TS51221 Datasheet, PDF (8/18 Pages) Semtech Corporation – High Efficiency Regulator IC for Wireless Power Receiver Applications

Internal Protection Details
Internal Current Limit
The current through the high side FET is sensed on a cycle
by cycle basis and if current limit is reached, it will abbreviate
the cycle.In addition, the device senses the FB pin to identify
hard short conditions and will direct the VSW output to skip 4
cycles if current limit occurs when FB is low. This allows current
built up in the inductor during the minimum on time to decay
sufficiently.Current limit is always active when the regulator
is enabled.Soft start ensures current limit does not prevent
regulator startup.
VCC Under-Voltage Lockout
The device is held in the off state until VCC reaches 4.5V
(typical). There is a 500mV hysteresis on this input, which
requires the input to fall below 4.0V (typical) before the device
will disable.
Under extended over current conditions (such as a short),
the device will automatically disable.Once the over current
condition is removed, the device returns to normal operation
automatically.(Alternately the factory can configure the
device’s NVM to shutdown the regulator if an extended over
current event is detected and require a toggle of the Enable
pin to return the device to normal operation.)
Thermal Shutdown
If the temperature of the die exceeds 170°C (typical), the VSW
outputs will tri-state to protect the device from damage.The
PG and all other protection circuitry will stay active to inform
the system of the failure mode. Once the device cools to 160°C
(typical), the device will start up again, following the normal
soft start sequence. If the device reaches 170°C, the shutdown/
restart sequence will repeat.
Reference Soft Start
The reference in this device is ramped at a rate of 4ms to
prevent the output from overshoot during startup.This ramp
restarts whenever there is a rising edge sensed on the Enable
pin.This occurs in both the fixed and adjustable versions.
During the soft start ramp, current limit is still active, and will
still protect the device in case of a short on the output.
Output Overvoltage
If the output of the regulator exceeds 103% of the regulation
voltage, the VSW outputs will tri-state to protect the device
from damage. This check occurs at the start of each switching
cycle.If it occurs during the middle of a cycle, the switching
for that cycle will complete, and the VSW outputs will tri-state
at the beginning of the next cycle.
TS51221
Final Datasheet
April 6, 2015
Rev 1.1
www.semtech.com
8 of 18
Semtech