AN2839 datasheet(35/40 Pages) STMICROELECTRONICS

35 / 40 page

AN2839

Demonstration board

Doc ID 15104 Rev 1

35/40

resistive divider from an external voltage rail and GND (possibly the one supplying the µC or

the rest of the application).

Otherwise, a very simple way to obtain a variable voltage without using a DAC is to low-pass

filter a PWM output of a µC.

The input lines CW/CCW, control, half/full, EN and reset are connected to ground through a

pull-down resistor which sets as default the low logic level on these lines. An external signal

can be applied to change each input status.

D1, C1 and C4 make up a charge-pump circuit, which generates the supply voltage for the

high-side integrated MOSFETs. Due to voltage and current switching at relatively high

frequencies, these components are connected together through short paths in order to

minimize induced noise on other circuitries.

R1 and C5 are used by the overcurrent protection’s integrated circuitry (the disable time

tDISABLE is about 200 µs and delay time tDELAY about 1 µs with the values in Table 4).

R6, C6 and R7, C7 are used to set the off time tOFF of the two PWM channels at about

50 µs. The off time should be adjusted according to the motor’s electrical characteristics and

supply voltage by changing the R6, C6 and R7, C7 values.

R11, R12, C8 and R13, R14, C9 are low-pass filters used to provide an external reference

voltage through a PWM output of a µC.

Figure 39 and Figure 41 show the components’ placement and the two layers of the

EVAL6228QR reference design board. A GND area has been used to improve the IC’s

power dissipation.

Figure 39.

EVAL6228QR component placement

AN2839 Datasheet(PDF) 35 Page - STMicroelectronics