NSC LM56CIMM Dual output low power thermostat Datasheet

LM56
Dual Output Low Power Thermostat
General Description
Features
The LM56 is a precision low power thermostat. Two stable
temperature trip points (VT1 and VT2) are generated by dividing down the LM56 1.250V bandgap voltage reference using
3 external resistors. The LM56 has two digital outputs. OUT1
goes LOW when the temperature exceeds T1 and goes
HIGH when the the temperature goes below (T1–THYST).
Similarly, OUT2 goes LOW when the temperature exceeds
T2 and goes HIGH when the temperature goes below
(T2–THYST). THYST is an internally set 5˚C typical hysteresis.
The LM56 is available in an 8-lead Mini-SO8 surface mount
package and an 8-lead small outline package.
n
n
n
n
n
n
Key Specifications
n Power Supply Voltage
2.7V–10V
n Power Supply Current
230 µA (max)
1.250V ± 1% (max)
n VREF
Applications
n
n
n
n
n
n
n
n
Digital outputs support TTL logic levels
Internal temperature sensor
2 internal comparators with hysteresis
Internal voltage reference
Currently available in 8-pin SO plastic package
Future availability in the 8-pin Mini-SO8 package
n Hysteresis Temperature
Microprocessor Thermal Management
Appliances
Portable Battery Powered 3.0V or 5V Systems
Fan Control
Industrial Process Control
HVAC Systems
Remote Temperature Sensing
Electronic System Protection
5˚C
n Internal Temperature Sensor
Output Voltage
(+6.20 mV/˚C x T) +395 mV
n Temperature Trip Point Accuracy:
LM56BIM
± 2˚C (max)
± 2˚C (max)
± 3˚C (max)
+25˚C
+25˚C to +85˚C
−40˚C to +125˚C
LM56CIM
± 3˚C (max)
± 3˚C (max)
± 4˚C (max)
Simplified Block Diagram and Connection Diagram
DS012893-2
DS012893-1
Order
Number
NS
Package
Number
Transport
Media
Package
Marking
LM56BIM LM56BIMX
LM56CIM LM56CIMX
LM56BIMM
LM56BIMMX
LM56CIMM
LM56CIMMX
M08A
M08A
M08A
M08A
MUA08A
MUA08A
MUA08A
MUA08A
SOP-8
SOP-8
SOP-8
SOP-8
MSOP-8
MSOP-8
MSOP-8
MSOP-8
2500 Units
2500 Units
3500 Units
3500 Units
Rail
Tape &
Reel
Rail
Tape &
Reel
Rail
Tape & Reel
Rail
Tape & Reel
LM56BIM
LM56BIM
LM56CIM
LM56CIM
T02B
T02B
T02C
T02C
© 2000 National Semiconductor Corporation
DS012893
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LM56 Dual Output Low Power Thermostat
April 2000
LM56
Typical Application
DS012893-3
VT1 = 1.250V x (R1)/(R1 + R2 + R3)
VT2 = 1.250V x (R1 + R2)/(R1 + R2 + R3)
where:
(R1 + R2 + R3) = 27 kΩ and
VT1 or T2 = [6.20 mV/˚C x T] + 395 mV therefore:
R1 = VT1/(1.25V) x 27 kΩ
R2 = (VT2/(1.25V) x 27 kΩ) − R1
R3 = 27 kΩ − R1 − R2
FIGURE 1. Microprocessor Thermal Management
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2
Input Voltage
Input Current at any pin (Note 2)
Package Input Current(Note 2)
Package Dissipation at TA = 25˚C
(Note 3)
ESD Susceptibility (Note 4)
Human Body Model
Machine Model
Soldering Information
SO Package (Note 5) :
Vapor Phase (60 seconds)
Infrared (15 seconds)
Storage Temperature
12V
5 mA
20 mA
215˚C
220˚C
−65˚C to + 150˚C
Operating Ratings(Note 1)
900 mW
Operating Temperature Range
LM56BIM, LM56CIM
Positive Supply Voltage (V+)
Maximum VOUT1 and VOUT2
1000V
200V
TMIN ≤ TA ≤ TMAX
−40˚C ≤ TA ≤ +125˚C
+2.7V to +10V
+10V
LM56 Electrical Characteristics
The following specifications apply for V+ = 2.7 VDC, and VREF load current = 50 µA unless otherwise specified. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25˚C unless otherwise specified.
Symbol
Parameter
Conditions
Typical
LM56BIM
LM56CIM
Units
(Note 6)
Limits
Limits
(Limits)
(Note 7)
(Note 7)
±2
±2
±3
±3
±3
±4
3
3
˚C (min)
6
6
˚C (max)
3.5
˚C (min)
˚C (max)
Temperature Sensor
Trip Point Accuracy (Includes
VREF, Comparator Offset, and
+25˚C ≤ TA ≤ +85˚C
Temperature Sensitivity errors)
−40˚C ≤ TA ≤ +125˚C
Trip Point Hysteresis
TA = −40˚C
4
˚C (max)
˚C (max)
˚C (max)
TA = +25˚C
5
3.5
6.5
6.5
TA = +85˚C
6
4.5
4.5
˚C (min)
7.5
7.5
˚C (max)
4
4
˚C (min)
8
8
˚C (max)
TA = +125˚C
Internal Temperature
6
+6.20
mV/˚C
Sensitivity
Temperature Sensitivity Error
±2
±3
±3
±4
˚C (max)
˚C (max)
Output Impedance
−1 µA ≤ IL ≤ +40 µA
1500
1500
Ω (max)
Line Regulation
+
+3.0V ≤ V ≤ +10V,
+25 ˚ C ≤ TA ≤ +85 ˚ C
± 0.36
± 0.36
mV/V (max)
+3.0V ≤ V+ ≤ +10V,
−40 ˚ C ≤ TA < 25 ˚ C
± 0.61
± 0.61
mV/V (max)
+2.7V ≤ V+ ≤ +3.3V
± 2.3
± 2.3
mV (max)
300
300
nA (max)
VT1 and VT2 Analog Inputs
IBIAS
VIN
Analog Input Bias Current
150
Analog Input Voltage Range
+
V −1
V
GND
VOS
Comparator Offset
2
V
8
8
mV (max)
±1
±1
% (max)
± 12.5
± 12.5
mV (max)
VREF Output
VREF
VREF Nominal
1.250V
VREF Error
∆VREF/∆V
+
∆VREF/∆IL
Line Regulation
Load Regulation Sourcing
V
+3.0V ≤ V ≤ +10V
0.13
0.25
0.25
mV/V (max)
+2.7V ≤ V+ ≤ +3.3V
0.15
1.1
1.1
mV (max)
0.15
0.15
mV/µA
(max)
+
+30 µA ≤ IL ≤ +50 µA
3
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LM56
Absolute Maximum Ratings (Note 1)
LM56
LM56 Electrical Characteristics
The following specifications apply for V+ = 2.7 VDC, and VREF load current = 50 µA unless otherwise specified. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25˚C unless otherwise specified.
Symbol
Parameter
Conditions
Typical
Limits
Units
(Note 6)
(Note 7)
(Limits)
V+ = +10V
230
µA (max)
V+ = +2.7V
230
µA (max)
V+ = +5.0V
1
µA (max)
0.4
V (max)
V+ Power Supply
IS
Supply Current
Digital Outputs
IOUT(“1”)
Logical “1” Output Leakage
VOUT(“0”)
Logical “0” Output Voltage
Current
IOUT = +50 µA
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. The guaranteed specifications apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed test conditions.
Note 2: When the input voltage (VI) at any pin exceeds the power supply (VI < GND or VI > V+), the current at that pin should be limited to 5 mA. The 20 mA maximum package input current rating limits the number of pins that can safely exceed the power supplies with an input current of 5 mA to four.
Note 3: The maximum power dissipation must be derated at elevated temperatures and is dictated by TJmax (maximum junction temperature), θJA (junction to ambient thermal resistance) and TA (ambient temperature). The maximum allowable power dissipation at any temperature is PD = (TJmax–TA)/θJA or the number given
in the Absolute Maximum Ratings, whichever is lower. For this device, TJmax = 125˚C. For this device the typical thermal resistance (θJA) of the different package
types when board mounted follow:
Package Type
θJA
M08A
110˚C/W
MUA08A
250˚C/W
Note 4: The human body model is a 100 pF capacitor discharge through a 1.5 kΩ resistor into each pin. The machine model is a 200 pF capacitor discharged directly
into each pin.
Note 5: See AN450 “Surface Mounting Methods and Their Effects on Product Reliability” or the section titled “Surface Mount” found in any post 1986 National Semiconductor Linear Data Book for other methods of soldering surface mount devices.
Note 6: Typicals are at TJ = TA = 25˚C and represent most likely parametric norm.
Note 7: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).
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LM56
Typical Performance Characteristics
Quiescent Current vs
Temperature
VREF Output Voltage vs
Load Current
DS012893-4
OUT1 and OUT2 Voltage
Levels vs Load Current
DS012893-5
DS012893-32
Trip Point Hysteresis vs
Temperature
Temperature Sensor
Output Voltage vs
Temperature
DS012893-7
Trip Point
Accuracy vs Temperature
Temperature Sensor
Output Accuracy vs
Temperature
DS012893-8
Comparator Bias Current
vs Temperature
DS012893-10
OUT1 and OUT2 Leakage
Current vs Temperature
DS012893-11
5
DS012893-9
DS012893-12
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LM56
Typical Performance Characteristics
(Continued)
VTEMP Output
Line Regulation vs Temperature
DS012893-31
VREF Start-Up Response
VTEMP Start-Up Response
DS012893-13
DS012893-14
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LM56
Functional Description
DS012893-15
1.0
V+
PIN DESCRIPTION
GND
VREF
VTEMP
OUT1
OUT2
This is the positive supply voltage pin. This pin
should be bypassed with 0.1 µF capacitor to
ground.
This is the ground pin.
This is the 1.250V bandgap voltage reference output pin. In order to maintain trip point accuracy this
pin should source a 50 µA load.
This is the temperature sensor output pin.
This is an open collector digital output. OUT1 is active LOW. It goes LOW when the temperature is
greater than T1 and goes HIGH when the temperature drops below T1–5˚C. This output is not intended to directly drive a fan motor.
This is an open collector digital output. OUT2 is active LOW. It goes LOW when the temperature is
greater than the T2 set point and goes HIGH when
the temperature is less than T2–5˚C. This output is
not intended to directly drive a fan motor.
VT1
This is the input pin for the temperature trip point
voltage for OUT1.
VT2
This is the input pin for the low temperature trip
point voltage for OUT2.
DS012893-16
VT1 = 1.250V x (R1)/(R1 + R2 + R3)
VT2 = 1.250V x (R1 + R2)/(R1 + R2 + R3)
where:
(R1 + R2 + R3) = 27 kΩ and
VT1 or T2 = [6.20 mV/˚C x T] + 395 mV therefore:
R1 = VT1/(1.25V) x 27 kΩ
R2 = (VT2/(1.25V) x 27 k)Ω–R1
R3 = 27 kΩ − R1 − R2
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LM56
range of −40˚C to +125˚C, for example, is specified at ± 3˚C
for the LM56BIM. Note this trip point error specification does
not include any error introduced by the tolerance of the actual resistors used, nor any error introduced by power supply
variation.
Application Hints
2.0
LM56 TRIP POINT ACCURACY SPECIFICATION
For simplicity the following is an analysis of the trip point accuracy using the single output configuration show in Figure 2
with a set point of 82˚C.
If the resistors have a ± 0.5% tolerance, an additional error of
± 0.4˚C will be introduced. This error will increase to ± 0.8˚C
when both external resistors have a ± 1% tolerance.
Trip Point Error Voltage = VTPE,
Comparator Offset Error for VT1E
3.0 BIAS CURRENT EFFECT ON
TRIP POINT ACCURACY
Bias current for the comparator inputs is 300 nA (max) each,
over the specified temperature range and will not introduce
considerable error if the sum of the resistor values are kept
to about 27 kΩ as shown in the typical application of Figure
1 . This bias current of one comparator input will not flow if
the temperature is well below the trip point level. As the temperature approaches trip point level the bias current will start
to flow into the resistor network. When the temperature sensor output is equal to the trip point level the bias current will
be 150 nA (max). Once the temperature is well above the trip
point level the bias current will be 300 nA (max). Therefore,
the first trip point will be affected by 150 nA of bias current.
The leakage current is very small when the comparator input
transistor of the different pair is off (see Figure 3) .
The effect of the bias current on the first trip point can be defined by the following equations:
Temperature Sensor Error = VTSE
Reference Output Error = VRE
DS012893-17
FIGURE 2. Single Output Configuration
1. VTPE = ± VT1E − VTSE + VRE
Where:
2. VT1E = ± 8 mV (max)
3. VTSE = (6.20 mV/˚C) x ( ± 3˚C) = ± 18.6 mV
4. VRE = 1.250V x ( ± 0.01) R2/(R1 + R2)
where IB = 300 nA (the maximum specified error).
The effect of the bias current on the second trip point can be
defined by the following equations:
Using Equations from page 1 of the datasheet.
VT1 =1.25VxR2/(R1+R2)=(6.20 mV/˚C)(82˚C) +395 mV
Solving for R2/(R1 + R2) = 0.7227
then,
5. VRE = 1.250V x ( ± 0.01) R2/(R1 + R2) = (0.0125) x
(0.7227) = ± 9.03 mV
The individual errors do not add algebraically because, the
odds of all the errors being at their extremes are rare. This is
proven by the fact the specification for the trip point accuracy
stated in the Electrical Characteristic for the temperature
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where IB = 300 nA (the maximum specified error).
The closer the two trip points are to each other the more significant the error is. Worst case would be when VT1 = VT2 =
VREF/2.
8
LM56
Application Hints
(Continued)
DS012893-18
FIGURE 3. Simplified Schematic
As with any IC, the LM56 and accompanying wiring and circuits must be kept insulated and dry, to avoid leakage and
corrosion. This is especially true if the cirucit may operate at
cold temperatures where condensation can occur.
Printed-circuit coatings and varnishes such as Humiseal and
epoxy paints or dips are often used to ensure that moisture
cannot corrode the LM56 or its connections.
4.0 MOUNTING CONSIDERATIONS
The majority of the temperature that the LM56 is measuring
is the temperature of its leads. Therefore, when the LM56 is
placed on a printed circuit board, it is not sensing the temperature of the ambient air. It is actually sensing the temperature difference of the air and the lands and printed circuit
board that the leads are attached to. The most accurate temperature sensing is obtained when the ambient temperature
is equivalent to the LM56’s lead temperature.
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LM56
Application Hints
5.0
(Continued)
VREF AND VTEMP CAPACTIVE LOADING
DS012893-19
FIGURE 4. Loading of VREF and VTEMP
The circuit shown inFigure 5 will reduce the effective bias
current error for VT2 as discussed in Section 3.0 to be
equivalent to the error term of VT1. For this circuit the effect
of the bias current on the first trip point can be defined by the
following equations:
The LM56 VREF and VTEMP outputs handle capacitive loading well. Without any special precautions, these outputs can
drive any capacitive load as shown in Figure 4 .
6.0 NOISY ENVIRONMENTS
Over the specified temperature range the LM56 VTEMPoutput has a maximum output impedance of 1500Ω. In an extremely noisy environment it may be necessary to add some
filtering to minimize noise pickup. It is recommended that 0.1
µF be added from V+ to GND to bypass the power supply
voltage, as shown in Figure 4 . In a noisy environment it may
be necessary to add a capacitor from the VTEMP output to
ground. A 1 µF output capacitor with the 1500Ω output impedance will form a 106 Hz lowpass filter. Since the thermal
time constant of the VTEMP output is much slower than the
9.4 ms time constant formed by the RC, the overall response
time of the VTEMP output will not be significantly affected. For
much larger capacitors this additional time lag will increase
the overall response time of the LM56.
7.0
where IB = 300 nA (the maximum specified error).
Similarly, bias current affect on VT2 can be defined by:
APPLICATIONS CIRCUITS
where IB = 300 nA (the maximum specified error).
The current shown in Figure 6 is a simple overtemperature
detector for power devices. In this example, an audio power
amplifier IC is bolted to a heat sink and an LM56 Celsius
temperature sensor is mounted on a PC board that is bolted
to the heat sink near the power amplifier. To ensure that the
sensing element is at the same temperature as the heat sink,
the sensor’s leads are mounted to pads that have feed
throughs to the back side of the PC board. Since the LM56 is
sensing the temperature of the actual PC board the back
side of the PC board also has large ground plane to help
conduct the heat to the device. The comparator’s output
goes low if the heat sink temperature rises above a threshold
set by R1, R2, and the voltage reference. This fault detection
output from the comparator now can be used to turn on a
cooling fan. The circuit as shown in design to turn the fan on
when heat sink temperature exceeds about 80˚C, and to turn
the fan off when the heat sink temperature falls below approximately 75˚C.
DS012893-20
FIGURE 5. Reducing Errors Caused by Bias Current
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LM56
Application Hints
(Continued)
DS012893-21
FIGURE 6. Audio Power Amplifier Overtemperature Detector
DS012893-22
FIGURE 7. Simple Thermostat
11
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LM56
Physical Dimensions
inches (millimeters) unless otherwise noted
8-Lead (0.150" Wide) Molded Small Outline Package, JEDEC
Order Number LM56BIM, LM56BIMX, LM56CIM or LM56CIMX
NS Package Number M08A
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12
LM56 Dual Output Low Power Thermostat
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
8-Lead Molded Mini Small Outline Package (MSOP)
(JEDEC REGISTRATION NUMBER M0-187)
Order Number LM56BIMM, LM56BIMMX, LM56CIMM, or LM56CIMMX
NS Package Number MUA08A
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