TPS53624_15 Datasheet, PDF (16/47 Pages) Texas Instruments – Dual Phase, D-CAP+™, Eco-mode™ Step-Down Controller with 8-Bit DAC

TPS53624
SLUSB66 – MARCH 2013
www.ti.com
Figure 6 shows a two-phase converter. The energy in the inductor is transferred to the capacitance on the V_CORE
node above and the output voltage (green trace) overshoots the desired level (lower cursor, also green). In this
case, the magnitude of the overshoot is approximately 40 mV. The LLx waveforms (yellow and blue traces)
remain flat during the overshoot, indicating the DRVLx signals are on.
The performance of the same dual phase circuit, but with OSR enabled is shown in Figure 7. In this case, the
low side FETs shut off when overshoot is detected and the energy in the inductor is partially dissipated by the
body diodes. The overshoot is reduced by 25 mV. The dips in the LLx waveforms show the DRVLx signals are
OFF only long enough to reduce the overshoot.
Figure 6. Circuit Performance Without Overshoot Figure 7. Transient Release Performance Improved
Reduction
with Overshoot Reduction
Implementation
OSR is implemented using a comparator between the DROOP and ISUM nodes. To implement OSR, simply
terminate the OSRSEL pin to the desired voltage to set the threshold voltage for the comparator. The settings
are:
• GND = Minimum voltage (Maximum reduction)
• VREF = Medium voltage
• +3.3V = Maximum voltage
• 5V = OSR off
Use the highest setting that provides the desired level of overshoot reduction to eliminate the possibility of false
OSR operation.
Light Load Power Saving Features
The TPS53624 has several power saving features to provide excellent efficiency over a very large load range.
This feature is implemented with PCNT pin.. This pin is a VCCP I/O level. A LO on this pin puts the converter
into single phase mode, thus eliminating the quiescent power of phase two when high power is not needed.
In addition, the TPS53624 has an automatic pulse skipping skip mode. Regardless of the state of the logic
inputs, the converter senses negative inductor current flow and prevents it by shutting off the low-side
MOSFET(s). This saves power by eliminating recirculating current.
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