MAX15022_11 Datasheet, PDF (13/28 Pages) Maxim Integrated Products – Dual, 4A/2A, 4MHz, Step-Down DC-DC Regulator with Dual LDO Controllers

Dual, 4A/2A, 4MHz, Step-Down DC-DC
Regulator with Dual LDO Controllers
Coincident/Ratiometric Tracking
The enable inputs in conjunction with digital soft-start
and soft-stop provide coincident/ratiometric tracking.
Track an output voltage by connecting a resistive
divider from the output being tracked to its enable
input. For example, for V_OUT2 to coincidentally track
V_OUT1, connect the same resistive divider used for
FB2, from V_OUT1 to EN2 to SGND (see Figure 2).
Track ratiometrically by connecting EN_ to SGND. This
synchonizes the soft-start and soft-stop of all the regu-
lator references, and hence their respective output volt-
ages will track ratiometrically (see Figure 2).
When the MAX15022 regulators are configured as volt-
age trackers, output short-circuit fault conditions at
either master or slave output are handled carefully—nei-
ther the master nor slave output will remain energized
when the other output is shorted to ground. When the
slave is shorted and enters into hiccup mode, the mas-
ter will soft-stop. When the master is shorted and the
part enters into hiccup mode, the slave will ratiometrical-
ly soft-stop. Coming out of hiccup mode, both outputs
will soft-start coincidently or ratiometrically depending
on their initial configuration. During the thermal shut-
down or power-off when the input falls below its UVLO,
the output voltages track down depending on the
respective output capacitance and load.
See Figure 1 for a graphical representation of coinci-
dent/ratiometric tracking.
Sequencing
When sequencing, the voltage at the enable inputs
must exceed 1.225V (typ) for each PWM controller to
start (see Figure 1c).
a)
RATIOMETRIC TRACKING
VPVIN1
b)
COINCIDENT TRACKING
VPVIN1
c)
COINCIDENT TRACKING
VPVIN2
EN1
EN1
EN2
EN2
SEL
AVIN
OUTPUT 1 IS THE MASTER AND
OUTPUT 2 IS THE SLAVE.
VPVIN2
EN2
EN1
VOUT1
RA
EN2
RB
VOUT2
RA
FB2
RB
VOUT2
RC
EN1
RD
VOUT1
RC
FB1
RD
SEL
UNCONNECTED
OUTPUT 2 IS THE MASTER AND
OUTPUT 1 IS THE SLAVE.
SEL
AVIN
OUTPUT 1 IS THE MASTER AND
OUTPUT 2 IS THE SLAVE.
Figure 2. Ratiometric Tracking and Coincident Tracking Configurations
SEL
UNCONNECTED
OUTPUT 2 IS THE MASTER AND
OUTPUT 1 IS THE SLAVE.
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