AMS2954CT-3.3 [ASI]
Fixed Positive LDO Regulator,;型号: | AMS2954CT-3.3 |
厂家: | ADVANCED SEMICONDUCTOR |
描述: | Fixed Positive LDO Regulator, |
文件: | 总15页 (文件大小:188K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
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
ADDITIONAL FEATURES (ADJ ONLY)
• 1.24V to 29V Programmable Output
• Error Flag Warning of Voltage Output Dropout
• Logic Controlled Electronic Shutdown
• Battery Powered Systems
• Portable Consumer Equipment
• Cordless Telephones
• Portable (Notebook) Computers
• Portable Instrumentation
• Radio Control Systems
• Automotive Electronics
• Avionics
• Low-Power Voltage Reference
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 PDIP TEMP. RANGE
8 LEAD SOIC
AMS2954ACT-X AMS2954ACM-X AMS2954ACD-X AMS2954AC-X AMS2954ACS-X AMS2954CP-X
AMS2954CT-X AMS2954CM-X AMS2954CD-X AMS2954C-X AMS2954CS-X AMS2954CP-X
X = 2.5V, 3.0V, 3.3V, 5.0V
IND.
IND
SOT-223 TOP VIEW
3L TO-220 FRONT VIEW
PIN CONNECTIONS
3
OUTPUT
TAB IS
GND
GND
2
1
INPUT
8L SOIC/ 8L PDIP
1
2
3
OUTPUT
SENSE
1
2
3
4
8
7
6
5
INPUT
FEEDBACK
VTAP
INPUT GND OUTPUT
TO-252 FRONT VIEW
3L TO-263 FRONT VIEW
SHUTDOWN
GROUND
ERROR
OUTPUT
3
2
1
3
OUTPUT
GND
TAB IS
GND
TAB IS
GND
2
1
INPUT
INPUT
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AMS2954
ABSOLUTE MAXIMUM RATINGS (Note 1)
Input Supply Voltage
SHUTDOWN Input Voltage,
Error Comparator Output
Voltage,(Note 9)
-0.3 to +30V
Soldering Temperature (25 sec)
265°C
FEEDBACK Input Voltage
(Note 9) (Note 10)
Power Dissipation
Junction Temperature
Storage Temperature
ESD
-1.5 to +30V
OPERATING RATINGS (Note 1)
Internally Limited
+150°C
Max. Input Supply Voltage
Junction Temperature Range
(TJ) (Note 8)
40V
-65°C to +150°C
2kV
AMS2954AC-X
AMS2954C-X
-40°C to +125°C
ELECTRICAL CHARACTERISTICS at V =Vout+1V, Ta=25°C, unless otherwise noted.
s
AMS2954AC
AMS2954C
Parameter
Conditions
Units
(Note 2)
Min.
2.488
Typ.
Max.
Min.
2.475
Typ.
Max.
2.525
2.5 V Versions (Note 16)
T = 25°C
(Note 3)
J
Output Voltage
2.5
2.5
2.5
2.512
2.5
2.5
2.5
V
V
V
-25°C ≤T ≤85°C
J
2.475
2.525
2.450
2.550
Full Operating Temperature
Range
2.470
2.530
2.440
2.560
100 µA ≤I ≤250 mA
L
Output Voltage
2.5
2.5
V
2.463
2.537
2.448
2.562
T ≤T
J
JMAX
3.0 V Versions (Note 16)
T = 25°C
J
(Note 3)
Output Voltage
2.985
2.970
2.964
3.0
3.0
3.0
3.015
3.030
3.036
2.970
2.955
2.940
3.0
3.0
3.0
3.030
3.045
3.060
V
V
V
-25°C ≤T ≤85°C
J
Full Operating Temperature
Range
100 µA ≤I ≤250 mA
L
Output Voltage
3.0
3.0
V
2.958
3.042
2.928
3.072
T ≤T
J
JMAX
3.3 V Versions (Note 16)
T = 25°C
J
(Note 3)
Output Voltage
3.284
3.267
3.260
3.3
3.3
3.3
3.317
3.333
3.340
3.267
3.251
3.234
3.3
3.3
3.3
3.333
3.350
3.366
V
V
V
-25°C ≤T ≤85°C
J
Full Operating Temperature
Range
100 µA ≤I ≤250 mA
L
Output Voltage
3.3
3.3
V
3.254
3.346
3.221
3.379
T ≤T
J
JMAX
5 V Versions (Note 16)
T = 25°C
J
(Note 3)
Output Voltage
4.975
4.95
4.94
5.0
5.0
5.0
5.025
4.95
4.925
4.90
5.0
5.0
5.0
5.05
5.075
5.10
V
V
V
-25°C ≤T ≤85°C
J
5.050
Full Operating Temperature
Range
5.06
100 µA ≤I ≤250 mA
L
Output Voltage
5.0
5.0
V
4.925
5.075
100
4.88
5.12
T ≤T
J
JMAX
All Voltage Options
Output Voltage
Temperature Coefficient
ppm/°C
20
50
150
(Note 12) (Note 4)
6V ≤V ≤30V (Note 15)
Line Regulation (Note 14)
Load Regulation (Note 14)
0.03
0.04
0.1
0.04
0.1
0.2
0.2
%
%
in
100 µA ≤I ≤ 250 mA
0.16
L
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AMS2954
ELECTRICAL CHARACTERISTICS (Note 2) (Continued)
AMS2954AC
AMS2954C
PARAMETER
CONDITIONS
Units
Min.
Typ.
Max.
Min.
Typ.
Max.
80
(Note 2)
I
I
= 100µ A
Dropout Voltage
(Note 5)
50
80
50
mV
mV
L
L
= 250 mA
380
600
380
600
I
I
= 100 µA
Ground Current
75
15
120
20
75
15
120
20
µA
L
L
= 250 mA
mA
Current Limit
V
= 0
200
500
0.2
200
500
0.2
mA
out
Thermal Regulation
(Note 13)
0.05
0.05
%/W
C
C
C
= 1µF
L
L
L
Output Noise,
430
160
100
430
160
100
µV rms
µV rms
µV rms
= 200 µF
= 13.3 µF
10Hz to 100KHz
(Bypass = 0.01 µF pins 7 to 1)
8-Pin Versions only
AMS2954AC
AMS2954C
Reference Voltage
Reference Voltage
1.22
1.235
1.25
1.21
1.235
1.26
V
V
Over Temperature (Note 7)
1.19
1.27
1.185
1.285
Feedback Pin Bias Current
40
20
60
40
60
nA
Reference Voltage Temperature
Coefficient
50
ppm/°C
( Note 12 )
Feedback Pin Bias Current
Temperature Coefficient
Error Comparator
0.1
0.1
nA/°C
Output Leakage Current
V
= 30V
0.01
150
1
0.01
150
1
µA
OH
V
I
= 4.5V
Output Low Voltage
in
250
250
mV
= 400µA
OL
(Note 6)
(Note 6)
(Note 6)
40
60
75
15
40
60
75
15
mV
mV
mV
Upper Threshold Voltage
Lower Threshold Voltage
95
95
Hysteresis
Shutdown Input
Low (Regulator ON)
High (Regulator OFF)
1.3
1.3
V
V
0.7
0.7
Input logic Voltage
2
2
Vs = 2.4V
30
50
30
50
µA
µA
Shutdown Pin Input Current
(Note 3)
V = 30V
s
450
600
450
600
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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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
AMS2954-XX
3 Lead Packages
8 Lead Packages
VOUT
IL 150mA
UNREGULATED DC
≤
UNREGULATED DC
+
7
8
1
INPUT
+
FEED-
INPUT
OUTPUT
BACK
VOUT
IL 150mA
OUTPUT
≤
2
6
+
-
SENSE
+
-
ERROR
AMPLIFIER
SEE APPLICATION
HINTS
+
+
SEE APPLICATION
HINTS
3
ERROR
AMPLIFIER
FROM
CMOS
OR TTL
SHUT-
DOWN
VTAP
330k
Ω
5
+
+
-
TO CMOS
OR TTL
50mV
ERROR
+
1.23V
REFERENCE
4
+
1.23V
REFERENCE
GROUND
GROUND
ERROR DETECTION COMPARATOR
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AMS2954
TYPICAL PERFORMANCE CHARACTERISTICS
Quiescent Current
Dropout Characteristics
Input Current
20
10
6
5
4
250
225
5V OUTPUT
5V OUTPUT
200
175
150
IO=1mA
125
100
3
2
IO=250mA
RL=
∞
1
75
50
1
25
0
0
0.1
50
100 150 200
1
3
4
5
6
0
1
2
3
4
5
6
7
8
9 10
2
1
250
0
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
LOAD CURRENT (mA)
Temperature Drift of 3
Representative Units
Quiescent Current
Input Current
270
240
210
180
150
120
5.06
160
140
120
100
80
5V OUTPUT
5V OUTPUT
5V OUTPUT
IO=250mA
5.04
5.02
IL= 1 mA
90
75
60
45
30
15
5.0
IL= 0mA
60
4.98
40
0.2%
4.96
4.94
20
0
0
0
1
2
3
4
5
6
7
8
9
10
-75 -50 -25
0
25 50 75 100 125 150
0
1
2
3
4
5
6
7
8
INPUT VOLTAGE (V)
TEMPERATURE (° C)
INPUT VOLTAGE (V)
Quiescent Current
Quiescent Current
Quiescent Current
120
110
100
90
35
30
25
20
24
21
18
15
12
9
5V OUTPUT
5V OUTPUT
IL= 100
µ
A
5V OUTPUT
VIN= 6V
IL= 250mA
VIN= 6V
IL= 250mA
80
15
10
70
6
60
3
50
-75
5
-75
0
-50 -25
0
25 50 75 100 125 150
-50 -25
0
25 50 75 100 125 150
0
1
2
3
4
5
6
7
8
TEMPERATURE (° C)
TEMPERATURE (° C)
INPUT VOLTAGE (V)
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AMS2954
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
Dropout Voltage
Short Circuit Current
Dropout Voltage
450
400
350
300
250
200
150
100
600
500
400
500
400
300
200
IL= 250mA
300
100
50
~
~
TJ = 25°C
100
0
IL= 100µA
0
-75 -50 -25
0
25 50 75 100 125 150
-75 -50 -25
0
25 50 75 100 125 150
100
µA
10mA
100mA
250mA
TEMPERATURE (° C)
TEMPERATURE (° C)
OUTPUT CURRENT
AMS2954 Minimum Operating Voltage
AMS2954 Feedback Bias Current
AMS2954 Feedback Pin Current
20
10
50
2.2
2.1
PIN 7 DRVEN BY EXTERNAL
SOURCE (REGULATOR RUN
OPEN LOOP)
0
-50
2.0
1.9
0
TA = 125°C
-100
-10
-150
-200
-250
1.8
1.7
TA
25°C
=
-20
-30
TA = -55°C
1.6
-75
125
0
0.5
0
100
150
125
-75 -50 -25
0
25 50 75 100
150
-2.0 -1.5 -1.0 -0.5
1.0
-50 -25
25 50
75
TEMPERATURE (° C)
TEMPERATURE (° C)
FEEDBACK VOLTAGE (V)
AMS2954 Error Comparator Output
AMS2954 Comparator Sink Current
Line Transient Response
100
mV
50
9
8
2.5
VOUT= 5V
TA
=
125°C
mV
2.0
1.5
1.0
0.5
0.0
7
6
5
50k RESISTOR TO
EXTERNAL 5V SUPPLY
0
TA
=
CL= 1
µF
-50
mV
25°C
IL= 1mA
HYSTERESIS
4
3
2
1
0
VOUT= 5V
~
~
8V
6V
TA = -55°C
50k
RESISTOR
TO VOUT
4V
7
0
1
2
3
4
5
6
8
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
OUTPUT LOW VOLTAGE (V)
0
200
400
s)
600
800
INPUT VOLTAGE (V)
TIME (
µ
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AMS2954
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
Load Transient Response
Load Transient Response
AMS2954 Enable Transient
250
200
150
100
50
80
60
40
20
0
7
6
CL= 1 µF
5
4
3
IL= 10 mA
VIN = 8V
VOUT = 5V
0
-20
-40
-60
CL= 10
µF
2
1
CL= 10 µF
-50
-100
VOUT = 5V
CL= 1 µF
0
2
VOUT = 5V
~
~
~
~
~
~
250
250
mA
mA
0
100
100
µ
A
µ
A
-2
-100
0
1
2
3
4
5
0
4
8
12
16
20
106
105
0
100 200 300 400 500 600 700
TIME ( s)
TIME (ms)
TIME (ms)
µ
Ripple Rejection
Ripple Rejection
Output Impedance
90
80
70
60
50
40
30
20
90
80
70
60
50
40
30
20
10
5
IO= 100µA
2
1
CL= 1 µF
VIN= 6V
VOUT = 5V
IO= 250mA
IL= 1mA
IO= 1 mA
IL= 0
0.5
0.2
0.1
VOUT = 5V
CL= 1
IL= 100µA
µ
F
CL= 1 µF
0.05
VIN= 6V
VOUT = 5V
0.02
0.01
IL= 10mA
105
105
106
102
103
104
102
103
104
101
101
10
100
1K
10K 100K 1M
FREQUENCY (Hz)
FREQUENCY (Hz)
FREQUENCY (Hz)
Ripple Rejection
AMS2954 Output Noise
AMS2954 Divider Resistance
80
70
60
50
40
30
20
10
400
300
3.5
5V
OUTPUT
IL= 250mA
IL= 50mA
3.0
2.5
2.0
CL= 1 µF
IL= 250mA
200
100
0
CL= 220 µF
CL= 1µF
1.5
1.0
CL= 3.3 µF
VIN= 6V
VOUT= 5V
0.01 µF
0.5
0.0
BYPASS
PIN 1 TO
PIN 7
105
FREQUENCY (Hz)
102
103
104
102
103
104
-75 -50 -25
106
150
0 25 50 75 100 125
TEMPERATURE (° C)
101
FREQUENCY (Hz)
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AMS2954
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
AMS2954 Maximum Rated
Output Current
Shutdown Treshold Voltage
Line Regulation
1.8
30
25
20
15
10
5
300
8 PIN MOLDED
DIP SOLDERED
TO PC BOARD
IL= 100
µ
A
250
200
1.6
1.4
TJMAX= 125° C
VOUT = 5V
REGULATOR OFF
TJ = 150° C
IL= 1mA
TA= 25° C
1.2
1.0
0
150
~
~
TA= 50° C
REGULATOR ON
10
100
50
0
IL= 100
µA
TJ = 125° C
5
0
-5
0.8
0.6
TA= 85° C
-10
-75 -50 -25
0
25 50 75 100 125
5
10
15
20
25
10
30
150
30
0
5
15
20
25
TEMPERATURE (° C)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
AMS2954 Maximum Rated
Output Current
Thermal Response
300
5
SOT-223 PACKAGE
SOLDERED TO PC
BOARD
4
2
0
250
200
TJMAX= 125° C
150
-2
1
TA= 25° C
~
~
100
50
0
1.25W
TA= 85° C
0
-1
10
INPUT VOLTAGE (V)
30
0
10
20
TIME (
30
s)
40
50
0
5
15
20
25
µ
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AMS2954
APPLICATION HINTS
External Capacitors
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.
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.
4.75V
OUTPUT
VOLTAGE
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.
ERROR*
5V
INPUT
VOLTAGE
1.3V
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.
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 low-
level logic signal during any fault condition, while still allowing a
valid high logic level during normal operation.
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.
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.
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 ).
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.
Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723
AMS2954
APPLICATION HINTS (Continued)
IIN
+VIN
5V
IL
VIN
IN
OUT
AMS2954
+
LOAD
*
1µF
GND
8
100k
VOUT
+VIN
IG
1.2
30V
5
3
1
ERROR
OUPUT
ERROR*
VOUT
IIN = IL +IG
AMS2954
*
+
**SHUTDOWN
INPUT
* See external capacitors
PTotal = (VIN -5)IL +(VIN)IG
3.3µF
SD
GND
R1
.01µ
F
FB
1.23
V
4
7
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.
R2
VREF
The next parameter which must be calculated is the maximum allowable
temperature rise, TR(max). This is calculated using the formula:
FIGURE 2. Adjustable Regulator
*See Application Hints.
TR(max) =TJ(max) - TA(max)
Vout = VREF × (1 + R1/ R2)
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
**Drive with TTL- high to shut down. Ground or leave if
shutdown feature is not used.
Note: Pins 2 and 6 are left open.
junction to ambient thermal resistance θ(J-A), can be determined:
Reducing Output Noise
θ(J-A) = TR(max) /P(max)
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.
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)
Noise could also be reduced fourfold by a bypass capacitor across
R1, since it reduces the high frequency gain from 4 to unity. Pick
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.
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.
Output Isolation
Heatsink Requirements
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.
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.
Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723
AMS2954
TYPICAL APPLICATIONS (Continued)
Wide Input Voltage Range Current Limiter
+VIN
8
+VIN
*VOUT ≈ VΙΝ
5
3
1
ERROR
OUPUT
VOUT
ERROR
AMS2954
SHUTDOWN
INPUT
SD
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
5Volt Current Limiter
+V = 2
30V
IL
LOAD
5V BUS
8
VIN
+VIN
1
VOUT
AMS2954 -5.0
*VOUT ≈ 5V
AMS2954
VOUT
3
SHUTDOWN
INPUT
SD
GND
0.1µF
1µF
FB
GND
4
7
+
R
1%
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
+VIN
+5V
C - MOS
GATE
4.7kΩ
*SLEEP
INPUT
4
20mA
*OUTPUT
5
1
8
47kΩ
470kΩ
+VIN
8
1
7
VOUT
+VIN
ERROR
OUPU
T
+VOUT
AMS2954
4
5
1
VOUT
ERROR
1N4001
2
FB
AMS2954
200
1%
100
kΩ
3
SHUTDOWN
INPUT
GND
4
SD
GND
100pF
+
3.3µ
F
0.1µF
2N3906
360
FB
1N457
k
Ω
4
7
1%
MIN. VOLTAGE
≈ 4V
100kΩ
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AMS2954
TYPICAL APPLICATIONS (Continued)
2 Ampere Low Dropout Regulator
Regulator with Early Warning and Auxiliary Output
CURRENT
LIMIT
SECTION
+VIN
+VIN = VOUT +.5V
D1
8
2
+VIN
0.05
SENSE
5V MEMORY
SUPPLY
680
D2
6
7
1
VTAP
AMS2954
#1
VOUT
20
5
470
+
FB
ERROR
1µF
3.6V
NICAD
GND
4
MJE2955
2N3906
4.7M
+VOUT @ 2A
10kΩ
Ω
8
+VIN
27 k
Ω
ERROR
FLAG
5
ERROR
+
+
100µF
EARLY WARNING
R1
D3
4.7
2.7M
Q1
Ω
AMS2954
TANT.
7
3
D4
SD
GND
FB
1%
R2
VOUT
1
220
8
2
SENSE
VOUT
AMS2954
4
RESET
330 k
Ω
+VIN
20kΩ
µP
6
MAIN 5V OUTPUT
.033
VDD
VTAP
7
3
FB
SD
#2
5
+
ERROR
1µF
GND
4
VOUT = 1.23V(1+R1/R2)
•
•
•
Early warning flag on low input voltage
Main output latches off at lower input voltages
Battery backup on auxiliary output
For 5V VOUT, use internal resistors. Wire pin 6 to 7 and pin 2 to +VOUTBuss.
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
10
kΩ
0.01µF
1µ
F
SUPERTEX
VP12C
470k
Ω
8
VOUT
+VIN
8
5
3
1
7
VOUT
ERROR
IN
OUTPUT
5V ± 1% @
0 TO 1A
470k
Ω
2
6
7
VTAP
SENSE
AMS2954
R1
R2
+
220µ
F
AMS2954
+
SD
FB
1µF
1
RESET
GND
4
FB
OUT
GND
4
2kΩ
1ΜΩ
0.002µF
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
0.165-0.180
(4.191-4.572)
0.390-0.415
(9.906-10.541)
(3.734-3.937)
0.045-0.055
(1.143-1.397)
DIA
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)
0.050
(1.270)
TYP
0.013-0.023
(0.330-0.584)
0.095-0.115
(2.413-2.921)
0.028-0.038
(0.711-0.965)
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)
0.258-0.262
(6.553-6.654)
0.208-0.212
(5.283-5.384)
0.020-0.030
0.085-0.095
(0.508-0.762)
0.033-0.037
(2.159-2.413)
0.030-0.034
(0.762-0.863)
0.020-0.030
(0.508-0.762)
(0.838-0.939)
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
0.038-0.042
(0.965-1.066)
0.099-0.103
(2.514-2.615)
0.024±0.002
(0.610±0.0508)
0.088-0.092
(2.235-2.336)
0.030
(0.762)
TYP
0.018-0.022
(0.451-0.558)
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
0.025-0.033
(0.64-0.84)
0.025-0.033
Advanced Monolithic Systems, Inc. www.advanced-monoic.com Phoe ) 443-0722 Fax (925) 443-0723
(0.31)
(0.64-0.84)
MIN
(SOT-223 ) AMS DRW# 042292
0.181
(4.60)
NOM
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
(0.254-0.508)
x 45°
0.053-0.069
(1.346-1.752)
0.004-0.010
(0.101-0.254)
0.008-0.010
(0.203-0.254)
0°-8° TYP
0.014-0.019
(0.355-0.483)
0.050
(1.270)
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
0.255±0.015*
(6.477±0.381)
1
2
3
4
0.300-0.325
(7.620-8.255)
0.130±0.005
(3.302±0.127)
0.045-0.065
(1.143-1.651)
0.065
(1.651)
TYP
0.009-0.015
0.125
(3.175)
MIN
(0.229-0.381)
0.005
(0.127)
MIN
0.015
(0.380)
MIN
+0.025
-0.015
+0.635
0.325
0.100±0.010
(2.540±0.254)
0.018±0.003
(0.457±0.076)
(
8.255
)
-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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