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AMS2954AC-25 [ADMOS]

250mA LOW DROPOUT VOLTAGE REGULATOR; 250毫安低压差稳压器
AMS2954AC-25
型号： AMS2954AC-25
厂家： ADVANCED MONOLITHIC SYSTEMS    ADVANCED MONOLITHIC SYSTEMS
描述：

250mA LOW DROPOUT VOLTAGE REGULATOR
250毫安低压差稳压器

稳压器
文件： 总15页 (文件大小：172K)
中文：  中文翻译
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Advanced  
Monolithic  
Systems  
AMS2954  
250mA LOW DROPOUT VOLTAGE REGULATOR  
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 (1mF) 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  
TO-252 SOT-223  
OPERATING  
TEMP. RANGE  
IND.  
8 LEAD SOIC  
8 LEAD PDIP  
3 LEAD TO-220 3 LEAD TO-263  
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  
SOT-223 TOP VIEW  
3L TO-220 FRONT VIEW  
PIN CONNECTIONS  
3
2
1
OUTPUT  
TAB IS  
GND  
GND  
INPUT  
8L SOIC/ 8L PDIP  
1
2
3
OUTPUT  
SENSE  
1
2
3
4
8
7
6
5
INPUT  
INPUT GND OUTPUT  
FEEDBACK  
VTAP  
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  
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140  
AMS2954  
ABSOLUTE MAXIMUM RATINGS (Note 1)  
Input Supply Voltage  
SHUTDOWN Input Voltage,  
Error Comparator Output  
Voltage,(Note 9)  
-0.3 to +30V  
Soldering Dwell Time, Temperature  
Wave  
Infrared  
Vapor Phase  
4 seconds, 260°C  
4 seconds, 240°C  
4 seconds, 219°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  
-65°C to +150°C  
2kV  
Max. Input Supply Voltage  
Junction Temperature Range  
(TJ) (Note 8)  
40V  
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 mA £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 mA £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 mA £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 mA £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 mA £I £ 250 mA  
0.16  
L
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140  
AMS2954  
ELECTRICAL CHARACTERISTICS (Note 2) (Continued)  
AMS2954AC  
AMS2954C  
PARAMETER  
CONDITIONS  
Units  
Min.  
Typ.  
Max.  
Min.  
Typ.  
Max.  
80  
(Note 2)  
I
I
= 100m A  
Dropout Voltage  
(Note 5)  
50  
80  
50  
mV  
mV  
L
L
= 250 mA  
380  
600  
380  
600  
I
I
= 100 mA  
Ground Current  
75  
15  
120  
20  
75  
15  
120  
20  
mA  
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
= 1mF  
L
L
L
Output Noise,  
430  
160  
100  
430  
160  
100  
mV rms  
mV rms  
mV rms  
= 200 mF  
= 13.3 mF  
10Hz to 100KHz  
(Bypass = 0.01 mF 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  
0.1  
0.1  
nA/°C  
Error Comparator  
Output Leakage Current  
V
= 30V  
0.01  
150  
1
0.01  
150  
1
mA  
OH  
V
I
= 4.5V  
Output Low Voltage  
in  
250  
250  
mV  
= 400mA  
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  
mA  
mA  
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  
mA  
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 mA and CL = 1 mF for 5V versions and 2.2mF 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, 100mA£IL£ 250 mA, TJ £ TJMAX  
.
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140  
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 j 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 ³ 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 mA 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  
V
I
OUT  
150mA  
UNREGULATED DC  
£
UNREGULATED DC  
L
+
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  
V
TAP  
330k  
W
5
+
+
-
TO CMOS  
OR TTL  
50mV  
+
ERROR  
+
1.23V  
REFERENCE  
4
1.23V  
REFERENCE  
GROUND  
GROUND  
ERROR DETECTION COMPARATOR  
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140  
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  
5.06  
160  
140  
120  
100  
80  
5V OUTPUT  
5V OUTPUT  
5V OUTPUT  
IO=250mA  
5.04  
5.02  
180  
150  
120  
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  
I = 100  
A
5V OUTPUT  
m
L
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)  
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140  
AMS2954  
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)  
Dropout Voltage  
Short Circuit Current  
Dropout Voltage  
450  
400  
350  
300  
250  
200  
150  
100  
600  
500  
400  
300  
500  
400  
300  
200  
IL= 250mA  
~
~
TJ = 25°C  
100  
50  
0
100  
0
IL= 100mA  
-75 -50 -25  
0
25 50 75 100 125 150  
-75 -50 -25  
0
25 50 75 100 125 150  
100mA  
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  
=
C = 1  
F
m
-50  
mV  
L
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  
600  
800  
INPUT VOLTAGE (V)  
TIME (ms)  
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140  
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 mF  
5
4
3
IL= 10 mA  
VIN = 8V  
VOUT = 5V  
0
-20  
-40  
-60  
CL= 10  
mF  
2
1
CL= 10 mF  
-50  
-100  
VOUT = 5V  
CL= 1 mF  
0
2
VOUT = 5V  
~
~
~
~
~
~
250  
250  
mA  
mA  
0
100  
100  
mA  
mA  
-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 (ms)  
TIME (ms)  
TIME (ms)  
Ripple Rejection  
Ripple Rejection  
Output Impedance  
90  
80  
70  
60  
50  
40  
30  
20  
90  
80  
70  
60  
50  
40  
30  
20  
10  
5
I = 100  
A
m
O
2
1
C = 1  
F
m
IO= 250mA  
IL= 1mA  
L
VIN= 6V  
VOUT = 5V  
IO= 1 mA  
IL= 0  
0.5  
0.2  
0.1  
VOUT = 5V  
CL= 1  
IL= 100mA  
m
F
CL= 1 mF  
0.05  
VIN= 6V  
VOUT = 5V  
0.02  
0.01  
IL= 10mA  
105  
105  
106  
10  
100  
1K  
10K 100K 1M  
101  
102  
103  
104  
101  
102  
103  
104  
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 mF  
IL= 250mA  
200  
100  
0
C = 220  
F
m
C = 1  
F
m
L
L
1.5  
1.0  
CL= 3.3 mF  
VIN= 6V  
VOUT= 5V  
0.01 mF  
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)  
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140  
AMS2954  
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)  
AMS2954 Maximum Rated  
Output Current  
Shutdown Treshold Voltage  
Line Regulation  
1.8  
30  
25  
300  
8 PIN MOLDED  
DIP SOLDERED  
TO PC BOARD  
20  
15  
10  
5
IL= 100  
m
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
I = 100  
A
m
L
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
4
SOT-223 PACKAGE  
SOLDERED TO PC  
BOARD  
250  
200  
2
0
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  
30  
40  
50  
0
5
15  
20  
25  
m
TIME ( s)  
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140  
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 400mA, this sink current adds to battery  
drain in a low battery condition. Suggested values range from  
100K to 1MW. The resistor is not required if this output is unused.  
A 1.0 mF 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 (2.2m 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 W 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 mF for  
currents below 10 mA or 0.1 mF 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 3.3mF (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 1mA is  
recommended.  
A 1mF 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 k 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 mF 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 mA forces an upper limit of 1.2  
MW 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 mA. Since the AMS2954 typically draws 60  
mA at no load with Pin 2 open-circuited, this is a small price to  
pay.  
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140  
AMS2954  
APPLICATION HINTS (Continued)  
IIN  
+VIN  
5V  
IL  
VIN  
IN  
OUT  
AMS2954  
+
LOAD  
*
m
F
1
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  
3.3  
F
m
SD  
GND  
R1  
.01m  
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 q(J-A), can be determined:  
Reducing Output Noise  
q(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 mF to 220 mF only decreases the noise from 430  
mV to 160 mV 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:  
q(H-A) = q(J-A) - q(J-C) - q(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:  
q(J-C) is the junction-to-case thermal resistance, which is specified as  
3°C/W maximum for the AMS2954.  
q(C-H) is the case-to-heatsink thermal resistance, which is dependent on  
the interfacing material (if used).  
q(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 q(H-A) calculated from the above listed formula.  
CBYPASS @ 1 / 2pR1 ´ 200 Hz  
or about 0.01 mF. When doing this, the output capacitor must be  
increased to 3.3 mF to maintain stability. These changes reduce  
the output noise from 430 mV to 100 mV 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. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140  
AMS2954  
TYPICAL APPLICATIONS (Continued)  
Wide Input Voltage Range Current Limiter  
+VIN  
8
+VIN  
*VOUT » VIN  
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  
0.1mF  
m
1 F  
FB  
GND  
4
7
+
R
1%  
1mF  
*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  
4.7k  
W
*SLEEP  
INPUT  
4
20mA  
*OUTPUT  
5
1
8
47kW  
k
W
470  
+VIN  
8
1
7
VOUT  
+VIN  
ERROR  
OUPU  
T
+VOUT  
AMS2954  
4
5
1
VOUT  
ERROR  
1N4001  
2
FB  
AMS2954  
200  
1%  
100  
k
k
k
W
3
SHUTDOWN  
INPUT  
GND  
4
SD  
GND  
pF  
100  
+
3.3m  
F
0.1mF  
2N3906  
360  
FB  
1N457  
W
4
7
1%  
MIN. VOLTAGE  
» 4V  
100  
W
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140  
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  
1
F
m
3.6V  
NICAD  
GND  
4
MJE2955  
2N3906  
4.7M  
+VOUT @ 2A  
10k  
W
W
8
+VIN  
27 k  
W
ERROR  
FLAG  
5
ERROR  
+
+
100mF  
EARLY WARNING  
R1  
D3  
4.7  
2.7M  
Q1  
W
AMS2954  
TANT.  
7
3
D4  
SD  
GND  
FB  
VOUT  
1%  
R2  
220  
8
2
SENSE  
VOUT  
AMS2954  
4
1
RESET  
330 k  
W
+VIN  
20k  
W
P
m
6
MAIN 5V OUTPUT  
.033  
VDD  
VTAP  
7
3
FB  
SD  
#2  
5
+
ERROR  
1mF  
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  
k
F
0.01m  
10 W  
F
1m  
SUPERTEX  
VP12C  
470k  
W
8
VOUT  
+VIN  
8
5
3
1
7
VOUT  
ERROR  
IN  
OUTPUT  
5V ± 1% @  
0 TO 1A  
470k  
W
2
1
6
7
VTAP  
SENSE  
AMS2954  
R1  
R2  
+
220mF  
AMS2954  
+
SD  
FB  
1mF  
RESET  
GND  
4
FB  
OUT  
GND  
4
k
2 W  
1MW  
0.002mF  
IQ @ 400mA  
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140  
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)  
0.165-0.180  
(4.191-4.572)  
0.060  
(1.524)  
0.390-0.415  
(9.906-10.541)  
0.045-0.055  
(1.143-1.397)  
TYP  
+0.008  
-0.004  
+0.203  
0.004  
0.330-0.370  
(8.382-9.398)  
(
)
0.102  
-0.102  
0.095-0.115  
(2.413-2.921)  
0.108  
(2.74)  
0.199-0.218  
(5.05-5.54 )  
TYP  
0.90-0.110  
(2.29-2.79)  
0.090-0.110  
(2.286-2.794)  
0.032  
(0.81)  
TYP  
0.013-0.023  
(0.330-0.584)  
M (DD3) AMS DRW# 042191R1  
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140  
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  
(0.31)  
MIN  
0.025-0.033  
(0.64-0.84)  
0.025-0.033  
(0.64-0.84)  
(SOT-223 ) AMS DRW# 042292  
0.181  
(4.60)  
NOM  
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140  
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. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140  

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