General description

LM131 /LM231/LM331 series voltage frequency ratio converter is very suitable for simple low-cost circuits, for modulus conversion, accurate frequency-voltage conversion conversion , Long -term integration, linear frequency modulation or demodulation, and many other functions. The frequency of the output pulse sequence of the voltage-frequency converter and the applied input voltage. Therefore, it provides all the inherent advantages of voltage-frequency conversion technology, and is easy to apply to all standard voltage-frequency converter applications. In addition, LM131A/LM231A/LM331A realizes a new high -precision vertical temperature, which can only be achieved by extending voltage to the frequency module. In addition, LM131 is very suitable for use in a low -power power supply voltage digital system, and can provide a low -cost modular conversion version in the microprocessor control system. Moreover, the frequency of the voltage of the battery power to the frequency converter can easily transmit it through a simple optical isolationer, thereby providing a high -co -module level. LM131/LM231/LM331 uses a new temperature compensation band -based standard circuit, providing excellent accuracy power supply as low as 4.0V throughout the working temperature range. The precision timer circuit has a low bias current for 100 kHz voltage-frequency conversion without lowering rapid response. And the output can drive 3 TTL loads, or high voltage output up to 40V, but can prevent short -circuit VCC.

Features

ensure the maximum linear 0.01%

improved the performance of the existing voltage frequency ratio

Convert application

Division for confession Or single supply operation

Work on a single 5V power supply

Y pulse output compatible with all logical forms

Excellent temperature stability, G50 PPM/§C maximum value

Low power consumption, 5V at 15 mW

Broad -dynamic range, 10 kHz full marking is 100 db min

frequency

full scale The frequency range is wide, 1 HZ to 100 kHz

Low cost

Absolutely maximum rated value (Note 1)

LM131A/LM131 LM231A/LM231 LM331A/LM331

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Power supply voltage 40V 40V 40V

Output continues to continue the short -circuit of the ground on the ground

Output for VCC short circuit continues

Input voltage B0.2V to AVS B0 to AVS B0 .2v to AVS B0.2V to AVS TMIN TMAX TMIN TMIN TMAX

Working ringThe temperature range B55 §C to A125 §C B25 §C to A85 §C 0 §C to A70 §C

Power consumption (PD at 25 ° C)

and thermal resistance ( IJA)

(H package) PD 670 mwija 150 §C/W

(n packaging) PD 1.25W 1.25W

IJA 100 §C/W 100 §C /W (m package) PD 1.25W

IJA 85 §C/W

Lead temperature (welding, 10 seconds)

Double -column direct -inserted packaging (plastic) 260 §C 260 §C 260 §C

Metal tank packaging (to-5) 260 §C

Static discharge sensitivity (Note 4)

Metal tank packaging ( TO-5) 2000V

Other packaging 500V 500V

Electrical characteristics TAE25 §C, unless there are other regulations (Note 2)

Electrical characteristics TAE25 §C, unless there are other regulations (Note 2) (continued)

Note 1: Absolute maximum rated value indicates the limit of damage to the device. During operation, DC and AC electrical specifications are not applicable to devices that exceed the prescribed operating conditions.

Note 2: Unless otherwise explained, all specifications are applicable to Figure 3 circuit with a voltage of 4.0VSVSS40V.

Note 3: Non -linearity means that when the circuit is adjusted to zero errors at 10 Hz and 10 kHz, the deviation of Fout and VIN C (10 kHz/B10 VDC), the frequency range is 1 Hz to 11 to 11 kilohertz. For timing capacitors CT, NPO ceramics, polytefluoroethylene or polystyrene are used.

Note 4: Human model, 100 PF through 1.5 kx resistance to power.

Typical performance features

(Unless otherwise explained, all electrical characteristics are applicable to the circuit in FIG.)

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Typical application (continued)

Simplified operation principle

Voltage-frequency converter

LM131 is a single-chip circuit, design for design for design Multifunctional operations (V-TO-F) converter or frequency-voltage (F-V) converter at the time of accuracy and as a voltage frequency ratio. The simplified box diagram of the LM131 is composed of the switching current source, the input terminal composition, and a single timer. The operation of these blocks is best to pass the working cycle of the basic V-F converter, Figure 2, including LM131 and various resistors and capacitors connected to it. The voltage comparator is compared with a positive input voltage, V1 with 7 stitches and 6 pins and 6 stitches. If V1 is large, the comparator will trigger a single timer. The output timer will turn on the switch current source of the frequency output transistor and the cycle to TE1.1RTCT. During this period, the current I will flow out of the switch current source and provide a fixed amount of costs, QEI C T capacitor, CL. This usually charges VX until the higher level is higher than V1. At the end of the time period, the current I will be closed and the timer will automatically reset. There is no current flowing out of the pin 1, and the capacitor CL will gradually discharge from RL until VX drops to V1 level. The comparator then trigger the timer to start another cycle. The current flowing into the CL is exactly the IAVE E I C (1.1CRCT) C F. If the vehicle recognition number (VIN) doubles, the frequency will double to maintain this balance. Even a simple V-F converter can provide a frequency that is accurate to the accurate input voltage in a wide range of frequency.

Figure 2. Single-machine simplified box voltage-frequency converter display LM131 and external components

The operation details, function block

Figure (Figure 1A) box diagram shows a band gap benchmark that provides a stable 1.9 VDC output. This 1.9 volt DC power regulation is well regulated in the voltage range of 3.9V to 40V. It also has a flat, low temperature coefficient, usually changes less than (/2%more than 100 degrees Celsius. . Precision current reflex provides a current to the current switch to the current I. The current switch switches the current to the pin 1 or ground, depending on the state of the RS trigger. External RTCT network. When? The voltage of the input comparator detects 7 pins is higher than the pin 6, it sets the RS trigger, the current switch is turned on and the output drive transistor. The comparator causes the RS trigger to reset. The reset crystal tube is then connected and the current switch is turned off. However, if the input comparator still detects that the needle pin 7 is higher when the pin is poured 5)/3 VCC, the trigger will not reset will not be reset. The current of one pin 1 will continue to try to make the voltage of the needle 6 higher than the pin 7. This condition is usually applicable to the overload voltage of the start -up condition or the signal input. It should be noticed that the output frequency will be 0 during this overload period; once the signal recovery working range, the output frequency will be restored. The function of the output drive transistor is about 50 times with a pitch resistance. If a voltage occurs, the output current is limited to below 50 mA. NeedleThe voltage adjustment at the two places is 1.90 VDC, and the all values u200bu200bare between 10 mAh and 500 mA. It can be used as a voltage reference to other components, but it must be paid to ensuring that the current will not be taken away from it, otherwise the accuracy of the converter will be reduced.

The working principle of the basic voltage-frequency converter (Figure 1) Simple independent V-F converter as shown in Figure 1 and some basic circuits and some components shown in Figure 2 to improve performance. Add a resistor RINE100 KXG 10%to the pin 7 to the path, so that the bias current (typical B80 NA) of the pin 7 will eliminate the impact of the bias current of the pin 6 to provide minimum frequency offset. The resistance RS at the pin 2 of the needle is adjusted by the 12 KX fixed resistor plus a 5kx (preferably a metal ceramic) gain RHEO STAT. The function of this adjustment is the tolerance of pruning gain LM131, and the tolerance of RT, RL and CT

Typical application (continued)

In order to achieve the best effect, all components should be stable and low Temperature coefficient components, such as metal film resistance. The capacitor should have a low -agent electric absorption; according to the required temperature characteristics, the NPO is best for ceramics, polystyrene, polytefluorolythene or polypropylene. The capacitor CIN is added from the pin 7 to the ground as a VIN filter. The value of 0.01 mf to 0.1 mf is in most cases; however, 1 mf capacitor can be used when better filtering. When the RC time constant is matched at the pins 6 and the pin of the needle, the voltage level jump vehicle recognition number (VIN) will lead to the fourth -order jump. If CIN is much less instead of CL, one step at VIN may cause Fout temporarily. A 47X resistor connects with 1 mf cll to provide a lagging effect to help the input comparator provide good linearity (typical value is 0.03%). Precision V-TO-F operation details converter (Figure 3) In this circuit, traditional computing amplifiers and feedback capacitors are used for points. When the output of the integrator exceeds the nominal threshold, the timing cycle at the LM131 pin 6 is started. The average current (needle 2) of the input amplifier (needle pin 2) is i C (1.1 RTCT) C f, and Bvin/forest. In this circuit, the voltage offset input comparator of LM131 does not affect the independent V-F converter converter; the LM131 bias current or bias current will not change. In contrast, the size of the offset voltage and offset current is the only restriction signal that can be accurately converted. Because the voltage offset of the operation amplifier is less than 1 millivolt, the offset current is 2 mAh, and the cost is low. It is recommended to use this circuit to obtain the optimal accuracy of a small signal. This circuit will immediately respond to any change in the input signal (where the independent circuit is not) makes the output frequency accurately represent the vehicle identification number, and the fastest 2 output pulse interval can be measured. In the precision mode, because the current source (pin 1) is always at the grounding potential, and the voltage does not change with VIN or FOUTIt can get good linearity. (In the independent V-F converter, the main reason for non-linearity is that the output impedance of the pins 1 that causes I change is the function of VIN). The circuit in Figure 4 is the same as Figure 3, but with the changes required for high -speed operation.

1. Use stable parts with lower temperature factor. See typical application parts.

2. For VSE8V to 22V, the resistance can be 5kx or 10kx, but for VSE4.5V to 8V, this resistance must be 10kx.

3.A1: Recommended models LM108, LM308A, LF411A use low offset voltage and low offset current operation amplifier

Figure 3 Standard test circuit and application circuit, precision voltage-frequency converter

Typical application (continued)

Operation details, frequency-voltage converters (Figure 5 and 6) In these applications, the pulse input of the fins has the following differences in C-R network and pinnacles 6 The negative edge of 6 causes the input comparator of the timer circuit. Just like a V-TO-F converter, the average current flowing out of the pin 1 is the average E i C (1.1 RTCT) C F. In the simple circuit in FIG. 5, this current is filtered into the network RL E 100 KX and 1 mf. Ripples will have less peaks exceeding 10 millivolves, but the response will be 0.1 seconds of time constant, 0.7 seconds 0.1%accuracy. In the precision circuit, the computing amplifier provides a buffer output and can also be used as a 2 pole filter. When the ripples are more frequent than 1 kHz, the peak value will be less than 5 mv, and the response time is much faster than Figure 5. However, for the input frequency of less than 200 Hz, the circuit is worse than Figure 5. The filter engineering time constant to obtain sufficient response and small Ripple only need to study the manufacture. In essence, the response of the V-TO-F converter can be fast, but the F-to-V reaction cannot.

1. Use stable parts with lower temperature factor. See typical application parts.

2. For VSE8V to 22V, the resistance can be 5 kx or 10 kx, but for VSE4.5V to 8V, it must be 10 kx.

3.A1 uses low bias voltage and low bias current amplifier: Recommended model LF411A or LF356.

Typical application (continued)