Datasheet

EN=2V/div
Vout1=1V/div
Vout2=1V/div
Time=20msec/div
EN=2V/div
Vout1=1V/div
Vout2=1V/div
Time=20msec/div
TPS54620
www.ti.com SLVS949C –MAY 2009– REVISED MAY 2011
Figure 28. Ratio-metric Startup with Vout2 Leading Vout1
Figure 29. Simultaneous Startup
Output Overvoltage Protection (OVP)
The device incorporates an output overvoltage protection (OVP) circuit to minimize output voltage overshoot. For
example, when the power supply output is overloaded the error amplifier compares the actual output voltage to
the internal reference voltage. If the VSENSE pin voltage is lower than the internal reference voltage for a
considerable time, the output of the error amplifier demands maximum output current. Once the condition is
removed, the regulator output rises and the error amplifier output transitions to the steady state voltage. In some
applications with small output capacitance, the power supply output voltage can respond faster than the error
amplifier. This leads to the possibility of an output overshoot. The OVP feature minimizes the overshoot by
comparing the VSENSE pin voltage to the OVP threshold. If the VSENSE pin voltage is greater than the OVP
threshold the high-side MOSFET is turned off preventing current from flowing to the output and minimizing output
overshoot. When the VSENSE voltage drops lower than the OVP threshold, the high-side MOSFET is allowed to
turn on at the next clock cycle.
Overcurrent Protection
The device is protected from overcurrent conditions by cycle-by-cycle current limiting on both the high-side
MOSFET and the low-side MOSFET.
High-side MOSFET overcurrent protection
The device implements current mode control which uses the COMP pin voltage to control the turn off of the
high-side MOSFET and the turn on of the low-side MOSFET on a cycle by cycle basis. Each cycle the switch
current and the current reference generated by the COMP pin voltage are compared, when the peak switch
current intersects the current reference the high-side switch is turned off.
Low-side MOSFET overcurrent protection
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