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TPSM8D6C24: some problems in design

lou.jichen
Prodigy 40 points
Part Number: TPSM8D6C24

Hi:

    Some questions about the 7.2 Typical Application in the TPSM8D6C24 datasheet are as follows:

Q1: Do AGND and PGND need an external connection?

Q2: If the output voltage is set to 3.3V, the VSEL Resistor Divider Code should be 9 according to Table 6-12, and the VSEL Resistor to AGND Code calculated according to Table 6-13 and formula 8 is 7.5. So should Code choose 7 or 8?

Q3: Section 7.2.2.7 states that "In this single-phase design, resistor divider code 3 is selected for 5-ms soft start and resistor to AGND code 0 is selected for the highest current limit thresholds and standalone configuration. "According to this statement, MSEL2 pin should select 9.09kΩ resistance and pull it up to BP1V5, 4.64kΩ resistance and pull it down to AGND. But why do MSEL2_A and MSEL2_B choose 0Ω resistance to ground in P147 reference circuit?

Q4: Can ADRSEL_A and ADRSEL_B be set to the same for dual-channel output?

Q5: What is the difference between NONE and Float in Table 6-17? Do both of these mean no resister to BP1V5?

Thanks,

   Jochen

  • 0
    TI__Mastermind 29410 points

    Hello Jochen, 

    I assigned this to Savith to help answering the rest of the questions: 

    Q1: Yes AGND need to be connect to PGND pin directly to the thermal pad on

    Q5: do you mean table 6-14? 

    Thanks 

    Tahar

  • 0
    TI__Intellectual 1870 points

    Hello Jochen,

    Q2:

    For 3.3Vout through pin strap,

    Vout=Vout_command(offset)+[R2G_code*Vout_commad(step)]

    Rdivider code=9

    for R2G_code=7

    Vout=3+(7*0.040)=3.28V

    for R2G_code=8

    Vout=3+(8*0.040)=3.32V

    for regulating the Vout at 3.3V pls use PMBus commands

    Q3:

    For Resistor to gnd on MSEL2 both Code0 (4.64kohms) and Short(0ohm) set the device in same config i.e. 0 loop followers, standalone, Highest current limit 

    Q4:

    Set different address for Standalone devices and for Multiphase applications set the address for controller device

    Q5:

    For Adr sel, MSEL2, MSEL1: Float implies pin is floating and None implies there is no resistor 

    For Vsel: Float and None are same i.e. no resistor

    Thank you

    Savith

  • 0 in reply to Savith Kumar Rayakanti
    Prodigy 40 points

    Hi Savith:

        Thank you for your answer. Just as Tahar said: AGND need to be connect to PGND pin directly to the thermal pad on. I understand that AGND should be connected to pin52、54、57、59 through a single point of 0 ohm resistance, but I can't find the connection point of AGND and PGND on the TPSM8D6C24EVM-2PH schematic diagram, how are they connected?

    Thanks,

    Jochen

  • +1 in reply to lou.jichen
    TI__Intellectual 1870 points

    Jochen, 

    Agnd and Pgnd are connected internally to thermal pad on the module

    Thank you

    Savith