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PDF LMP7300 Data sheet ( Hoja de datos )
| Número de pieza | LMP7300 | |
| Descripción | Micropower Precision Comparator and Precision Reference | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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September 2007
LMP7300
Micropower Precision Comparator and Precision
Reference with Adjustable Hysteresis
General Description
The LMP7300 is a combination comparator and reference
with ideal specifications for precision threshold detecting. The
precision 2.048V reference comes with a 0.25% maximum
error. The comparator features micopower (35 µW), low offset
voltage (.75 mV max), and independent adjustable positive
and negative hysteresis.
Hysteresis control for the comparator is accomplished
through two external pins. The HYSTP pin sets the positive
hysteresis and the HYSTN pin sets the negative hysteresis.
The comparator design isolates the VIN source impedance
and the programmable hysteresis components. This isolation
prevents any undesirable interaction allowing the IC to main-
tain a precise threshold voltage during level detection.
The combination of low offset voltage, external hysteresis
control, and precision voltage reference provides an easy to
use micropower precision threshold detector.
The LMP7300 open collector output makes it ideal for mixed
voltage system designs. The output voltage upper rail is un-
constrained by VCC and can be pulled above VCC to a maxi-
mum of 12V. The LMP7300 is a member of the LMP®
precision amplifier family.
Features
(For VS = 5V, typical unless otherwise noted)
■ Supply current
13 μA
■ Propagation delay
4 μs
■ Input offset voltage
0.3 mV
■ CMRR
100 dB
■ PSRR
100 dB
■ Positive and negative hysteresis control
■ Adjustable hysteresis
1 mV/mV
■ Reference voltage
2.048V
■ Reference voltage accuracy
0.25%
■ Reference voltage source current
1 mA
■ Wide supply voltage range
2.7V to 12V
■ Operating temperature range ambient −40°C to 125°C
Applications
■ Precision threshold detection
■ Battery monitoring
■ Battery management systems
■ Zero crossing detectors
Typical Application
Micropower Precision Battery Low Voltage Detector for 3
Cell Discharge Voltage
20175646
LMP® is a registered trademark of National Semiconductor Corporation.
© 2007 National Semiconductor Corporation 201756
20175642
www.national.com
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Connection Diagram
8-Pin MSOP/SOIC
Top View
20175606
Pin Descriptions
Pin
Name
Description
+IN Non-Inverting
Comparator Input
The +IN has a common-mode voltage range from 1V above the negative rail to, and including,
the positive rail. Internal ESD diodes, connected from the +IN pin to the rails, protect the input
stage from overvoltage. If the input voltage exceeds the rails, the diodes turn on and clamp
the input to a safe level.
−IN Inverting Comparator The −IN has a common-mode voltage range from 1V above the negative rail to, and including,
Input
the positive rail. Internal ESD diodes, connected from the −IN pin to the rails, protects the
input stage from overvoltage. If the input voltage exceeds the rails, the diodes turn on and
clamp the input to a safe level.
GND Ground
This pin may be connected to a negative DC voltage source for applications requiring a dual
supply. If connected to a negative supply, decouple this pin with 0.1 µF ceramic capacitor to
ground. The internal reference output voltage is referenced to this pin. GND is the die
substrate connection.
OUT Comparator Output
The output is an open-collector. It can drive voltage loads by using a pullup resistor, or it can
drive current loads by sinking a maximum output current. This pin may be taken to a
maximum of +12V with respect to the ground pin, irrespective of supply voltage.
HYSTN Negative Hysteresis Pin
This pin sets the lower trip voltage VIL. The common mode range is from 1V above the
negative rail to VCC. The input signal must fall below VIL for the comparator to switch from
high to low state.
HYSTP Positive Hysteresis pin
This pin sets the upper trip voltage VIH. The common mode range is from 1V above the
negative rail to VCC. The input signal must rise above VIH for the comparator to switch from
low to high state.
REF
Reference Voltage
Output Pin
This is the output pin of a 2.048V band gap precision reference.
V+ Positive Supply Terminal The supply voltage range is 2.7V to 12V. Decouple this pin with 0.1 μF ceramic capacitor to
ground.
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In the general case, as demonstrated with both positive and
negative hysteresis bands in Figure 6, noise within these
bands will have no affect on the state of the comparator out-
put. In Example #1 the noise is well behaved and in band. The
output is clean and well behaved. In Example #2, a significant
amount of out of band noise is present but due to hysteresis
no false triggers occur on the rising positive or falling negative
edges. The hysteresis forces the signal level to move higher
or lower before the output is set to the opposite state.
20175628
FIGURE 6. Output Response with Input Noise Less than
Hysteresis Band
How Much Hysteresis Is Correct?
An effective way of determining the minimum hysteresis nec-
essary for clean switching is to decrease the amount of hys-
teresis until false triggering is observed, and then use a
multiple of say three times that amount of hysteresis in the
final circuit. This is most easily accomplished in the bread-
board phase by making R1 and R2 potentiometers. For appli-
cations near or above +100°C a minimum of 5 mV hysteresis
is recommended due to peaking of the LMP7300 noise sen-
sitivity at high temperatures.
LAYOUT RECOMMENDATIONS
A good PCB layout is always important to reduce output to
input coupling. Positive feedback noise reduces performance.
For the LMP7300 output coupling is minimized by the unique
package pinout. The output is kept away from the non-invert-
ing and inverting inputs, the reference and the hysteresis pins.
EVALUATION BOARDS
National Semiconductor provides the following PCB boards
as an aid in evaluating the LMP7300 performance.
Device
Package
Evaluation Board
Ordering ID
LMP7300MA 8-Pin SOIC LMP7300MA-EVAL
LMP7300MM 8-Pin MSOP LMP7300MM-EVAL
WINDOW COMPARATOR
Figure 8 shows two LMP7300s configured as a micropower
window detector in a temperature level detection application.
The circuit shown monitors the ambient temperature change.
If the temperature rises outside the 15°C to 35°C window, ei-
ther comparator 1 for high temp, or comparator 2 for low temp,
will set low, indicating a fault condition has occurred. The
open collector outputs are pulled up separately but can be
wire-OR’d for a single fault indication. If the temperature re-
turns inside the window it must overcome the 22 mV asym-
metric hysteresis band established on either comparator. For
the high side the temperature must drop below 34°C and for
the low side the temperature must rise above 16°C for the
outputs to reset high and remove the fault indication. The
temperature is sensed by a 30 kΩ @ 25°C Omega Precision
NTC Thermistor #44008 (±0.2% tol).
20175629
FIGURE 7. Temperature Controlled Window Detector to Monitor Ambient Temperature
11
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| PDF Descargar | [ Datasheet LMP7300.PDF ] | |
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