The AMS2942 are micropower voltage regulators ideally suited for use with high voltage powered systems. This device
feature very low quiescent current (typ.130µA), 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 Dwell Time, Temperature
Wave
Infrared
Vapor Phase
-0.3 to +50V
Internally Limited
+150°C
-65°C to +150°C
4 seconds, 260°C
4 seconds, 240°C
4 seconds, 219°C
ESD
2000V
OPERATING RATINGS
(Note 1)
Max. Input Supply Voltage
Junction Temperature Range
(T
J
) (Note 8)
45V
-40°C to +125°C
ELECTRICAL CHARACTERISTICS
at V
S
=V
OUT
+1V, T
A
=25°C, 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)
1.22
1.19
Min.
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
µA
mA
mA
%/W
µV
rms
µV
rms
µV
rms
nA
ppm/°C
nA/°C
100
µA ≤I ≤
100 mA
L
I = 100µ A
L
L
I = 100 mA
I = 100
µA
L
L
I = 100 mA
Current Limit
Thermal Regulation
Output Noise,
10Hz to 100KHz
V
OUT
=0
(Note 11)
C = 1µF
C = 200
µF
C = 13.3
µF
(Bypass = 0.01
µF
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)
V
S
= 2.5V
V = 42V
S
( Note 10)
20
0.1
V
OH
IN
= 42V
OL
0.05
= 400µA
40
150
60
75
15
2
250
40
95
0.05
150
60
75
15
2
250
µA
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
µA
µA
µA
(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
V
O
= 38V
+
FROM
CMOS
OR TTL
SHUT-
DOWN
+
-
ERROR
AMPLIFIER
298kΩ
FEED-
BACK
10kΩ
ERROR
GROUND
TO CMOS
OR TTL
INPUT
OUTPUT
+
10µF
330kΩ
+
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 V
IN
= ( V
ONOM
+1)V, I
L
= 100
µA
and C
L
= 1
µF.
Limits appearing in
boldface
type apply over the
entire junction temperature range for operation. Limits appearing in normal type apply for T
A
= T
J
= 25°C, V
SHUTDOWN
≤
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
V
IN
= ( V
ONOM
+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 V
out
as V
out
is varied, with the dropout warning occurring at typically 5% below nominal, 7.5% guaranteed.
Note 7:
V
ref
≤V
out
≤
(V
in
- 1V), 2.3
≤V
in
≤42V,
100µA≤I
L
≤
100 mA, T
J
≤
T
JMAX
.
Note 8:
The junction-to-ambient thermal resistance is 120°C/W for the molded plastic SO-8 (S), when the package is soldered directly to the PCB.
Note 9:
V
SHUTDOWN
≥
2.5V, V
IN
≤
42V, V
OUT
=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 V
IN
=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 150°C for I
L
= 1 mA. For I
L
= 100
µA
and T
J
= 125°C, line regulation is guaranteed by design to 0.2%. See typical
performance characteristics for line regulation versus temperature and load current.
