Understanding the Figure 7 of STEVAL-IPMM15B Schematic

[yeewei]

Hi,

I recently purchased the STEVAL-IPMM15B motor control board and am studying its schematic (Figure 7 as attached). However, I am having trouble understanding the role of certain resistors in the circuit.

From my analysis:

R44, R45, and R46 appear to be pull-up resistors.
R47, R48, and R49 seem to function as current-limiting resistors.
R50, R51, and R52—their purpose is unclear to me.

I have the following questions:

1. If SW13, SW14, and SW15 are open (disconnected) and H1/A+ of J5 provides a HIGH signal (+5V), will M_phase_A output a HIGH signal (+5V)?

2. If SW13, SW14, and SW15 are closed (connected) and H1/A+ of J5 provides a HIGH signal (+5V), will M_phase_A still output a HIGH signal (+3.4V)?

3. Can R50, R51, and R52 be considered a voltage divider circuit along with R47, R48, and R49 (i.e., R47 in series with R50, R48 in series with R51, and R49 in series with R52)? or R50, R51 and R52 serve as another purposes?

I appreciate any clarification on how these components interact.

Thanks you.

Regards
YW

[Peter BENSCH]

Welcome @yeewei, to the community!

Your assumption is correct, they are switchable voltage dividers if a 5V type is connected as an encoder.

Regards
/Peter

[yeewei]

Hi Peter,

Thank you for clarifying my doubt.

I have a follow-up question regarding this circuit.

To better understand its configuration, I simulated it using PSIM. I considered four different cases.

In these simulations, SW9 and SW16 are connected to a 5V supply, and the Hall effect sensor signals from J5 pin 1 to 3 are replaced with 1000 Hz, 5V square waves, each phase-shifted by 120° from its adjacent phase.

Note that VA and m_phase_A in the following simulated waveform correspond to the square wave (represent hall effect sensor signal) and M_phase_A (shown in Fig. 7), respectively.

#####

CASE-A
SW10, SW11, SW12, SW13, SW14 and SW15 are unconnected.

The output voltage waveforms are shown below.
Note that the m_phase_A varied from +1.69V to +5V.

CASE-B
SW10, SW11 and SW12 are connected
SW13, SW14 and SW15 are unconnected.

The output voltage waveforms are shown below.
Note that the m_phase_A varied from 0V to +5V.

CASE-C
SW10, SW11 and SW12 are unconnected
SW13, SW14 and SW15 are connected.

The output voltage waveforms are shown below.
Note that the m_phase_A varied from +1.26V to +3.73V.

CASE-D
SW10, SW11, SW12, SW13, SW14 and SW15 are connected.

The output voltage waveforms are shown below.
Note that the m_phase_A varied from 0V to +5V. (Similar to CASE-B)

#####

May I know the purpose of reducing these voltages to a limited range, particularly in CASE-A (where the voltage exceeds 3.3V) and CASE-C (where it is restricted to +1.26V to +3.73V)?

Additionally, how should these signals be interfaced with a microcontroller, considering that the voltage levels exceed 3.3V?

I am asking this because the STEVAL-IPMM15B datasheet does not provide a clear description of the configuration in Figure 7.

I would also appreciate it if you could point out the correct configuration on the circuit in Figure 7.

Kindly refer the datasheet of STEVAL-IPMM15B in the attachment.

Thanks you in advance.

Regards
YW

[Peter BENSCH]

I was too quick with the previous statement - SW10...SW15 are switchable filter functions. Switching for 5V to 3.3V Hall sensors is done with SW9.

However, I do not have any information on the exact function of R50...R52. You may be able to get help with a personal ticket via the Online Support OLS.

Good luck!
/Peter