Datasheet

15
LTC3834-1
38341f
TIME
(4a) Coincident Tracking
V
X
(MASTER)
V
OUT
(SLAVE)
OUTPUT VOLTAGE
3834-1 F04A
V
X
(MASTER)
V
OUT
(SLAVE)
TIME
3834-1 F04B
(4b) Ratiometric Tracking
OUTPUT VOLTAGE
LTC3834-1
V
OUT
V
x
V
FB
TRACK/SS
38341 F05
RB
RA
R
TRACKA
R
TRACKB
Figure 5. Using the TRACK/SS Pin for Tracking
Figure 4. Two Different Modes of Output Voltage Tracking
APPLICATIO S I FOR ATIO
WUUU
Alternatively, the TRACK/SS pin can be used to track two
(or more) supplies during start-up, as shown qualitatively
in Figures 4a and 4b. To do this, a resistor divider should
be connected from the master supply (V
X
) to the TRACK/
SS pin of the slave supply (V
OUT
), as shown in Figure 5.
During start-up V
OUT
will track V
X
according to the ratio set
by the resistor divider:
V
V
R
R
RR
RR
X
OUT
A
TRACKA
TRACKA TRACKB
AB
=
+
+
•
For coincident tracking (V
OUT
= V
X
during start-up),
R
A
= R
TRACKA
R
B
= R
TRACKB
INTV
CC
Regulator
The LTC3834-1 features an internal P-channel low drop-
out linear regulator (LDO) that supplies power at the
INTV
CC
pin from the V
IN
supply pin. INTV
CC
powers the
gate drivers and much of the LTC3834-1’s internal cir-
cuitry. The V
IN
LDO regulates the voltage at the INTV
CC
pin
to 5.25V. It can supply a peak current of 50mA and must
be bypassed to ground with a minimum of 4.7μF ceramic
capacitor. The ceramic capacitor placed directly adjacent
to the INTV
CC
and PGND IC pins is highly recommended.
Good bypassing is needed to supply the high transient
currents required by the MOSFET gate drivers and to
prevent interaction between the channels.