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TMS320F28027F: f28027

Ahsan
Intellectual 625 points
Part Number: TMS320F28027F

Hi,

I am using f28027f for PWM generation based on values of ADC. I am implementing schematics of that MCU and JTAG for PCB. Following are some confusion that I want to ask.

1) As in my case XCLKIN and XCLKOUT is not required because I am not using external oscillator, so I have only connected X1 to ground. and left these both pins and X2 unconnected. Is that fine?

2) I have left XRS' pin unconnected. Does this ensure the normal behavious of device? What is the purpose of that pin? What is the purpose of connecting it to 3.3 V with 2.2k resistor as it has been done in f28027f launchpad?

3) What is the purpose of using internal regulator? I have connected capacitor from Vdd to ground. But left VREGENZ' open. Does this make any difference?

4) In launchpad f28027f, the test pin is connected to ground, but I have kept it unconnected according to datasheet. Is that fine?

  • 0
    TI__Guru* 95315 points

    1. Yes.

    2. -XRS pin can be used to assert an external reset. The pin has an internal pull-up; however it is a weak pull-up. To make the pin level more robust (and hence make it more immune to noise), an external PU is also used in conjunction with the internal PU. A capacitor is also recommended for noise immunity.

    3. The internal regulator eliminates the need for an external 1.8v solution. -VREGENZ has an internal pull-down. However, it is a weak PD. An external PD resistor is recommended.

    4. Please follow datasheet recommendation.

  • 0 in reply to Hareesh Janakiraman
    Intellectual 625 points

    Hi Hareesh,

    From point 3, what is the purpose of 1.8V that has to be provided by internal voltage regulator. It is recommended that VREGENZ should be directly connected to ground instead of pull down resistor according to launhapd f28027 schematic. If we have to provide PD resistor then what should be the value of that resistor?.

    Regards,

  • 0 in reply to Ahsan
    TI__Guru* 95315 points

    Ammad,

    what is the purpose of 1.8V that has to be provided by internal voltage regulator?

    As stated in the datasheet, 1.8v is needed for the CPU and Logic. 

    Connecting -VREGENZ directly to VSS is acceptable.