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LM3489: Fast response power management

user4090349
Intellectual 811 points
Part Number: LM3489
Other Parts Discussed in Thread: LM61495-Q1, LM61460-Q1, LMZM23601,

Hello

I want a fast response power management chip.

1. response time < 400us

2. ripple < 20mV

3. output voltage, 3.3V

4. Input voltage, 4.5V ~21V

  • 0
    TI__Guru 50120 points

    Hi,

    For response time, are you referring to transient performance? 

    I would suggest you take a look at some of the converter portfolio such as the LM61460-Q1 or LM61495-Q1 to get a starting evaluation.

    Response time and output ripple would be dependent on your output capacitance and load current.

    What is your maximum output current requirement?

    Regards,

    Jimmy 

  • 0 in reply to Jimmy Hua
    Intellectual 811 points

    Hello

    The max current should be 25mA

  • 0 in reply to user4090349
    TI__Guru 50120 points

    Hi,

    If your max current is 25mA which is very low currents, I would suggest looking at the lower current devices.

    Perhaps even the power module (internal FETS and inductor) and you can start with the LMZM23601. 

    Regards,

    Jimmy

  • 0 in reply to Jimmy Hua
    Intellectual 811 points

    Hello

    It seems the start up time of the part is roughly 6ms. Is there any part which has the fast start up time?

  • +1 in reply to user4090349
    TI__Guru 50120 points

    Hi,

    The part has an internal soft-start of 3.5ms. 

    That in addition to the delay between EN high to when VOUT soft-start occurs and the delay between VOUT regulation to when PGOOD flag is asserted high appears to measure 6ms as you've shown. 

    I might have mistaken what you previously meant by response time. If response time is the meant to be start-up time, then even the LM3489 would not work since looking at Figure 17 the time when VEN asserts high to when inductor current is stable and VOUT is regulating shows about 1.5DIV which is roughly 600us. 

    Perhaps in this case, you might want a LDO which should have faster start-up time but will be limited in power capability. 

    Regards,

    Jimmy