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pin FuncTions
V
IN
(Bank 1): Power Input Pins. Apply input voltage be-
tween these pins and PGND pins. Recommend placing
input
decoupling capacitance directly between V
IN
pins
and PGND pins.
V
OUT
(Bank 5): Power Output Pins. Apply output load
between these pins and PGND pins. Recommend placing
output decoupling capacitance directly between these pins
and PGND pins.
PGND (Bank 6): Power Ground Pins for Both Input and
Output Returns.
SW1, SW2 (Bank 4, Bank 2): Switch Nodes. The power
inductor is connected between SW1 and SW2.
R
SENSE
(Bank 3): Sensing Resistor Pin. The sensing resis-
tor is connected from this pin to PGND.
SENSE
+
(Pin A4): Positive Input to the Current Sense and
Reverse Current Detect Comparators.
SENSE
(Pin A5): Negative Input to the Current Sense and
Reverse Current Detect Comparators.
EXTV
CC
(Pin F6): External V
CC
Input. When EXTV
CC
exceeds
5.7V, an internal switch connects this pin to INTV
CC
and
shuts down the internal regulator so that the controller and
gate drive power is drawn from EXTV
CC
. Do not exceed
7V at this pin and ensure that EXTV
CC
< V
IN
.
INTV
CC
(Pin F5): Internal 6V Regulator Output. This pin
is for additional decoupling of the 6V internal regulator.
PLLIN (
Pin B9): External Clock Synchronization Input
to the Phase Detector. This pin is internally terminated
to SGND with a 50k resistor. The phase-locked loop will
force the rising bottom gate signal of the controller to be
synchronized with the rising edge of PLLIN signal.
PLLFLTR (Pin B8): The lowpass filter of the phase-locked
loop is tied to this pin. This pin can also be used to set the
frequency of the internal oscillator with an AC or DC volt
-
age. See the Applications Information section for details.
SS (Pin A6): Soft-Start Pin. Soft-start reduces the input
surge current from the power source by gradually increas
-
ing the controller’s current limit.
STBYMD (Pin A10): LDO Control Pin. Determines whether
the internal LDO remains active when the controller is
shut down. See the Operations section for details. If the
STBYMD pin is pulled to ground, the SS pin is internally
pulled to ground to disable start-up and thereby provid
-
ing a
single control pin for turning off the controller. An
internal decoupling capacitor is tied to this pin.
V
FB
(Pin B6): The Negative Input of the Error Amplifier.
Internally, this pin is connected to V
OUT
with a 100k preci-
sion resistor. Different output
voltages can be programmed
with an additional resistor between V
FB
and SGND pins.
See the Applications Information section.
FCB (Pin A9): Forced Continuous Control Input. The
voltage applied to this pin sets the operating mode of the
module. When the applied voltage is less than 0.8V, the
forced continuous current mode is active. When this pin
is allowed to float, the Burst Mode operation is active in
boost operation and the skip cycle mode is active in buck
operation. When the pin is tied to INTV
CC
, the constant
frequency discontinuous current mode is active in buck or
boost operation. See the Applications Information section.
SGND (Pin A7): Signal Ground Pin. This pin connects to
PGND at output capacitor point.
COMP (Pin B7): Current Control Threshold and Error
Amplifier Compensation Point. The current comparator
threshold increases with this control voltage. The voltage
ranges from 0V to 2.4V.
PGOOD (Pin B5): Output Voltage Power Good Indicator.
Open drain logic output that is pulled to ground when the
output voltage is not within ±10% of the regulation point,
after a 25µs power bad mask timer expires.
RUN
(Pin A8): Run Control Pin. A voltage below 1.6V will
turn
off the module. There is a 100k resistor between the
RUN pin and SGND in the module. Do not apply more than
6V to this pin. See the Applications Information section.
LTM4607
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siMpliFieD block DiagraM
EXTV
CC
INTV
CC
PGOOD
PLLIN
RUN
ON/OFF
STBYMD
M1
4607 BD
SW2
4.5V TO 36V
SW1
L
V
IN
C
IN
CONTROLLER
C1
100k
0.1µF
FCB
TO PGND PLANE AS
SHOWN IN FIGURE 15
1000pF
SS
SS
0.1µF
M2
COMP
M3
12V
5A
V
FB
R
SENSE
V
OUT
C
OUT
CO1
M4
100k
R
FB
7.15k
R
SENSE
INT
COMP
PLLFLTR
INT
FILTER
INT
FILTER
PGND
SGND
SENSE
SENSE
+
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
C
IN
External Input Capacitor Requirement
(V
IN
= 4.5V to 36V, V
OUT
= 12V)
I
OUT
= 5A 10 µF
C
OUT
External Output Capacitor Requirement
(V
IN
= 4.5V to 36V, V
OUT
= 12V)
I
OUT
= 5A 200 300 µF
T
A
= 25°C. Use Figure 1 configuration.
Decoupling requireMenTs
Figure 1. Simplified LTM4607 Block Diagram
LTM4607
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operaTion
Power Module Description
The LTM4607 is a non-isolated buck-boost DC/DC power
supply. It can deliver a wide range output voltage from 0.8V
to 24V over a wide input range from 4.5V to 36V, by only
adding the sensing resistor, inductor and some external
input and output capacitors. It provides precisely regulated
output voltage programmable via one external resistor.
The typical application schematic is shown in Figure 18.
The LTM4607 has an integrated current mode buck-boost
controller, ultralow R
DS(ON)
FETs with fast switching speed
and integrated Schottky diodes. With current mode control
and internal feedback loop compensation, the LTM4607
module has sufficient stability margins and good transient
performance under a wide range of operating conditions
and with a wide range of output capacitors. The operating
frequency of the LTM4607 can be adjusted from 200kHz
to 400kHz by setting the voltage on the PLLFLTR pin.
Alternatively, its frequency can be synchronized by an in-
put clock signal from the PLLIN pin. The typical switching
frequency is 400kHz.
The Burst Mode and skip-cycle mode operations can be
enabled at light loads to improve efficiency, while the forced
continuous mode and discontinuous mode operations are
used
for constant frequency applications. Foldback current
limiting is activated in an overcurrent condition as V
FB
drops. Internal overvoltage and undervoltage compara-
tors pull
the open-drain PGOOD output low if the output
feedback
voltage exits the ±10% window around the
regulation point. Pulling the RUN pin below 1.6V forces
the controller into its shutdown state.
If an external bias supply is applied on the EXTV
CC
pin,
then an efficiency improvement will occur due to the re-
duced power
loss in the internal linear regulator. This is
especially true at the higher end of the input voltage range.
applicaTions inForMaTion
The typical LTM4607 application circuit is shown in
Figure 18. External component selection is primarily
determined by the maximum load current and output
voltage. Refer to Table 3 for specific external capacitor
requirements for a particular application.
Output Voltage Programming
The PWM controller has an internal 0.8V reference voltage.
As shown in the Block Diagram, a 100k internal feedback
resistor connects V
OUT
and V
FB
pins together. Adding a
resistor R
FB
from the V
FB
pin to the SGND pin programs
the output voltage:
V
OUT
= 0.8V
100k
+
R
FB
R
FB
Table 1. R
FB
Resistor (0.5%) vs Output Voltage
V
OUT
0.8V 1.5V 2.5V 3.3V 5V 6V 8V
R
FB
Open 115k 47.5k 32.4k 19.1k 15.4k 11k
V
OUT
9V 10V 12V 15V 16V 20V 24V
R
FB
9.76k 8.66k 7.15k 5.62k 5.23k 4.12k 3.4k
Operation Frequency Selection
The LTM4607 uses current mode control architecture at
constant switching frequency, which is determined by the
internal oscillator’s capacitor. This internal capacitor is
charged by a fixed current plus an additional current that
is proportional to the voltage applied to the PLLFLTR pin.
The PLLFLTR pin can be grounded to lower the frequency
to 200kHz or tied to 2.4V to yield approximately 400kHz.
When PLLFLTR is left open, the PLLFLTR pin goes low,
forcing the oscillator to its minimum frequency.
A graph for the voltage applied to the PLLFLTR pin vs
frequency is given in Figure 2. As the operating frequency
increases, the gate charge losses will be higher, thus the
efficiency is lower. The maximum switching frequency is
approximately 400kHz.
FREQUENCY SYNCHRONIZATION
The LTM4607 can also be synchronized to an external
source via the PLLIN pin instead of adjusting the voltage on
the PLLFLTR pin directly. The power module has a phase-
locked loop comprised of an internal voltage
controlled

LTM4607EV#PBF

Mfr. #:
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators 24VOUT, 5A Buck-boost Module Regulator
Lifecycle:
New from this manufacturer.
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