Datasheet

LM5026
www.ti.com SNVS363D –AUGUST 2005–REVISED APRIL 2013
The two ground pins (AGND, PGND) must be connected together with a short direct connection to avoid jitter
due to relative ground bounce.
If the internal dissipation of the LM5026 produces high junction temperatures during normal operation, the use of
multiple vias under the IC to a ground place can help conduct heat away from the IC. Judicious positioning of the
PC board within the end product, along with use of any available air flow (forced or natural convection) can help
reduce the junction temperatures.
Application Circuit Example
The following schematic shows an example of an LM5026 controlled 100W active clamp forward power
converter. The input voltage range (V
PWR
) is 36V to 78V, and the output voltage is 3.3V. The output current
capability is 30 Amps. Current sense transformer T2 provides information to the CS pin for current mode control
and current limit protection. The error amplifiers and reference U3 and U4 provide voltage feedback via
optocoupler U2. Synchronous rectifiers Q3-Q6 minimize rectification losses in the secondary. An auxiliary
winding on inductor L2 provides power to the LM5026 VCC pin when the output is in regulation. The input
voltage UVLO levels are ≈34V for increasing V
PWR
, and ≈32V for decreasing V
PWR
. The circuit can be shut down
by forcing the ON/OFF input (J2) below 1.25V. An external synchronizing frequency can be applied to the SYNC
input (J11) or like converters can be self-synchronized by connections of (J3). The regulator output is current
limited at ≈32A.
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