ADMOS AMS2954AC-X 250ma low dropout voltage regulator Datasheet

Advanced
Monolithic
Systems
AMS2954
250mA LOW DROPOUT VOLTAGE REGULATOR
RoHS compliant
FEATURES
APPLICATIONS
• 2.5V, 3.0V, 3.3V and 5.0V Versions
• High Accuracy Output Voltage
• Extremely Low Quiescent Current
• Low Dropout Voltage
• Extremely Tight Load and Line Regulation
• Very Low Temperature Coefficient
• Current and Thermal Limiting
• Needs Minimum Capacitance (1µF) for Stability
• Unregulated DC Positive Transients 60V
• Battery Powered Systems
• Portable Consumer Equipment
• Cordless Telephones
• Portable (Notebook) Computers
• Portable Instrumentation
• Radio Control Systems
• Automotive Electronics
• Avionics
• Low-Power Voltage Reference
ADDITIONAL FEATURES (ADJ ONLY)
• 1.24V to 29V Programmable Output
• Error Flag Warning of Voltage Output Dropout
• Logic Controlled Electronic Shutdown
GENERAL DESCRIPTION
The AMS2954 series are micropower voltage regulators ideally suited for use in battery-powered systems. These devices
feature very low quiescent current (typ.75µA), and very low dropout voltage (typ.50mV at light loads and 380mV at 250mA)
thus prolonging battery life. The quiescent current increases only slightly in dropout. The AMS2954 has positive transient
protection up to 60V and can survive unregulated input transient up to 20V below ground. The AMS2954 was designed to
include a tight initial tolerance (typ. 0.5%), excellent load and line regulation (typ. 0.05%), and a very low output voltage
temperature coefficient, making these devices useful as a low-power voltage reference.
The AMS2954 is available in the 3L TO-220 package, 3L TO-263, SOT-223, TO-252 and in 8-pin plastic SOIC and DIP
packages. In the 8L SOIC and PDIP packages the following additional features are offered: an error flag output warns of a low
output voltage, often due to failing batteries on input; the logic-compatible shutdown input enables the regulator to be switched
on and off; the device may be pin-strapped for a, 2.5, 3.0V, 3.3V or 5V output, or programmed from 1.24V to 29V with an
external pair of resistors.
ORDERING INFORMATION
PACKAGE TYPE
OPERATING
8
LEAD
SOIC
8
LEAD
PDIP
TEMP.
RANGE
3 LEAD TO-220 3 LEAD TO-263
TO-252
SOT-223
AMS2954ACT-X AMS2954ACM-X AMS2954ACD-X AMS2954AC-X AMS2954ACS-X AMS2954CP-X
IND.
AMS2954CT-X AMS2954CM-X AMS2954CD-X AMS2954C-X AMS2954CS-X AMS2954CP-X
IND
X = 2.5V, 3.0V, 3.3V, 5.0V
SOT-223 TOP VIEW
3L TO-220 FRONT VIEW
PIN CONNECTIONS
TAB IS
GND
1
SENSE 2
SHUTDOWN 3
GROUND 4
8 INPUT
OUTPUT
2
GND
INPUT
1
8L SOIC/ 8L PDIP
OUTPUT 1
3
2
3
INPUT GND OUTPUT
7 FEEDBACK
6 VTAP
TO-252 FRONT VIEW
5 ERROR
TAB IS
GND
3
2
1
OUTPUT
INPUT
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3L TO-263 FRONT VIEW
TAB IS
GND
3
OUTPUT
2
GND
1
INPUT
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AMS2954
ABSOLUTE MAXIMUM RATINGS (Note 1)
Input Supply Voltage
SHUTDOWN Input Voltage,
Error Comparator Output
Voltage,(Note 9)
FEEDBACK Input Voltage
(Note 9) (Note 10)
Power Dissipation
Junction Temperature
Storage Temperature
ESD
-0.3 to +30V
Soldering Temperature (25 sec)
265°C
-1.5 to +30V
OPERATING RATINGS (Note 1)
Internally Limited
+150°C
-65°C to +150°C
2kV
Max. Input Supply Voltage
Junction Temperature Range
(TJ) (Note 8)
AMS2954AC-X
AMS2954C-X
40V
-40°C to +125°C
ELECTRICAL CHARACTERISTICS at Vs=Vout+1V, Ta=25°C, unless otherwise noted.
AMS2954AC
Parameter
AMS2954C
Conditions
(Note 2)
Min.
Typ.
Max.
Min.
Typ.
Max.
Units
2.5 V Versions (Note 16)
Output Voltage
Output Voltage
TJ = 25°C
(Note 3)
-25°C ≤TJ ≤85°C
Full Operating Temperature
Range
100 µA ≤IL ≤250 mA
TJ ≤TJMAX
2.488
2.5
2.512
2.475
2.5
2.525
V
2.475
2.5
2.525
2.450
2.5
2.550
V
2.470
2.5
2.530
2.440
2.5
2.560
V
2.463
2.5
2.537
2.448
2.5
2.562
V
2.985
3.0
3.015
2.970
3.0
3.030
V
2.970
3.0
3.030
2.955
3.0
3.045
V
2.964
3.0
3.036
2.940
3.0
3.060
V
2.958
3.0
3.042
2.928
3.0
3.072
V
3.284
3.3
3.317
3.267
3.3
3.333
V
3.267
3.3
3.333
3.251
3.3
3.350
V
3.260
3.3
3.340
3.234
3.3
3.366
V
3.254
3.3
3.346
3.221
3.3
3.379
V
4.975
5.0
5.025
4.95
5.0
5.05
V
4.95
5.0
5.050
4.925
5.0
5.075
V
4.94
5.0
5.06
4.90
5.0
5.10
V
4.925
5.0
5.075
4.88
5.0
5.12
V
3.0 V Versions (Note 16)
Output Voltage
Output Voltage
TJ = 25°C
(Note 3)
-25°C ≤TJ ≤85°C
Full Operating Temperature
Range
100 µA ≤IL ≤250 mA
TJ ≤TJMAX
3.3 V Versions (Note 16)
Output Voltage
Output Voltage
TJ = 25°C
(Note 3)
-25°C ≤TJ ≤85°C
Full Operating Temperature
Range
100 µA ≤IL ≤250 mA
TJ ≤TJMAX
5 V Versions (Note 16)
Output Voltage
Output Voltage
TJ = 25°C
(Note 3)
-25°C ≤TJ ≤85°C
Full Operating Temperature
Range
100 µA ≤IL ≤250 mA
TJ ≤TJMAX
All Voltage Options
Output Voltage
Temperature Coefficient
Line Regulation (Note 14)
(Note 12) (Note 4)
6V ≤Vin ≤30V (Note 15)
20
100
50
150
ppm/°C
0.03
0.1
0.04
0.2
%
Load Regulation (Note 14)
100 µA ≤IL ≤ 250 mA
0.04
0.16
0.1
0.2
%
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AMS2954
ELECTRICAL CHARACTERISTICS (Note 2) (Continued)
AMS2954AC
PARAMETER
Min.
(Note 2)
Dropout Voltage
(Note 5)
AMS2954C
CONDITIONS
Typ.
IL = 100µ A
IL = 250 mA
Max.
Min.
Typ.
Max.
Units
50
80
50
80
mV
380
600
380
600
mV
75
120
75
120
µA
15
20
15
20
mA
Vout = 0
200
500
200
500
mA
Thermal Regulation
(Note 13)
0.05
0.2
0.05
0.2
%/W
Output Noise,
10Hz to 100KHz
CL = 1µF
430
430
µV rms
160
160
µV rms
100
100
µV rms
AMS2954AC
AMS2954C
Ground Current
Current Limit
IL = 100 µA
IL = 250 mA
CL = 200 µF
CL = 13.3 µF
(Bypass = 0.01 µF pins 7 to 1)
8-Pin Versions only
Reference Voltage
Reference Voltage
1.22
Over Temperature (Note 7)
Feedback Pin Bias Current
Reference Voltage Temperature
Coefficient
1.26
V
1.285
V
60
nA
20
50
ppm/°C
0.1
0.1
nA/°C
40
V
OH
= 30V
1.21
1.185
60
1.235
40
0.01
1
0.01
1
µA
150
250
150
250
mV
Output Low Voltage
Vin = 4.5V
IOL = 400µA
Upper Threshold Voltage
(Note 6)
Lower Threshold Voltage
(Note 6)
75
Hysteresis
Shutdown Input
(Note 6)
15
Input logic Voltage
1.25
1.27
( Note 12 )
Feedback Pin Bias Current
Temperature Coefficient
Error Comparator
Output Leakage Current
1.235
1.19
Low (Regulator ON)
High (Regulator OFF)
40
60
1.3
40
95
60
75
mV
95
15
0.7
2
mV
mV
1.3
0.7
V
2
V
Shutdown Pin Input Current
(Note 3)
Vs = 2.4V
Vs = 30V
30
450
50
600
30
450
50
600
µA
Regulator Output Current in
Shutdown (Note 3)
(Note 11)
3
10
3
10
µA
Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of the
device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the
Electrical Characteristics tables.
Note 2: Unless otherwise specified all limits guaranteed for VIN = ( VONOM +1)V, IL = 100 µA and CL = 1 µF for 5V versions and 2.2µF for 3V and 3.3V
versions. Limits appearing in boldface type apply over the entire junction temperature range for operation. Limits appearing in normal type apply for TA = TJ =
25°C Additional conditions for the 8-pin versions are FEEDBACK tied to VTAP, OUTPUT tied to SENSE and VSHUTDOWN ≤ 0.8V.
Note 3: Guaranteed and 100% production tested.
Note 4: Guaranteed but not 100% production tested. These limits are not used to calculate outgoing AQL levels.
Note 5: Dropout voltage is defined as the input to output differential at which the output voltage drops 100 mV below its nominal value measured at 1V
differential. At very low values of programmed output voltage, the minimum input supply voltage of 2V ( 2.3V over temperature) must be taken into account.
Note 6: Comparator thresholds are expressed in terms of a voltage differential at the feedback terminal below the nominal reference voltage measured at
VIN = ( VONOM +1)V. To express these thresholds in terms of output voltage change, multiply by the error amplifier gain = Vout/Vref = (R1 + R2)/R2. For
example, at a programmed output voltage of 5V, the error output is guaranteed to go low when the output drops by 95 mV x 5V/1.235 = 384 mV. Thresholds
remain constant as a percent of Vout as Vout is varied, with the dropout warning occurring at typically 5% below nominal, 7.5% guaranteed.
Note 7: Vref ≤Vout ≤ (Vin - 1V), 2.3 ≤Vin≤30V, 100µA≤IL≤ 250 mA, TJ ≤ TJMAX.
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µA
AMS2954
Note 8: The junction-to-ambient thermal resistance are as follows:60°C/W for the TO-220 (T), 73°C/W for the TO-263 (M), 80°C/W for the TO-252 (D),
90°C/W for the SOT-223 (with package soldering to copper area over backside ground plane or internal power plane ϕ JA can vary from 46°C/W to >90°C/W
depending on mounting technique and the size of the copper area), 105°C/W for the molded plastic DIP (P) and 160°C/W for the molded plastic SO-8 (S).
Note 9: May exceed input supply voltage.
Note 10: When used in dual-supply systems where the output terminal sees loads returned to a negative supply, the output voltage should be diode-clamped to
ground.
Note 11: Vshutdown ≥ 2V, Vin ≤ 30V, Vout =0, Feedback pin tied to 5VTAP.
Note 12: Output or reference voltage temperature coefficients defined as the worst case voltage change divided by the total temperature range.
Note 13: Thermal regulation is defined as the change in output voltage at a time T after a change in power dissipation is applied, excluding load or line
regulation effects. Specifications are for a 50mA load pulse at VIN =30V (1.25W pulse) for T =10 ms.
Note 14: Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output voltage due to heating effects
are covered under the specification for thermal regulation.
Note 15: Line regulation for the AMS2954 is tested at 150°C for IL = 1 mA. For IL = 100 µA and TJ = 125°C, line regulation is guaranteed by design to 0.2%.
See typical performance characteristics for line regulation versus temperature and load current.
BLOCK DIAGRAM AND TYPICAL APPLICATIONS
AMS2954-XX
3 Lead Packages
AMS2954-XX
8 Lead Packages
VOUT
IL≤ 150mA
UNREGULATED DC
UNREGULATED DC
+
INPUT
7
FEEDBACK
+
VOUT
IL≤ 150mA
OUTPUT
8
INPUT
1
OUTPUT
2
+
-
+
SENSE
+
ERROR
AMPLIFIER
1.23V
REFERENCE
+
SEE APPLICATION
HINTS
FROM
CMOS
OR TTL
-
3
SHUTDOWN
+
50mV
+
GROUND
ERROR
AMPLIFIER
6
VTAP
330kΩ
TO CMOS
OR TTL
ERROR
4
GROUND
ERROR DETECTION COMPARATOR
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Phone (925) 443-0722
SEE APPLICATION
HINTS
5
+
1.23V
REFERENCE
+
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AMS2954
TYPICAL PERFORMANCE CHARACTERISTICS
Quiescent Current
Dropout Characteristics
20
Input Current
6
250
225
10
1
50
100 150 200
LOAD CURRENT (mA)
1
3
IO=250mA
2
1
0
250
IO=1mA
2 3 4 5 6 7 8
INPUT VOLTAGE (V)
50
1
9 10
5.02
5.0
4.98
0.2%
4.96
120
IL= 1 mA
100
80
IL= 0mA
60
40
20
4.94
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (° C)
90
80
70
60
50
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (° C)
QUIESCENT CURRENT (mA)
VIN= 6V
100
9 10
5V OUTPUT
0
0
1
Quiescent Current
IL= 100µA
2 3 4 5 6 7 8
INPUT VOLTAGE (V)
140
8
24
5V OUTPUT
5V OUTPUT
30
25
20
2 3 4 5 6 7
INPUT VOLTAGE (V)
Quiescent Current
35
5V OUTPUT
0
Quiescent Current
QUIESCENT CURRENT (µA)
OUTPUT VOLTAGE (V)
INPUT CURRENT (mA)
6
5.04
Quiescent Current
QUIESCENT CURRENT (µA)
75
5V OUTPUT
IO=250mA
1
RL= ∞
160
5V OUTPUT
0
125
100
25
0
5.06
120
110
3
4
5
2
INPUT VOLTAGE (V)
175
150
Temperature Drift of 3
Representative Units
Input Current
270
240
210
180
150
120
90
75
60
45
30
15
0
1
0
5V OUTPUT
200
VIN= 6V
IL= 250mA
15
10
5
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (° C)
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QUIESCENT CURRENT (mA)
0.1
4
INPUT CURRENT (µA)
OUTPUT VOLTAGE (V)
GROUND CURRENT (mA)
5V OUTPUT
5
21
18
15
IL= 250mA
12
9
6
3
0
0
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1
2 3 4 5 6 7
INPUT VOLTAGE (V)
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8
AMS2954
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
Short Circuit Current
300
250
200
150
100
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (° C)
500
400
300
~
~
100
50
AMS2954 Minimum Operating Voltage
2.1
10
1.8
1.7
400
300
200
TJ = 25°C
100
0
100µA
AMS2954 Feedback Bias Current
20
1.9
IL= 100µA
0
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (° C)
2.2
2.0
IL= 250mA
0
-10
-20
10mA
100mA
OUTPUT CURRENT
250mA
AMS2954 Feedback Pin Current
50
FEEDBACK CURRENT (µA)
350
500
DROPOUT VOLTAGE (mV)
DROPOUT VOLTAGE (mV)
400
BIAS CURRENT (nA)
PIN 7 DRVEN BY EXTERNAL
SOURCE (REGULATOR RUN
OPEN LOOP)
0
-50
TA = 125°C
-100
-150
TA =
25°C
-200
TA = -55°C
AMS2954 Error Comparator Output
AMS2954 Comparator Sink Current
2.5
7
50k RESISTOR TO
EXTERNAL 5V SUPPLY
6
5
4
HYSTERESIS
3
50k
RESISTOR
TO V OUT
2
1
0
0
1
2 3 4 5 6 7
INPUT VOLTAGE (V)
8
SINK CURRENT (mA)
VOUT= 5V
8
-250
-2.0
-30
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (° C)
1.6
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (° C)
2.0
1.5
TA =
125°C
TA =
25°C
1.0
TA = -55°C
0.5
0.0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
OUTPUT LOW VOLTAGE (V)
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INPUT OUTPUT VOLTAGE
VOLTAGE
CHANGE
SHORT CIRCUIT CURRENT (mA)
MINIMUM OPERATING VOLTAGE (V)
600
9
ERROR OUTPUT (V)
Dropout Voltage
Dropout Voltage
450
0
0.5 1.0
-1.5 -1.0 -0.5
FEEDBACK VOLTAGE (V)
Line Transient Response
100
mV
50
mV
0
-50
mV
CL= 1µF
IL= 1mA
~
~
VOUT= 5V
8V
6V
4V
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0
200
400
TIME (µs)
600
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800
AMS2954
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
250
mA
100
µA
1
2
3
TIME (ms)
4
5
0
RIPPLE REJECTION (dB)
0.5
VOUT = 5V
CL= 1 µF
0.05
0.02
0.01
16
OUTPUT
VOLTAGE (V)
20
4
3
2
1
0
2
80
70
IL= 0
50
IL= 100µA
CL= 1 µF
VIN= 6V
VOUT = 5V
30
~
~
Ripple Rejection
80
40
CL= 10 µF
IL= 10 mA
VIN = 8V
VOUT = 5V
0
-2
-100 0 100 200 300 400 500 600 700
TIME (µs)
90
60
CL= 1 µF
5
90
70
CL= 1 µF
VIN= 6V
VOUT = 5V
IL= 1mA
60
50
40
30
IL= 10mA
10
10K 100K
100
1K
FREQUENCY (Hz)
20
101
1M
Ripple Rejection
60
IL= 50mA
IL= 250mA
50
40
CL= 1µF
VIN= 6V
30
VOUT= 5V
20
10
101
10
3.5
VOLTAGE NOISE SPECTRAL
DENSITY(mV/√Hz)
70
2
102
105
103
104
FREQUENCY (Hz)
3
105
4
10
10
FREQUENCY (Hz)
20
101
106
AMS2954 Output Noise
80
RIPPLE REJECTION (dB)
8
12
TIME (ms)
106
5V
OUTPUT
IL= 250mA
CL= 1 µF
2.5
2.0
CL= 3.3 µF
CL= 220 µF
1.0
0.5
0.0
0.01 µF
BYPASS
PIN 1 TO
PIN 7
102
10
105
103
104
FREQUENCY (Hz)
106
AMS2954 Divider Resistance
3.0
1.5
2
400
PIN 2 TO PIN 4 RESISTANCE (kΩ)
OUPUT IMPEDANCE (Ω)
IO= 250mA
IO= 1 mA
0.2
0.1
4
7
6
Ripple Rejection
IO= 100µA
2
1
VOUT = 5V
~
~
Output Impedance
10
5
CL= 10 µF
RIPPLE REJECTION (dB)
0
250
mA
100
µA
AMS2954 Enable Transient
SHUTDOWN PIN
VOLTAGE (V)
CL= 1 µF
VOUT = 5V
~
~
OUTPUT VOLTAGE
CHANGE (mV)
Load Transient Response
80
60
40
20
0
-20
-40
-60
LOAD
CURRENT
LOAD
CURRENT
OUTPUT VOLTAGE
CHANGE (mV)
Load Transient Response
250
200
150
100
50
0
-50
-100
103
104
FREQUENCY (Hz)
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105
300
200
100
0
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (° C)
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AMS2954
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
1.6
REGULATOR OFF
1.2
1.0
REGULATOR ON
0.8
0.6
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (° C)
30
25
20
15
10
5
0
300
OUTPUT CURRENT (mA)
1.8
1.4
AMS2954 Maximum Rated
Output Current
Line Regulation
OUTPUT VOLTAGE CHANGE (V)
SHUTDOWN TRESHOLD VOLTAGE (V)
Shutdown Treshold Voltage
IL= 100µA
T J = 150° C
IL= 1mA
~
~
10
5
0
-5
-10
IL= 100µA
TJ = 125° C
15
20
25
10
INPUT VOLTAGE (V)
200
TJMAX= 125° C
150
TA= 25° C
100
TA= 85° C
0
25
30
POWER
OUTPUT VOLTAGE
DISSIPATION (W) CHANGE (mV)
OUTPUT CURRENT (mA)
250
SOT-223 PACKAGE
SOLDERED TO PC
BOARD
10
5
15
20
INPUT VOLTAGE (V)
T JMAX= 125° C
VOUT = 5V
200
TA= 25° C
150
TA= 50° C
100
50
T A= 85° C
30
10
5
15
20
INPUT VOLTAGE (V)
0
Thermal Response
300
0
250
0
5
AMS2954 Maximum Rated
Output Current
50
8 PIN MOLDED
DIP SOLDERED
TO PC BOARD
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5
4
2
0
-2
1
~
~
1.25W
0
-1
0
10
20
30
TIME (µs)
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40
50
Fax (925) 443-0723
25
30
AMS2954
APPLICATION HINTS
External Capacitors
A 1.0 µF or greater capacitor is required between output and
ground for stability at output voltages of 5V or more. At lower
output voltages, more capacitance is required (2.2µ or more is
recommended for 2.5V, 3.0V and 3.3V versions). Without this
capacitor the part will oscillate. Most types of tantalum or
aluminum electrolytic works fine here; even film types work but
are not recommended for reasons of cost. Many aluminum types
have electrolytes that freeze at about -30°C, so solid tantalums are
recommended for operation below -25°C. The important
parameters of the capacitor are an ESR of about 5 Ω or less and
resonant frequency above 500 kHz parameters in the value of the
capacitor. The value of this capacitor may be increased without
limit.
At lower values of output current, less output capacitance is
required for stability. The capacitor can be reduced to 0.33 µF for
currents below 10 mA or 0.1 µF for currents below 1 mA. Using
the adjustable versions at voltages below 5V runs the error
amplifier at lower gains so that more output capacitance is needed.
For the worst-case situation of a 300mA load at 1.23V output
(Output shorted to Feedback) a 3.3µF (or greater) capacitor should
be used.
Unlike many other regulators, the AMS2954, will remain stable
and in regulation with no load in addition to the internal voltage
divider. This is especially important in CMOS RAM keep-alive
applications. When setting the output voltage of the AMS2954
version with external resistors, a minimum load of 1µA is
recommended.
A 1µF tantalum or aluminum electrolytic capacitor should be
placed from the AMS2954/AMS2954 input to the ground if there
is more than 10 inches of wire between the input and the AC filter
capacitor or if a battery is used as the input.
Stray capacitance to the AMS2954 Feedback terminal can cause
instability. This may especially be a problem when using a higher
value of external resistors to set the output voltage. Adding a 100
pF capacitor between Output and Feedback and increasing the
output capacitor to at least 3.3 µF will fix this problem.
Error Detection Comparator Output
The comparator produces a logic low output whenever the
AMS2954 output falls out of regulation by more than
approximately 5%. This figure is the comparator’s built-in offset
of about 60 mV divided by the 1.235 reference voltage (Refer to
the block diagram). This trip level remains “5% below normal”
regardless of the programmed output voltage of the 2951. For
example, the error flag trip level is typically 4.75V for a 5V output
or 11.4V for a 12V output. The out of regulation condition may be
due either to low input voltage, current limiting, or thermal
limiting.
Figure 1 gives a timing diagram depicting the ERROR signal and
the regulator output voltage as the AMS2954 input is ramped up
and down. For 5V versions the ERROR signal becomes valid
(low) at about 1.3V input. It goes high at about 5V input (the input
voltage at which Vout = 4.75 ).
Since the AMS2954’s dropout voltage is load dependent (see
curve in typical performance characteristics), the input voltage trip
point (about 5V) will vary with the load current. The output
voltage trip point (approx. 4.75V) does not vary with load.
The error comparator has an open-collector output which requires
an external pull-up resistor. This resistor may be returned to the
output or some other supply voltage depending on system
requirements. In determining a value for this resistor, note that the
output is rated to sink 400µA, this sink current adds to battery
drain in a low battery condition. Suggested values range from
100K to 1MΩ. The resistor is not required if this output is unused.
OUTPUT
VOLTAGE
4.75V
ERROR*
5V
INPUT
VOLTAGE
1.3V
FIGURE 1. ERROR Output Timing
*When VIN ≤1.3V the error flag pin becomes a high impedance,
and the error flag voltage rises to its pull-up voltage. Using Vout as
the pull-up voltage (see Figure 2), rather than an external 5V
source, will keep the error flag voltage under 1.2V (typ.) in this
condition. The user may wish to drive down the error flag voltage
using equal value resistors (10 kΩ suggested), to ensure a lowlevel logic signal during any fault condition, while still allowing a
valid high logic level during normal operation.
Programming the Output Voltage
The AMS2954 may be pin-strapped for the nominal fixed output
voltage using its internal voltage divider by tying the output and
sense pins together, and also tying the feedback and VTAP pins
together. Alternatively, it may be programmed for any output
voltage between its 1.235V reference and its 30V maximum
rating. As seen in Figure 2, an external pair of resistors is
required.
The complete equation for the output voltage is:
Vout = VREF × (1 + R1/ R2)+ IFBR1
where VREF is the nominal 1.235 reference voltage and IFB is the
feedback pin bias current, nominally -20 nA. The minimum
recommended load current of 1 µA forces an upper limit of 1.2
MΩ on value of R2, if the regulator must work with no load (a
condition often found in CMOS in standby) IFB will produce a 2%
typical error in VOUT which may be eliminated at room
temperature by trimming R1. For better accuracy, choosing R2 =
100k reduces this error to 0.17% while increasing the resistor
program current by 12 µA. Since the AMS2954 typically draws 60
µA at no load with Pin 2 open-circuited, this is a small price to
pay.
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Phone (925) 443-0722
Fax (925) 443-0723
AMS2954
APPLICATION HINTS (Continued)
IIN
+VIN
VIN
5V
AMS2954
+
*
5 ERROR*
**SHUTDOWN
INPUT
3
1.2
VOUT 1
AMS2954
SD
GND
4
LOAD
VOUT
+VIN
ERROR
OUPUT
1µF
GND
8
100k
IL
OUT
IN
R1
FB
7
30V
* +
.01µ
F
R2
FIGURE 2. Adjustable Regulator
*See Application Hints.
Vout = VREF × (1 + R1/ R2)
**Drive with TTL- high to shut down. Ground or leave if
shutdown feature is not used.
Note: Pins 2 and 6 are left open.
FIGURE 3. Basic 5V Regulator
Figure 3 shows the voltages and currents which are present in a 5V
regulator circuit. The formula for calculating the power dissipated in the
regulator is also shown in Figure 3.
The next parameter which must be calculated is the maximum allowable
temperature rise, TR(max). This is calculated using the formula:
TR(max) =TJ(max) - TA(max)
Where TJ(max) is the maximum allowable junction temperature, and
TA(max) is the maximum ambient temperature.
Using the calculated values for TR(max) and P(max), the required value for
junction to ambient thermal resistance θ(J-A), can be determined:
Reducing Output Noise
In reference applications it may be an advantageous to reduce the
AC noise present at the output. One method is to reduce the
regulator bandwidth by increasing the size of the output
capacitor. This is the only way that noise can be reduced on the 3
lead AMS2954 but is relatively inefficient, as increasing the
capacitor from 1 µF to 220 µF only decreases the noise from 430
µV to 160 µV rms for a 100 kHz bandwidth at 5V output.
Noise could also be reduced fourfold by a bypass capacitor across
R1, since it reduces the high frequency gain from 4 to unity. Pick
CBYPASS ≅ 1 / 2πR1 × 200 Hz
or about 0.01 µF. When doing this, the output capacitor must be
increased to 3.3 µF to maintain stability. These changes reduce
the output noise from 430 µV to 100 µV rms for a 100 kHz
bandwidth at 5V output. With the bypass capacitor added, noise
no longer scales with output voltage so that improvements are
more dramatic at higher output voltages.
IG
* See external capacitors
PTotal = (VIN -5)IL +(VIN)IG
3.3µF
1.23
V
VREF
IIN = IL +IG
θ(J-A) = TR(max) /P(max)
If the value obtained is 60°C/W or higher, the regulator may be operated
without an external heatsink. If the calculated value is below 60°C/W, an
external heatsink is required. To calculate the thermal resistance of this
heatsink use the formula:
θ(H-A) = θ(J-A) - θ(J-C) - θ(C-H)
where:
θ(J-C) is the junction-to-case thermal resistance, which is specified as
3°C/W maximum for the AMS2954.
θ(C-H) is the case-to-heatsink thermal resistance, which is dependent on
the interfacing material (if used).
θ(H-A) is the heatsink-to-ambient thermal resistance. It is this
specification which defines the effectiveness of the heatsink. The
heatsink selected must have a thermal resistance equal or lower than the
value of θ(H-A) calculated from the above listed formula.
Output Isolation
Heatsink Requirements
A heatsink might be required when using AMS2954, depending
on the maximum power dissipation and maximum ambient
temperature of the application. The heatsink must be chosen
considering that under all operating condition, the junction
temperature must be within the range specified under Absolute
Maximum Ratings.
To determine if a heatsink is required, the maximum power
dissipated by the regulator must be calculated. It is important to
consider, that if the regulator is powered from a transformer
connected to the AC line, the maximum specified AC input
voltage must be used.
The regulator output can be left connected to an active voltage source
with the regulator input power turned off, as long as the regulator ground
pin is connected to ground. If the ground pin is left floating, damage to
the regulator can occur if the output is pulled up by an external voltage
source.
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Phone (925) 443-0722
Fax (925) 443-0723
AMS2954
TYPICAL APPLICATIONS (Continued)
Wide Input Voltage Range Current Limiter
+VIN
8
+VIN
5
ERROR
OUPUT
VOUT 1
ERROR
*VOUT ≈ VΙΝ
AMS2954
SHUTDOWN 3
SD
INPUT
GND
FB
4
7
*Minimum Input-Output voltage ranges from 40mV to 400mV, depending on load current. Current limit is typically 260 mA
Low Drift Current Source
+V = 2
IL
5Volt Current Limiter
30V
LOAD
5V BUS
8
VIN
+VIN
VOUT 1
*VOUT ≈ 5V
AMS2954 -5.0
VOUT
AMS2954
SHUTDOWN 3
SD
INPUT
0.1µF
GND
4
1µF
FB
7
R
1%
GND
1µF
+
*Minimum Input-Output voltage ranges from 40mV to 400mV, depending on
load current. Current limit is typically 260 mA
5V Regulator with 2.5V Sleep Function
Open Circuit Detector for 4 to 20mA Current Loop
+5V
+VIN
C - MOS
GATE
*SLEEP
INPUT
4.7kΩ
4
20mA
*OUTPUT
1
8
47kΩ
470kΩ
+VIN
8
ERROR
OUPU
T
VOUT
+VIN
5
ERROR
SHUTDOWN 3
SD
INPUT
+VOUT
VOUT 1
GND
4
4
7
1%
+
2N3906
2
FB
200kΩ
100pF
FB
7
1
AMS2954
1N4001
AMS2954
5
3.3µF
100kΩ
1%
100kΩ
Advanced Monolithic Systems, Inc. www.advanced-monolithic.com
0.1µF
GND
4
1N457
360
MIN. VOLTAGE ≈ 4V
Phone (925) 443-0722
Fax (925) 443-0723
AMS2954
TYPICAL APPLICATIONS (Continued)
2 Ampere Low Dropout Regulator
CURRENT
LIMIT
SECTION
Regulator with Early Warning and Auxiliary Output
+VIN
+VIN = VOUT +.5V
8
+VIN
0.05
680
6
470
7
4.7MΩ
FB
VOUT
7
FB
GND
4
ERROR
FLAG
5
AMS2954
220
1µF
3.6V
NICAD
27 kΩ
ERROR
SD
20
+
GND
4
+VIN
3
5V MEMORY
SUPPLY
D2
1
AMS2954
#1
5
ERROR
+VOUT @ 2A
10kΩ
8
2
SENSE
VTAP
MJE2955
2N3906
D1
+
R1
+
4.7
TANT.
100µF
D4
1%
VOUT
R2
1
EARLY WARNING
D3
2.7MΩ
Q1
20kΩ
8
+VIN
6
.033
2
SENSE
VOUT
VTAP
7
330 kΩ
MAIN 5V OUTPUT
FB AMS2954
#2
5
SD
ERROR
3
+
RESET
µP
VDD
1µF
GND
4
VOUT = 1.23V(1+R1/R2)
For 5V VOUT, use internal resistors. Wire pin 6 to 7 and pin 2 to +VOUTBuss.
•
Early warning flag on low input voltage
•
Main output latches off at lower input voltages
•
Battery backup on auxiliary output
Operation: Reg.#1’s VOUT is programmed one diode drop above 5V. It’s error flag
becomes active when VIN≤ 5.7V. When VIN drops below 5.3V, the error flag of
Reg.#2 becomes active and via Q1 latches the main output off. When VIN again
exceeds 5.7V Reg.#1 is back in regulation and the early warning signal rises,
unlatching Reg.#2 via D3.
1A Regulator with 1.2V Dropout
Latch Off When Error Flag Occurs
+VIN
UNREGULATE
D INPUT
10kΩ
1µF
0.01µF
SUPERTEX
VP12C
470kΩ
8
IN
6
VTAP
SENSE
1Μ Ω
FB
+
470kΩ
AMS2954
0.002µ F
R1
220µF
1
RESET
VOUT
+VIN
1
VOUT
ERROR
3 SD
OUT
GND
4
OUTPUT
5V ± 1% @
0 TO 1A
2
AMS2954
7
8
5
FB
GND
4
+
7
1µF
R2
2kΩ
IQ ≅ 400µA
Advanced Monolithic Systems, Inc. www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
AMS2954
PACKAGE DIMENSIONS inches (millimeters) unless otherwise noted.
3 LEAD TO-220 PLASTIC PACKAGE (T)
0.147-0.155
(3.734-3.937)
DIA
0.390-0.415
(9.906-10.541)
0.165-0.180
(4.191-4.572)
0.045-0.055
(1.143-1.397)
0.230-0.270
(5.842-6.858)
0.570-0.620
(14.478-15.748)
0.460-0.500
(11.684-12.700)
0.330-0.370
(8.382-9.398)
0.980-1.070
(24.892-27.178)
0.218-0.252
(5.537-6.401)
0.520-0.570
(13.208-14.478)
0.090-0.110
(2.286-2.794)
0.028-0.038
(0.711-0.965)
0.050
(1.270)
TYP
0.013-0.023
(0.330-0.584)
0.095-0.115
(2.413-2.921)
T (TO-220) AMS DRW# 042193
3 LEAD TO-263 PLASTIC DD (M)
Advanced Monolithic Systems, Inc. www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
AMS2954
PACKAGE DIMENSIONS inches (millimeters) unless otherwise noted (Continued).
TO-252 PLASTIC PACKAGE (D)
0.020-0.030
(0.508-0.762)
0.258-0.262
(6.553-6.654)
0.208-0.212
(5.283-5.384)
0.020-0.030
(0.508-0.762)
0.085-0.095
(2.159-2.413)
0.033-0.037
(0.838-0.939)
0.030-0.034
(0.762-0.863)
0.038-0.042
(0.965-1.066)
7.0°
0.023-0.027
(0.584-0.685)
45.0°
0.175-0.180
(4.191-4.445)
0.235-0.245
(5.969-6.223)
0.057-0.067
(0.144-0.170)
DIA
0.025
(0.635)
TYP
0.038
(0.965)
TYP
0.099-0.103
(2.514-2.615)
0.088-0.092
(2.235-2.336)
0.030
(0.762)
TYP
0.018-0.022
(0.451-0.558)
0.038-0.042
(0.965-1.066)
0.024±0.002
(0.610±0.0508)
D (D3) AMS DRW# 042891
3 LEAD SOT-223 PLASTIC PACKAGE
0.248-0.264
(6.30-6.71)
0.116-0.124
(2.95-3.15)
0.264-0.287
(6.71-7.29)
0.130-0.146
(3.30-3.71)
0.033-0.041
(0.84-1.04)
0.090
(2.29)
NOM
10°-16°
10°
MAX
0.071
(1.80)
MAX
0.010-0.014
(0.25-0.36)
10°-16°
0.012
Advanced Monolithic Systems, Inc. 0.025-0.033
www.advanced-monolithic.com
(0.31)
(0.64-0.84)
MIN
0.181
(4.60)
NOM
0.025-0.033
Phone
(925) 443-0722
(0.64-0.84)
Fax (925) 443-0723
(SOT-223 ) AMS DRW# 042292
AMS2954
PACKAGE DIMENSIONS inches (millimeters) unless otherwise noted (Continued).
8 LEAD SOIC PLASTIC PACKAGE (S)
0.189-0.197*
(4.801-5.004)
8
7
6
5
0.228-0.244
(5.791-6.197)
0.150-0.157**
(3.810-3.988)
1
2
3
4
0.010-0.020 x 45°
(0.254-0.508)
0.053-0.069
(1.346-1.752)
0.004-0.010
(0.101-0.254)
0.014-0.019
(0.355-0.483)
0.008-0.010
(0.203-0.254)
0.050
(1.270)
TYP
0°-8° TYP
0.016-0.050
(0.406-1.270)
S (SO-8 ) AMS DRW# 042293
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
8 LEAD PLASTIC DIP PACKAGE (P)
0.400*
(10.160)
MAX
8
7
6
5
1
2
3
4
0.255±0.015*
(6.477±0.381)
0.045-0.065
(1.143-1.651)
0.300-0.325
(7.620-8.255)
0.130±0.005
(3.302±0.127)
0.065
(1.651)
TYP
0.005
(0.127)
MIN
0.100±0.010
(2.540±0.254)
0.125
(3.175)
MIN
0.009-0.015
(0.229-0.381)
0.015
(0.380)
MIN
0.018±0.003
(0.457±0.076)
0.325 +0.025
-0.015
(8.255 +0.635 )
-0.381
P (8L PDIP ) AMS DRW# 042294
*DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTUSIONS.
MOLD FLASH OR PROTUSIONS SHALL NOT EXCEED 0.010" (0.254mm)
Advanced Monolithic Systems, Inc. www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
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