Datasheet

TPS53313
SLUSAS8 –DECEMBER 2011 www.ti.com
UVLO FUNCTION
The TPS53313 provides UVLO protection for input voltage, VIN. If the input voltage is lower than UVLO
threshold voltage minus the hysteresis, the device shut off. When the voltage rises above the threshold voltage,
the device restarts. The typical UVLO rising threshold is 4.23 V. Hysteresis of 200 mV for input voltage is
provided to prevent glitch.
OVERCURRENT (OC) PROTECTION
The TPS53313 provides peak current protection and continuously monitors the current flowing through high-side
and low-side MOSFETs. If the current through the high-side FET exceeds the current limit threshold, the
high-side FET turns off and the low-side FET turns on. An overcurrent (OC) counter starts to increment every
switching cycle to count the occurrence of the overcurrent events. The converter shuts down immediately when
the OC counter reaches 4. The OC counter resets if the detected current is less than 6 A (with 6-A OC setting)
after an OC event.
Another set of overcurrent circuitry monitors the current through low-side FET. If the current through the low-side
FET exceeds 6 A (with 6-A OC setting), the overcurrent protection is engaged and turns off both high-side and
low-side FETs immediately.
Therefore, the device is fully protected against overcurrent during both on-time and off-time. Also, the OC
threshold is selectable and can be set to 4.5 A, 6 A or 9 A by connecting different capacitor in parallel with
MODE/SS pin. After OC events, the device stops switching and enters hiccup mode. A re-start is attempted after
a hiccup waiting time. If the fault condition is not cleared, hiccup mode operation may continue indefinitely
OVERVOLTAGE AND UNDERVOLTAGE PROTECTION
The TPS53313 monitors the voltage divided feedback voltage to detect the overvoltage and undervoltage
conditions. When the feedback voltage is greater than 117% of the reference, overvoltage protection is triggered,
the high-side MOSFET turns off and the low-side MOSFET turns on. Then the output voltage drops and the FB
voltage reaches the undervoltage threshold. At that point the low-side MOSFET turns off and the device goes
into tri-state logic.
When the feedback voltage is lower than 83% of the reference voltage, the undervoltage protection counter
starts. If the feedback voltage remains lower than the undervoltage threshold voltage after 10 μs, the device
turns off both the high-side and low-side MOSFETs and then goes into tri-state logic.
After the undervoltage events, the device stops switching and enters hiccup mode. A restart is attempted after a
hiccup waiting time. If the fault condition is not cleared, hiccup mode operation may continue indefinitely.
OVERTEMPERATURE PROTECTION
The TPS53313 continuously monitors the die temperature. If the die temperature exceeds the threshold value
(140°C typical), the device shuts off. When the device is cooled to 40°C below the overtemperature threshold, it
restarts and returns to normal operation.
OUTPUT DISCHARGE
When the EN pin is low, the TPS53313 discharges the output capacitors through an internal MOSFET switch
between SW and GND while the high-side and low-side MOSFETs are maintained in the OFF state. The typical
discharge switch on resistance is 120 Ω. This function is disabled when V
VIN
is less than 1 V.
SWITCHING FREQUENCY SETTING AND SYNCHRONIZATION
The clock frequency is programmed by the value of the resistor connected from the RT/SYNC pin to GND. The
switching frequency is programmable between 250 kHz and 1.5 MHz.
Also, TPS53313 is able to synchronize to external clock. The synchronization is fulfilled by connecting the
RT/SYNC pin to external clock source. If no external pulse is received from RT/SYNC pin, the device continues
to operate the internal clock.
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