Datasheet

TPS54262-Q1
SLVS996C –SEPTEMBER 2009–REVISED JUNE 2010 www.ti.com
Figure 17. Active Mode CCM Figure 18. PSM at Low VIN
• Likewise, at higher input voltages when the ON time (t
ON
) of the switching FET becomes close to or slightly
less than the minimum ON time (t
ON-Min
) and the V
Reg
start losing regulation, the device enters in PSM. If ON
time is much smaller than t
ON-Min
, there is a risk that the part stops switching and regulation is lost until power
is re-cycled with ON time greater than t
ON-Min
.
• At nominal input voltages during very light output loading. This mode of operation is shown in Figure 19.
Comparing Figure 16 and Figure 19, in both cases the device is operating in discontinuous conduction mode;
however, pulse skipping happens in Figure 19 because of very light output loading for similar input voltage.
LPM pin must be set high (i.e., disabled) for this to happen.
Figure 19. PSM at Nominal VIN
4) Low Power Mode (LPM)
In this mode of operation the device briefly operates in discontinuous conduction mode and then turns off until
V
Reg
< VReg_UV threshold and this cycle is repeated. The LPM pin must be enabled to enable LPM mode of
operation. When total load is less than I
L_DISCONT
, the device operates in LPM for VIN ~8.5 V to ~32 V. This
mode of operation is shown in Figure 20 and Figure 21 (zoomed out).
14 Submit Documentation Feedback Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): TPS54262-Q1