LTC3828_15 Datasheet, PDF (13/32 Pages) Linear Technology – Dual, 2-Phase Step-Down Controller with Tracking

OPERATION (Refer to Functional Diagram)
3.0
2.5
SINGLE-PHASE
DUAL CONTROLLER
2.0
1.5
2-PHASE
DUAL CONTROLLER
1.0
0.5 _{VO1 = 5V/3A}
V_O2 = 3.3V/3A
0
0
10
20
30
INPUT VOLTAGE (V)
40
3828 F03
Figure 3. RMS Input Current Comparison
LTC3828
APPLICATIONS INFORMATION
Output Voltage Tracking
The LTC3828 allows the user to program how the channel
outputs ramp up by means of the TRCKSS pins. Through
these pins, the channel outputs can be set up to either
coincidentally or ratiometrically tracking, as shown in
Figure 4.
The TRCKSS pins act as clamps on the channels’ reference
voltages. V_OUT is referenced to the TRCKSS voltage when
the TRCKSS < 0.8V and to the internal precision reference
when TRCKSS > 0.8V.
To implement the tracking in Figure 4a, connect an extra
resistive divider to the output of the master channel and
connect its midpoint to the slave channel’s TRCKSS pin.
The ratio of this divider should be selected the same as
that of channel 2’s feedback divider (Figure 5). In this
tracking mode, the master channel’s output must be
set higher than slave channel’s output. To implement
the ratiometric tracking in Figure 4b, no extra divider is
needed; simply connect one of TRCKSS pins to the other
channel’s V_FB pin (Figure 5).
V_OUT1
V_OUT1
V_OUT2
V_OUT2
TIME
(4a) Coincident Tracking
TIME
3828 F04
(4b) Ratiometric Tracking
Figure 4. Two Different Modes of Output Voltage Tracking
3828fc
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