LTC3834-1 Datasheet, PDF (15/28 Pages) Linear Technology – 30μA IQ Synchronous Step-Down Controller

LTC3834-1
APPLICATIO S I FOR ATIO
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_{X =} R_{A •} R_TRACKA + R_TRACKB
V_OUT R_TRACKA
R_A + R_B
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.
V_X (MASTER)
V_OUT (SLAVE)
V_X (MASTER)
V_OUT (SLAVE)
TIME
3834-1 F04A
(4a) Coincident Tracking
TIME
3834-1 F04B
(4b) Ratiometric Tracking
Figure 4. Two Different Modes of Output Voltage Tracking
V_x
V_OUT
RB
RA
R_TRACKB
R_TRACKA
LTC3834-1
V_FB
TRACK/SS
38341 F05
Figure 5. Using the TRACK/SS Pin for Tracking
38341f
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