MAX15046AAEE+T Maxim Integrated Products, MAX15046AAEE+T Datasheet - Page 11

• Manufacturer Part Number: MAX15046AAEE+T
• Description: DC/DC Switching Controllers 40V Synchronous Buck Controller
• Manufacturer: Maxim Integrated Products

Specifications of MAX15046AAEE+T

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

to function properly. The stray impedance in the gate
discharge path can cause the sense circuitry to interpret
the MOSFET gate as “off” while the V
is still high. To minimize stray impedance, use very short,
wide traces.
Synchronous rectification reduces conduction losses in
the rectifier by replacing the normal low-side Schottky
catch diode with a low-resistance MOSFET switch. The
MAX15046 features a robust internal pulldown transistor
with a typical 1I R
resistance prevents DL from being pulled up during the
fast rise time of the LX node, due to capacitive coupling
from the drain to the gate of the low-side synchronous
rectifier MOSFET.
An external Schottky diode between BST and DH is
required to boost the gate voltage above LX providing
the necessary gate-to-source voltage to turn on the high-
side MOSFET. The boost capacitor connected between
BST and LX holds up the voltage across the gate driver
during the high-side MOSFET on-time.
Figure 1. Power On-Off Sequencing
High-Side Gate-Drive Supply (BST)
DAC_VREF
UVLO
V
V
OUT
DH
EN
DL
CC
______________________________________________________________________________________
DS(ON)
DAC_VREF
SYMBOL
UVLO
V
DH
V
DL
EN
OUT
A
A
CC
40V, High-Performance, Synchronous
to drive DL low. This low on-
Undervoltage threshold value is provided in
the Electrical Characteristics table.
Internal 5.25V linear regulator output.
Active-high enable input.
Regulator output voltage.
Regulator internal soft-start and soft-stop signal.
Regulator high-side gate-driver output.
Regulator low-side gate-driver output.
V
EN is low.
B
CC
rising while below the UVLO threshold.
C
GS
DEFINITION
of the MOSFET
D
2048 CLOCK
CYCLES
E
The charge lost in the boost capacitor for delivering the
gate charge is replenished when the high-side MOSFET
turns off and the LX node goes to ground. When LX is
low, the external diode between V
es the boost capacitor. See the Boost Capacitor and
Diode Selection section in the Applications Information
to choose the right boost capacitor and diode.
Drive EN high to turn on the MAX15046. A soft-start
sequence starts to increase (step-wise) the reference
voltage of the error amplifier. The duration of the soft-
start ramp is 2048 switching cycles and the resolution is
1/64th of the steady-state regulation voltage allowing a
smooth increase of the output voltage. A logic-low on EN
initiates a soft-stop sequence by stepping down the ref-
erence voltage of the error amplifier. After the soft-stop
sequence is completed, the MOSFET drivers are both
turned off. See Figure 1.
Connect EN to V
the accurate turn-on/-off thresholds, EN can be used
as a UVLO adjustment input, and for power sequencing
together with the PGOOD outputs.
Enable Input (EN), Soft-Start, and Soft-Stop
SYMBOL
G
H
I
C
D
E
F
F
B
V
EN is pulled high. DH and DL start switching.
Normal operation.
V
V
start switching. Normal operation.
EN is pulled low. V
EN is pulled high. DH and DL start switching.
Normal operation.
V
CC
CC
CC
CC
2048 CLOCK
CYCLES
is higher than the UVLO threshold. EN is low.
drops below UVLO.
goes above the UVLO threshold. DH and DL
drops below UVLO.
G
Buck Controller
CC
DEFINITION
OUT
for always-on operation. Owing to
enters soft-stop.
H
DRV
I
and BST recharg-
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