LTM4712
OPERATION
The LTM4712 is a standalone nonisolated buck-boost
switching DC/DC power supply. The buck-boost topol-
ogy allows the LTM4712 to regulate its output voltage
for input voltages both above and below the magnitude of
the output. The maximum output current depends upon
the input voltage. Higher input voltages yield higher max-
imum output current.
The output voltage of the LTM4712 is set by connecting
the FB pin to a resistor between FB pin and GND.
In addition to regulating output voltage, the LTM4712 is
equipped with average current control loops for either the
input or output. Add a current sense resistor to limit the
input or output current below maximum value. When the
resistor is present, the IMON pin reflects the current flow-
ing though the sense resistor between input or output.
This converter provides a precisely regulated output volt-
age programmable via an external resistor divider from
1V to 36V. The input voltage range is 5V to 36V. See the
Block Diagram (Figure 1).
The LTM4712 features an integrated compensation net-
work for most conditions. Some applications, however,
benefit from a different compensation network. In such
cases, apply an appropriate external compensation net-
work for optimal and proper operation.
The LTM4712 contains a constant frequency, peak current
mode controller, power switching elements, power induc-
tor and a modest amount of input and output capacitance.
The LTM4712 is a constant frequency PWM regulator.
The operating frequency can be adjusted from 100kHz to
600kHz by connecting the appropriate resistor value from
the FREQ pin to SGND. Alternatively, its frequency can be
synchronized by an input clock signal on the SYNC pin.
The typical switching frequency is 400kHz.
If an external bias supply is applied on the EXTV pin,
CC
then an efficiency improvement occurs due to the reduced
power loss in the internal linear regulator. This is espe-
cially true at the higher end of the input voltage range.
Rev. 0
9
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