ZHCSH35B November 2017 – May 2021 LM73605-Q1 , LM73606-Q1
PRODUCTION DATA
Pulse-frequency-modulation (PFM) mode is activated when peak current is lower than IPEAK-MIN, only in auto mode. Peak current is kept constant and VOUT is regulated by frequency. Efficiency is greatly improved by lowered switching losses, especially at very light loads.
In PFM operation, a small DC positive offset appears on VOUT. The lower the frequency is folded back in PFM, the more the DC offset is on VOUT. See the VOUT regulation curves in the Section 9.2.3. If the DC offset on VOUT is not acceptable, a dummy load at VOUT, or lower RFBT and RFBB resistance values can be used to reduce the offset. Alternatively, the device can be run in FPWM mode where the switching frequency is constant, and no offset is added to affect the VOUT accuracy unless tON_MIN is reached.