General description

lm231 /lm 331 series voltage-frequency converter is very suitable -The voltage conversion conversion, long -term integration, linear frequency regulation or demodulation and other functions. When the output is used as a voltage, the inverter is a pulse trains the frequency of accurate proportional proportion to the applied input voltage. Therefore, it provides voltage-frequency conversion technology, which is simply easy to apply for inverter applications with all standard voltage. In addition, LM231A/LM331A reaches a new height and accuracy level and temperature, and can only be maintained with an expensive voltage-frequency module. In addition, LM231/331 is very suitable for digital application low -power voltage system low -cost modulus conversion microprocessor control system. Moreover, the frequency of the battery power supply voltage to the inverter can easily guide the isolation high -co -mode level through a simple optical isolation. LM231/LM331 uses a new temperature compensation band -based standard circuit, providing excellent accuracy within the entire operating temperature range, as low as 4.0V at the power supply. The precision timer circuit has a low bias current and does not decrease 100 Qianhe voltage-frequency conversion. And the output can drive 3 TTL loads or high -voltage output up to 40V, but there is short -circuit protection for VCC.

Features

Guarantee the maximum linear 0.01%

Performance conversion application that improves the existing voltage frequency ratio

Division or single supply operation

Working on a single 5V power supply

Pulse output is compatible with all logic forms

Excellent temperature stability, the maximum value is ± 50 ppm/℃

Low work Consumption, 15 MW, typical voltage is 5 volts

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

The width range of the full bidding frequency, 1 Hz to 100 Qianhe

Low cost

Absolutely maximum rated value (Note 1)

LM231A/LM231 LM331A/LM331

Power voltage 40V 40V [ 123]

The output is continuously short-circuit of the ground

Output to VCC continuous short circuit

Input voltage -0.2V to+vs-0.2V to+vs tmin tmin tmax

] The working environment temperature range -25 ℃ ～+85 ℃ ～+70 ℃

Power consumption (PD at 25 degrees Celsius)

and thermal resistance (θja)

( N pack) PD 1.25W 1.25W

θJa 100 ° C/W 100 ° C/W

Lead temperature (welding, 10 seconds)

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

Static discharge sensitivity (Note 4)

n pack 500V 500V

electrical characteristics

TA 25 degrees Celsius, unless there is other regulations, there are other regulations (Note 2)

Electric characteristics (continued)

TA 25 degrees Celsius, unless otherwise regulated (Note 2)

[ 123]

Note 1: Absolutely maximum rated value indicates the limit that the device may be damaged. During operation, DC and AC electrical specifications exceed the devices that exceed the prescribed operating conditions.

Note 2: All specifications are applicable to Figure 4 circuit, 4.0V ≤VS ≤ 40V, unless there are other instructions.

Note 3: The non-linear definition is when the circuit is adjusted when the circuit is at 10 Hitz and 10 kilowators due to zero errors, the deviation of FOUT and vehicle identification number X (10 kilg hh/-10 volt DC) deviations) The frequency range is 1h to Herz to 11 kilo. For timing capacitors CT, use NPO ceramics, Teflon #174; or polystyrene.

Note 4: Human model, 100 PF passes through 1.5 kΩ resistance.

Figure Figure

Typical performance features

(Unless otherwise explained, all electrical characteristics are suitable for the circuit in Figure 4. )

Typical performance characteristics (continued)

Typical application

Simplified operating voltage voltage -HD converter LM231/331 is a single-chip circuit, which is used as a voltage frequency converter or frequency-voltage (F-TO-V) converter. The schematic diagram of the simplified block LM231/331 is shown in Figure 3, including switching current sources, input comparators, and single -shot timer. The operation of these blocks is best to connect through the working cycle of the basic V-TO-F converter, including LM231/331 and various resistors and capacitors. The voltage comparator is compared with a positive input voltage, V1, the pins 7 to the voltage VX, and the pin 6. If the V1 larger comparator will trigger a timer at a time. The output timer will also turn on the frequency output transistor and cycle T 1.1RTCT switch current source. During this time, the current I will flow out of the switch current to provide a fixed number of charge, Q I X T capacitor, CL. This usually charges VX to a higher level higher than V1. At the end of the time, the current I will be closed and the timer will automatically reset. There is no current nowFrom the pins 1 out, the capacitor CL will gradually discharge from RL until VX drops to the level 1. The comparison device will then trigger the timer and start another cycle. The current flowing into the CL is exactly the IAVE I X (1.1xrtct) 10 F. The current flowing out of the CL is exactly VX/RL #8773; VIN/RL. If the vehicle recognition number doubles, the frequency will double to maintain balance. Even a simple V-TO-F transform can be provided in a wide range of frequency frequency range that is proportional to the input voltage.

Operation details, function block

Chart (Figure 2)

Fragics show a belt that can provide stable 1.9 VDC output bands Gap base. This 1.9 voltage voltage adjustment is well adjusted in the VS range of 3.9V to 40V. It also has a flat, low temperature coefficient, and usually changes less than 1/2%more than 100 degrees Celsius. The voltage of the current pump circuit forced needle 2 is 1.9V, and the current flows I 1.90V/RS. For RS 14K, i 135 Weian. The precision current reflector provides i with current equal to the current switch. The current from the current switch to the pin 1 or ground depends on the RS trigger. The timing function is connected to an external RTCT network by a RS trigger and a timer composition. The input comparator detects the voltage of 7 pins than the pin 6, and it sets the RS trigger, which opens the current switch and the output drive transistor. When the voltage rises to 2/3 VCC, the timer comparator causes the RS trigger to reset. Then, the crystal pipe was turned on and the current was turned off. However, if the input comparator still detects the pins 7 higher. When inserting the pin 5 through the 2/3 VCC, the current of the trigger will continue to flow, making Foot 7.

Typical application (continued)

Conditions are usually suitable for starting conditions or signal input overload voltage. It should be noticed that the output frequency will be 0 during this overload period; once the signal resume work range, the output frequency will be restored. The role of the output drive transistor is to make the pin 3 saturated resistor of the pin of the pins of about 50Ω. When the voltage is overvoltage, the output current is effectively limited below 50 mA. The voltage adjustment at the needle 2 is 1.90 VDC, and the all values are between 10 micro -security and 500 microan. It can be used as the voltage benchmark of other components, but it must be noticed not to obtain the current from it to avoid reducing the accuracy of the converter.

The working principle of the basic voltage-frequency converter (Figure 1)

The simple independent V-TO-F converter shown in FIG. Some components for improving performance. A resistor RIN 100kΩ ± 10%, which has been added to the pin 7, so that the bias current (typical value of -80 na) of 7 pins willCancel the influence of the bias current at the pin 6 and help provide the minimum frequency offset. The resistance RS at the pin 2 consists of a 12 kΩ fixed resistor and the 5 kΩ (preferably metal ceramic) gain adjustment variable resistor. The function of this adjustment is to trim the tolerance of LM231/331 and RT, left ventricle and CT.

In order to get the best results, all components should be a stable low -temperature coefficient element, such as metal membrane resistors. The capacitor should have a low -agency absorption; it depends on the required temperature characteristics. NPO ceramics, polystyrene, polytefan fluoride, or polypropylene are preferably suitable. Add the capacitor CIN to the ground from the pin 7 to the vehicle identification number for the filter. In most cases, the value of 0.01 to 0.1 micro F is sufficient, but if you need better filtering, you can use 1 μF capacitor. When the RC time constant is matched with the pin 6 and the pin of the needle, the voltage level jump at the vehicle recognition number will cause a step -by -step change. If CIN is far less than CL, the vehicle recognition number may cause the vehicle to stop temporarily. Add a 47Ω resistor connected with 1 μF CL to give the lagging effect to help the input comparator with good linearity (typical value is 0.03%).

Precision V-TO-F operating details converter (Figure 4) In this circuit, points are achieved by using traditional computing amplifiers and feedback capacitors. When the output of the integror exceeds the nominal threshold, it starts at 6 pins of LM231/331, and starts the timing cycle. The average current (pin 2) of the input computing amplifier is the I X (1.1 RTCT) x f and the -vehicle identification number/identification number. In this circuit, the voltage offset input comparator of LM231/331 does not affect the independent V-TO-F converter, as is the V-TO-F converter; No exception. In contrast, the bias voltage and bias current of the computing amplifier are the only factor that limits the size of the signal can be accurately converted. Because the voltage is disconnected, the setting of the operation amplifier is far lower than 1 millivolttil, and the offset current is far lower than the cost of the circuit. It is recommended to use the best communication accuracy of a small signal. The circuit also responded immediately to any change in the input signal (no independent circuit), so that the output frequency was to accurately represent the vehicle recognition number, and the fastest 2 output pulse #39; the spacing can be measured. In the precision mode, because the current source (pin 1) is always in the ground potential, it has obtained a good linear voltage without changing the vehicle identification number or the type of failure. (In the independent V-TO-F converter, the main reason for non-linearity is the function that causes I to change to a vehicle recognition number). The circuit working method of Figure 5 is the same as Figure 4, but it is necessary to make necessary changes for high -speed operation.

Use a stable component with a low temperature coefficient. See typical application chapters.

For vs 8V to 22V, the resistance can be 5 kΩ or 10 kΩ, butIn VS 4.5V to 8V, the resistance must be 10 kΩ. A1 uses low bias voltage and low bias current amplifier: Recommended model LF411A Figure 4. Precision voltage-frequency converter standard test circuit and application circuit

Typical application (continued)

Work details, frequency-voltage converter (Figure 6 and 7) The upper pulse input is input comparator of the timer circuit from the negative edge of the C-R network and the six pins. Just like a V-TO-F converter, the average current flowing out of the pin 1 is the average value I X (1.1 RTCT) x. In the simple circuit in FIG. 6, the current is in the network RL 100 KΩ and 1 μF. The ripple will be less than 10mv, but the response will be very slow, 0.1 seconds of time constant, the accuracy is 0.7 seconds to 0.1%. In the precision circuit, the computing amplifier provides a buffer output and can also be used as a 2 pole filter. Ripples will be less than 5 mv for all frequencies higher than 1 kHz, and the response time will be much faster than Figure 6. However, for the input frequency of less than 200 Hz, the circuit will make the ripple larger than Figure 6. Filter engineering is made enough to achieve a sufficient response and a small time constant. Ripple only needs to study the manufacture. In essence, the response of the V-TO-F converter may be very fast, but the F-to-V response cannot.

Use a stable component with a low temperature coefficient. See typical application chapters. For VS 8V to 22V, the resistance can be 5 kΩ or 10 kΩ, but for VS 4.5V to 8V, the resistance must be 10 kΩ. A1 uses a low bias voltage and low bias current amplifier: Recommended model LF411A or LF356.