An additional useful application for the LTC3639 is to generate a negative voltage from a positive one. The part’s wide voltage range makes even large negative output voltages realizable. This figure shows the implementation of a –15V output regulator from a 4V to 135V input. Since the output is connected to the ground pin, the maximum input voltage is limited to the sum of 150V and the –15V regulated output, or 135V. The maximum output current for the LTC3639 in this positive-to-negative configuration is about 100mA • VIN/(VIN+|VOUT|).