Datasheet

LTC3614
21
3614fa
Figure 7a. Setup for Coincident Tracking
Figure 7b. Setup for Ratiometric Tracking
V
FB2
R4
R2
R4
R2
R3
R2
R4 ≤ R3
V
OUT2
V
OUT1
LTC3614
TRACK/SS2
V
FB1
V
IN
LTC3614
LTC3614 CHANNEL 2
SLAVE
LTC3614 CHANNEL 1
MASTER
TRACK/SS1
3614 F07a
V
FB2
R1
R2
R5
R6
R3 R1/R2 < R5/R6
R4
V
OUT2
V
OUT1
LTC3614
TRACK/SS2
V
FB1
V
IN
3614 F07b
LTC3614
LTC3614 CHANNEL 2
SLAVE
LTC3614 CHANNEL 1
MASTER
TRACK/SS1
To implement the coincident tracking behavior in Fig-
ure 6a, connect an extra resistive divider to the output
of the master channel and connect its midpoint to the
TRACK/SS pin for the slave channel. The ratio of this
divider should be selected to be the same as that of the
slave channel’s feedback divider (Figure 7a).
In this track-
ing mode, the master channel’s output must be set higher
than slave channel’s output. To implement the ratiometric
tracking behavior in Figure 6b, different resistor divider
values must be used as specifi ed in Figure 7b.
For coincident start-up, the voltage value at the TRACK/SS
pin for the slave channel needs to reach the fi nal reference
value after the internal soft-start time (around 1ms). The
master start-up time needs to be adjusted with an external
capacitor and resistor to ensure this.
External Reference Input (DDR Mode)
If the DDR pin is tied to SV
IN
(DDR mode), the run state
is entered when V
TRACK/SS
exceeds 0.3V and tracking
down behavior is possible if the V
TRACK/SS
voltage is
below 0.6V.
This allows TRACK/SS to be used as an external reference
between 0.3V and 0.6V if desired. During the run state in
DDR mode, the power good window moves in relation
to the actual TRACK/SS pin voltage if the voltage value
is between 0.3V and 0.6V. Note: if TRACK/SS voltage is
0.6V, either the tracking circuit or the internal reference
can be used.
During up/down tracking the output current foldback is
disabled and the PGOOD pin is always pulled down (see
Figure 9).
APPLICATIONS INFORMATION