The MAX98090 headphone outputs can drive an arbitrarily-low impedance, but the output is current limited to around 90mA peak. This is actually a result of the limited output current of the charge pump supplying the headphone amp. On a simple bench test we are able to drive a 4Ω load and can get 16mW at 1% THD+N. For a 16Ω load happens to be around the peak achievable output power at around 40mW; With higher impedance loads the output power is limited by output voltage swing and with lower impedance loads the output power is limited by charge pump current.