The TPSM41625 is a fixed frequency converter. The major limitation for any fixed frequency converter is that during transient load step up, the output voltage drops until the next clock cycle of the converter before it can respond to the load change. The TPSM41625 implements a special circuitry to improve transient performance. During a load step up, the converter can issue an additional PWM pulse before the next available clock cycle to stop output voltage from further dropping, thus reducing the undershoot voltage. The additional pulse during a transient means that the device is not fixed frequency during the transient.

During load step-down, the TPSM41625 implements a body-brake function that turns off both high-side and low-side FET, and allows power to dissipate through the low-side body diode, reducing overshoot. This approach is very effective while having some impact on efficiency during transient.

In stand-alone mode, choose whether the transient response feature is enabled by placing either a 78.7-kΩ or 187-kΩ resistor between the MODE pin and AGND. A 78.7-kΩ MODE resistor is recommended when the output voltage is 0.6 V to 1.8 V or in applications that are more susceptible to noise. Leave the MODE pin open to operate in fixed frequency during a load step, (see Table 7-8).