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LP5912-Q1: PG state understanding

Ross Parlour
Intellectual 1240 points
Part Number: LP5912-Q1
Other Parts Discussed in Thread: TPS3700-Q1, TPS3702-Q1

Hi There,

I am using the LP5912-Q1 as a 1V2 linear supply off of a 1V8 PMIC SMPS output.

Looking at the PG function of the regulator I think I understand this as : the PG is low when the output voltage is below the PG(LTH) and goes high when above the PG(HTH)  i.e at nominally 1V2, it will be HIGH .

If say due to an internal fault , the output climbs to 1V8 , will the PG remain high?

This is not typical of TI regulators, where normally the PG is only high (valid) if the output voltage is within say, 10% of the target value?

Can you explain this rational? Or have I misunderstood something here?

Also, is there more detailed information on the variation of the PG(HTH) or PG(LTH) and the tP(PGD). There are only typical values in the data sheet.

Many thanks in advance for your time and expertise.

Ross

  • 0
    TI__Guru 55940 points

    Hi Ross,

    The PG for LP5912-Q1 is an integrated voltage supervisor (SVS).  The output voltage is compared to the reference voltage.  When the output voltage is above 94% of its nominal value, the pulldown FET is released after a 140 us delay.  The FET will remain off (PG logic high) until Vout falls below 90% of its nominal value at which point the FET will pulldown the PG signal.  As such, if Vout is biased above the nominal output voltage, PG will remain logic high.

    A window comparator, such as TPS3700-Q1 or TPS3702-Q1, provides the functionality you described where the output will only be logic high when the SENSE voltage is within a window of the nominal value.  To accomplish this there are two internal comparators as shown in the block diagram of the TPS3702-Q1 below.

    The primary function of the LP5912-Q1 is as a voltage regulator.  Only the voltage regulator portion of this device is fully tested and characterized.  For more precise voltage supervisors and comparators, please refer to www.ti.com/.../overview.html

    Very Respectfully,

    Ryan