1. Features

The rated temperature range is 55 ° C to 130 ° C

within the temperature range from 55 ° C to 130 ° C from 55 ° C to 130 ° C SC70 and DSBGA packaging. Power work

predictable curvature error

The accuracy of remote application

30 ° C ± 1.5 to ± 4 ° C (maximum value)

] 130 ° C and 55 ° C ± 2.5 to ± 5 ° C (maximum value)

Power supply voltage range 2.4 V to 5.5 V

current consumption of 10 μA (

Non-linear ± 0.4%(typical)

Output impedance 160Ω (maximum)

Load adjustment 0 mia lt; IL LT; 16 mAh-2.5 millival (Maximum)

2. Application

Mobile phone

Computer

Power module

Battery management

[

[ 123] Fax

Printer

HVAC

Disk drive

Equipment

3. Explanation

LM20 is a precision analog output CMOS integrated temperature sensor higher than 55 ° C to 130 ° C. The working range of the power supply is 2.4V ~ 5.5V. The transmission function of the LM20 is mainly linear, but there is a predictable parabolic line rate. When the parabolic line transmission function is ± 1.5 ° C, the ambient temperature is 30 ° C error increased linearity, and the maximum value is ± 2.5 ° C at the extreme temperature range. This temperature range is affected by the power supply. At the power supply voltage of 2.7 V to 5.5 V, the extreme temperature range is 130 ° C 55 ° C. The power supply voltage is reduced to 2.4 V to change the negative extreme to 30 ° C, and the positive extreme temperature is kept at a static current of 130 ° CLM20 less than 10 μA. Therefore, in the static air, the heating temperature is lower than 0.02 ° C. The closing ability of the LM20 is inherent, because its inherent low power consumption allows it to power the power directly by many logical doors or not need to be closed

Absolutely maximum rated value

Beyond the free air temperature range of work free air air temperature range (Unless there are other instructions) (1) (2)

(1) The stress that exceeds the absolute maximum rated value may cause permanent damage to the device. These are the stress level only applicable to the following situationIt does not mean that the device runs the operating conditions under any other conditions under these conditions or other conditions. Long -term exposure may affect the reliability of the device under absolute maximum rated conditions.

(2) The welding process must comply with TI's return welding temperature curve specification. Reference/Packaging.

(3) When the input voltage (VI) of any pins exceeds the power supply (VI LT; GND or Vi GT; V+), the current of the pin should be limited to 5 mAh.

Electric characteristics: lm20b

Unless otherwise explained, these specifications are suitable for V+ 2.7 VDC. All limit ta tj tmin to TMAX, unless there is another explanation.

(1) Ensure that TI's AOQL (average shipment quality level) is limited.

(2) The typical value is TJ TA 25 ° C, which represents the most likely parameter specifications.

(3) The accuracy refers to the voltage, current, and temperature (represented by ° C) in the specified voltage.

Electric characteristics: LM20B (continued)

Unless otherwise explained, these specifications are suitable for V+ 2.7 VDC. All limit ta tj tmin to TMAX, unless there is another explanation.

(4) Non -linearity refers to the temperature range of the calculated output voltage and temperature curve and the optimal fit line.

(5) LM20 can absorb up to 1 μA source 16 μA.

(6) Load regulation or output impedance specifications are suitable for the power supply voltage range of 2.4 to 5.5 V.

(7) The adjustment is measured by using a low -occupied pulse test under constant knot temperature. The output change effect caused by heating can be calculated by the internal dissipation by the heat resistance.

(8) Calculating the power supply input voltage by minimizing the output voltage from the highest output voltage from the lowest output voltage.

Electric characteristics: LM20C

Unless otherwise explained, these specifications are suitable for V+ 2.7 VDC. All limit ta tj tmin to TMAX, unless there is another explanation.

(1) Ensure that TI's AOQL (average shipment quality level) is limited.

(2) The typical value is TJ TA 25 ° C, which represents the most likely parameter specifications.

(3) The accuracy refers to the voltage, current, and temperature (represented by ° C) in the specified voltage.

(4) Non -linearity refers to the temperature range of the calculated output voltage and temperature curve and the best bias of the line that fit the optimal fitEssence

(5) LM20 can absorb up to 1 μA source 16 μA.

(6) Load adjustment or output impedance specifications are suitable for the power supply voltage range of 2.4 to 5.5 V

Electric characteristics: LM20C (continued)

Otherwise these specifications are suitable for V+ 2.7 VDC. All limit ta tj tmin to TMAX, unless there is another explanation.

(7) The adjustment is measured by using a low -occupied pulse test under constant knot temperature. The output change effect caused by heating can be calculated by the internal dissipation by the heat resistance.

(8) Calculating the power supply input voltage by minimizing the output voltage from the highest output voltage from the lowest output voltage.

Detailed instructions

Overview

LM20 device is a precision analog output CMOS integrated circuit temperature sensor, which is the temperature range of 55 ° C to 130 ° C. The power supply range is 2.4 V to 5.5 V. The transmission function LM20 is mainly linear, but there is a slight predictable parabolic line rate. When the ambient temperature is 30 ° C, the specified value of the parabolic transmission function is usually ± 1.5 ° C error increased linearity, reaching a maximum ± 2.5 ° C within the extreme temperature range of LM20. This temperature range is affected by the power supply voltage. The extreme temperature range at the power supply voltage of 2.7 V to 5.5 V is 130 ° C and 55 ° C. Reducing the power supply voltage to 2.4 V will change the negative extreme to 30 ° C, while the positive extreme is kept at 130 ° C. The static current of LM20 is less than 10 μA. Therefore, in static air, the heating temperature is less than 0.02 ° C. The performance of turning off the LM20 is inherent, because its inherent low power consumption allows it to directly supply power from the output of many logical doors, and it does not need to be turned off at all. The temperature sensing element consists of a simple base of the base, which emit the polar knot from the current source. The temperature sensor is then buffered and provided to the output pin. The amplifier has a simple class A output level, so it can provide a low impedance output sinking 1 μA from 16μA.

function description

LM20 transfer function

LM20 transfer function can be described in different methods, and the accuracy is different. Simple linear 25 ° C has good accuracy transmission functions: vo 11.69 millival/°cXT+ 1.8663 volt (1) at the entire work of 55 ° C to 130 ° C Within the temperature range, use the parabolic wire transmission function.

VO ( 3.88 × 10 6 × T2)+( 1.15 × 10 2 × T) +1.8639 (2) Use equations 2, which can generate the following temperature-voltage output characteristic table.

Application information

The characteristics of LM20 make it applicable to many general temperature sensing applications. Multiple program package options extend their flexibility.

Capacity load

LM20 can handle the capacitance load well. Without any preventive measures, LM20 can drive any capacitance load greater than 300 PF, as shown in Figure 2. Within the specified temperature range, the LM20 has a maximum output impedance of 160Ω. In a very noisy environment, some filtering may need to be added to minimize noise sensors. It is recommended to add 0.1 μF+ground to the power supply voltage from V, as shown in Figure 4. In a noisy environment, you may even need to add a capacitor to the ground to the ground to ground with a series resistor, as shown in Figure 4. The maximum output of 1 μF output capacitor with 160Ω and a 200Ω series resistance will form a 442 Hz low -pass filter. Because the hot time constant LM20 is much slower, the overall response time of the LM20 will not be significantly affected. When the circuit output is applied to a transient load current, the series resistance value may increase any sound that may be observed.

LM20 DSBGA sensitivity

Packaging LM20 DSBGA exposure in the bright sun may cause the output reading of the LM20 to decrease by 1.5 V. In the normal office environment, the output voltage is minimized (less than A's millivolva drop). In any case, TI recommends that LM20 DSBGA is placed in a certain type of shell, which can reduce light. Most chassis provides sufficient protection. LM20 cannot maintain permanent injury caused by light. Remove the light source will cause the output voltage of the LM20 to return to the appropriate value.

Typical application

The full -scale degree of brilliant (Celsius) temperature sensor ( 55 ° C to 130 ° C) LM20 of a single -section lithium -ion battery pack is very low, The power supply range is wide; therefore, it can easily drive by the battery as shown in Figure 5.

Design requirements

Because LM20 is a simple temperature sensor, which provides analog output, the design requirements are more important than electrical requirements. For detailed explanations, see the layout part.

Detailed design program

LM20 transmission function can be described in different methods, and the accuracy is also different. Simple linear 25 ° CThe transmission function with good accuracy is: VO 11.69 millival/° CXT+ 1.8663 volts (4) The entire working temperature range from 55 ° C to 130 ° C is used function. VO ( 3.88 × 10 6 × T2)+( 1.15 × 10 2 × T) +1.8639 (5)

Another choice of the secondary equation is to use the minimum second multiplication method to determine the second -order transmission function: T ( 2.3654 × vo2)+( 78.154 × vo) +153.857

] T is the temperature, the unit is ° C, VO is the output voltage, and the unit is volt. (7) By calculating a linear temperature transmission function, the best result of a limited temperature change range can be obtained in this range. Linear transmission function can be by LM20. The slope of the linear transmission function can use equations 8 calculations: m 7.76 × 10 6 × T #872222,

T is the middle value of the temperature range of interest, M is v in v, v /° C is unit. (8) For example, for the temperature range TMIN 30 to tmax 100 ° C: temperature 35 ° C (9) and m 11.77 millival/degrees Celsius (10) linear transmission function partial partial partial partial The displacement can be calculated by equation 11 equations: B (vop (tmax)+vop (t) m × (tmax+t))/2

VOP (tmax) is the parabolic line of VO The output voltage calculated at TMAX #8226; VOP (T) is the output voltage calculated using VO's parabolic transmission function at T. (11) Table 3 Calculates the best fit linear transmission function of many commonly used temperature range. As shown in Table 3, the error introduced by the linear transmission function increases with the temperature range.

Design requirements

Use reference (LM4040) and comparator (LM7211) to create a simple constant thermostat , Figure 7 shown in the middle.

Detailed design program

You can use Formula 12 and Formula 13 to calculate the threshold.

System Example

Keep power consumption when you shut down

LM20 consumes very little electricity; therefore, it can be simply closed, through The output of its power pins is a logical door, as shown in Figure 9.

Model converter input level

Most of the CMOS ADC found in ASIC has sampling data comparator input structures. This is the infamous sadness to simulation output devices, such as LM20 and many operational amplifiers. The reason for this grief is the instant charging requirements of the input capacitance in ADC. This requirement is easy to accommodate by adding a capacitor. Because not all ADC Figure 10 has the same input level, the charging requirements will be different, so different compensation capacitors are needed. This ADC is displayed for reference only. If you need digital output temperature, see LM74 and other devices.

Power recommendation

LM20 has a very wide 2.4-V to 5.5-V power supply voltage range, which is an ideal choice for many applications. In a noisy environment, TIs are recommended to increase at least 0.1 μF from V+to GND to bypass the power supply voltage. A larger capacitor may be required, which depends on the noise of power.

Layout

layout guide

Like other integrated circuit temperature sensors, LM20 can be easily applied. You can stick to the surface with glue. The temperature of the LM20 sensing is on the surface temperature connected to the LM20 lead. Realizing the integrated circuit temperature sensor assumes that the air temperature is almost the same as the surface temperature; if the air temperature is much higher than or lower than the surface temperature, the actual measurement temperature should be at the surface temperature and air temperature. In order to ensure good thermal conductivity, the back of the LM20 mold is directly connected to the sales of 2 GND. The traces of this ground temperature and other leads of LM20 will also affect the temperature feel. Alternatively, the LM20 can be installed in the sealing end metal tube, and then it can be immersed in the slot or screwed into the screw hole of the fuel tank. Like any integrated circuit, the routes and circuits that are attached to the LM20 and its attached must be insulated and dry to prevent leakage and corrosion. If the circuit may work at low temperature, this is particularly correct. Printing circuit coatings and varnish, such as presuppable coating epoxy or impregnation agent, are usually used to ensure that moisture does not corrode LM20 or its connecting parts.

Thermal factors

Thermal resistance -matching environment temperature (RθJA) is the temperature generated by the temperature rising parameters used to calculate the temperature of the device due to its power consumption. For LM20, the equation temperature used to calculate the ascending mold as follows: TJ TA+Rθja [(V+IQ)+(V+-VO) IL]

IQ is static current and IL

The load current on the output end. Because the knot temperature of the LM20 is to measure the load current required for LM20 when measured the actual temperature.