MAX15035 Maxim Integrated Products, MAX15035 Datasheet - Page 18

• Manufacturer Part Number: MAX15035
• Description: 15A Step-Down Regulator
• Manufacturer: Maxim Integrated Products

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15A Step-Down Regulator with Internal Switches
Although REFIN is limited to a 0 to 2V range, the out-
put-voltage range is unlimited since the MAX15035 uti-
lizes a high-impedance feedback input (FB). By adding
a resistive voltage-divider from the output to FB to ana-
log ground (Figure 6), the MAX15035 supports output
voltages above 2V. However, the controller also uses
FB to determine the on-time, so the voltage-divider
influences the actual switching frequency, as detailed
in the On-Time One-Shot section.
An integrator amplifier forces the DC average of the FB
voltage to equal the target voltage. This internal amplifi-
er integrates the feedback voltage and provides a fine
adjustment to the regulation voltage (Figure 2), allowing
accurate DC output-voltage regulation regardless of the
compensated feedback ripple voltage and internal
slope-compensation variation. The integrator amplifier
has the ability to shift the output voltage by ±55mV (typ).
Figure 6. High Output-Voltage Application Using a Feedback Divider
18
SEE TABLE 1 FOR COMPONENT SELECTION.
______________________________________________________________________________________
GND/OPEN/REF/V
5V BIAS
SUPPLY
ON
AGND
AGND
OFF
DD
Output Voltages Greater than 2V
1000pF
1µF
C2
100kΩ
C3
1µF
R10
C1
PWR
37
38
36
34
35
4
2
PWR
3, 28, EP1
Internal Integration
PGOOD
EN
SKIP
REF
REFIN
V
V
DD
CC
MAX15035
AGND
AGND
PGND
TON
ILIM
BST
LX
FB
IN
33
29
18–26, EP3
30
6–15
32
5, 16, EP2
R5
49.4kΩ
AGND
332kΩ
R
TON
PWR
49.9kΩ
The MAX15035 disables the integrator by connecting the
amplifier inputs together at the beginning of all downward
REFIN transitions done in pulse-skipping mode. The inte-
grator remains disabled until 20µs after the transition is
completed (the internal target settles) and the output is in
regulation (edge detected on the error comparator).
PGOOD is the open-drain output that continuously
monitors the output voltage for undervoltage and over-
voltage conditions. PGOOD is actively held low in shut-
down (EN = GND), and during soft-start and
soft-shutdown. Approximately 200µs (typ) after the soft-
start terminates, PGOOD becomes high impedance as
long as the feedback voltage is above the UVP thresh-
old (REFIN - 200mV) and below the OVP threshold
(REFIN + 300mV). PGOOD goes low if the feedback
voltage drops 200mV below the target voltage (REFIN)
or rises 300mV above the target voltage (REFIN), or the
SMPS controller is shut down. For a logic-level PGOOD
C
0.1µF
R4
BST
L1
13.0kΩ
REF
R6
Power-Good Outputs (PGOOD)
R7
20kΩ
AGND
7V TO 15V
OPTIONAL
INPUT
PWR
C
C
PWR
IN
OUT
and Fault Protection
7V TO 24V
OUTPUT
1kΩ
INPUT
3.3V
5.6V
5V
BIAS
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