Serial data interface chip supply bipolar voltage-Serial-Data Int

Some of the interface ICs currently available for serial-data transmission not only operate from low VCC levels (5V or 3.3V); they also generate bipolar dc voltages (± 6.5V to ± 10V) to support the minimum driver-output levels as specified by EIA / TIA-232. With care, you can steal useful amounts of power from these voltage rails without interfering with the IC's operaTIon.

In Figure 1, the IC's switch-mode controller operates with an external inductor, two diodes, and two capacitors to produce ± 6.5V. FETs Q1 and Q2 ensure start-up for the circuit by disconnecTIng the load unTIl these switch-mode supply voltages are present. Note that Q1 must be a logic-level device.

Figure 1. For data rates and driver-output loads less than the maximum allowed, the V + and V- outputs of this serial interface IC can supply modest amounts of current to an external curcuit.
Figure 1. For data rates and driver-output loads less than the maximum allowed, the V + and V- outputs of this serial interface IC can supply modest amounts of current to an external curcuit.

Unlike ICs designed to generate supply voltages, an interface IC generally doesn't specify how much current you can draw from its internally generated supply rails. The amount available depends almost entirely on loads connected to the driver outputs. IC1, for example, guarantees that one transmitter can drive a parallel combination of 3kΩ and 1000pF at 250kbps while the other two maintain dc outputs across 3kΩ loads. These conditions let you calculate the chip's maximum output current capability, but you can't expect to draw extra current while delivering that maximum .

To calculate the maximum output current available, superimpose the ac and dc components: Output current flows alternately from each rail as the NRZ output waveform swings between the guaranteed minimum output levels (± 5V). Assuming the output requires one whole data period (4µs at 250kbps) to slew from -5V to + 5V, the ac component equals CLOAD (dv / dt) = 1000pF (10V / 4µs) = 2.5mA. For the dc component, Ohm's Law gives I = E / R = 5V / 3kΩ = 1.67mA from one transmitter, so the three transmitters together represent a dc load of 5mA. Adding the ac and dc components together gives a conservative maximum rating of 2.5mA + 5mA = 7.5mA.

The 3kΩ load is an EIA-232 requirement, but the data rate and load capacitance are application-dependent parameters. Lower values ​​for these parameters make more current available for external use. A remote-sensing system, for instance, might operate at 2400 bits / sec (2400bps) with a load of 3kΩ in parallel with 1000pF (50 feet of cable at 20pF / ft). The dc load for three transmitters is 5mA, and the ac load for one transmitter (72µA) is almost negligible in this low -data-rate application. So, the available current in this case is calculated as 7.5mA-(5mA + 72µA) = 2.428mA.

The above calculation is conservative: with VCC = 2.7V and the three transmitters loaded with 3kΩ || 1000pF, a circuit transmitting valid EIa-232 levels at 2400bps will actually deliver 6.7mA to an external load (even more for VCC = 3V and up ). As mentioned, Q1 and Q2 enable the circuit to start under these conditions. If you disconnect the transmitter loads, the maximum external load current that allows start-up is 11.5mA. With Q1 and Q2 removed, the maximum is only 5.7mA .

Lock Motor product introduction:

Safe Lock Motor, also known as The anti-theft lock motor,  in the field of electronic Lock technology, Safe Lock Motor is a mechanical Lock components associated with the electronic control unit of the important parts.


Safe Lock Motor the product effectively combines the advantages of traditional electronic locks and electromagnetic lock overcame the electric lock too much noise, electromagnetic lock power shortage and the development of new products, and spiritual compared with electric control lock and magnetic locks, lock its performance more perfect, more obvious advantages.


Functions: it is widely used in various intelligent locks, such as Shared bicycle lock, fingerprint lock, glass lock, safe lock, hotel lock, family lock, inductive smart lock, etc


Features: Motor For Safe Lock is based on micro precision reducer development, small intelligent micro precision reducer can do 10 mm in diameter, is widely used in safe, locks, smart locks, sensor intelligent lock;

This kind of motor has the characteristics of low noise, low energy consumption, small volume, light quality, high precision, large torque and durability

Method of use: the best stable in horizontal plane, installed on the Safe Lock Motor output shaft parts, cannot use a hammer to knock, knock prone to press into the dc Safe Lock Motor drive, may cause damage to internal components, and cannot be used in the case of blocked.

Lock motor

Operating temperature range:

Gear Motor For Safe Lock should be used at a temperature of -10~60℃.

The figures stated in the catalog specifications are based on use at  ordinary room temperature catalog specifications re based on use at ordinary room temperature  (approximately20~25℃.

If a  Safe Lock Motor is used outside the prescribed temperature range,the grease on the gearhead area will become unable to function normally and the motor will become unable to start.Depending on the temperature conditions ,it may be possible to deal with them by changing the grease of the motor's parts.Please feel free to consult with us about this.


Storage temperature range:

Gear Motor For Safe Lock should be stored ta a temperature of -15~65℃.

In case of storage outside this range,the grease on the gearhead area will become unable to function normally and the motor will become unable to start.


Service life:

The longevity of Dc Motor For Safe Lock is greatly affected by the load conditions , the mode of operation,the environment of use ,etc.Therefore,it is necessary to check the conditions under which the product will actually be used .The following conditions will have a negative effect on longevity.Please consult with us should any of them apply.



●Use with a load that exceeds the rated torque

●Frequent starting

●Momentary reversals of turning direction

●Impact loads

●Long-term continuous operation

●Forced turning using the output shaft

●Use in which the permitted overhang load or the permitted thrust load is exceeded

●A pulse drive ,e.g.,a short break,counter electromotive force,PWM control

●Use of a voltage that is nonstandard as regards the rated voltage

●Use outside the prescribed temperature or relative-humidity range,or in a special environment.

●Please consult with us about these or any other conditions of use that may apply,so that we can be sure that you select the most appropriate model.


when it come to volume production,we're a major player as well .each month,we rurn out  600000 units,all of which are compliant with the rohs directive.Have any questions or special needed, please contact us, we have the engineer group and best sales department to service to you

Looking forward to your inquiry. Welcome to our factory.

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