LP2953AI3.3MDC [NSC]
FIXED/ADJUSTABLE POSITIVE LDO REGULATOR, 0.8V DROPOUT, UUC, DIE;
| 型号： | LP2953AI3.3MDC |
| 厂家： | 
National Semiconductor |
| 描述： | FIXED/ADJUSTABLE POSITIVE LDO REGULATOR, 0.8V DROPOUT, UUC, DIE 输出元件 调节器 |
| 文件： | 总23页 (文件大小：640K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
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information and details on our current products and services.
May 1999
LP2952/LP2952A/LP2953/LP2953A
Adjustable Micropower Low-Dropout Voltage Regulators
General Description
Features
n Output voltage adjusts from 1.23V to 29V
n Guaranteed 250 mA output current
n Extremely low quiescent current
n Low dropout voltage
The LP2952 and LP2953 are micropower voltage regulators
with very low quiescent current (130 µA typical at 1 mA load)
and very low dropout voltage (typ. 60 mV at light load and
470 mV at 250 mA load current). They are ideally suited for
battery-powered systems. Furthermore, the quiescent cur-
rent increases only slightly at dropout, which prolongs bat-
tery life.
n Extremely tight line and load regulation
n Very low temperature coefficient
n Current and thermal limiting
n Reverse battery protection
n 50 mA (typical) output pulldown crowbar
n 5V and 3.3V versions available
The LP2952 and LP2953 retain all the desirable characteris-
tics of the LP2951, but offer increased output current, addi-
tional features, and an improved shutdown function.
The internal crowbar pulls the output down quickly when the
shutdown is activated.
LP2953 Versions Only
n Auxiliary comparator included with CMOS/TTL
compatible output levels. Can be used for fault
detection, low input line detection, etc.
The error flag goes low if the output voltage drops out of
regulation.
Reverse battery protection is provided.
The internal voltage reference is made available for external
use, providing a low-T.C. reference with very good line and
load regulation.
Applications
n High-efficiency linear regulator
n Regulator with under-voltage shutdown
n Low dropout battery-powered regulator
n Snap-ON/Snap-OFF regulator
The parts are available in DIP and surface mount packages.
Block Diagrams
LP2952
LP2953
DS011127-2
DS011127-1
© 1999 National Semiconductor Corporation
DS011127
www.national.com
Pinout Drawings
LP2952
LP2953
14-Pin DIP
16-Pin DIP
DS011127-11
DS011127-13
LP2952
LP2953
16-Pin SO
16-Pin SO
DS011127-12
DS011127-14
Ordering Information
LP2952
LP2953
Temp.
Package
NSC
Temp.
Package
NSC
Drawing
Number
N16A
Order
Range
Number
(TJ) ˚C
Order
Number
Drawing
Number
N14A
Range
(TJ) ˚C
LP2952IN,
−40 to
+125
14-Pin
Molded
DIP
LP2953IN,
LP2953AIN,
LP2953IN-3.3,
LP2953AIN-3.3
−40 to
+125
16-Pin
Molded DIP
LP2952AIN,
LP2952IN-3.3,
LP2952AIN-3.3
LP2952IM,
−40 to
+125
16-Pin
Surface
Mount
M16A
LP2953IM,
−40 to
+125
16-Pin
Surface
Mount
M16A
LP2952AIM,
LP2952IM-3.3,
LP2952AIM-3.3
LP2953AIM,
LP2953IM-3.3,
LP2953AIM-3.3
LP2953AMJ/883
−55 to
+150
16-Pin
Ceramic
DIP
5962-9233601MEA
LP2953AMJ-QMLV
5962-9233601VEA
J16A
LP2953AMWG/883
5962-9233601QXA
LP2953AMWG-QMLV
5962-9233601VXA
−55 to
+150
16-Pin
Ceramic
Surface
Mount
WG16A
www.national.com
2
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Maximum Junction Temperature
LP2952I, LP2953I, LP2952AI,
LP2953AI, LP2952I-3.3,
LP2953I-3.3, LP2952AI-3.3,
LP2953AI-3.3
+125˚C
+150˚C
LP2953AM
Storage Temperature Range
−65˚C ≤ TA ≤ +150˚C
Input Supply Voltage
−20V to +30V
−0.3V to +5V
−0.3V to +30V
−0.3V to +30V
−0.3V to +30V
2 kV
Operating Temperature Range
LP2952I, LP2953I, LP2952AI,
LP2953AI, LP2952I-3.3,
LP2953I-3.3, LP2952AI-3.3,
LP2953AI-3.3
Feedback Input Voltage (Note 3)
Comparator Input Voltage (Note 4)
Shutdown Input Voltage (Note 4)
Comparator Output Voltage (Note 4)
ESD Rating (Note 15)
−40˚C ≤ TJ ≤ +125˚C
−55˚C ≤ TA ≤ +125˚C
260˚C
LP2953AM
Lead Temp. (Soldering, 5 seconds)
Power Dissipation (Note 2)
Internally Limited
=
Electrical Characteristics Limits in standard typeface are for TJ 25˚C, bold typeface applies over the full
operating temperature range. Limits are guaranteed by production testing or correlation techniques using standard Statistical
=
=
=
Quality Control (SQC) methods. Unless otherwise specified: VIN VO(NOM) + 1V, IL 1 mA, CL 2.2 µF for 5V parts and
4.7µF for 3.3V parts. Feedback pin is tied to V Tap pin, Output pin is tied to Output Sense pin.
3.3V Versions
Symbol
Parameter
Conditions
Typical
3.3
LP2952AI-3.3, LP2953AI-3.3
LP2952I-3.3, LP2953I-3.3 Units
Min
Max
3.317
3.340
3.346
Min
Max
3.333
3.366
3.379
VO
Output Voltage
3.284
3.260
3.254
3.267
3.234
3.221
V
1 mA ≤ IL ≤ 250 mA
3.3
5V Versions
Symbol
Parameter
Conditions
Typical
LP2952AI, LP2953AI,
LP2952I, LP2953I
Units
LP2953AM (Note 17)
Min
Max
5.025
5.060
5.070
Min
Max
5.050
5.100
5.120
VO
Output Voltage
5.0
5.0
4.975
4.940
4.930
4.950
4.900
4.880
V
1 mA ≤ IL ≤ 250 mA
All Voltage Options
Electrical Characteristics
=
Limits in standard typeface are for TJ 25˚C, bold typeface applies over the full operating temperature range. Limits are guar-
anteed by production testing or correlation techniques using standard Statistical Quality Control (SQC) methods. Unless other-
=
=
=
wise specified: VIN VO(NOM) + 1V, IL 1 mA, CL 2.2 µF for 5V parts and 4.7µF for 3.3V parts. Feedback pin is tied to V
Tap pin, Output pin is tied to Output Sense pin.
Symbol
Parameter
Conditions
Typical
LP2952AI,
LP2953AI,
LP2952I, LP2953I, Units
LP2952I-3.3,
LP2952AI-3.3,
LP2953AI-3.3,
LP2953AM
LP2953I-3.3
(Notes 16, 17)
Min
Max
Min
Max
150
REGULATOR
Output Voltage Temp.
Coefficient
(Note 5)
20
100
ppm/˚C
=
Output Voltage Line
Regulation
VIN VO(NOM) + 1V to 30V
0.03
0.04
0.1
0.2
0.2
0.4
%
%
=
Output Voltage Load
Regulation (Note 6)
IL 1 mA to 250 mA
0.16
0.20
0.20
0.30
=
IL 0.1 mA to 1 mA
3
www.national.com
Electrical Characteristics (Continued)
=
Limits in standard typeface are for TJ 25˚C, bold typeface applies over the full operating temperature range. Limits are guar-
anteed by production testing or correlation techniques using standard Statistical Quality Control (SQC) methods. Unless other-
=
=
=
wise specified: VIN VO(NOM) + 1V, IL 1 mA, CL 2.2 µF for 5V parts and 4.7µF for 3.3V parts. Feedback pin is tied to V
Tap pin, Output pin is tied to Output Sense pin.
Symbol
Parameter
Conditions
Typical
LP2952AI,
LP2953AI,
LP2952I, LP2953I, Units
LP2952I-3.3,
LP2952AI-3.3,
LP2953AI-3.3,
LP2953AM
LP2953I-3.3
(Notes 16, 17)
Min
Max
Min
Max
REGULATOR
=
V
IN–VO
Dropout Voltage
(Note 7)
IL 1 mA
60
240
310
470
130
1.1
4.5
21
100
150
300
420
400
520
600
800
170
200
2
100
150
300
420
400
520
600
800
170
200
2
mV
=
IL 50 mA
=
IL 100 mA
=
IL 250 mA
=
IGND
Ground Pin Current
(Note 8)
IL 1 mA
µA
=
IL 50 mA
mA
2.5
6
2.5
6
=
IL 100 mA
8
8
=
IL 250 mA
28
28
33
33
=
IGND
Ground Pin Current at
Dropout
VIN VO(NOM) −0.5V
165
210
240
140
210
240
140
µA
=
IL 100 µA
IGND
Ground Pin Current at
Shutdown (Note 8)
VSHUTDOWN ≤ 1.1V
105
380
µA
=
ILIMIT
Current Limit
VOUT
0
500
530
0.2
500
530
0.2
mA
Thermal Regulation
(Note 10)
0.05
%/W
=
en
Output Noise Voltage
(10 Hz to 100 kHz)
CL 4.7 µF
400
260
µV
RMS
=
CL 33 µF
=
IL 100 mA
=
CL 33 µF (Note 11)
80
VREF
Reference Voltage
(Note 12)
1.230
1.215
1.245
1.255
0.1
1.205
1.255
1.270
0.2
V
1.205
1.190
=
Reference Voltage
Line Regulation
VIN 2.5V to VO(NOM) + 1V
0.03
0.25
%
=
VIN VO(NOM) + 1V to 30V
0.2
0.4
(Note 13)
=
Reference Voltage
Load Regulation
IREF 0 to 200 µA
0.4
0.8
%
0.6
1.0
Reference Voltage
Temp. Coefficient
(Note 5)
20
ppm/˚C
nA
IB(FB)
Feedback Pin Bias
Current
20
40
40
60
60
I
O(SINK) Output “OFF” Pulldown (Note 9)
Current
30
30
mA
20
20
www.national.com
4
Electrical Characteristics (Continued)
=
Limits in standard typeface are for TJ 25˚C, bold typeface applies over the full operating temperature range. Limits are guar-
anteed by production testing or correlation techniques using standard Statistical Quality Control (SQC) methods. Unless other-
=
=
=
wise specified: VIN VO(NOM) + 1V, IL 1 mA, CL 2.2 µF for 5V parts and 4.7µF for 3.3V parts. Feedback pin is tied to V
Tap pin, Output pin is tied to Output Sense pin.
Symbol
Parameter
Conditions
Typical
LP2952AI,
LP2953AI,
LP2952I, LP2953I, Units
LP2952I-3.3,
LP2952AI-3.3,
LP2953AI-3.3,
LP2953AM
LP2953I-3.3
(Notes 16, 17)
Min
Max
Min
Max
DROPOUT DETECTION COMPARATOR
=
IOH
Output “HIGH”
Leakage
VOH 30V
0.01
150
−60
−85
15
1
1
µA
mV
mV
mV
mV
mV
2
2
=
VOL
Output “LOW” Voltage
VIN VO(NOM) − 0.5V
250
400
−35
−25
−55
−40
250
400
−35
−25
−55
−40
=
IO(COMP) 400 µA
VTHR
(MAX)
Upper Threshold
Voltage
(Note 14)
(Note 14)
(Note 14)
−80
−95
−80
−95
VTHR
(MIN)
Lower Threshold
Voltage
−110
−160
−110
−160
HYST
Hysteresis
SHUTDOWN INPUT (Note 15)
±
VOS
Input Offset
Voltage
(Referred to VREF
)
3
−7.5
7.5
−7.5
7.5
−10
10
−10
10
HYST
IB
Hysteresis
Input Bias
Current
6
mV
nA
=
VIN(S/D) 0V to 5V
10
−30
−50
−30
−75
30
50
30
75
−30
−50
−30
50
LP2953AM
10
AUXILIARY COMPARATOR (LP2953 Only)
±
±
VOS
Input Offset Voltage
(Referred to VREF
)
3
3
−7.5
−10
−7.5
−12
7.5
10
−7.5
−10
7.5
10
mV
LP2953AM
7.5
12
HYST
IB
Hysteresis
6
mV
nA
=
Input Bias Current
VIN(COMP) 0V to 5V
10
−30
−50
−30
−75
30
50
30
75
1
−30
−50
30
50
LP2953AM
10
=
IOH
Output “HIGH”
Leakage
VOH 30V
0.01
0.01
150
150
1
2
µA
=
V
IN(COMP) 1.3V
2
LP2953AM
1
2.2
250
400
250
420
=
VOL
Output “LOW” Voltage
VIN(COMP) 1.1V
250
400
mV
=
I
O(COMP) 400 µA
LP2953AM
Note 1: Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating the de-
vice outside of its rated operating conditions.
Note 2: The maximum allowable power dissipation is a function of the maximum junction temperature, T (MAX), the junction-to-ambient thermal resistance, θ
,
J–A
J
and the ambient temperature, T . The maximum allowable power dissipation at any ambient temperature is calculated using the equation for P(MAX),
A
.
5
www.national.com
Electrical Characteristics (Continued)
Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. See APPLICATION
HINTS for additional information on heatsinking and thermal resistance.
Note 3: When used in dual-supply systems where the regulator load is returned to a negative supply, the output voltage must be diode-clamped to ground.
Note 4: May exceed the input supply voltage.
Note 5: Output or reference voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range.
Note 6: Load regulation is measured at constant junction temperature using low duty cycle pulse testing. Two separate tests are performed, one for the range of 100
µA to 1 mA and one for the 1 mA to 250 mA range. Changes in output voltage due to heating effects are covered by the thermal regulation specification.
Note 7: Dropout voltage is defined as the input to output differential at which the output voltage drops 100 mV below the value measured with a 1V differential. At
very low values of programmed output voltage, the input voltage minimum of 2V (2.3V over temperature) must be observed.
Note 8: Ground pin current is the regulator quiescent current. The total current drawn from the source is the sum of the ground pin current, output load current, and
current through the external resistive divider (if used).
=
V (NOM).
O
Note 9:
V
≤ 1.1V, V
OUT
SHUTDOWN
Note 10: Thermal regulation is the change in output voltage at a time T after a change in power dissipation, excluding load or line regulation effects. Specifications
=
=
V (NOM)+15V (3W pulse) for T 10 ms.
O
are for a 200 mA load pulse at V
IN
Note 11: Connect a 0.1 µF capacitor from the output to the feedback pin.
Note 12: ≤ V ≤ (V − 1V), 2.3V ≤ V ≤ 30V, 100 µA ≤ I ≤ 250 mA.
V
REF
OUT IN IN
L
Note 13: Two separate tests are performed, one covering 2.5V ≤ V ≤ V (NOM)+1V and the other test for V (NOM)+1V ≤ V ≤ 30V.
IN IN
O
O
Note 14: Comparator thresholds are expressed in terms of a voltage differential at the Feedback terminal below the nominal reference voltage measured at
=
=
(R1 + R2)/R2
V
V
(NOM) + 1V. To express these thresholds in terms of output voltage change, multiply by the Error amplifier gain, which is V
/V
IN
O
O
U
T
R
E
F
(refer to Figure 4).
Note 15: Human body model, 200 pF discharged through 1.5 kΩ.
Note 16: Drive Shutdown pin with TTL or CMOS-low level to shut regulator OFF, high level to turn regulator ON.
Note 17:
A military RETS specification is available upon request. For more information on military products, please refer to the Mil-Aero web page at
http://www.national.com/appinfo/milaero/index.html.
=
=
=
Typical Performance Characteristics Unless otherwise specified: VIN 6V, IL 1 mA, CL 2.2 µF,
=
=
=
VSD 3V, TA 25˚C, VOUT 5V.
Quiescent Current
Quiescent Current
Ground Pin Current vs Load
DS011127-27
DS011127-28
DS011127-29
Ground Pin Current
Ground Pin Current
Output Noise Voltage
DS011127-30
DS011127-31
DS011127-32
www.national.com
6
=
=
=
Typical Performance Characteristics Unless otherwise specified: VIN 6V, IL 1 mA, CL 2.2 µF,
=
=
=
VSD 3V, TA 25˚C, VOUT 5V. (Continued)
Ripple Rejection
Ripple Rejection
Ripple Rejection
DS011127-33
DS011127-34
DS011127-35
Line Transient Response
Line Transient Response
Load Transient Response
Enable Transient
Output Impedance
DS011127-36
DS011127-37
DS011127-38
Load Transient Response
Dropout Characteristics
DS011127-39
DS011127-40
DS011127-41
Enable Transient
Short-Circuit Output Current
and Maximum Output Current
DS011127-43
DS011127-42
DS011127-44
7
www.national.com
=
=
=
Typical Performance Characteristics Unless otherwise specified: VIN 6V, IL 1 mA, CL 2.2 µF,
=
=
=
VSD 3V, TA 25˚C, VOUT 5V. (Continued)
Feedback Bias Current
Feedback Pin Current
Error Output
DS011127-45
DS011127-46
DS011127-47
Comparator Sink Current
Divider Resistance
Dropout Detection
Comparator Threshold
Voltages
DS011127-48
DS011127-49
DS011127-50
Thermal Regulation
Minimum Operating Voltage
Dropout Voltage
DS011127-51
DS011127-52
DS011127-53
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8
Schematic Diagram
DS011127-6
the ground pins of the IC, and into the copper of the PC
board. Details on heatsinking using PC board copper are
covered later.
Application Hints
HEATSINK REQUIREMENTS (Industrial Temperature
Range Devices)
To determine if a heatsink is required, the maximum power
dissipated by the regulator, P(max), must be calculated. It is
important to remember that if the regulator is powered from
a transformer connected to the AC line, the maximum
specified AC input voltage must be used (since this pro-
duces the maximum DC input voltage to the regulator). Fig-
ure 1 shows the voltages and currents which are present in
the circuit. The formula for calculating the power dissipated
in the regulator is also shown in Figure 1:
The maximum allowable power dissipation for the LP2952/
LP2953 is limited by the maximum junction temperature
(+125˚C) and the external factors that determine how quickly
heat flows away from the part: the ambient temperature and
the junction-to-ambient thermal resistance for the specific
application.
The industrial temperature range (−40˚C ≤ TJ ≤ +125˚C)
parts are manufactured in plastic DIP and surface mount
packages which contain a copper lead frame that allows
heat to be effectively conducted away from the die, through
9
www.national.com
Application Hints (Continued)
DS011127-7
=
FIGURE 1. PTOTAL (VIN − VOUT) IL + (VIN) IG
Current/Voltage Diagram
The next parameter which must be calculated is the maxi-
mum allowable temperature rise, TR(max). This is calculated
by using the formula:
=
=
TR(max) TJ(max) − TA(max)θ(J–A) TR(max)/P(max)
where: TJ(max) is the maximum allowable junction tem-
perature
TA(max) is the maximum ambient temperature
Using the calculated values for TR(max) and P(max), the re-
quired value for junction-to-ambient thermal resistance,
θ(J–A), can now be found:
The heatsink is made using the PC board copper. The heat
is conducted from the die, through the lead frame (inside the
part), and out the pins which are soldered to the PC board.
The pins used for heat conduction are given in Table 1.
DS011127-8
=
* For best results, use L 2H
*
* 14-Pin DIP is similar, refer to Table 1 for pins designated for heatsinking.
FIGURE 2. Copper Heatsink Patterns
TABLE 1. Heat Conducting Pins
Part
Package
Pins
TABLE 2. Thermal Resistance for Various Copper
Heatsink Patterns
LP2952IN, LP2952AIN,
14-Pin DIP
3, 4, 5,
LP2952IN-3.3,
LP2952AIN-3.3
10, 11, 12
Package
L (in.)
H (in.)
0.5
1
θJ–A (˚C/W)
16-Pin DIP
1
2
3
4
6
1
2
3
1
2
3
6
4
2
70
60
58
66
66
65
51
49
83
70
67
69
71
73
LP2953IN, LP2953AIN,
16-Pin DIP
4, 5, 12, 13
1, 8, 9, 16
LP2953IN-3.3,
LP2953AIN-3.3
1.5
0.19
0.19
0.5
1
LP2952IM, LP2952AIM,
16-Pin
Surface
Mount
LP2952IM-3.3,
LP2952AIM-3.3,
14-Pin DIP
LP2953IM, LP2953AIM,
LP2953IM-3.3,
LP2953AIM-3.3
1.5
0.5
1
Surface Mount
Figure 2 shows copper patterns which may be used to dissi-
pate heat from the LP2952 and LP2953. Table 2 shows
some values of junction-to-ambient thermal resistance (θJ–A
1.5
0.19
0.19
0.19
)
for values of L and W for 1 oz. copper.
HEATSINK REQUIREMENTS (Military Temperature
Range Devices)
The maximum allowable power dissipation for the
LP2953AMJ is limited by the maximum junction temperature
(+150˚C) and the two parameters that determine how quickly
heat flows away from the die: the ambient temperature and
the junction-to-ambient thermal resistance of the part.
The military temperature range (−55˚C ≤ TJ ≤+150˚C) parts
are manufactured in ceramic DIP packages which contain a
www.national.com
10
MINIMUM LOAD
Application Hints (Continued)
When setting the output voltage using an external resistive
divider, a minimum current of 1 µA is recommended through
the resistors to provide a minimum load.
KOVAR lead frame (unlike the industrial parts, which have a
copper lead frame). The KOVAR material is necessary to at-
tain the hermetic seal required in military applications.
It should be noted that a minimum load current is specified in
several of the electrical characteristic test conditions, so this
value must be used to obtain correlation on these tested
limits.
The KOVAR lead frame does not conduct heat as well as
copper, which means that the PC board copper can not be
used to significantly reduce the overall junction-to-ambient
thermal resistance in applications using the LP2953AMJ
part.
The power dissipation calculations for military applications
are done exactly the same as was detailed in the previous
section, with one important exception: the value for θ(J–A)
,
the junction-to-ambient thermal resistance, is fixed at
95˚C/W and can not be changed by adding copper foil pat-
terns to the PC board. This leads to an important fact: The
maximum allowable power dissipation in any application us-
ing the LP2953AMJ is dependent only on the ambient tem-
perature:
DS011127-26
FIGURE 3. Power Derating Curve for LP2953AMJ
PROGRAMMING THE OUTPUT VOLTAGE
Figure 3 shows a graph of maximum allowable power dissi-
pation vs. ambient temperature for the LP2953AMJ, made
using the 95˚C/W value for θ(J–A) and assuming a maximum
junction temperature of 150˚C (caution: the maximum ambi-
ent temperature which will be reached in a given application
must always be used to calculate maximum allowable power
dissipation).
The regulator may be pin-strapped for 5V operation using its
internal resistive divider by tying the Output and Sense pins
together and also tying the Feedback and 5V Tap pins to-
gether.
Alternatively, it may be programmed for any voltage between
the 1.23V reference and the 30V maximum rating using an
external pair of resistors (see Figure 4). The complete equa-
tion for the output voltage is:
EXTERNAL CAPACITORS
A 2.2 µF (or greater) capacitor is required between the out-
put pin and ground to assure stability when the output is set
to 5V. Without this capacitor, the part will oscillate. Most type
of tantalum or aluminum electrolytics will work here. Film
types will work, but are more expensive. Many aluminum
electrolytics contain electrolytes which freeze at −30˚C,
which requires the use of solid tantalums below −25˚C. The
important parameters of the capacitor are an ESR of about
5Ω or less and a resonant frequency above 500 kHz (the
ESR may increase by a factor of 20 or 30 as the temperature
is reduced from 25˚C to −30˚C). The value of this capacitor
may be increased without limit.
where VREF is the 1.23V reference and IFB is the Feedback
pin bias current (−20 nA typical). The minimum recom-
mended load current of 1 µA sets an upper limit of 1.2 MΩ on
the value of R2 in cases where the regulator must work with
no load (see MINIMUM LOAD ). IFB will produce a typical 2%
error in VOUT which can be eliminated at room temperature
=
by trimming R1. For better accuracy, choosing R2 100 kΩ
will reduce this error to 0.17% while increasing the resistor
program current to 12 µA. Since the typical quiescent current
is 120 µA, this added current is negligible.
At lower values of output current, less output capacitance is
required for stability. The capacitor can be reduced to
0.68 µF for currents below 10 mA or 0.22 µF for currents be-
low 1 mA.
Programming the output for voltages below 5V runs the error
amplifier at lower gains requiring more output capacitance
for stability. At 3.3V output, a minimum of 4.7 µF is required.
For the worst-case condition of 1.23V output and 250 mA of
load current, a 6.8 µF (or larger) capacitor should be used.
A 1 µF capacitor should be placed from the input pin to
ground if there is more than 10 inches of wire between the in-
put and the AC filter capacitor or if a battery input is used.
Stray capacitance to the Feedback terminal can cause insta-
bility. This problem is most likely to appear when using high
value external resistors to set the output voltage. Adding a
100 pF capacitor between the Output and Feedback pins
and increasing the output capacitance to 6.8 µF (or greater)
will cure the problem.
11
www.national.com
Application Hints (Continued)
DS011127-10
* In shutdown mode, ERROR will go high if it has been pulled up to an
external supply. To avoid this invalid response, pull up to regulator output.
*
* Exact value depends on dropout voltage. (See Application Hints)
FIGURE 5. ERROR Output Timing
DS011127-9
*
See Application Hints
**
OUTPUT ISOLATION
Drive with TTL-low to shut down
The regulator output can be left connected to an active volt-
age source (such as a battery) with the regulator input power
shut 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.
FIGURE 4. Adjustable Regulator
DROPOUT VOLTAGE
The dropout voltage of the regulator is defined as the mini-
mum input-to-output voltage differential required for the out-
put voltage to stay within 100 mV of the output voltage mea-
sured with
a 1V differential. The dropout voltage is
independent of the programmed output voltage.
REDUCING OUTPUT NOISE
In reference applications it may be advantageous to reduce
the AC noise present on the output. One method is to reduce
regulator bandwidth by increasing output capacitance. This
is relatively inefficient, since large increases in capacitance
are required to get significant improvement.
DROPOUT DETECTION COMPARATOR
This comparator produces a logic “LOW” whenever the out-
put falls out of regulation by more than about 5%. This figure
results from the comparator’s built-in offset of 60 mV divided
by the 1.23V reference (refer to block diagrams on page 1).
The 5% low trip level remains constant regardless of the pro-
grammed output voltage. An out-of-regulation condition can
result from low input voltage, current limiting, or thermal lim-
iting.
Noise can be reduced more effectively by a bypass capacitor
placed across R1 (refer to Figure 4). The formula for select-
ing the capacitor to be used is:
Figure 5 gives a timing diagram showing the relationship be-
tween the output voltage, the ERROR output, and input volt-
age as the input voltage is ramped up and down to a regula-
tor programmed for 5V output. The ERROR signal becomes
low at about 1.3V input. It goes high at about 5V input, where
the output equals 4.75V. Since the dropout voltage is load
dependent, the input voltage trip points will vary with load
current. The output voltage trip point does not vary.
This gives a value of about 0.1 µF. When this is used, the
output capacitor must be 6.8 µF (or greater) to maintain sta-
bility. The 0.1 µF capacitor reduces the high frequency gain
of the circuit to unity, lowering the output noise from 260 µV
to 80 µV using a 10 Hz to 100 kHz bandwidth. Also, noise is
no longer proportional to the output voltage, so improve-
ments are more pronounced at high output voltages.
The comparator has an open-collector output which requires
an external pull-up resistor. This resistor may be connected
to the regulator output or some other supply voltage. Using
the regulator output prevents an invalid “HIGH” on the com-
parator output which occurs if it is pulled up to an external
voltage while the regulator input voltage is reduced below
1.3V. In selecting a value for the pull-up resistor, note that
while the output can sink 400 µA, this current adds to battery
drain. Suggested values range from 100 kΩ to 1 MΩ. This
resistor is not required if the output is unused.
AUXILIARY COMPARATOR (LP2953 only)
The LP2953 contains an auxiliary comparator whose invert-
ing input is connected to the 1.23V reference. The auxiliary
comparator has an open-collector output whose electrical
characteristics are similar to the dropout detection compara-
tor. The non-inverting input and output are brought out for
external connections.
SHUTDOWN INPUT
When VIN ≤ 1.3V, the error flag pin becomes a high imped-
ance, allowing the error flag voltage to rise to its pull-up volt-
age. Using VOUT as the pull-up voltage (rather than an exter-
nal 5V source) will keep the error flag voltage below 1.2V
(typical) in this condition. The user may wish to divide down
the error flag voltage using equal-value resistors (10 kΩ sug-
gested) to ensure a low-level logic signal during any fault
condition, while still allowing a valid high logic level during
normal operation.
A logic-level signal will shut off the regulator output when a
<
“LOW” ( 1.2V) is applied to the Shutdown input.
To prevent possible mis-operation, the Shutdown input must
be actively terminated. If the input is driven from
open-collector logic, a pull-up resistor (20 kΩ to 100 kΩ rec-
ommended) should be connected from the Shutdown input
to the regulator input.
www.national.com
12
ground, the reverse-battery protection feature which protects
the regulator input is sacrificed if the Shutdown input is tied
directly to the regulator input.
Application Hints (Continued)
If the Shutdown input is driven from a source that actively
pulls high and low (like an op-amp), the pull-up resistor is not
required, but may be used.
If reverse-battery protection is required in an application, the
pull-up resistor between the Shutdown input and the regula-
tor input must be used.
If the shutdown function is not to be used, the cost of the
pull-up resistor can be saved by simply tying the Shutdown
input directly to the regulator input.
IMPORTANT: Since the Absolute Maximum Ratings state
that the Shutdown input can not go more than 0.3V below
Typical Applications
Basic 5V Regulator
5V Current Limiter with Load Fault Indicator
DS011127-15
DS011127-16
* Output voltage equals +V minum dropout voltage, which varies with
IN
output current. Current limits at a maximum of 380 mA (typical).
** Select R1 so that the comparator input voltage is 1.23V at the output
voltage which corresponds to the desired fault current value.
Low T.C. Current Sink
5V Regulator with Error Flags for
LOW BATTERY and OUT OF REGULATION
DS011127-18
* Connect to Logic or µP control inputs.
LOW BATT flag warns the user that the battery has discharged down to
about 5.8V, giving the user time to recharge the battery or power down
some hardware with high power requirements. The output is still in
regulation at this time.
OUT OF REGULATION flag indicates when the battery is almost
completely discharged, and can be used to initiate a power-down
sequence.
DS011127-17
13
www.national.com
Typical Applications (Continued)
5V Battery Powered Supply with Backup and Low Battery Flag
DS011127-19
The circuit switches to the NI-CAD backup battery when the main battery voltage drops below about 5.6V, and returns to the main battery when its voltage is
recharged to about 6V.
The 5V MAIN output powers circuitry which requires no backup, and the 5V MEMORY output powers critical circuitry which can not be allowed to lose power.
* The BATTERY LOW flag goes low whenever the circuit switches to the NI-CAD backup battery.
5V Regulator with Timed Power-On Reset
Timing Diagram for Timed Power-On Reset
DS011127-21
=
=
0.1 µF
* R
T
1 MEG, C
T
DS011127-20
www.national.com
14
Typical Applications (Continued)
5V Regulator with Snap-On/Snap-Off
Feature and Hysteresis
5V Regulator with Error Flags for
LOW BATTERY and OUT OF REGULATION
with SNAP-ON/SNAP-OFF Output
DS011127-22
=
=
* Turns ON at V
5.87V
5.64V
IN
DS011127-23
Turns OFF at V
IN
* Connect to Logic or µP control inputs.
(for component values shown)
OUTPUT has SNAP-ON/SNAP-OFF feature.
LOW BATT flag warns the user that the battery has discharged down to
about 5.8V, giving the user time to recharge the battery or shut down
hardware with high power requirements. The output is still in regulation at
this time.
OUT OF REGULATION flag goes low if the output goes below about 4.7V,
which could occur from a load fault.
OUTPUT has SNAP-ON/SNAP-OFF feature. Regulator snaps ON at about
5.7V input, and OFF at about 5.6V.
5V Regulator with Timed Power-On Reset, Snap-On/Snap-Off Feature and Hysteresis
Timing Diagram
DS011127-25
=
=
Td (0.28) RC 28 ms for components shown.
DS011127-24
15
www.national.com
Physical Dimensions inches (millimeters) unless otherwise noted
16-Pin Ceramic DIP
Order Number LP2953AMJ/883, 5962-9233601MEA, LP2953AMJ-QMLV, 5962-9233601VEA
NS Package Number J16A
16-Pin Surface Mount
Order Number LP2952IM, LP2952AIM, LP2952IM-3.3, LP2952AIM-3.3,
LP2953IM, LP2953AIM, LP2953IM-3.3 or LP2953AIM-3.3
NS Package Number M16A
www.national.com
16
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
14-Pin Molded DIP
Order Number LP2952IN, LP2952AIN, LP2952IN-3.3 or LP2952AIN-3.3
NS Package Number N14A
16-Pin Molded DIP
Order Number LP2953IN, LP2953AIN, LP2953IN-3.3 or LP2953AIN-3.3
NS Package Number N16A
17
www.national.com
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
16-Pin Ceramic Surface-Mount
Order Number LP2953AMWG/883, 5962-9233601QXA, LP2953AMWG-QMLV, 5962-9233601VXA
NS Package Number WG16A
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DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or
systems which, (a) are intended for surgical implant
into the body, or (b) support or sustain life, and
whose failure to perform when properly used in
accordance with instructions for use provided in the
labeling, can be reasonably expected to result in a
significant injury to the user.
2. A critical component is any component of a life
support device or system whose failure to perform
can be reasonably expected to cause the failure of
the life support device or system, or to affect its
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Tel: 1-800-272-9959
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National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
See Wireless Products
Products > Analog - Regulators > Linear Regulators - Low Dropout Voltage > Positive Voltage - Adjustable
> LP2953
LP2953 Product Folder
Adjustable Micropower Low-Dropout Voltage Regulator
LP2956 - adds second regulator output.
See Also:
Generic P/N 2953
General
Package
& Models
Samples
& Pricing
Features
Datasheet
Description
Parametric Table
Multiple Output Capability
On/Off Pin
Parametric Table
No
Dropout Voltage, typ (Volt)
Quiescent Current, typ (mA)
Secondary Ouput Voltage (Volt)
Secondary Output Current (Amp)
Output Voltage, min (Volt)
Output Voltage, max (Volt)
Watchdog
.47
Yes
.13
-
Error Flag
Yes
Input Voltage, min (Volt)
Input Voltage, max (Volt)
Output Current, max
-20
-
30
1.23
29
-
250 mA
Datasheet
Size in
Kbytes
Title
Date
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View Online
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Jun-
99
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LP2952 LP2952A LP2953 LP2953A Adjustable Micropower 559
View Online Download
Low-Dropout Voltage Regulators
Kbytes
LP2952 LP2952A LP2953 LP2953A Adjustable Micropower
Low-Dropout Voltage Regulators (JAPANESE)
667
Kbytes
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LP2953AI MDC
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General Description
The LP2952 and LP2953 are micropower voltage regulators with very low quiescent current (130 µA typical
at 1 mA load) and very low dropout voltage (typ. 60 mV at light load and 470 mV at 250 mA load current).
They are ideally suited for battery-powered systems. Furthermore, the quiescent current increases only
slightly at dropout, which prolongs battery life.
The LP2952 and LP2953 retain all the desirable characteristics of the LP2951, but offer increased output
current, additional features, and an improved shutdown function.
The internal crowbar pulls the output down quickly when the shutdown is activated.
The error flag goes low if the output voltage drops out of regulation.
Reverse battery protection is provided.
The internal voltage reference is made available for external use, providing a low-T.C. reference with very
good line and load regulation.
The parts are available in DIP and surface mount packages.
Features
●
●
●
●
●
●
●
●
●
●
Output voltage adjusts from 1.23V to 29V
Guaranteed 250 mA output current
Extremely low quiescent current
Low dropout voltage
Extremely tight line and load regulation
Very low temperature coefficient
Current and thermal limiting
Reverse battery protection
50 mA (typical) output pulldown crowbar
5V and 3.3V versions available
Applications
●
Auxiliary comparator included with CMOS/TTL compatible output levels. Can be used for fault
detection, low input line detection, etc.
●
●
●
●
High-efficiency linear regulator
Regulator with under-voltage shutdown
Low dropout battery-powered regulator
Snap-ON/Snap-OFF regulator
[Information as of 5-Aug-2002]
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