When f_BUR is below the 8.5-kHz upper burst frequency threshold (f_SBP2(UP)), UCC28782 exits SBP1 mode and enters into SBP2 mode. Compared with the SBP1 mode, the pulse count is doubled and V_CST can be programmed by the IPC pin. The V_CST programmable range in SBP2 is between 0.27 V and 0.4 V. The purpose of SBP2 is to further lower f_BUR in order to minimize standby power.

The f_BUR condition to trigger the mode transition from SBP2 to SBP1 depends on the IPC pin voltage setting as well. If V_IPC is set lower than 0.9 V or the IPC pin is shorted to AGND, V_CST is equal to V_{CST_IPC(MIN)}, and the mode transition occurs when f_BUR is increased above the same 8.5-kHz threshold. On the other hand, if V_IPC is set higher than 0.9 V, V_CST is higher than 0.27 V, and the mode transition occurs when f_BUR is increased above the 1.7-kHz lower burst frequency threshold (f_SBP2(LR)). The purpose of skipping the burst frequency range between 1.7 kHz and 8.5 kHz is to avoid the most sensitive audible frequency range to the human ear. The frequency skipping is only enabled, when the peak current is set higher by V_IPC > 0.9 V.

Figure 8-30 PWM Pattern in SBP2