LTC3626_15 Datasheet, PDF (12/28 Pages) Linear Technology – 20V, 2.5A Synchronous Monolithic Step-Down Regulator with Current and Temperature Monitoring

LTC3626
Operation
Temperature Monitor and Limit
The LTC3626 produces a voltage at the TMON pin pro-
portional to the measured on-die temperature. The on-die
temperature-to-voltage scaling factor is 200°K/V. Thus, to
obtain the on-die temperature in degrees Kelvin, simply
multiply the voltage provided at the TMON pin by the scaling
factor. To obtain the on-die temperature in degrees Celsius,
subtract 273 from the value obtained in degrees Kelvin.
The voltage produced at TMON is continuously fed to a
limit comparator that has the voltage at the TSET pin as its
reference input. When triggered, this comparator generates
an overtemperature fault that will initiate part shutdown and
reset of soft-start. Thus, a maximum junction temperature
limit may be set by providing a voltage at the TSET pin
that corresponds to the temperature limit of interest. The
voltage at the TSET pin may be derived from a resistor
divider from INTV_CC, subject to the current constraints
listed in the Electrical Characteristics section, or may be
driven externally. The LTC3626 will clear the overtem-
perature fault and restart once the internal temperature
falls 10°C (typical) from the threshold given at TSET. The
voltage at the TSET pin has no impact on the secondary
overtemperature shutdown threshold within the LTC3626
as described in Note 4 of the Electrical Characteristics.
“Power Good” Status Output
The PGOOD open-drain output will be pulled low if the
regulator output exits a ±8% window around the regulation
point. This condition is released once regulation within a
±5% window is achieved. To prevent unwanted PGOOD
glitches during transients or dynamic V_OUT changes, the
LTC3626 PGOOD falling edge includes a filter time of
approximately 40μs.
PV_IN Overvoltage Protection
To protect the internal power MOSFET devices against tran-
sient voltage spikes, the LTC3626 continuously monitors
the PV_IN pin for an overvoltage condition. When PV_IN rises
above 21.5V (typical), the regulator suspends operation
by shutting off both power MOSFETs and resets soft-start.
Once PV_IN drops below 20.5V (typical), the regulator re-
starts normal operation by executing a soft-start.
3626fa
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