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Advanced Monolithic Systems
FEATURES
* 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 (1F) for Stability * Unregulated DC Positive Transients 60V * 1.24V to 29V Programmable Output * Error Flag Warning of Voltage Output Dropout * Logic Controlled Electronic Shutdown
AMS2954
250mA LOW DROPOUT VOLTAGE REGULATOR
APPLICATIONS
* 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)
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.75A), 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
TAB IS GND 3 2 1 1 2 3 OUTPUT GND INPUT
PIN CONNECTIONS
8L SOIC/ 8L PDIP
OUTPUT 1 SENSE 2 SHUTDOWN 3 GROUND 4 8 INPUT 7 FEEDBACK 6 VTAP 5 ERROR
TAB IS GND INPUT GND OUTPUT
TO-252 FRONT VIEW
3 2 1 OUTPUT
3L TO-263 FRONT VIEW
TAB IS GND 3 2 1 OUTPUT GND INPUT
INPUT
Top View 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) FEEDBACK Input Voltage (Note 9) (Note 10) Power Dissipation Junction Temperature Storage Temperature ESD -0.3 to +30V Soldering Dwell Time, Temperature Wave 4 seconds, 260C Infrared 4 seconds, 240C Vapor Phase 4 seconds, 219C
-1.5 to +30V
OPERATING RATINGS (Note 1)
Internally Limited +150C -65C to +150C 2kV Max. Input Supply Voltage Junction Temperature Range (TJ) (Note 8) AMS2954AC-X AMS2954C-X 40V
-40C to +125C
ELECTRICAL CHARACTERISTICS at Vs=Vout+1V, Ta=25C, unless otherwise noted.
AMS2954AC Parameter
2.5 V Versions (Note 16) Output Voltage -25C TJ 85C Full Operating Temperature Range 100 A IL 250 mA TJ TJMAX TJ = 25C (Note 3) 2.488 2.475 2.470 2.463 2.5 2.5 2.5 2.5 2.512 2.525 2.530 2.537 2.475 2.450 2.440 2.448 2.5 2.5 2.5 2.5 2.525 2.550 2.560 2.562 V V V V
AMS2954C
Min. Typ. Max.
Conditions
(Note 2) Min. Typ. Max.
Units
Output Voltage 3.0 V Versions (Note 16) Output Voltage
TJ = 25C (Note 3) -25C TJ 85C Full Operating Temperature Range 100 A IL 250 mA TJ TJMAX
2.985 2.970 2.964 2.958
3.0 3.0 3.0 3.0
3.015 3.030 3.036 3.042
2.970 2.955 2.940 2.928
3.0 3.0 3.0 3.0
3.030 3.045 3.060 3.072
V V V V
Output Voltage 3.3 V Versions (Note 16) Output Voltage
TJ = 25C (Note 3) -25C TJ 85C Full Operating Temperature Range 100 A IL 250 mA TJ TJMAX
3.284 3.267 3.260 3.254
3.3 3.3 3.3 3.3
3.317 3.333 3.340 3.346
3.267 3.251 3.234 3.221
3.3 3.3 3.3 3.3
3.333 3.350 3.366 3.379
V V V V
Output Voltage 5 V Versions (Note 16) Output Voltage
TJ = 25C (Note 3) -25C TJ 85C Full Operating Temperature Range 100 A IL 250 mA TJ TJMAX
4.975 4.95 4.94 4.925
5.0 5.0 5.0 5.0
5.025 5.050 5.06 5.075
4.95 4.925 4.90 4.88
5.0 5.0 5.0 5.0
5.05 5.075 5.10 5.12
V V V V
Output Voltage All Voltage Options Output Voltage Temperature Coefficient Line Regulation (Note 14) Load Regulation (Note 14)
(Note 12) (Note 4) 6V Vin 30V (Note 15) 100 A IL 250 mA
20 0.03 0.04
100 0.1 0.16
50 0.04 0.1
150 0.2 0.2
ppm/C % %
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AMS2954
ELECTRICAL CHARACTERISTICS (Note 2) (Continued)
AMS2954AC PARAMETER
Dropout Voltage (Note 5) Ground Current
AMS2954C
Min. Typ. 50 380 75 15 200 0.05 430 160 100 AMS2954C 1.25 1.27 1.21 1.185 40 1.235 1.26 1.285 60 50 V V nA ppm/C Max. 80 600 120 20 500 0.2
CONDITIONS
(Note 2)
IL = 100 A IL = 250 mA IL = 100 A IL = 250 mA Vout = 0 (Note 13) CL = 1F CL = 200 F Min. Typ. 50 380 75 15 200 0.05 430 160 100 AMS2954AC 1.22 Over Temperature (Note 7) 1.19 40 20 ( Note 12 ) 0.1 0.1 nA/C 1.235 Max. 80 600 120 20 500 0.2
Units
mV mV A mA mA %/W V rms V rms V rms
Current Limit Thermal Regulation Output Noise, 10Hz to 100KHz
CL = 13.3 F (Bypass = 0.01 F pins 7 to 1)
8-Pin Versions only Reference Voltage Reference Voltage Feedback Pin Bias Current Reference Voltage Temperature Coefficient Feedback Pin Bias Current Temperature Coefficient Error Comparator Output Leakage Current Output Low Voltage Upper Threshold Voltage Lower Threshold Voltage Hysteresis Shutdown Input Input logic Voltage Shutdown Pin Input Current (Note 3) Regulator Output Current in Shutdown (Note 3) V
OH
60
= 30V
0.01 150 40 60 75 15
1 250 40 95
0.01 150 60 75 15
1 250
A mV mV
Vin = 4.5V IOL = 400A (Note 6) (Note 6) (Note 6) Low (Regulator ON) High (Regulator OFF) Vs = 2.4V Vs = 30V (Note 11)
95
mV mV
1.3 2 30 450 3
0.7 2 50 600 10
1.3 30 450 3
0.7 50 600 10
V V A A A
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 A and CL = 1 F for 5V versions and 2.2F 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 = T J = 25C 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 Vin30V, 100AIL 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:60C/W for the TO-220 (T), 73C/W for the TO-263 (M), 80C/W for the TO-252 (D), 90C/W for the SOT-223 (with package soldering to copper area over backside ground plane or internal power plane JA can vary from 46C/W to >90C/W depending on mounting technique and the size of the copper area), 105C/W for the molded plastic DIP (P) and 160C/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 150C for IL = 1 mA. For IL = 100 A and TJ = 125C, 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
UNREGULATED DC
UNREGULATED DC
VOUT I L 150mA 8 INPUT 1 OUTPUT 2 + SENSE ERROR AMPLIFIER 6 VTAP 5 ERROR 4 GROUND + 330k TO CMOS OR TTL SEE APPLICATION HINTS
+
INPUT OUTPUT + ERROR AMPLIFIER + SEE APPLICATION HINTS VOUT IL 150mA
+
7 FEEDBACK
FROM CMOS OR TTL
3 SHUTDOWN + 50mV +
-
+
+
1.23V REFERENCE
GROUND
1.23V REFERENCE
ERROR DETECTION COMPARATOR
Advanced Monolithic Systems, Inc.
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AMS2954
TYPICAL PERFORMANCE CHARACTERISTICS
Quiescent Current 20 GROUND CURRENT (mA) OUTPUT VOLTAGE (V) 6
Dropout Characteristics
5V OUTPUT
Input Current 250 225 INPUT CURRENT (A) 200 175 150 125 100 75 50 25 0
RL= 5V OUTPUT
5 4 3
IO=250mA IO=1mA
10
1
2 1 0 1 3 4 5 2 INPUT VOLTAGE (V) 6
0.1
1
50 100 150 200 LOAD CURRENT (mA)
250
0
0
1
2345678 INPUT VOLTAGE (V)
9 10
Input Current 270 240 210 180 150 120 90 75 60 45 30 15 0 5.06
5V OUTPUT
Temperature Drift of 3 Representative Units 160
5V OUTPUT
Quiescent Current
5V OUTPUT
OUTPUT VOLTAGE (V)
IO=250mA
INPUT CURRENT (mA)
5.04 5.02 5.0 4.98 4.96
0.2%
QUIESCENT CURRENT (A)
140 120 100 80
IL= 0mA IL= 1 mA
60 40 20 0 0 1 234567 INPUT VOLTAGE (V) 8
0
1
2345678 INPUT VOLTAGE (V)
9 10
4.94 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE ( C)
Quiescent Current 120 QUIESCENT CURRENT (mA) QUIESCENT CURRENT (A)
5V OUTPUT
Quiescent Current 35
VIN= 6V
Quiescent Current 24 QUIESCENT CURRENT (mA)
5V OUTPUT
110 100 90 80 70 60
IL= 100A
5V OUTPUT
30 25 20 15 10 5 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE ( C)
VIN= 6V IL= 250mA
21 18 15 12 9 6 3 0 0 1 234567 INPUT VOLTAGE (V) 8
IL= 250mA
50 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE ( C)
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AMS2954
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
Short Circuit Current 450 SHORT CIRCUIT CURRENT (mA) DROPOUT VOLTAGE (mV) 400 350 300 250 200 150 100 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE ( C) 600 500 400 300
Dropout Voltage 500 DROPOUT VOLTAGE (mV) 400 300 200 100
Dropout Voltage
IL= 250mA
~ ~
100 50
IL= 100A
TJ = 25C
0 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE ( C)
0 100A
10mA 100mA OUTPUT CURRENT
250mA
MINIMUM OPERATING VOLTAGE (V)
AMS2954 Minimum Operating Voltage 2.2 2.1 2.0 1.9 1.8 1.7 1.6 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE ( C) BIAS CURRENT (nA) 20
AMS2954 Feedback Bias Current 50 FEEDBACK CURRENT (A) 0 -50
AMS2954 Feedback Pin Current
PIN 7 DRVEN BY EXTERNAL SOURCE (REGULATOR RUN OPEN LOOP)
10 0 -10 -20 -30 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE ( C)
TA = 125C
-100 -150 -200
TA = -55C TA = 25C
-250 -2.0
0 0.5 -1.5 -1.0 -0.5 FEEDBACK VOLTAGE (V)
1.0
AMS2954 Error Comparator Output 9 8 ERROR OUTPUT (V) 7 6 5 4 3 2 1 0 0 1 234567 INPUT VOLTAGE (V) 8
50k RESISTOR TO V OUT HYSTERESIS 50k RESISTOR TO EXTERNAL 5V SUPPLY V OUT= 5V
AMS2954 Comparator Sink Current
TA = 125C
SINK CURRENT (mA)
2.0 1.5 1.0
INPUT OUTPUT VOLTAGE VOLTAGE CHANGE
2.5
100 mV 50 mV 0 -50 mV 8V 6V 4V
Line Transient Response
TA = 25C
CL= 1F IL= 1mA
~ ~
VOUT= 5V
TA = -55C
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)
0
200 400 TIME (s)
600
800
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AMS2954
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
Load Transient Response 250 200 150 100 50 0 -50 -100 80 60 40 20 0 -20 -40 -60 OUTPUT VOLTAGE CHANGE (mV) OUTPUT VOLTAGE CHANGE (mV)
Load Transient Response OUTPUT VOLTAGE (V) 7 6 5 4 3 2 1 0 2
AMS2954 Enable Transient
CL= 1 F
CL= 10 F VOUT = 5V
CL= 10 F
IL= 10 mA VIN = 8V VOUT = 5V
LOAD CURRENT
250 mA 100 A 0 1 2 3 TIME (ms) 4 5
LOAD CURRENT
~ ~
~ ~
250 mA 100 A 0 4 8 12 TIME (ms) 16 20
SHUTDOWN PIN VOLTAGE (V) RIPPLE REJECTION (dB)
CL= 1 F V OUT = 5V
~ ~
0 -2 -100 0 100 200 300 400 500 600 700 TIME (s)
Output Impedance 10 5 OUPUT IMPEDANCE () 2 1 0.5 0.2 0.1 0.05 0.02 0.01 10 100 1K 10K 100K FREQUENCY (Hz) 1M
VOUT = 5V CL= 1 F
Ripple Rejection 90 90 80 70 60 50 40 30
Ripple Rejection
IO= 100 A
RIPPLE REJECTION (dB)
80 70 60 50 40 30 20 101
CL= 1 F VIN= 6V V OUT = 5V IL= 100A IL= 0
IO= 250mA IO= 1 mA
IL= 1mA
CL= 1 F VIN= 6V VOUT = 5V
IL= 10mA
10
2
10 10 FREQUENCY (Hz)
3
4
105
106
20 101
10
2
105 104 103 FREQUENCY (Hz)
106
Ripple Rejection 80 RIPPLE REJECTION (dB) 70 60 50 40 30 20 10 101 102 105 103 104 FREQUENCY (Hz) 106
CL= 1F VIN= 6V VOUT= 5V
AMS2954 Output Noise 3.5 VOLTAGE NOISE SPECTRAL DENSITY(mV/Hz)
IL= 250mA
AMS2954 Divider Resistance 400 PIN 2 TO PIN 4 RESISTANCE (k) 105
IL= 50mA
5V OUTPUT
3.0 2.5 2.0 1.5 1.0 0.5 0.0
0.01 F BYPASS PIN 1 TO PIN 7 CL= 3.3 F CL= 220 F CL= 1 F
IL= 250mA
300
200
100
102
103 104 FREQUENCY (Hz)
0 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE ( C)
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AMS2954
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
Shutdown Treshold Voltage SHUTDOWN TRESHOLD VOLTAGE (V) OUTPUT VOLTAGE CHANGE (V) 1.8 1.6 1.4 1.2 1.0 0.8 0.6 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE ( C)
REGULATOR ON REGULATOR OFF
Line Regulation 30 25 20 15 10 5 0 300 OUTPUT CURRENT (mA)
IL= 100A TJ = 150 C IL= 1mA
AMS2954 Maximum Rated Output Current
8 PIN MOLDED DIP SOLDERED TO PC BOARD TJMAX= 125 C VOUT = 5V TA= 25 C TA= 50 C
250 200 150 100 50 0
~ ~
10 5 0 -5 -10
TJ = 125 C IL= 100A
TA= 85 C
5
10 15 20 25 INPUT VOLTAGE (V)
30
0
10 5 15 20 INPUT VOLTAGE (V)
25
30
AMS2954 Maximum Rated Output Current
SOT-223 PACKAGE SOLDERED TO PC BOARD TJMAX= 125 C
Thermal Response POWER OUTPUT VOLTAGE DISSIPATION (W) CHANGE (mV) 5 4 2 0 -2 1 0 -1 0 10 20 30 TIME (s) 40 50
300 OUTPUT CURRENT (mA) 250 200 150
TA= 25 C
100 50 0 0 10 5 15 20 INPUT VOLTAGE (V) 25 30
TA= 85 C
~ ~
1.25W
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AMS2954
APPLICATION HINTS
External Capacitors A 1.0 F 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 (2.2 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 -30C, so solid tantalums are recommended for operation below -25C. The important parameters of the capacitor are an ESR of about 5 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 F for currents below 10 mA or 0.1 F 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 3.3F (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 1A is recommended. A 1F 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 F 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 400A, this sink current adds to battery drain in a low battery condition. Suggested values range from 100K to 1M. The resistor is not required if this output is unused.
OUTPUT VOLTAGE 4.75V
ERROR*
INPUT VOLTAGE 1.3V
5V
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 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 x (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 A forces an upper limit of 1.2 M 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 A. Since the AMS2954 typically draws 60 A at no load with Pin 2 open-circuited, this is a small price to pay.
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AMS2954
APPLICATION HINTS (Continued)
+V IN IIN V IN * 100k ERROR OUPUT **SHUTDOWN INPUT 5 ERROR* 3 8 +V IN VOUT 1 VOUT 1.2 30V GND IG IN OUT + 1F AMS2954 5V IL LOAD
IIN = IL +IG
R1 * .01 F + 3.3F
AMS2954 SD GND 4 FB 7 1.23 V R2
* See external capacitors PTotal = (V IN -5)IL +(V IN)IG
V REF
FIGURE 2. Adjustable Regulator
*See Application Hints. Vout = VREF x (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. 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 F to 220 F only decreases the noise from 430 V to 160 V 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 / 2R1 x 200 Hz or about 0.01 F. When doing this, the output capacitor must be increased to 3.3 F to maintain stability. These changes reduce the output noise from 430 V to 100 V 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. 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.
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 (J-A), can be determined: (J-A) = TR(max) /P(max) If the value obtained is 60C/W or higher, the regulator may be operated without an external heatsink. If the calculated value is below 60C/W, an external heatsink is required. To calculate the thermal resistance of this heatsink use the formula: (H-A) = (J-A) - (J-C) - (C-H) where: (J-C) is the junction-to-case thermal resistance, which is specified as 3C/W maximum for the AMS2954. (C-H) is the case-to-heatsink thermal resistance, which is dependent on the interfacing material (if used). (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 (H-A) calculated from the above listed formula.
Output Isolation
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.
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
+V IN 8 +V IN ERROR OUPUT 5 ERROR V OUT 1 *VOUT V
AMS2954 SHUTDOWN 3 SD INPUT GND 4 FB 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 30V
5Volt Current Limiter
LOAD 5V BUS 8 VIN VOUT 1 AMS2954 +V IN AMS2954 -5.0 V OUT 0.1F FB 7 R 1% + GND 1F 4 *VOUT 5V
SHUTDOWN 3 SD INPUT GND
1F
*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
+V IN *SLEEP INPUT 47k 8 ERROR OUPU T +VIN 5 ERROR V OUT 1 +V OUT C - MOS GATE
Open Circuit Detector for 4 to 20mA Current Loop
+5V 4.7k 4 20mA 1 8 *OUTPUT 5
470k
+V IN V OUT AMS2954 1N4001 200k FB GND 3.3F 0.1F 4 1N457 360 7 2 1 4
SHUTDOWN 3 SD INPUT
AMS2954 100pF FB 7 2N3906 4
1%
+
GND
100k 1% 100k
MIN. VOLTAGE 4V
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
CURRENT LIMIT SECTION
Regulator with Early Warning and Auxiliary Output
+VIN 8 +VIN 6 VTAP 2 SENSE VOUT 1 D2 5V MEMORY SUPPLY
+V IN = V OUT +.5V
D1
680
0.05
470 7 2N3906 4.7M 8 +V IN ERROR AMS2954 3 SD GND 4 FB VOUT 1 5 ERROR FLAG 7 R1 1% R2 Q1 6 7 3 + + 4.7 TANT. 100F 2.7M 10k MJE2955 +V OUT @ 2A
FB
AMS2954 #1 5 ERROR GND 4
+ 1F
20 3.6V NICAD
27 k D3 D4 EARLY WARNING
220 20k .033
8 +VIN VTAP
2 SENSE VOUT
330 k MAIN 5V OUTPUT
RESET P VDD
FB AMS2954 #2 5 SD ERROR GND 4
+
1F
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
UNREGULATE D INPUT 1F 10k 0.01F SUPERTEX VP12C 8 IN 6 VTAP SENSE AMS2954 7 FB GND 4 OUT 1 2k IQ 400A 2 + 220F OUTPUT 5V 1% @ 0 TO 1A
Latch Off When Error Flag Occurs
+V IN
470k 5 470k
8 +V IN 1 VOUT ERROR AMS2954 3 SD FB GND 4 R2 7 R1 + 1F V OUT
RESET
1
0.002F
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)
0.390-0.415 (9.906-10.541)
0.147-0.155 (3.734-3.937) DIA 0.230-0.270 (5.842-6.858) 0.570-0.620 (14.478-15.748)
0.165-0.180 (4.191-4.572) 0.045-0.055 (1.143-1.397)
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)
0.390-0.415 (9.906-10.541)
0.060 (1.524) TYP
0.165-0.180 (4.191-4.572)
0.045-0.055 (1.143-1.397)
0.330-0.370 (8.382-9.398)
0.004 +0.008 -0.004
(0.102 +0.203 )
-0.102 0.108 (2.74) TYP 0.095-0.115 (2.413-2.921) 0.90-0.110 (2.29-2.79) 0.013-0.023 (0.330-0.584)
0.199-0.218 (5.05-5.54 ) 0.090-0.110 (2.286-2.794) 0.032 (0.81) TYP
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)
0.020-0.030 (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) 0.033-0.037 (0.838-0.939) 45.0 0.057-0.067 (0.144-0.170) DIA
0.085-0.095 (2.159-2.413)
0.030-0.034 (0.762-0.863) 0.038-0.042 (0.965-1.066)
0.023-0.027 (0.584-0.685) 0.175-0.180 (4.191-4.445)
7.0
0.235-0.245 (5.969-6.223)
0.025 (0.635) TYP 0.088-0.092 (2.235-2.336)
0.099-0.103 (2.514-2.615) 0.030 (0.762) TYP
0.038 (0.965) TYP
0.038-0.042 (0.965-1.066) 0.0240.002 (0.6100.0508)
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)
0.090 (2.29) NOM
0.033-0.041 (0.84-1.04)
10-16 0.071 (1.80) MAX 10 MAX 0.010-0.014 (0.25-0.36) 10-16 0.025-0.033 (0.64-0.84) 0.181 (4.60) NOM 0.012 (0.31) MIN 0.025-0.033 (0.64-0.84)
(SOT-223 ) AMS DRW# 042292
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
0.053-0.069 (1.346-1.752) 0.004-0.010 (0.101-0.254) 0.008-0.010 (0.203-0.254)
0.010-0.020 x 45 (0.254-0.508) 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
0.2550.015* (6.4770.381)
1
2
3
4
0.045-0.065 (1.143-1.651)
0.1300.005 (3.3020.127)
0.300-0.325 (7.620-8.255)
0.065 (1.651) TYP 0.005 (0.127) MIN 0.1000.010 (2.5400.254) 0.125 (3.175) MIN 0.0180.003 (0.4570.076) 0.015 (0.380) MIN
0.009-0.015 (0.229-0.381) 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.
6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140

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