Datasheet

Heavy Load transient step

PFM mode at light load

current

PWM mode

Comparator High

Comparator low

Absolute Voltage drop

with positioning

3.5%

2.5%

TPS63020

TPS63021

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SLVS916C –JULY 2010–REVISED MARCH 2013

Figure 22. Power-Save Mode Thresholds and Dynamic Voltage Positioning

Dynamic voltage positioning

As detailed in Figure 22, the output voltage is typically 3% above the nominal output voltage at light load

currents, as the device is in Power Save Mode. This gives additional headroom for the voltage drop during a load

transient from light load to full load. This allows the converter to operate with a small output capacitor and still

have a low absolute voltage drop during heavy load transient changes. See Figure 22 for detailed operation of

the power save mode

Dynamic Current Limit

To protect the device and the application, the average inductor 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. If the supply voltage at VIN drops below 2.3V, the current limit is reduced. This can happen

when the input power source becomes weak. Increasing output impedance, when the batteries are almost

discharged, or an additional heavy pulse load is connected to the battery can cause the VIN voltage to drop. The

dynamic current limit has its lowest value when reaching the minimum recommended supply voltage at VIN. At

this voltage, the device is forced into burst mode operation trying to stay active as long as possible even with a

weak input power source.

If the die temperature increases above the recommended maximum temperature, the dynamic current limit

becomes active. Similar to the behavior when the input voltage at VIN drops, the current limit is reduced with

temperature increasing.

Device Enable

The device is put into operation when EN is set high. It is put into a shutdown mode when EN is set to GND. In

shutdown mode, the regulator stops switching, all internal control circuitry is switched off, and the load is

disconnected from the input. This means that the output voltage can drop below the input voltage during

shutdown. During start-up of the converter, the duty cycle and the peak current are limited in order to avoid high

peak currents flowing from the input.

Product Folder Links: TPS63020 TPS63021