MAX15021 Maxim Integrated Products, MAX15021 Datasheet - Page 11

• Manufacturer Part Number: MAX15021
• Description: Step-Down DC-DC Regulator
• Manufacturer: Maxim Integrated Products

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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
V
FB2, from V
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 MAX15021 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
Figure 2. Ratiometric Tracking and Coincident Tracking Configurations
OUT1
Regulator with Tracking/Sequencing Capability
OUTPUT 1 IS THE MASTER AND
OUTPUT 2 IS THE SLAVE.
OUTPUT 2 IS THE MASTER AND
OUTPUT 1 IS THE SLAVE.
, connect the same resistive divider used for
RATIOMETRIC TRACKING
V
V
RIN1
EN1
RIN2
EN2
SEL
EN2
EN1
SEL
OUT1
to EN2 to SGND (see Figure 2).
______________________________________________________________________________________
Coincident/Ratiometric Tracking
AVIN
UNCONNECTED
Dual, 4A/2A, 4MHz, Step-Down DC-DC
OUT2
to coincidentally track
OUTPUT 1 IS THE MASTER AND
OUTPUT 2 IS THE SLAVE.
COINCIDENT TRACKING
V
V
V
OUT1
OUT2
EN1
EN2
SEL
RIN1
FB2
when the other output is shorted to ground. When the
slave is shorted and enters hiccup mode, the master will
soft-stop. When the master is shorted and the part
enters in hiccup mode, the slave will ratiometrically soft-
stop. Coming out of hiccup mode, both outputs will soft-
start coincidently or ratiometrically depending on their
initial configuration. During the thermal shutdown or
power-off when the input falls below its UVLO, the out-
put voltages decrease at a rate depending on the
respective output capacitance and load.
See Figure 1 for a graphical representation of coinci-
dent/ratiometric tracking.
When sequencing, the voltage at the enable inputs
must exceed 1.225V (typ) for each PWM controller to
start (see Figure 1c).
AVIN
R
R
R
R
A
B
A
B
OUTPUT 2 IS THE MASTER AND
OUTPUT 1 IS THE SLAVE.
COINCIDENT TRACKING
V
V
V
OUT2
OUT1
EN2
EN1
RIN2
FB1
SEL
Sequencing
UNCONNECTED
R
R
R
R
C
D
C
D
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