Datasheet

TPS63036

SLVSB76 –AUGUST 2012

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Figure 24. Average Current Mode Control

Power-save mode and synchronization

The PS/SYNC pin can be used to select different operation modes. Power Save Mode is used to improve

efficiency at light load. To enable Power Save Mode, PS/SYNC must be set low. If PS/SYNC is set low then

Power Save Mode is entered when the average inductor current gets lower then about 100mA. At this point the

converter operates with reduced switching frequency and with a minimum quiescent current to maintain high

efficiency.

During the Power Save Mode, the output voltage is monitored with a comparator by the threshold comp low and

comp high. When the device enters Power Save Mode, the converter stops operating and the output voltage

drops. The slope of the output voltage depends on the load and the value of output capacitance. As the output

voltage falls below the comp low threshold, the device ramps up the output voltage again, by starting operation

using a programmed average inductor current higher than required by the current load condition. Operation can

last one or several pulses. The converter continues these pulses until the comp high threshold, is reached and

the average inductance current gets lower than about 100mA. When the load increases above the minimum

forced inductor current of about 100mA, the device will automatically switch to PWM mode.

The Power Save Mode can be disabled by programming high at the PS/SYNC. Connecting a clock signal at

PS/SYNC forces the device to synchronize to the connected clock frequency.

Synchronization is done by a PLL, so synchronizing to lower and higher frequencies compared to the internal

clock works without any issues. The PLL can also tolerate missing clock pulses without the converter

malfunctioning. The PS/SYNC input supports standard logic thresholds.

Current Limit

To protect the device and the application, the average input current is limited internally on the IC. At nominal

operating conditions, this current limit is constant. The current limit value can be found in the electrical

characteristics table. The current limit varies depending on the input voltage. A curve of the input current varying

with the input voltage is shown in figure 3 and figure 4 respectively showing the minimum and the maximum

current limit expected depending on input and output voltage.

Product Folder Links: TPS63036