LM34919C-Q1 Datasheet, PDF (16/29 Pages) Texas Instruments – LM34919C-Q1 Ultra Small 50V, 600 mA Constant On-Time Buck Switching Regulator

LM34919C-Q1
SNVS831A – SEPTEMBER 2013 – REVISED DECEMBER 2013
www.ti.com
Power Good Output
The Power Good Output (PGD) indicates when the voltage at the FB pin is close to the internal 2.52 V reference
voltage. The PGD pin remains low inside the device when the FB pin voltage is outside the range set by the
PGDUV and PGDOV thresholds (see Electrical Characteristics). The PGD pin is internally connected to the drain
of an N-channel MOSFET switch. An external pull-up resistor (RPGD), connected to an appropriate voltage not
exceeding 14 V, is required at PGD to indicate the status of LM34919C to other circuitry. For best results, pull up
the PGD pin to the output voltage. When PGD is low, the voltage at the pin is determined by the current into the
pin. See the graph "PGD Low Voltage vs. Sink Current." Upon powering, as VIN is increased, PGD stays low
until the output voltage takes the voltage at the FB pin above 92% of the internal reference voltage, at which time
PGD switches high. As VIN is decreased (e.g., during shutdown), PGD remains high until the voltage at the FB
pin falls below 90% (typ.) of the internal reference. PGD then switches low and remains low.
Thermal Shutdown
The LM34919C should be operated such that the junction temperature does not exceed 125°C. If the junction
temperature increases to 175°C (typical), an internal Thermal Shutdown circuit forces the controller to a low-
power reset state by disabling the buck switch. This feature helps prevent catastrophic failures from accidental
device overheating. When the junction temperature reduces below 155°C (hysteresis = 20°C) normal operation
resumes.
16
Submit Documentation Feedback
Product Folder Links: LM34919C-Q1
Copyright © 2013, Texas Instruments Incorporated