Long express launched high-precision low ripple voltage reference source -CYT431

The power supply system of professional design company, express Optoelectronics Technology Co. Ltd. to provide CYT431 voltage reference to the market in 2003, through continuous pursuit of perfection, request parameters close to the market, recently officially launched a new version of high precision and low ripple. Number reference source CYT431.

CYT431 principle can be seen as a variable voltage regulator diode, compared with the zener diode CYT431 regulator value is set. Programmable control within 36V. In the design of high power supply voltage, the zener diode can be used as reference source. CYT431 is widely used in switching power supply, mainly because of the precision requirements, all kinds of instruments are more accurate. As a result, long express launched CYT431 progress of up to + 0.5%. The accuracy of the reference source will be superimposed on the output voltage accuracy.

Typical temperature drift: 6 mV (range of 0 DEG C to 70 DEG C within), temperature drift is one of the important parameters of CYT431, the internal design of negative temperature coefficient compensation circuit, circuit device with internal temperature drift, temperature compensation circuit can accomplish the voltage stability within 6mV. In this regard, long express integrated circuit design team through years of correction, many times to modify the industry to achieve a good level. The reference source voltage offset is directly superimposed on the output power accuracy.

Low output noise, low output impedance 0.2, ultra low internal impedance can complete ripple absorption, suppress the output voltage ripple caused by power supply noise. The reference source noise will be amplified several times as reflected in the switching power supply, so the ripple coefficient is one of the important parameters of CYT431.

Absorption current capacity of 1 mA to 100 Ma, which is basically equivalent to zener diodes. It is very important for CYT431 to be applied as voltage regulator. As a benchmark source applications are generally used in a number of mA applications, especially for the static power requirements of the circuit, the absorption of the current design in particular small. As a reference source design, the absorption current is too small will affect the suppression of the ripple coefficient, so the selection of low internal resistance CYT431 is very important. In order to select the other type of reference source with large internal resistance, the absorption current can be increased properly.

Figure 1, A for the anode, the need to use the ground; K for the cathode, the need to limit the current through the resistance to the power supply; UREF is the switching power supply module output voltage of the UO set, the external resistor divider.

The equivalent circuit as shown in figure CYT431, mainly including the error amplifier A, the switching power supply module is connected with the input end from the in-phase resistance sampling voltage on the pressure sensor, power management chip is connected to the inverting terminal internal reference voltage 2.5V Uref, and the design of the UREF=Uref, UREF normally is 2.5V, so it is also called the benchmark at the end of the internal reference voltage source 2.5CV; Uref; the NPN type transistor VT, it plays a role in regulating the load current in the circuit; the protection diode VD, can prevent K-A power supply polarity instead of damaged chips.

The utility model is equivalent to an adjustable zener voltage regulator, and the output voltage of the switching power supply module is set by an external precision voltage divider resistor.