Datasheet AMS2954 Datasheet (Advanced Monolithic Systems)

http://www.BDTIC.com/AMS

Advanced AMS2954

Monolithic 250mA LOW DROPOUT VOLTAGE REGULATOR
Systems

RoHS compliant

FEATURES APPLICATIONS

• 2.5V, 3.0V, 3.3V and 5.0V Versions • Battery Powered Systems

• High Accuracy Output Voltage • Portable Consumer Equipment

• Extremely Low Quiescent Current • Cordless Telephones

• Low Dropout Voltage • Portable (Notebook) C omputers

• Extremely Tight Load and Line Regulation • Portable Instrumentation

• Very Low Temperature Coefficient • Radio Control Systems

• Current and Thermal Limiting • Automotive Electronics

• Needs Minimum Capacitance (1µF) for Stability • Avionics

• Unregulated DC Positive Transients 60V • Low-Power Voltage Reference

OUTPUT

INPUT

8 LEAD SOIC 8 LEAD PDIP

3L TO-220 FRONT VIEW

TAB IS

GND

3L TO-263 FRONT VIEW

TAB IS

GND

TEMP.

3
2
1

3
2

1

OUTPUT

GND
INPUT

OUTPUT
GND

INPUT

RANGE

ADDITIONAL FEATURES (ADJ ONLY)

• 1.24V to 29V Programmable Output

• Error Flag Warning of Voltage Output Dropout

• Logic Controlled Electronic Shutdown

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 sligh tly 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 inpu t enables the regu lator 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

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

PIN CONNECTIONS

8L SOIC/ 8L PDIP

1

OUTPUT

2

SENSE

SHUTDOWN

GROUND

3
4

8

INPUT

7

FEEDBACK

6V

TAP

5

ERROR

1

2

3

INPUT GND OUTPUT

TO-252 FRONT VIEW

TAB IS

GND

3
2
1

Advanced Monolithic Systems, Inc.

http://www.BDTIC.com/AMS

AMS2954

ABSOLUTE MAXIMUM RATINGS (Note 1)

Input Supply Voltage -0.3 to +30V Soldering Temperature (25 sec)
SHUTDOWN Input Voltage,
Error Comparator Output
Voltage,(Note 9)
FEEDBACK Input Voltage -1.5 to +30V
(Note 9) (Note 10)

OPERATING RATINGS (Note 1)

Power Dissipation Internally Limited
Junction Temperature
Storage Temperature

-65°C to +150°C

+150°C

ESD 2kV (T
AMS2954AC-X

Max. Input Supply Voltage 40V
Junction Temperature Range

) (Note 8)

J

-40°C to +125°C

AMS2954C-X

ELECTRICAL CHARACTERISTICS at V

Parameter

2.5 V Versions (Note 16)

Output Voltage

Output Voltage

3.0 V Versions (Note 16)
Output Voltage

Output Voltage

3.3 V Versions (Note 16)
Output Voltage

Output Voltage

5 V Versions (Note 16)
Output Voltage

Output Voltage

All Voltage Options
Output Voltage

Temperature Coefficient
Line Regulation (Note 14)

Load Regulation (Note 14)

Conditions

(Note 2)

TJ = 25°C (Note 3)

-25°C ≤TJ ≤85°C
Full Operating Temperature

Range
100 µA ≤IL ≤250 mA

TJ ≤T

TJ = 25°C (Note 3)

-25°C ≤TJ ≤85°C
Full Operating Temperature

Range
100 µA ≤IL ≤250 mA

TJ ≤T

TJ = 25°C (Note 3)

-25°C ≤TJ ≤85°C
Full Operating Temperature

Range
100 µA ≤IL ≤250 mA

TJ ≤T

TJ = 25°C (Note 3)

-25°C ≤TJ ≤85°C
Full Operating Temperature

Range
100 µA ≤IL ≤250 mA

TJ ≤T

(Note 12) (Note 4)
6V ≤Vin ≤30V (Note 15)

100 µA ≤IL ≤ 250 mA

JMAX

JMAX

JMAX

JMAX

=Vout+1V, Ta=25°C, unless otherwise noted.

s

AMS2954AC

Min. Typ. Max.

2.488

2.475

2.470

2.463

2.985

2.970

2.964

2.958

3.284

3.267

3.260

3.254

4.975

4.95

4.94

4.925

2.5

2.5

2.5

2.5

3.0

3.0

3.0

3.0

3.3

3.3

3.3

3.3

5.0

5.0

5.0

5.0

20 100 50 150

0.03 0.1 0.04 0.2 %

0.04 0.16 0.1 0.2 %

2.512

2.525

2.530

2.537 2.448

3.015

3.030

3.036

3.042 2.928

3.317

3.333

3.340

3.346 3.221

5.025

5.050

5.06

5.075 4.88

AMS2954C

Min. Typ. Max.

2.475

2.450

2.440

2.970

2.955

2.940

3.267

3.251

3.234

4.95

4.925

4.90

2.5

2.5

2.5

2.5

3.0

3.0

3.0

3.0

3.3

3.3

3.3

3.3

5.0

5.0

5.0

5.0

Advanced Monolithic Systems, Inc.

2.525

2.550

2.560

2.562

3.030

3.045

3.060

3.072

3.333

3.350

3.366

3.379

5.05

5.075

5.10

5.12

265°C

Units

V
V
V

V

V
V
V

V

V
V
V

V

V
V
V

V

ppm/°C

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AMS2954

ELECTRICAL CHARACTERISTICS (Note 2) (Continued)

A

Units

mV
mV

µA

mA

µV rms
µV rms
µV rms

V

µA

V
V

µA
µA

µA

= TJ =

PARAMETER

Dropout Voltage
(Note 5)

Ground Current

Current Limit

Thermal Regulation (Note 13) 0.05 0.2 0.05 0.2 %/W
Output Noise,

10Hz to 100KHz

8-Pin Versions only

Reference Voltage 1.22 1.235 1.25 1. 21 1.235 1.26 V
Reference Voltage Over Temperature (Note 7)

Feedback Pin Bias Current 40 60 40 60 nA

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)

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
versions. Limits appearing in boldface type apply over the entire junction temperature range for operation. Limits appearing in normal type apply for T
25°C Additional conditions for the 8-pin versions are FEEDBACK tied to V

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

= ( V

IN

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
Note 7: V

+1)V. To express these thresholds in terms of output voltage change, multiply by the error amplifier gain = Vout/Vref = (R1 + R2)/R2. For

ONOM

≤ (Vin - 1V), 2.3 ≤Vin≤30V, 100µA≤IL≤ 250 mA, TJ ≤ T

ref ≤Vout

CONDITIONS

(Note 2)

IL = 100µ A
IL = 250 mA

IL = 100 µA
IL = 250 mA

V

= 0 200 500 200 500 mA

out

CL = 1µF
CL = 200 µF
CL = 13.3 µF
(Bypass = 0.01 µF pins 7 to 1)

( Note 12 )

V

= 30V

OH

Vin = 4.5V
IOL = 400µA
(Note 6) 40 60 40 60 mV
(Note 6) 75 95 75 95 mV
(Note 6) 15 15 mV

Low (Regulator ON)
High (Regulator OFF)

Vs = 2.4V
Vs = 30V

(Note 11) 3 10 3 10

= ( V

IN

as V

is varied, with the dropout warning occurring at typically 5% below nominal, 7.5% guaranteed.

out

out

+1)V, IL = 100 µA and CL = 1 µF for 5V versions and 2.2µF for 3V and 3.3V

ONOM

TAP

.

JMAX

AMS2954AC

Min. Typ. Max.

1.19 1.27 1.185 1.285

0.01 1 0.01 1

2

, OUTPUT tied to SENSE and V

50

380

75
15

430
160
100

AMS2954AC

20 50 ppm/°C

0.1 0.1 nA/°C

150 250 150 250 mV

1.3

30
450

80

600
120

20

430

0.7

50
600

2

30

SHUTDOWN

AMS2954C

Min. Typ. Max.

75

≤ 0.8V.

50

380

15

160
100

AMS2954C

1.3

450

0.7

50
600

80

600
120

20

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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
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: V

≥ 2V, Vin ≤ 30V, V

shutdown

=0, Feedback pin tied to 5V

out

TAP

.

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 V

=30V (1.25W pulse) for T =10 ms.

IN

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 I

= 1 mA. For IL = 100 µA and TJ = 125°C, line regulation is guaranteed by design to 0.2%.

L

See typical performance characteristics for line regulation versus temperature and load current.

BLOCK DIAGRAM AND TYPICAL APPLICATIONS

AMS2954-XX

3 Lead Packages

UNREGULATED DC

+

+

-

+

1.23V
REFERENCE

INPUT

ERROR
AMPLIFIER

OUTPUT

GROUND

V

OUT

IL≤

+

SEE APPLICATION

150mA

HINTS

FROM
CMOS

OR TTL

UNREGULATED DC

+

FEED­BACK

3

SHUT­DOWN

ERROR DETECTION COMPARATOR

50mV

+

+

1.23V
REFERENCE

can vary from 46°C/W to >90°C/W

JA

AMS2954-XX

8 Lead Packages

INPUT OUTPUT

+

­ERROR

AMPLIFIER

+

-

187

SENSE

V

TAP

ERROR

GROUND

2

6

5

V

OUT

IL≤

150mA

SEE APPLICATION

+

Ω

330k

4

HINTS

TO CMOS
OR TTL

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http://www.BDTIC.com/AMS

TYPICAL PERFORMANCE CHARACTERISTICS

Quiescent Current

20

10

1

GROUND CURRENT (mA)

0.1

270
240
210
180
150

120

90
75
60
45

INPUT CURRENT (mA)

30
15

0

50 100

1

LOAD CURRENT (mA)

Input Current

1 23456789100

INPUT VOLTAGE (V)

150 200

IO=250mA

250

Dropout Characteristics

6

5V OUTPUT

5

4

3

2

OUTPUT VOLTAGE (V)

1

0

1

0

INPUT VOLTAGE (V)

Temperature Drift of 3
Representative Units

5.06

5.04

5.02

5.0

4.98

OUTPUT VOLTAGE (V)

4.96

4.94

5V OUTPUT5V OUTPUT 5V OUTPUT

-75 0 25 50 75 100 125

-50 -25
TEMPERATURE (° C)

IO=1mA

IO=250mA

345 6 123456789100

2

0.2%

150

AMS2954

Input Current

250
225

200

A)

µ

175
150

125
100

INPUT CURRENT (

160
140

A)

µ

120
100

QUIESCENT CURRENT (

5V OUTPUT

RL=

∞

75
50
25

0

INPUT VOLTAGE (V)

Quiescent Current

80
60
40
20

0

012345678

INPUT VOLTAGE (V)

IL= 0mA

IL= 1 mA

Quiescent Current

120

5V OUTPUT

110

A)

µ

100

90

80

70

60

QUIESCENT CURRENT (

50

-75

-50 -25

0 25 50 75 100 125

TEMPERATURE (° C)

IL= 100µA

VIN= 6V

Advanced Monolithic Systems, Inc.

150

Quiescent Current

5V OUTPUT

30

25

20

15

10

QUIESCENT CURRENT (mA)

5

-75

-50 -25

0 25 50 75 100 12535150

TEMPERATURE (° C)

VIN= 6V
IL= 250mA

Quiescent Current

24

5V OUTPUT

21
18
15
12

9
6
3

QUIESCENT CURRENT (mA)

0

012345678

INPUT VOLTAGE (V)

IL= 250mA

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TYPICAL PERFORMANCE CHARACTERISTICS (Continued)

Short Circuit Current

450

Dropout Voltage

600

AMS2954

Dropout Voltage

500
400

350

300

250

200

150

SHORT CIRCUIT CURRENT (mA)

100

-75 0 25 50 75 100 125

-50 -25
TEMPERATURE (° C)

AMS2954 Minimum Operating Voltage

2.2

2.1

2.0

1.9

1.8

1.7

1.6

MINIMUM OPERATING VOLTAGE (V)

-75 0

-50 -25

25 50

100

75

TEMPERATURE (° C)

125

150

150

500

400

300

~

~

100

50

DROPOUT VOLTAGE (mV)

0

-75 0 25 50 75 100 125

-50 -25
TEMPERATURE (° C)

AMS2954 Feedback Bias Current

20

10

0

-10

-20

BIAS CURRENT (nA)

-30

-50 -25

-75 0 25 50 75 100
TEMPERATURE (° C)

IL= 250mA

IL= 100µA

125

150

150

400

300

200

TJ = 25°C

100

DROPOUT VOLTAGE (mV)

0

100µA 10mA 100mA 250mA

OUTPUT CURRENT

AMS2954 Feedback Pin Current

50

PIN 7 DRVEN BY EXTERNAL
SOURCE (REGULATOR RUN

A)

µ

0

OPEN LOOP)

-50

TA = 125°C

-100

-150

-200

FEEDBACK CURRENT (

TA = -55°C

TA =
25°C

-250

-2.0 -1.5 -1.0 -0.5

0 0.5

FEEDBACK VOLTAGE (V)

1.0

AMS2954 Error Comparator Output

9

V

= 5V

8

OUT

7
6

50k RESISTOR TO
EXTERNAL 5V SUPPLY

5
4

3

ERROR OUTPUT (V)

2
1
0

0345678

50k
RESISTOR
TO V

12

OUT

HYSTERESIS

INPUT VOLTAGE (V)

Advanced Monolithic Systems, Inc.

AMS2954 Comparator Sink Current

2.5

2.0

1.5

1.0

SINK CURRENT (mA)

0.5

0.0

0.1 0.2

0.0 0.3 0.4 0.5 0.6 0.7 0.8
OUTPUT LOW VOLTAGE (V)

TA =
125°C

TA =
25°C

TA = -55°C

CHANGE

OUTPUT VOLTAGE

INPUT

VOLTAGE

0.9

Line Transient Response

100
mV

50

mV

0

-50

mV

~

~

8V

6V

4V

200 400 600

0

TIME (µs)

CL= 1µF

IL= 1mA

V

OUT

= 5V

800

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TYPICAL PERFORMANCE CHARACTERISTICS (Continued)

Load Transient Response

250
200
150
100

50

0

CHANGE (mV)

-50

OUTPUT VOLTAGE

-100

~

~

250

mA

100

LOAD

µ

A

CURRENT

01 23 4 5

TIME (ms)

CL= 1 µF
V

= 5V

OUT

OUTPUT VOLTAGE

LOAD

Load Transient Response

80
60
40
20

0

-20

CHANGE (mV)

-40

-60

~

~

250

mA

100

µ

A

CURRENT

04 8121620

TIME (ms)

CL= 10 µF

V

= 5V

OUT

AMS2954

AMS2954 Enable Transient

7
6

5
4
3

OUTPUT

VOLTAGE (V)

2
1

0

~

~

2
0

-2
0 100 200 300 400 500 600 700-100

VOLTAGE (V)

SHUTDOWN PIN

CL= 1 µF

CL= 10 µF

TIME (

IL= 10 mA
V

= 8V

IN

V

= 5V

OUT

µ

s)

Output Impedance

10

5

)

Ω

2
1

IO= 100µA

IO= 1 mA

0.5

0.2

0.1

0.05

OUPUT IMPEDANCE (

0.02

0.01
10 100 1K 100K

FREQUENCY (Hz)

Ripple Rejection

80

IL= 50mA

70

60

IL= 250mA

50

40

30

RIPPLE REJECTION (dB)

20

10

10

CL= 1µF

VIN= 6V

V

= 5V

OUT

2

1

10

10

FREQUENCY (Hz)

IO= 250mA

V

OUT

CL= 1 µF

10K 1M

4

3

10

= 5V

10

Ripple Rejection

90
80

70

60

IL= 0

50

10

IL= 100µA

4

10

5

10

6

40

CL= 1 µF

30

20

10

VIN= 6V

V

= 5V

OUT

2

1

10

10

3

RIPPLE REJECTION (dB)

FREQUENCY (Hz)

AMS2954 Output Noise

3.5

Hz)

√

3.0

2.5

5V
OUTPUT

IL= 250mA

CL= 1 µF

2.0

10

CL= 220 µF

3

10

4

10

5

1.5

1.0

DENSITY(mV/

0.5

VOLTAGE NOISE SPECTRAL

5

10

6

0.0

0.01 µF
BYPASS
PIN 1 TO
PIN 7

2

10

CL= 3.3 µF

FREQUENCY (Hz)

Ripple Rejection

90
80

70

IL= 1mA

60

50

40

RIPPLE REJECTION (dB)

30

20

10

1

10

IL= 10mA

2

10

4

3

10

FREQUENCY (Hz)

AMS2954 Divider Resistance

400

)

Ω

300

200

100

PIN 2 TO PIN 4 RESISTANCE (k

0

-50 -25

-75 0 25 50 75 100 125
TEMPERATURE (° C)

CL= 1 µF
VIN= 6V
V

= 5V

OUT

10

5

10

6

150

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TYPICAL PERFORMANCE CHARACTERISTICS (Continued)

AMS2954

Shutdown Treshold Voltage

1.8

1.6

1.4

1.2

1.0

0.8

0.6

-50 -25

-75 0 25 50 75 100 125

SHUTDOWN TRESHOLD VOLTAGE (V)

REGULATOR OFF

REGULATOR ON

TEMPERATURE (° C)

300

250

200

150

100

OUTPUT CURRENT (mA)

50

0

05

30
25
20
15
10

10

-5

OUTPUT VOLTAGE CHANGE (V)

150

AMS2954 Maximum Rated
Output Current

TA= 85° C

10

INPUT VOLTAGE (V)

-10

SOT-223 PACKAGE
SOLDERED TO PC
BOARD

T

= 125° C

JMAX

TA= 25° C

15 20 25

Line Regulation

IL= 100µA

TJ = 150° C

5
0

~

~

TJ = 125° C

5
0

10

5152025

INPUT VOLTAGE (V)

30

IL= 1mA

IL= 100µA

30

Thermal Response

5
4

2

0

CHANGE (mV)

OUTPUT VOLTAGE

-2

~

~

1

0

POWER

-1

DISSIPATION (W)

AMS2954 Maximum Rated
Output Current

300

250

200

150

TA= 50° C

100

OUTPUT CURRENT (mA)

50

0

05

1.25W

10 20 30 40 500

TIME (

µ

10

INPUT VOLTAGE (V)

s)

8 PIN MOLDED
DIP SOLDERED
TO PC BOARD

T

JMAX

V

OUT

TA= 85° C

15 20 25

= 125° C

= 5V

TA= 25° C

30

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APPLICATION HINTS

External Capacitors

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 type s 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.
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.
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.
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.

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 ).

AMS2954

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.

OUTPUT

VOLTAGE

ERROR*

INPUT

VOLTAGE

FIGURE 1. ERROR Output Timing

*When V
and the error flag voltage rises to its pull-up voltage. Using V
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 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 V
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:

V

where V
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 R
condition often found in CMOS in standby) I
typical error in V
temperature by trimming R
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.

≤1.3V the error flag pin becomes a high impedance,

IN

= V

out

is the nominal 1.235 reference voltage and IFB is the

REF

4.75V

5V

1.3V

× (1 + R1/ R2)+ IFBR

REF

, if the regulator must work with no load (a

2

which may be eliminated at room

OUT

. For better accuracy, choosing R2 =

1

1

will produce a 2%

FB

TAP

as

out

pins

Advanced Monolithic Systems, Inc.

http://www.BDTIC.com/AMS

APPLICATION HINTS (Continued)

+V

IN

ERROR
OUPUT

**SHUTDOWN
INPUT

100k

3

+V

ERROR*

AMS2954

SD

GND FB

8

IN

15

V

OUT

1.23

74

V

V

REF

1.2 30V

R

1

R

2

V

.01µ

OUT

+*

µ

F

3.3

F

FIGURE 2. Adjustable Regulator

*See Application Hints.

= V

V

out

**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 µF to 220 µF only decreases the noise from 430
µV to 160 µV rms for a 100 kHz bandwidth at 5V output.
Noise could also be reduced fourfold by a bypass capacitor across

, since it reduces the high frequency gain from 4 to unity. Pick

R

1

C

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.

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.

× (1 + R1/ R2)

REF

≅ 1 / 2πR1 × 200 Hz

BYPASS

AMS2954

I

IN

*

IIN = IL +I

IN

G

IN

AMS2954

OUTV

GND

* See external capacitors

P

= (VIN -5)IL +(VIN)I

Total

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, T

. This is calculated using the formula:

R(max)

T

R(max)

=T

J(max)

- T

A(max)

Where T

is the maximum ambient temperature.

T

A(max)

Using the calculated values for T

is the maximum allowable junction temperature, and

J(max)

R(max)

junction to ambient thermal resistance θ

θ

(J-A)

= T

R(max) /P(max)

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)

where:
θ

is the junction-to-case thermal resistance, which is specified as

(J-C)

3°C/W maximum for the AMS2954.

is the case-to-heatsink thermal resistance, which is dependent on

θ

(C-H)

the interfacing material (if used).

θ

is the heatsink-to-ambient thermal resistance. It is this

(H-A)

specification which defines the effectiveness of the heatsink. The
heatsink selected must have a thermal resistance equal or lower than the
value of θ

calculated from the above listed formula.

(H-A)

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.

5V

+

1µF

I

G

G

and P

(max)

, can be determined:

(J-A)

I

L

LOAD

, the required value for

Advanced Monolithic Systems, Inc.

http://www.BDTIC.com/AMS

TYPICAL APPLICATIONS (Continued)

*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

SHUTDOWN
INPUT

3

Wide Input Voltage Range Current Limiter

+V

IN

8

+V

ERROR
OUPUT

SHUTDOWN
INPUT

3

IN

ERROR

AMS2954

SD

GND FB

V

OUT

74

+V = 2

30V

I

L

LOAD

8

V

IN

1

V

OUT

AMS2954

SD

GND FB

1%

74

R

1µF

0.1µF

+

*V

≈

V

OUT

15

ΙΝ

5V BUS

+V

IN

AMS2954 -5.0

GND

AMS2954

*V

≈

5V

V

OUT

OUT

1µF

5V Regulator with 2.5V Sleep Function Open Circuit Detector for 4 to 20mA Current Loop

+V

IN

C - MOS

*SLEEP

INPUT

ERROR
OUPU
T

SHUTDOWN
INPUT

k

Ω

47

3

+V

ERROR

AMS2954

SD

GND FB

GATE

8

IN

15

V

OUT

74

Advanced Monolithic Systems, Inc.

100

*Minimum Input-Output voltage ranges from 40mV to 400mV, depending on
load current. Current limit is typically 260 mA

+5V

4.7k

4

20mA

470kΩ

+V

OUT

200kΩ

pF

2N3906

1%

100kΩ

1%

100

+

3.3µ

F

k

Ω

1N4001

0.1µF

8

+V

IN

AMS2954

GND

4

1

V

OUT

7

FB

1N457

MIN. VOLTAGE

Ω

*OUTPUT

1

2

360

≈

4V

5

4

http://www.BDTIC.com/AMS

TYPICAL APPLICATIONS (Continued)

CURRENT
LIMIT
SECTION

680

2N3906

4.7M

20k

Ω

VOUT = 1.23V(1+R1/R2)

For 5V V

, use internal resistors. Wire pin 6 to 7 and pin 2 to +V

OUT

UNREGULATE

D INPUT

Advanced Monolithic Systems, Inc.

2 Ampere Low Dropout Regulator Regulator with Early Warning and Auxiliary Output

+V

= V

+.5V

IN

OUT

470

MJE2955

10k

Ω

3

220

.033

SD

GND

8

+V

IN

ERROR

AMS2954

5

FB

V

OUT

14

Ω

ERROR
FLAG

7

1A Regulator with 1.2V Dropout Latch Off When Error Flag Occurs

10

k

1ΜΩ

1µ

F

6

7

IN

V

TAP

AMS2954

FB OUT

GND

8

4

Ω

SENSE

0.002µ

F

0.01µ

2

1

F

0.05

R

1%

R

1

2

2kΩ

+V

4.7

TANT.

SUPERTEX
VP12C

+

220µ

IQ ≅

OUT

@ 2A

++

OUT

F

400µA

100µF

Buss.

OUTPUT
5V ± 1% @
0 TO 1A

AMS2954

+V

IN

8

+V

IN

6

V

TAP

AMS2954

#1

FB

7

GND

4

2.7M

Ω

Q

1

6

7

3

+V

V

TAP

FB

SD

8

IN

AMS2954

#2

GND

D

4

• Early warning flag on low input voltage

• Main output latches off at lower input voltages

• Battery backup on auxiliary output

Operation: Reg.#1’s V
becomes active when V

is programmed one diode drop above 5V. It’s error flag

OUT

≤ 5.7V. When VIN drops below 5.3V, the error flag of

IN

Reg.#2 becomes active and via Q1 latches the main output off. When V
exceeds 5.7V Reg.#1 is back in regulation and the early warning signal rises,
unlatching Reg.#2 via D3.

470k

Ω

ERROR

470k

Ω

3

RESET

SENSE

V

ERROR

27 k

4

SENSE

V

ERROR

SD

2

1

OUT

5

Ω

2

OUT

5

+V

IN

8

+V

IN

AMS2954

GND

4

D

1

D

3

330 k

MAIN 5V OUTPUT

V

OUT

FB

D

2

+

1µF

EARLY WARNING

Ω

+

1µF

15

R

7

R

20

1

2

5V MEMORY
SUPPLY

3.6V
NICAD

RESET

µ

P

V

DD

V

OUT

+

1µF

again

IN

http://www.BDTIC.com/AMS

PACKAGE DIMENSIONS inches (millimeters) unless otherwise noted.

3 LEAD TO-220 PLASTIC PACKAGE (T)

0.165-0.180

(4.191-4.572)

(11.684-12.700)

0.980-1.070

(24.892-27.178)

0.460-0.500

0.520-0.570

(13.208-14.478)

0.390-0.415

(9.906-10.541)

0.147-0.155

(3.734-3.937)

0.230-0.270

(5.842-6.858)

0.330-0.370

(8.382-9.398)

0.218-0.252

(5.537-6.401)

DIA

0.570-0.620

(14.478-15.748)

0.045-0.055

(1.143-1.397)

AMS2954

0.090-0.110

(2.286-2.794)

Advanced Monolithic Systems, Inc.

0.028-0.038

(0.711-0.965)

0.050

(1.270)

TYP

0.013-0.023

(0.330-0.584)

3 LEAD TO-263 PLASTIC DD (M)

0.095-0.115

(2.413-2.921)

T (TO-220) AMS DRW# 042193

http://www.BDTIC.com/AMS

PACKAGE DIMENSIONS inches (millimeters) unless otherwise noted (Continued).

TO-252 PLASTIC PACKAGE (D)

0.258-0.262

(0.508-0.762)

0.023-0.027

(0.584-0.685)

0.020-0.030

0.175-0.180

(4.191-4.445)

(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)

7.0°

0.030-0.034

(0.762-0.863)

0.038-0.042
(0.965-1.066)

0.235-0.245
(5.969-6.223)

AMS2954

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

0.018-0.022

(0.451-0.558)

0.038-0.042
(0.965-1.066)

0.024±0.002

(0.610±0.0508)

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)

0.071
(1.80)

MAX

Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone [phone] Fax [phone]

0.025-0.033
(0.64-0.84)

0.181
(4.60)

NOM

0.012
(0.31)

MIN

10°

MAX

10°-16°

0.025-0.033
(0.64-0.84)

0.010-0.014
(0.25-0.36)

10°-16°

(SOT-223 ) AMS DRW# 042292

http://www.BDTIC.com/AMS

PACKAGE DIMENSIONS inches (millimeters) unless otherwise noted (Continued).

8 LEAD SOIC PLASTIC PACKAGE (S)

0.189-0.197*

(4.801-5.004)

87 65

AMS2954

0.050

(1.270)

TYP

0.150-0.157**

(3.810-3.988)

0.004-0.010

(0.101-0.254)

0.228-0.244

(5.791-6.197)

12 34

0.053-0.069

(1.346-1.752)

0.014-0.019

(0.355-0.483)

*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

87 65

0.255±0.015*

(6.477±0.381)

0.008-0.010

(0.203-0.254)

0.010-0.020
(0.254-0.508)

0.016-0.050

(0.406-1.270)

x 45°

0°-8° TYP

S (SO-8 ) AMS DRW# 042293

1234

0.045-0.065

(1.143-1.651)

0.065

(1.651)

TYP

0.005
(0.127)

MIN

0.100±0.010

(2.540±0.254)

*DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTUSIONS.
MOLD FLASH OR PROTUSIONS SHALL NOT EXCEED 0.010" (0.254mm)

Advanced Monolithic Systems, Inc.

0.130±0.005

(3.302±0.127)

0.125

(3.175)

0.018±0.003

(0.457±0.076)

MIN

0.015

(0.380)

MIN

0.300-0.325

(7.620-8.255)

0.009-0.015

(0.229-0.381)

+0.025

0.325

-0.015

+0.635

(

8.255

)

-0.381

P (8L PDIP ) AMS DRW# 042294