SNVSBW1C December 2021 – August 2024 LM63440-Q1 , LM63460-Q1
PRODUCTION DATA
The PGOOD function is implemented to replace a discrete reset device, reducing BOM count and cost. The PGOOD voltage goes low when the feedback (FB) voltage is outside of the specified PGOOD thresholds (see Figure 6-8). This can occur during current limit and thermal shutdown, as well as when disabled and during normal start-up. A glitch filter prevents false flag operation for short excursions of the output voltage, such as during line and load transients. Output voltage excursions that are shorter than tPGDFLT(fall) do not trip the PGOOD flag. Refer to Figure 7-5 to best understand PGOOD operation.
The PGOOD output consists of an open-drain N-channel transistor, requiring an external pullup resistor to a suitable logic supply or VOUT. When EN is pulled low, the flag output is also forced low. With EN low, PGOOD remains valid as long as the input voltage is above 1V (typical).
FAULT CONDITION INITIATED | FAULT CONDITION ENDS (AFTER WHICH tPGDFLT(rise) MUST PASS BEFORE PGOOD OUTPUT IS RELEASED)(1) |
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VOUT < VOUT-target × PGDUV AND t > tPGDFLT(fall) | Output voltage in regulation: VOUT-target × (PGDUV + PGDHYST) < VOUT < VOUT-target × (PGDOV – PGDHYST) (see Figure 6-8) |
VOUT > VOUT-target × PGDOV AND t > tPGDFLT(fall) | Output voltage in regulation |
TJ > TSHD | TJ < TSHD-F AND output voltage in regulation |
VEN < VEN-TH falling | VEN > VEN-TH rising AND output voltage in regulation |
VCC < VCC-UVLO - VCC-UVLO-HYST | VCC > VCC-UVLO AND output voltage in regulation |