MAX15046BAEE+T Maxim Integrated Products, MAX15046BAEE+T Datasheet - Page 10

• Manufacturer Part Number: MAX15046BAEE+T
• Description: IC CTLR SYNC BUCK 40V 16-QSOP
• Manufacturer: Maxim Integrated Products
• Type: Step-Down (Buck)r

Specifications of MAX15046BAEE+T

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.6 ~ 34 V
• Current - Output: 3A
• Frequency - Switching: 100kHz ~ 1MHz
• Voltage - Input: 4.5 ~ 40 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Power - Output: 771.5mW
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

40V, High-Performance, Synchronous
Buck Controller
The MAX15046 synchronous step-down controller oper-
ates from a 4.5V to 40V input-voltage range and gener-
ates an adjustable output voltage from 85% of the input-
voltage down to 0.6V while supporting loads up to 25A.
As long as the device supply voltage is within 5.0V to
5.5V, the input power bus (V
The MAX15046 offers adjustable switching frequency
from 100kHz to 1MHz with an external resistor. The
adjustable switching frequency provides design flex-
ibility in selecting passive components. The MAX15046
adopts an adaptive synchronous rectification to elimi-
nate external freewheeling Schottky diodes and improve
efficiency. The device utilizes the on-resistance of the
external low-side MOSFET as a current-sense element.
The current-limit threshold voltage is resistor-adjustable
from 30mV to 300mV and is temperature-compensated,
so that the effects of the MOSFET R
over temperature are reduced. This current-sensing
scheme protects the external components from damage
during output overloaded conditions or output short-
circuit faults without requiring a current-sense resistor.
Hiccup-mode current limit reduces power dissipation
during short-circuit conditions. The MAX15046 includes
a power-good output and an enable input with precise
turn-on/-off threshold to be used for monitoring and for
power sequencing.
The MAX15046 features internal digital soft-start that
allows prebias startup without discharging the output. The
digital soft-start function employs sink current limiting to
prevent the regulator from sinking excessive current when
the prebias voltage exceeds the programmed steady-
state regulation level. The digital soft-start feature prevents
the synchronous rectifier MOSFET and the body diode of
the high-side MOSFET from experiencing dangerous lev-
els of current while the regulator is sinking current from the
output. The MAX15046 shuts down at a +150NC junction
temperature to prevent damage to the device.
The MAX15046 step-down controller uses a PWM volt-
age-mode control scheme (see the Functional Diagram).
Control-loop compensation is external for providing max-
imum flexibility in choosing the operating frequency and
output LC filter components. An internal transconduc-
tance error amplifier produces an integrated error volt-
age at COMP that helps to provide higher DC accuracy.
The voltage at COMP sets the duty cycle using a PWM
10
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Detailed Description
DC-DC PWM Controller
IN
) can be as low as 3.3V.
DS(ON)
variation
comparator and a ramp generator. On the rising edge
of an internal clock, the high-side n-channel MOSFET
turns on and remains on until either the appropriate duty
cycle or the maximum duty cycle is reached. During
the on-time of the high-side MOSFET, the inductor cur-
rent ramps up. During the second-half of the switching
cycle, the high-side MOSFET turns off and the low-side
n-channel MOSFET turns on. The inductor releases the
stored energy as the inductor current ramps down, pro-
viding current to the output. Under overload conditions,
when the inductor current exceeds the selected valley
current-limit threshold (see the Current-Limit Circuit (LIM)
section), the high-side MOSFET does not turn on at the
subsequent clock rising edge and the low-side MOSFET
remains on to let the inductor current ramp down.
An internal linear regulator (V
nal supply to power the internal functions and to drive the
low-side MOSFET. Connect IN and V
using an external 5V Q10% power supply. The maximum
regulator input voltage (V
with a 1FF ceramic capacitor. Bypass the output of the
linear regulator (V
GND. The V
V
MAX15046 also employs an undervoltage lockout circuit
that disables the internal linear regulator when V
falls below 3.6V (typical). The 400mV UVLO hysteresis
prevents chattering on power-up/power-down.
DH and DL are optimized for driving large-size n-channel
power MOSFETs. Under normal operating conditions
and after startup, the DL low-side drive waveform
is always the complement of the DH high-side drive
waveform, with controlled dead time to prevent cross-
conduction or “shoot-through.” An adaptive dead-time
circuit monitors the DH and DL outputs and prevents the
opposite-side MOSFET from turning on until the MOSFET
is fully off. Thus, the circuit allows the high-side driver to
turn on only when the DL gate driver has turned off and
prevents the low side (DL) from turning on until the DH
gate driver has turned off.
The adaptive driver dead time allows operation without
shoot-through with a wide range of MOSFETs, minimiz-
ing delays and maintaining efficiency. There must be a
low-resistance, low-inductance path from DL and DH to
the MOSFET gates for the adaptive dead-time circuits
IN
is higher than 5.5V, V
CC
dropout voltage is typically 180mV. When
Internal 5.25V Linear Regulator
MOSFET Gate Drivers (DH, DL)
CC
) with a 4.7FF ceramic capacitor to
IN
VCC
) is 40V. Bypass IN to GND
CC
) provides a 5.25V nomi-
is typically 5.25V. The
CC
together when
VCC