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LM5122: LM5122

Neethu Joy
Prodigy 85 points
Part Number: LM5122
Other Parts Discussed in Thread: BQ24170

Tool/software:

Hi,

I want to design a DC-DC converter with input either 14.4V or 24V  (both are outputs of BQ24170). The required output is constant 24V with 8A output current. Will LM5122 suits my application?. If so, how can I implement the bypass mode when input is 24V. It would be helpful if you could suggest the design for the same.

Also please suggest if any other IC's are available or not.

 

  • 0
    TI__Mastermind 30080 points

    Hi Neethu,

    Thanks for your interest in the LM5122 device.

    Based on your specs, LM5122 should be the best suitable device.
    For 14.4V input, the device will operate in boost mode.
    For 24V input case, the device will enter bypass mode on its own and no specific settings have to be added.

    There is one point about LM5122 I want to highlight:
    Are there cases where you are starting the device with 24V input, so it would enter bypass directly from the start?
    If this is the case, special attention is required to make sure the device can enter bypass properly.
    The according app note can be found here:
    https://www.ti.com/lit/an/snvaaa5/snvaaa5.pdf

    If the start-up is with 14.4V input voltage, there is no problem.

    A general reference design can be found here:
    https://www.ti.com/tool/LM5122EVM-1PH

    If you have any additional question on this device, please let me know.
    Best regards,
    Niklas

  • 0 in reply to Niklas Schwarz
    Prodigy 85 points

    Hi Niklas,

    Thanks for your support.

    I have a query. As per the datasheet, if bypass mode is required, it is advised to configure the mode pin as forced PWM mode. For this, can we connect this directly to the VCC pin or external VCC / voltage source needs to be connected?

  • 0 in reply to Neethu Joy
    TI__Mastermind 30080 points

    Hi Neethu,

    To operate the device in FPWM, you can directly connect the MODE pin to the VCC pin.
    In general, it is recommend to place a 0 Ohm resistor between the pins, so it is still possible to test different mode settings on the initial test boards without major layout changes.

    Best regards,
    Niklas