SNVAA65 March 2023 LM63610-Q1 , LM63615-Q1 , LM63625-Q1 , LM63635-Q1
Changing to an inverting buck-boost topology will have an impact on the maximum possible output current. For an inverting buck-boost converter, the inductor current will always be larger than the output current. As a result, the maximum possible output current is calculated by:
where:
The duty cycle can be calculated as:
VOUT is represented as the negative output voltage of the inverting buck-boost converter. The efficiency term in the duty cycle equation helps account for power losses to provide a more accurate calculation of the output current. For example, if the output voltage is -5 V, the input voltage is 24 V, and the efficiency is assumed to be 85%, then the duty cycle is:
In the case of the LM63615-Q1, which has a maximum current of 1.5 A, the resulting maximum output current of the inverting buck-boost converter would be:
VOUT (V) | VIN (V) | IOUT_Buck (A) | η | D | IOUT (A) |
---|---|---|---|---|---|
–3.3 | 24 | 1.5 | 0.85 | 0.139 | 1.291 |
–5 | 24 | 1.5 | 0.85 | 0.197 | 1.205 |