermal resistance can be
decreased by approximately an additional 10% by attaching a
few square cm of copper area to the IN pin of the ADP3303.
REV. A
–7–
ADP3303
MJE253*
VIN = 5.5V TO 12V
OUT
IN
VIN = 6V TO 8V
VOUT = 5V/3.3V
C1
47mF
ADP3303-5.0
OUTPUT SELECT
VOUT = 5V @ 1A
R1
50V
SD
5V
GND
IN
C2
10mF
ADP3303-5
OUT
IN
C1
1.0mF
OUT
C2
0.47mF
ADP3303-3.3
C2984a–1–12/98
0V
ERR
SD
GND
SD
GND
*AAVID531002 HEATSINK IS USED
Figure 24. High Output Current Linear Regulator
Figure 23. Crossover Switch
Higher Output Current
Constant Dropout Post Regulator
The ADP3303 can source up to 200 mA without any heatsink
or pass transistor. If higher current is needed, an appropriate
pass transistor can be used, as in Figure 24, to increase the
output current to 1 A.
The circuit in Figure 25 provides high precision with low dropout for any regulated output voltage. It significantly reduces the
ripple from a switching regulator while providing a constant
dropout voltage, which limits the power dissipation of the LDO
to 60 mW. The ADP3000 used in this circuit is a switching
regulator in the step-up configuration.
L1
6.8mH
ADP3303-3.3
IN
C1
100mF
10V
R1
120V
ILIM
C2
100mF
10V
VIN
3.3V @ 160mA
OUT
GND
C3
2.2mF
SW1
ADP3000-ADJ
GND
R2
30.1kV
1%
SD
Q1
2N3906
FB
SW2
Q2
2N3906
R3
124kV
1%
R4
274kV
Figure 25. Constant Dropout Post Regulator
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8-Lead Small Outline IC
(SO-8)
0.1968 (5.00)
0.1890 (4.80)
0.1574 (4.00)
0.1497 (3.80)
PIN 1
0.0098 (0.25)
0.0040 (0.10)
SEATING
PLANE
8
5
1
4
PRINTED IN U.S.A.
VIN = 2.5V TO 3.5V
D1
1N5817
0.2440 (6.20)
0.2284 (5.80)
0.0688 (1.75)
0.0532 (1.35)
0.0500 0.0192 (0.49)
(1.27) 0.0138 (0.35)
BSC
0.0196 (0.50)
x 45°
0.0099 (0.25)
0.0098 (0.25)
0.0075 (0.19)
–8–
8°
0°
0.0500 (1.27)
0.0160 (0.41)
REV. A