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RM46L852: About sensor Interface of RM46L852

chunho cho
Prodigy 140 points
Part Number: RM46L852

Dear

I want to use the motor encoder and hall sensor inputs on RM46L852.

Which port should i use?
RM46_CNCD_Schematic in 'Three-Phase BLDC / PMSM Motor Drive with High-Performance Microcontrollers Reference Design' 
 https://www.ti.com/product/RM46L852#design-development##reference-designs
Looking at the reference circuit above, a specific port is input to the RM46L852 with a 50 ohm resistor isolated.
Is there a reason?
For example
DIMM-100 CON                                RM46L852
ETPWM7A   - - - - -    50Ohm - - - -    ECAP5
                      - - - - - - - - - - - - - - - -   ETPWM7A
  • 0
    TI__Guru**** 186226 points

    Hello Chunho,

    You can use either N2HET port or ETPWM ports to generate PWM signal for motor control, and use N2HET or ECAP to capture input signals. RM46 has two build-in 12-bit ADC modules to sample the current or voltage.

    The series resistor is used as terminator to reduce the signal reflection.

  • 0 in reply to QJ Wang
    Prodigy 140 points

    Dear Wang

    Thanks for your reply!

    Does this mean that the N2HET and ECAP ports can accept Hall sensor and encoder inputs?

    Is it not necessary to use the eQEP port for encoder input?

    And two port(ECAP5 and ETPWM7A) is used as one input(ETPWM7A) in your reference schematic.

    Wye use two port as one input?

  • 0 in reply to chunho cho
    TI__Guru**** 186226 points
    chunho cho said:

    And two port(ECAP5 and ETPWM7A) is used as one input(ETPWM7A) in your reference schematic.

    Wye use two port as one input?

    The control was developed for two different base boards which have different pinout for J1 connector. For DRV803x RevB EVM, the J1 pin 30 and pin 80 are used to capture HALL sensor signals and routed to ECAP5 and ECAP6. 

    chunho cho said:
    Does this mean that the N2HET and ECAP ports can accept Hall sensor and encoder inputs?

    You can use either ECAP or N2HET to capture HALL sensors' signals. The N2HET can also be programmed to act as EQEP.

    chunho cho said:
    Is it not necessary to use the eQEP port for encoder input?

    You don't have to use eQEP. But it is easier to use ECAP and eQEP than using N2HET.