UM2640L-SM1-R datasheet(6/8 Pages) UTC

6 / 8 page

UM2640

CMOS IC

UNISONIC TECHNOLOGIES CO., LTD

6 of 8

www.unisonic.com.tw

QW-R109-027.D



APPLI CAT I ON I N FORM AT I ON (Cont .)

2. Design of Ra and Ca

Ra and Ca must be used if VCC exceeds operating voltage range of UTC UM2640.

Example of VCC 60V Application

Given that current consumption of UTC UM2640 is 4mA (at VCC=48V), Ra is given by:

Ω

Ca is needed if UTC UM2640 is oscillated or shows unstable operation. A typical value of Ca is from 0.01µF to

0.1µF. A ceramic type is recommended and it must be placed near VCC and Gnd.

By insertion of Ra and Ca,the ESD immunity is improved greatly.

3. Design of D2

If an application requires active power on and off, TR1 (TR2) may be damaged or resulted in destruction.

In such application, adding diode between motor winding and Gnd will reduce the damage.

4. Design of ZD1 and ZD2

Zenner diodes are used for limiting kick back voltage of motor winding generated when power transistors is (TR1

and TR2) turned off from on.

There are two methods to consume kick back voltage:

1) Inserting ZD1 (zenner diode connected between Base and Collector of TR1) Energy of kick back voltage is

consumed by TR1 (or TR2). When ZD1 is in operation, Collector voltage is sum of Vbe and ZD1. Therefore,

breakdown voltage of ZD1 must be lower than that of TR1.

2) Inserting ZD2 (zenner diode connected between Collector and Emitter of TR1) Energy of kick back voltage is

consumed by ZD2. To protect TR1, breakdown voltage of ZD2 must be lower than that of TR1.

This method is generally used when Energy of kick back voltage is large. In such application, power rating of ZD

must take in consideration.

5. Selection of C1 and D1:

C1 is used to weaken noise. A typical value is 0.1uF.

Optimize the value in actual operating conditions if necessary. D1 is a diode for protecting against reverse voltage

supply. Silicon rectifier diode is appropriate.

6. Design of R1 and R2

Hall amplifier is a differential amplifier with hysteresis characteristics (24mV typical).

The common-mode input voltage is between 1.5V and VCC-2V and the input signal must be within the range.

Non-excitation hall bias voltage is to be set at a half of VCC for effective use of common-mode input voltage range.

Therefore the same value of hall bias resistors is selected for R1 and R2.

The output voltage of hall elements is effected by the bias current and magnetic flux density of hall elements.

The optimum input voltage of UTC UM2640 is 100mVp-p and higher. With such input voltage, the highest

efficiency can be obtained.

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