Если напряжение старта низкое, то не получиться, так как в 3845 старт при 8 вольтах, а в 3844 при 14.5.
[ссылка заблокирована по решению администрации проекта]
Differences between members of this family are the
under-voltage lockout thresholds and maximum duty
cycle ranges. The UC1842 and UC1844 have UVLO
thresholds of 16 VON and 10 VOFF, ideally suited to
off-line applications. The corresponding thresholds
for the UC1843 and UC1845 are 8.4 V and 7.6 V.
The UC1842 and UC1843 can operate to duty cycles
approaching 100%. A range of zero to 50% is
obtained by the UC1844 and UC1845 by the addition
of an internal toggle flip flop which blanks the output
off every other clock cycle
елки, ну вроде взрослый мужик! мы будем за Вас даташиты брать и сравнивать!