Datasheet
0
V
DHC_READY
V
RAIL(nom)
V
LED
V
RAIL
Time
t
ST-1
t
ST-2
t
ST-3
t
ST-1
open
R
ISR
Startup time
t
ST-2
high
t
ST-3
low
V
IN-UVLO
6.67V
0
V
DHC_READY
V
RAIL(nom)
V
RAIL(steady)
V
RAIL(peak)
V
RAIL
Time
Pushed up
by LM3463
Initiated by
primary power
supply
DHC activated
LM3463
www.ti.com
SNVS807A –MAY 2012–REVISED MAY 2013
Figure 24. Changes of V
RAIL
during system startup
Shortening System Startup Time
The system startup time can be shortened by sinking current from the ISR pin to ground through a resistor, R
ISR
.
The lower resistance the R
ISR
carries, the shorter time the system startup takes. Sinking current from the ISR pin
increases the charging current to the capacitor, C
DHC
and eventually increases the rate of the increasing of V
RAIL
during startup (V
RAIL
ramps up from V
RAIL(nom)
to V
DHC_READY
). Figure 25 shows how the system startup time is
shortened by using different value of R
ISR
.
Figure 25. Setting different startup time using different R
ISR
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