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LTM4602HVIV#PBF

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LTM4602HV
7
4602hvf
WU
DECOUPLI G REQUIRE E TS
U
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
C
IN
External Input Capacitor Requirement
(V
IN
= 4.5V to 28V, V
OUT
= 2.5V)
I
OUT
= 6A, 2x 10µF 35V Ceramic
Taiyo Yuden GDK316BJ106ML
20 µF
C
OUT
External Output Capacitor Requirement
(V
IN
= 4.5V to 28V, V
OUT
= 2.5V)
I
OUT
= 6A, Refer to Table 2 in the
Applications Information Section
100 200 µF
SI PLIFIED
W
BLOCK DIAGRA
W
T
A
= 25°C, V
IN
= 12V. Use Figure 1 confi guration.
Figure 1. Simplifi ed LTM4602HV Block Diagram
4602HV F01
RUN/SS
V
OSET
EXTV
CC
SGND
f
ADJ
V
IN
FCB
1000pF
Q1
Q2
V
OUT
2.5V
6A MAX
PGND
V
IN
4.5V TO 28V
ABS MAX
SV
IN
COMP
PGOOD
R
SET
31.6k
100k
0.5%
4.75k
110k
1.5µF
C
IN
15µF
6.3V
C
OUT
10Ω
INT
COMP
CONTROLLER
LTM4602HV
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4602hvf
OPERATIO
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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 simplifi ed 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 suffi cient
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 effi ciency 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.
LTM4602HV
9
4602hvf
APPLICATIO S I FOR ATIO
WUU
U
voltage is margined up. The output voltage is margined
down when Q
DOWN
is on and Q
UP
is off. If the output
voltage V
O
needs to be margined up/down by ±M%, the
resistor values of R
UP
and R
DOWN
can be calculated from
the following equations:
()••(%)
()
.
RR V M
RR k
V
SET UP O
SET UP
1
100
06
+
+Ω
=
RV M
RkR
V
SET O
SET DOWN
••(–%)
()
.
1
100
06
+Ω
=
Input Capacitors
The LTM4602HV µModule should be connected to a low
ac-impedance DC source. High frequency, low ESR input
capacitors are required to be placed adjacent to the mod-
ule. In Figure 20, the bulk input capacitor C
IN
is selected
for its ability to handle the large RMS current into the
converter. For a buck converter, the switching duty-cycle
can be estimated as:
D
V
V
O
IN
=
Without considering the inductor current ripple, the RMS
current of the input capacitor can be estimated as:
I
I
DD
CIN RMS
OMAX
()
()
%
••( )=−
η
1
In the above equation, η% is the estimated effi ciency of
the power module. C1 can be a switcher-rated electrolytic
aluminum capacitor, OS-CON capacitor or high volume
ceramic capacitors. Note the capacitor ripple current
ratings are often based on only 2000 hours of life. This
makes it advisable to properly derate the input capacitor,
or choose a capacitor rated at a higher temperature than
required. Always contact the capacitor manufacturer for
derating requirements.
In Figure 16, the input capacitors are used as high frequency
input decoupling capacitors. In a typical 6A output applica-
tion, 1-2 pieces of very low ESR X5R or X7R, 10µF ceramic
capacitors are recommended. This decoupling capacitor
should be placed directly adjacent the module input pins
The typical LTM4602HV application circuit is shown in
Figure 20. External component selection is primarily
determined by the maximum load current and output
voltage.
Output Voltage Programming and Margining
The PWM controller of the LTM4602HV has an internal
0.6V±1% reference voltage. As shown in the block diagram,
a 100k/0.5% internal feedback resistor connects V
OUT
and
FB pins. Adding a resistor R
SET
from V
OSET
pin to SGND
pin programs the output voltage:
VV
kR
R
O
SET
SET
=
+
06
100
.•
Table 1 shows the standard values of 1% R
SET
resistor
for typical output voltages:
Table 1
R
SET
(kΩ)
Open 100 66.5 49.9 43.2 31.6 22.1 13.7
V
O
(V)
0.6 1.2 1.5 1.8 2 2.5 3.3 5
Voltage margining is the dynamic adjustment of the output
voltage to its worst case operating range in production
testing to stress the load circuitry, verify control/protec-
tion functionality of the board and improve the system
reliability. Figure 2 shows how to implement margining
function with the LTM4602HV. In addition to the feedback
resistor R
SET
, several external components are added.
Turn off both transistor Q
UP
and Q
DOWN
to disable the
margining. When Q
UP
is on and Q
DOWN
is off, the output
Figure 2
PGND SGND
4602HV F02
LTM4602HV
V
OUT
V
OSET
R
SET
R
UP
Q
UP
100k
2N7002
R
DOWN
Q
DOWN
2N7002
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LTM4602HVIV#PBF

Mfr. #:
Buy LTM4602HVIV#PBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators 28V, 6A Step-down Module Regulator
Lifecycle:
New from this manufacturer.
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