ZHCSIR1C June 2018 – May 2021 LM2775-Q1
PRODUCTION DATA
To minimize quiescent current during light load operation, the LM2775-Q1 provides a PFM operation option (selectable via the PFM pin. '1' = PFM allowed, '0' = Fixed frequency). By allowing the charge pump to only switch when the VOUT voltage decays to a typical 5.05 V, the quiescent current drawn from the power source is minimized. The frequency of pulsed operation is not limited and can drop into the sub-1-kHz range when unloaded. As the load increases, the frequency of pulsing increases.
When PFM mode is disabled, the device operates in a constant frequency mode. In this mode, the quiescent current remains at normal levels even when the load current is decreased. The main advantages of fixed frequency operation include a lower output voltage ripple level due to the constant switching and a predictable switching frequency that stays at 2 MHz which can be important in noise sensitive applications.