LTM4602HV Datasheet, PDF (8/24 Pages) Linear Technology – 6A, 28VIN High Effi ciency DC/DC μModule

LTM4602HV
U
OPERATIO
µModule Description
The LTM4602HV is a standalone non-isolated synchronous
switching DC/DC power supply. It can deliver up to 6A of
DC output current with only bulk external input and output
capacitors. This module provides a precisely regulated
output voltage programmable via one external resistor from
0.6V_DC to 5.0V_DC. The input voltage range is 4.5V to 28V.
A simplified block diagram is shown in Figure 1 and the
typical application schematic is shown in Figure 21.
The LTM4602HV contains an integrated LTC constant
on-time current-mode regulator, ultra-low R_DS(ON) FETs
with fast switching speed and integrated Schottky diode.
The typical switching frequency is 800kHz at full load.
With current mode control and internal feedback loop
compensation, the LTM4602HV module has sufficient
stability margins and good transient performance under a
wide range of operating conditions and with a wide range
of output capacitors, even all ceramic output capacitors
(X5R or X7R).
Current mode control provides cycle-by-cycle fast current
limit. In addition, foldback current limiting is provided
in an over-current condition while V_FB drops. Also, the
LTM4602HV has defeatable short circuit latch off. Internal
overvoltage and undervoltage comparators pull the open-
drain PGOOD output low if the output feedback voltage exits
a ±10% window around the regulation point. Furthermore,
in an overvoltage condition, internal top FET Q1 is turned
off and bottom FET Q2 is turned on and held on until the
overvoltage condition clears.
Pulling the RUN/SS pin low forces the controller into its
shutdown state, turning off both Q1 and Q2. Releasing the
pin allows an internal 1.2µA current source to charge up
the softstart capacitor. When this voltage reaches 1.5V,
the controller turns on and begins switching.
At low load current the module works in continuous cur-
rent mode by default to achieve minimum output voltage
ripple. It can be programmed to operate in discontinuous
current mode for improved light load efficiency when the
FCB pin is pulled up above 0.8V and no higher than 6V.
The FCB pin has a 10k resistor to ground, so a resistor to
V_IN can set the voltage on the FCB pin.
When EXTV_CC pin is grounded or open, an integrated 5V
linear regulator powers the controller and MOSFET gate
drivers. If a minimum 4.7V external bias supply is ap-
plied on the EXTV_CC pin, the internal regulator is turned
off, and an internal switch connects EXTV_CC to the gate
driver voltage. This eliminates the linear regulator power
loss with high input voltage, reducing the thermal stress
on the controller. The maximum voltage on EXTV_CC pin is
6V. The EXTV_CC voltage should never be higher than the
V_IN voltage. Also EXTV_CC must be sequenced after V_IN.
Recommended for 24V operation to lower temperature
in the µModule.
4602hvf
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