View AMS294208_4785526.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

Advanced Monolithic Systems
FEATURES
* Adjustable from 1.23V to 42V * High Accuracy Output Voltage * Extremely Low Quiescent Current * Low Dropout Voltage * Tight Load and Line Regulation * Low Temperature Coefficient * Current and Thermal Protection * Unregulated DC Positive Transients 60V * Error Flag Warning of Voltage Output Dropout * Logic Controlled Electronic Shutdown
AMS2942
HIGH VOLTAGE LOW DROPOUT REGULATOR
RoHS compliant
APPLICATIONS
* Telephone Systems * High Voltage Power Supply * Cordless Telephones * Laboratory Instrumentation * Radio Control Systems * Automotive Electronics * Avionics
GENERAL DESCRIPTION
The AMS2942 are micropower voltage regulators ideally suited for use with high voltage powered systems. This device feature very low quiescent current (typ.130A), and very low dropout voltage (typ.45mV at light loads and 380mV at 100mA). The quiescent current increases only slightly in dropout. The AMS2942 has positive transient protection up to 60V and can survive unregulated input transient up to 20V below ground. AMS2942 is designed with a tight initial voltage reference tolerance, 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 regulator in telephone applications, using the telephone line as a power source. The AMS2942 is available in a special 8-pin plastic SOIC in which pin 2 and 3 are fused together with the package paddle serving also as heat sink. An error flag output warns of a low output voltage, often due to failing voltage on input line. A logic-compatible shutdown input is available, which enables the regulator to be switched on and off. The output voltage can be programmed from 1.23V to 42V with an external pair of resistors.
ORDERING INFORMATION
PACKAGE TYPE 8 LEAD SOIC AMS2942AS AMS2942BS OPERATING TEMP. RANGE IND IND
PIN CONNECTION
8L SOIC
OUTPUT 1 GROUND 2 GROUND 3 ON/OFF 4 8 INPUT 7 FEEDBACK 6 N/C 5 ERROR
Top View
Advanced Monolithic Systems, Inc.
www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
AMS2942
ABSOLUTE MAXIMUM RATINGS (Note 1)
Input Supply Voltage Power Dissipation Junction Temperature Storage Temperature Soldering (25 Sec.) -0.3 to +50V Internally Limited +150C -65C to +150C 265C ESD 2000V
OPERATING RATINGS (Note 1)
Max. Input Supply Voltage Junction Temperature Range (TJ) (Note 8) 45V -40C to +125C
ELECTRICAL CHARACTERISTICS at VS=VOUT+1V, TA=25C, unless otherwise specified.
Parameter
Reference Voltage Reference Voltage Output Voltage Temperature Coefficient Line Regulation (Note 12) Load Regulation (Note 12) Dropout Voltage (Note 5) Ground Current Over Temperature (Note 7) (Note 10) (Note 4) 6V V 45V (Note 13)
IN
Conditions
(Note 2) Min. 1.22 1.19
AMS2942A
Typ. 1.235 Max. 1.25 1.27 20 0.05 0.05 50 380 120 8 160 0.05 430 160 100 40 80 0.2 0.2 80 450 180 12 200 0.2 Min. 1.21 1.185
AMS2942B
Typ. 1.235 Max. 1.26 1.285 50 0.1 0.1 50 380 120 8 160 0.05 430 160 100 40 50 0.1 80 0.4 0.4 80 450 180 12 200 0.2
Units
V V ppm/C % % mV mV A mA mA %/W V rms V rms V rms nA ppm/C nA/C
100 A I 100 mA
L
I = 100 A
L L
I = 100 mA I = 100 A
L L
I = 100 mA Current Limit Thermal Regulation Output Noise, 10Hz to 100KHz V
OUT
=0
(Note 11) C = 1F C = 200 F C = 13.3 F (Bypass = 0.01 F pins 7 to 1)
L L L
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) Low (Regulator ON) High (Regulator OFF) VS = 2.5V V = 42V
S
( Note 10)
20 0.1
V
OH IN
= 42V
OL
0.05 = 400A 40 150 60 75 15
2 250 40 95
0.05 150 60 75 15
2 250
A mV mV
V = 4.5V, I (Note 6) (Note 6) (Note 6)
95
mV mV
1.3 2.5 30 600 15
0.7 2.5 60 850 50
1.3 30 600 15
0.7 60 850 50
V V A A A
(Note 9)
Advanced Monolithic Systems, Inc.
www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
AMS2942
BLOCK DIAGRAM AND TYPICAL APPLICATIONS
AMS2942
39V to 45V UNREGULATED DC VO = 38V + FROM CMOS OR TTL SHUTDOWN + ERROR AMPLIFIER 298k FEEDBACK 10k ERROR GROUND TO CMOS OR TTL INPUT OUTPUT + 10F 330k
+ 50mV +
+
1.23V REFERENCE
ERROR DETECTION COMPARATOR
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. Limits appearing in boldface type apply over the entire junction temperature range for operation. Limits appearing in normal type apply for TA = TJ = 25C, 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 Vin42V, 100AIL 100 mA, TJ TJMAX. Note 8: The junction-to-ambient thermal resistance is 120C/W for the molded plastic SO-8 (S), when the package is soldered directly to the PCB. Note 9: VSHUTDOWN 2.5V, VIN 42V, VOUT =0. Note 10: Output or reference voltage temperature coefficients defined as the worst case voltage change divided by the total temperature range. Note 11: 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 =42V (1.25W pulse) for T =10 ms. Note 12: 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 13: Line regulation 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.
Advanced Monolithic Systems, Inc.
www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
AMS2942
TYPICAL PERFORMANCE CHARACTERISTICS
Quiescent Current 10 QUIESCENT CURRENT ( A) GROUND CURRENT (mA) 160
Quiescent Current 10 QUIESCENT CURRENT (mA)
Quiescent Current
140 120 100 80
IL= 0 IL= 1 mA
1
9
VIN= VOUT+1V IL= 100mA
0.1
60 40 20 0 0 1 23 4 56 INPUT VOLTAGE (V) 7 8
8
0.01 0.1
1 10 LOAD CURRENT (mA)
100
7 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE ( C)
Short Circuit Current 170 SHORT CIRCUIT CURRENT ( mA) DROPOUT VOLTAGE (mV) 160 150 140 130 120 110 100 -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
Dropout Voltage
IL= 100mA
~ ~
100 50
IL= 100A
TJ = 25C
100 0 100A
0 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE ( C)
1mA 10mA OUTPUT CURRENT
100mA
Minimum Operating Voltage MINIMUM OPERATING VOLTAGE (V) 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
Feedback Bias Current 50 FEEDBACK CURRENT ( A) 0 -50
Feedback Pin Current
PIN 7 DRVEN BY EXTERNAL SOURCE (REGULATOR RUN OPEN LOOP)
10 0 -10
TA = 125C
-100 -150
TA = 25C
-20 -30 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE ( C)
-200
TA = -55C
-250 -2.0
0 0.5 -1.5 -1.0 -0.5 FEEDBACK VOLTAGE (V)
1.0
Advanced Monolithic Systems, Inc.
www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
AMS2942
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
Enable Transient
CL= 1 F
IL= 10 mA VIN = 8V CL= 10 F
CL= 10 F
LOAD CURRENT
LOAD CURRENT
~ ~
100 mA 100 A 0 1 2 3 TIME (ms)
~ ~
100 mA 100 A 0 4 8 12 TIME (ms) 16 20
SHUTDOWN PIN VOLTAGE (V) RIPPLE REJECTION (dB)
CL= 1 F
~ ~
4
5
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 IO= 100mA IO= 1 mA
Ripple Rejection 90 90 80 70 60 50 40 30
Ripple Rejection
IO= 100A
RIPPLE REJECTION (dB)
80 70 60 50 40 30 20 10 1
CL= 1 F VIN= 6V VOUT = 5V IL= 100A IL= 0
IL= 1mA
CL= 1 F VIN= VOUT+1V
IL= 10mA
10 2
10 5 10 3 10 4 FREQUENCY (Hz)
10 6
20 10 1
10 2
10 5 10 3 10 4 FREQUENCY (Hz)
10 6
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 VOUT HYSTERESIS 50k RESISTOR TO EXTERNAL 5V SUPPLY VOUT= 5V
Error Comparator Sink Current 2.5 2.0 1.5
TA = 25C TA = 125C
INPUT OUTPUT VOLTAGE VOLTAGE CHANGE
SINK CURRENT (mA)
100 mV 50 mV 0 -50 mV 8V 6V 4V
Line Transient Response
CL= 1F IL= 1mA
1.0
TA = -55C
~ ~
VOUT= 5V
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
Advanced Monolithic Systems, Inc.
www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
AMS2942
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. 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. At voltages below 5V the error amplifier operates at lower gains so that more output capacitance is needed. For the worst-case situation of a 100mA load at 1.23V output (Output shorted to Feedback) a 3.3F (or greater) capacitor should be used. A 1F tantalum or aluminum electrolytic capacitor should be placed between input to 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 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 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. This trip level remains "5% below normal" regardless of the programmed output voltage. 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 AMS2942 input is ramped up and down. Since the dropout voltage is load dependent the input voltage trip point will vary with the load current. The output voltage trip point does not vary with load. The error comparator has an opencollector output which requires an external pullup 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. Suggested values range from 100K to 1M. The resistor is not required if error flag terminal is unused. Setting the Output Voltage The AMS2942 it may be programmed for any output voltage between its 1.235V reference and its 42V 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%.
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. Noise could 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.
Advanced Monolithic Systems, Inc.
www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
AMS2942
APPLICATION HINTS (Continued)
+VIN
OUTPUT VOLTAGE
4.75V
100k
8 +VIN 5 ERROR* 4 1 VOUT 1.2 30V
ERROR*
ERROR OUPUT **SHUTDOWN INPUT
VOUT
AMS2942 SD GND 3 2 FB 7 R1 1.23 V R2
INPUT VOLTAGE 1.3V
5V
*+ .01 F
3.3F
VREF
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.
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.
PACKAGE DIMENSIONS inches (millimeters) unless otherwise noted.
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
Advanced Monolithic Systems, Inc.
www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723

▲Up To Search▲

Price & Availability of AMS294208

	To Download AMS294208 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .