ZHCSPC5 October 2022 LM51231-Q1
PRODUCTION DATA
The device provides the maximum duty cycle limit (DMAX) / minimum off-time to cover the non-ideal factors caused by resistive elements. DMAX decides the minimum input supply voltage (VSUPPLY(MIN)) which can achieve the target output voltage (VLOAD) during CCM operation, but VSUPPLY(MIN) which can achieve the target output voltage during DCM operation is not limited by DMAX. VSUPPLY(MIN), which can achieve the target output voltage during CCM operation, can be estimated as follows.
where
At very light load condition or when VSUPPLY is close to VOUT-REG, the device skips the low-side driver pulses if the required on-time is less than tON-MIN. This pulse skipping appears as a random behavior. If VSUPPLY is further increased to the voltage higher than VOUT-REG, the required on-time becomes zero and eventually the device can start bypass operation which turns on the high-side driver 100% when the VOUT pin voltage is greater than VOVTH.