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find the NMOS high driver to output linear power

xingmeng
Intellectual 305 points
Other Parts Discussed in Thread: OPA2192, THS3121, LM7321, OPA541, OPA549

Hi Team

There is a linear power project, the design diagram is below , it use MCU DAC output the linear voltage, then use the amplifier as buffer and driver NMOS. Maybe it works, can you give some other solutions? The amplifier is OPA2192 that had been use. Can you give the appropriate part number?

below is design diagram:

this is the power output linear

  • 0
    TI__Guru* 77541 points

    Hi ,

    Q: can you give some other solutions?

    Please provide some of information below:

    Input Voltage: 5-9Vdc

    Output Voltage: 3.8Vdc (VBAT)? and/or 5.0V (VBUS)?

    Load: What is the load type (resistive, capacitive or other complex load) and output current? What is ripple voltage? How well the output voltage needs to be regulated (%load_regulation) and heat dissipation (efficiency)?

    Voltage Reference: Are you using DAC as voltage reference to control the output voltage in the linear regulator? It looks like that DAC reference is in staircase with 40-50msec duration. How fast do you need to achieve the voltage transition from one to another? 

    Use OPA2192 as error amplifier for the design is a good choice, but it does not require to power with 24Vdc if output voltage is only 3.8Vdc or 5.0Vdc. Is this a Li+ battery charging application? 

    The block diagram above is shown in discrete linear regulator design. We may use power amplifier to achieve the same thing, but I will need the above design requirements. Alternatively, we may use LDO to accomplish the same thing. How much PCB space do you have for the design?

    Best,

    Raymond

  • 0 in reply to Raymond Zhang1
    Intellectual 305 points

    Dear Raymond

    Thanks for your quickly reply .

    1. The input voltage is 5-9Vdc.

    2. There are two channel output , one is the max voltage 3.8V, another is max voltage 5.0V

    3.LOAD, is  cell phone board, maybe is complex load, the output peak current is 4A, the ripple voltage %1 of the output current is ok. As little heat as possible.

    4.Yes , I plan  use the DAC as voltage reference to control the output voltage in the linear regular , The step voltage as fast as possible .

    5.I plan use the amplifier to control MOSFET rd resister , then control the output voltage .

    6. There is no PCB space require .

    I search some other amplifier can direct drive POWER MOSFET such  as  ths3121,lm7321.

    update the diagram

  • 0 in reply to xingmeng
    TI__Guru* 77541 points

    Hi ,

    Power amplifier like OPA541 or OPA549 may be an option, if the complex load type is known as alternative to discrete power regulator design.

    OPA2192 should have enough voltage and current to drive P-MOSFET for the design. NMOS configuration may work as well, but you may need higher gate to source voltage. 

    If cell phone boards' loads are unknown or changes with products, then linear regulator will make more sense. LDO may work as well, but it may not give you a tight load regulation and output precision. 

    BTW, how long is the power leads to cell phone. If it is long, then you may consider to include sensing leads in a design. 4A of current may have good amount of IR drop at a load (10mOhm @4A will have a IR drop of 40mV). 

    Please let me know your decision. 

    Best,

    Raymond