Features

From 1V to 40V, the induction voltage is used to establish a working current in LM134 , 64mV at 25 ° C, directly 0.02%/volt current adjustment and adjustment and adjustment and regulation Absolute temperature (K) proportions. This programmable, from 1 μA to 10mA, is the simplest external resistance connection, and then the current of the current of the real double -end operation ≈+0.33%/degree Celsius temperature dependencies. The zero drift operation can be used with another resistor and a diode at a completely specified temperature. The initial accuracy of the sensor current source is ± 3%, including partial pressure network, surge protection, low power reference,

Description

slope generation, LED drive, and temperature sensing. LM234-3 and LM234-6 are specified as LM134/LM234/LM334 is the three-ends adjustable real temperature sensor. It has an initial current source of 10000: 1, and the working accuracy is ± 3 ° C and ± 6 ° C, respectively. These currents, good current regulation and extensive equipment are the ideal remote application dynamic voltage range of 1V to 40V. The current is because the connected resistance is not established in the running resistance and has no other impact accuracy with an external resistance and no other impact accuracy. In addition, only 2 wires are needed. Need parts. The initial current accuracy is ± 3%. LM134/LM234/LM334 is a real floating current LM134 is a power supply without a separate power supply. -55 ° C to+125 ° C, LM234 from -25 ° C to+100 ° C. In addition, from 0 ° C to+70 ° C, the voltage of up to the ups and downs of 20V and LM334. These devices have only dozens of Weian currents, which can be used for sealing, to-92 and SOIC-8 allowed devices to act as rectifies and plastic packaging at the same time. The current source in the exchange application.

Electric characteristics (1)

(1) Unless otherwise regulations, it should be in tj 25 ° [[ Porter pulse test under C so that the knot temperature will not change during the test

(2) Set the current that flows into V+pins. For the basic double -end current source circuits shown in FIG. 13. Iset has determined through the following formulas: Iset 67.7 articles (@25 ° C). Set the current error represents the deviation percentage from the value. The degree Celsius 25 degrees Celsius (227 micro -volt/degrees Celsius) when Isert increases 0.336%/TJ.

(3) Iset is proportional to the absolute temperature (K). An ISET at any temperature can be calculated from the following formula: Iset IO (T/TO), where IO measuring the temperature to (℃).

LM134 designIt is to facilitate application, but general discussion on its design characteristics is to make designers familiarize the characteristics of the equipment. These characteristics may not be obvious. This includes the effects of rotation, power consumption, capacitance, noise and contact resistance. Calculating the total current of the RSET through the LM134 (ISET) is to set the current (IR) current and the bias current (IBIA) of the LM134, as shown in Figure 13.

In typical performance, the characteristics of the two current ratio are provided under the ratio of ISET to IBIAS. The current flowing through the RSET is determined by VR, and the VR is about 214 μV/° K (64

MV/298 ° K ~ 214 μV/° K).

Since (for the settings of the settings) IBIAS is just a percentage of ISET, so the equation can be rewritten

is the ratio of ISET and IBIAS. As shown in Figure (2), as the electrical characteristics stipulates that for 2 μA≤ISET ≤ 1MA, N is usually 18, and the equation can be further simplified to

turnover rate

at higher than giving it than to give it than to give it than to give it than to give it than to give it than to give it than to give it than to give it than to give it than to give it than to give it than to give it than to give. At the conversion rate of a fixed threshold (see curve), the LM134 may display non -linear current offset. The rate of this situation is directly proportional to the ISET. When ISET 10 μA, the maximum DV/DT is 0.01 volts/μs; in ISET 1 mAh, the limit is 1 volt/microsecond. The rotation rate higher than the limit will not damage LM134, nor will it cause large current flow.

Thermal effect

Internal heating has a significant impact on the current adjustment of the ISET than 100 μA. For example, when ISET 1 milliang, an increase in 1V through LM134 will increase the knot temperature at 0.4 points in the static air. The temperature coefficient of the output current (ISET) is 0.33%/degree Celsius, so the current changes caused by the increase in temperature (0.4 points) (0.33 points) 0.132%. Compared with the real electric effect, this is a 10: 1 of 10: 1 Regulating degradation. As a result, when DC regulation is important and ISET exceeds 100 μA, the impact must be considered. The heat sinks to package or the to-92 wire can reduce this effect above 3: 1.

Parallel capacitance

In certain applications, due to the load problem or because it limits the AC output impedance of the current source. This is easy to achieve as shown in the application and buffer LM134 by the use field effect pipe. This can reduce the capacitor to less than 3 PF, and increase at least one order of magnitude. DC characteristics (exceptions are not affected.

Noise

The current noise generated by LM134 is about 4 times the scattered noise of the transistor.The source load of the amplifier will increase the reference noise of about 12dB. In many cases, this is acceptable, and a single amplifier can establish a voltage gain of more than 2000.

Lead resistance

Determine the sensing voltage of the working current of LM134 less than 100MV. At this level, the resistance of the thermocouple or lead resistance should be set to the minimum closer to the device through physical positioning current. If possible, avoid using sockets. Only the contact resistance of 0.7Ω can reduce the output current at 1%at 1 mA.

Temperature

LM134 is an ideal remote temperature sensor, because its current mode operation will not lose the accuracy of long wires. The output current is proportional to the absolute temperature, and the unit is Kaijizhi. According to the following formulas:

Because most initial errors are due to the gain (slope error) and not offset. This means that the calibration of only gain adjustment will be trimmed at the same time and zero point.此外，增益调整是一个单点微调，因为LM134在0°K时外推至零，与RSET或任何初始误差无关

LM134的这一特性在The attachment is explained. The ABC is the previous sensor current trimming. A'B′C #39; line is the required output. The fine -tuning of the completion of the T2 will move the output from B to B ′, and the cosmetic rate at the same time will be correct to make the output at T1 and T3 correctly. Generous fine -tuning can be used in RSET or load resistors for termination of LM134. The slope error after trimming is usually less than ± 1%. However, in order to maintain this accuracy, low -temperature coefficient resistors must be used for RSET. RSET's 33 PPM/℃ drift will generate a 1%slope error, because the resistor usually sees roughly the same result temperature changes such as LM134. The separation of RSET and LM134 requires 3 guide lines, and there is a problem of leading resistance, so it is usually not recommended. The metal membrane resistor that drifts less than 20PPM/° C is available. If the best stability is required, you can also use a wire winding resistor.

Application of zero -temperature coefficient current source

Add a diode and a resistor to the standard LM134 configuration to cancel the characteristics of LM134 related to temperature -related. The circuit balance in FIG. 15 The positive temperature (about +0.23 points mv/° C) of the LM134, and the negative temperature of the positive biased silicon diode (about -2.5 millival/degrees Celsius).

Set current (ISET) is the sum of i1 and i2, each accounts for about 50%of the set current, and IBIA. IBIA is usually included in the I1 VR value increased by 5.9%. (See calculating RSET.)

The first step is to use itThe following equations minimize the temperature coefficient of the circuit. The temperature coefficient of using+227μV/℃ as the LM134 (including IBIAS components), -2.5 MV/℃ as the temperature coefficient of the diode (in order to obtain the best results, the value should be measured directly or obtained the diode from the manufacturer).

After the ratio of R1 to R2 is determined, the value of R1 and R2 should be determined to give the required setting current. The formula of the setting current when calculating T 25 ° C is shown below, and then a hypothesis drops by 0.6 volts through the front voltage of the diode (VD), and the voltage on the R1 is 67.7 millival (64 millivolta+5.9%calculation accounts. For iBias) and R2/R1 10 (based on previous calculations).

This circuit will eliminate the temperature coefficient of most LM134, even if the estimation of the characteristics of the diode is inaccurate (as shown in the following example). At the lowest temperature, when a specific diode is in the required ISET, the circuit should be established and tested at temperature. If the measurement temperature of the Iset is positive, R2 should be reduced. If the Tempco obtained is negative, R2 should increase. The diode recommended in this circuit is 1N457, because its TEMPCO is located at the Tempco of 11 by LM134, allowing R2 10 R1. You can also use this circuit to create a current source by setting the TEMPCO component of the TEMPCO equation to the required value instead of 0 to achieve non -zero TEMPCOS. Example: 1 millimeter zero temperature current source

The value of R1 and R2 can be changed to the standard 1%resistance value (R1 133Ω, R2 1.33 million ω) Less 0.75%error than one. If the forward voltage of the diode drops 0.65 volts instead of estimated 0.6 volts (8%of the error), the actual setting current will be

The error is less than 5%. If the TEMPCO estimation value of the diode drops is off, the TEMPCO elimination is still quite effective. Suppose the temperature of the diode is 2.6 millival/degrees Celsius instead of 2.5 millollers/degrees Celsius (4%error). The TEMPCO of this circuit is now:

The setting resistance of the 1MA LM134 current source without temperature compensation is 68Ω and the temperature generated

Therefore, even if the temperature of the diodes compare The estimation value changes ± 4%, and the circuit still eliminates the inherent temperature of 98%of the LM134.

Select R3 VREF/583MA. VREF can be a stable positive voltage fine -tuning R3 to calibration

The output impedance of LM134 at the R " pins is about

Among them