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PDF 5962-9233601MEA Data sheet ( Hoja de datos )
| Número de pieza | 5962-9233601MEA | |
| Descripción | Adjustable Micropower Low-Dropout Voltage Regulators | |
| Fabricantes | National Semiconductor | |
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May 1999
LP2952/LP2952A/LP2953/LP2953A
Adjustable Micropower Low-Dropout Voltage Regulators
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 cur-
rent increases only slightly at dropout, which prolongs bat-
tery life.
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.
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
n Output voltage adjusts from 1.23V to 29V
n Guaranteed 250 mA output current
n Extremely low quiescent current
n Low dropout voltage
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
LP2953 Versions Only
n Auxiliary comparator included with CMOS/TTL
compatible output levels. Can be used for fault
detection, low input line detection, etc.
Applications
n High-efficiency linear regulator
n Regulator with under-voltage shutdown
n Low dropout battery-powered regulator
n Snap-ON/Snap-OFF regulator
Block Diagrams
LP2952
LP2953
DS011127-1
© 1999 National Semiconductor Corporation DS011127
DS011127-2
www.national.com
1 page  
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,
LP2952AI-3.3,
LP2953AI-3.3,
LP2953AM
(Notes 16, 17)
LP2952I, LP2953I, Units
LP2952I-3.3,
LP2953I-3.3
Min
Max
Min Max
DROPOUT DETECTION COMPARATOR
IOH Output “HIGH”
Leakage
VOH = 30V
0.01
1
2
1 µA
2
VOL Output “LOW” Voltage VIN = VO(NOM) − 0.5V
150
250
250 mV
IO(COMP) = 400 µA
400 400
VTHR
(MAX)
Upper Threshold
Voltage
(Note 14)
−60 −80
−95
−35 −80 −35 mV
−25 −95 −25
VTHR
(MIN)
Lower Threshold
Voltage
(Note 14)
−85 −110
−160
−55 −110 −55 mV
−40
−160
−40
HYST Hysteresis
(Note 14)
15
mV
SHUTDOWN INPUT (Note 15)
VOS Input Offset
Voltage
(Referred to VREF)
±3 −7.5 7.5 −7.5 7.5 mV
−10 10 −10 10
HYST Hysteresis
6
mV
IB Input Bias
Current
VIN(S/D) = 0V to 5V
10 −30
−50
30 −30 −30 nA
50 −50 50
LP2953AM 10
−30
30
−75 75
AUXILIARY COMPARATOR (LP2953 Only)
VOS
Input Offset Voltage
(Referred to VREF)
±3 −7.5
−10
LP2953AM ±3
−7.5
7.5 −7.5 7.5 mV
10 −10 10
7.5
−12 12
HYST Hysteresis
6
mV
IB
Input Bias Current
VIN(COMP) = 0V to 5V
10 −30
−50
30 −30 30 nA
50 −50 50
LP2953AM 10
−30
30
−75 75
IOH Output “HIGH”
Leakage
VOH = 30V
VIN(COMP) = 1.3V
LP2953AM
0.01
0.01
1
2
1
1 µA
2
2.2
VOL Output “LOW” Voltage VIN(COMP) = 1.1V
150
250
250 mV
IO(COMP) = 400 µA
400 400
LP2953AM 150
250
420
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, TJ(MAX), the junction-to-ambient thermal resistance, θJ–A,
and the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperature is calculated using the equation for P(MAX),
.
5 www.national.com
5 Page 
Application Hints (Continued)
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.
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:
MINIMUM LOAD
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.
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.
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).
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.
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.
DS011127-26
FIGURE 3. Power Derating Curve for LP2953AMJ
PROGRAMMING THE OUTPUT VOLTAGE
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:
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.
11 www.national.com
11 Page | ||
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| PDF Descargar | [ Datasheet 5962-9233601MEA.PDF ] | |
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