EFP01 datasheet(16/158 Pages) SILABS

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3.2.1.7 NTM Buck/Boost Transitional Mode

When DCDC A is in the Buck/Boost configuration and programmed to Autonomous (or Buck/Boost) mode, (i.e, BB_CTRL3.BB_MODE

= 1), the DCDC converter will automatically switch between one of three operating modes:

• Buck: Traditional Buck operation used when VDDB is much greater than VOA

• Boost: Traditional Boost operation used when VDDB is much lower than VOA

• NTM: Transitional mode between Buck and Boost modes, used when VDDB is close to VOA

The Boost-to-NTM and NTM-to-Buck mode transition voltage thresholds are controlled by the NTM_LDO_THRSH bit field in the

BB_CTRL3 register. For example, the figures below show the DCDC A operating mode versus the battery voltage for various

NTM_LDO_THRSH settings for a Buck/Boost application with a 3.3V output.

Figure 3.4. Operating Mode vs Battery Voltage, NTM_LDO_THRSH=3

Figure 3.5. Operating Mode vs Battery Voltage, NTM_LDO_THRSH=5

Figure 3.6. Operating Mode vs Battery Voltage, NTM_LDO_THRSH=7

3.2.1.8 VOA Switch (VOA_SW)

The VOA output has an internal switch connecting it to the VOA_SW pin. This optional VOA_SW output can be used to completely

power down high-leakage external circuitry when entering the 3.3.3 EM2 and/or 3.3.4 EM4 modes. The VOA_SW state is controlled by

the VOA_SW_CON bitfield in the BIAS_SW register.

Note that if a large capacitive load is attached to the VOA_SW output, the VOA output may see momentary voltage droops when

VOA_SW is enabled.

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EFP01 Datasheet(PDF) 16 Page - Silicon Laboratories