Datasheet

LTC4253B
23
4253bf
applicaTions inForMaTion
Live Insertion with Short Pin Control of UV/OV
In the example shown in Figure 8, power is delivered
through long connector pins whereas the UV/OV divider
makes contact through a short pin. This ensures the power
connections are firmly established before the LTC4253B
is activated. At time point 1, the power pins make contact
and V
IN
ramps through V
LKO
. At time point2, the UV/OV
divider makes contact and its voltage exceeds V
UVHI
. In
Figure 8. Power-Up Timing with a Short Pin (All Waveforms Are Referenced to VEE)
GATE
START-UP
INITIAL TIMING
V
UVHI
V
LKO
V
GATEL
V
SQTMRH
V
SQTMRL
GND – V
EE
OR
(–48RTN) – (–48V)
UV/OV
V
IN
TIMER
GATE
SENSE
UV CLEARS V
UVHI
, CHECK OV < V
OVHI
, RESET < 0.8V, GATE < V
GATEL
,
SENSE < V
CB
, SS < 20 • V
OS
AND TIMER < V
TMRL
V
OUT
1 2 3 4 5 6 7 89
TIMER CLEARS V
TMRL
, CHECK GATE < V
GATEL
, SENSE < V
CB
AND SS < 20 • V
OS
SS
DRAIN
PWRGD1
A B
PWRGD2
PWRGD3
SQTIMER
EN2
EN3
C D
5µA
5µA
V
SQTMRH
4253b F08
V
SQTMRL
V
TMRH
V
ACL
V
CB
V
TMRL
20 • (V
ACL
+ V
OS
)
20 • (V
CB
+ V
OS
)
20 • V
OS
5µA
5µA
5µA
50µA
50µA
50µA
V
DRNCL
V
DRNL
V
IN
– V
GATEH
200µA + 8 • I
DRN