Figure 63. The transition from Low current to Normal current and the effect on modulation
This should be considered when configuring the LDO drop curve (see LDO output voltage configuration).
9.1.5 SOVP clamp resistor selection
SOVP clamp resistors, also known as IEXT resistors, are used as a part of the SOVP protection. When triggered,
STWLC38 pulls VRECT to ground through those resistors in an attempt to lower the VRECT voltage. Therefore,
the resistance value must be selected according to the selected SOVP threshold and power dissipation
capabilities of the resistors. IEXT pins’ current capabilities must also be considered, as the internal switches can
only withstand up to 300 mA of current.
9.1.6 ESD/TVS diodes
STEVAL-WLC38 also features two external TVS diodes which protect the STWLC38’s input pins (AC1 and AC2)
against excessive input voltage. The breakdown voltage of those diodes is 14.4 V.
9.1.7 NTC thermistor connection
The figure below shows external NTC connection. Together with the R7 pull-up resistor the NTC forms a voltage
divider, which is connected to the STWLC38 NTC pin. It is recommended to design the voltage divider to reach
the (low) NTC threshold at the highest allowed temperature.
ntc =
accumulated
ADC
2
10
× acc
× 2 × 2.25 × 0.8 + 1.8
ADC raw data two's complement (2 bytes)
acc constant default value 16
ntc calculated value in mV
UM3154
External component design
UM3154 - Rev 2
page 57/81
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