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MAX15035 Datasheet, PDF (18/27 Pages) Maxim Integrated Products – 15A Step-Down Regulator with Internal Switches
15A Step-Down Regulator with Internal Switches
5V BIAS
SUPPLY
AGND
ON OFF
GND/OPEN/REF/VDD
4 VDD
C1
1µF
C2 PWR
1µF
37 VCC
R10
100kΩ
38 PGOOD
2 EN
36 SKIP
TON 29
RTON
332kΩ
18–26, EP3
IN
30
BST
5, 16, EP2
LX
CBST
0.1µF L1
PGND 6–15
PWR
32
FB
R6
13.0kΩ
CIN
PWR
COUT
PWR
C3
1000pF
AGND
MAX15035
35 REF
34 REFIN
33
ILIM
AGND
3, 28, EP1
SEE TABLE 1 FOR COMPONENT SELECTION.
PWR AGND
R4
49.9kΩ
R5
49.4kΩ
AGND
R7
20kΩ
AGND
REF
7V TO 15V
INPUT
OPTIONAL
INPUT
7V TO 24V
OUTPUT
3.3V
1kΩ
5VBIAS
5.6V
Figure 6. High Output-Voltage Application Using a Feedback Divider
Output Voltages Greater than 2V
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.
Internal Integration
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).
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).
Power-Good Outputs (PGOOD)
and Fault Protection
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
18 ______________________________________________________________________________________