LTM8026_1208 LINER [Linear Technology], LTM8026_1208 Datasheet - Page 12

• Manufacturer Part Number: LTM8026_1208
• Description: 36VIN, 5A CVCC Step-Down ?Module Regulator
• Manufacturer: LINER [Linear Technology]

LTM8026
operaTion
The LTM8026 is a standalone nonisolated step-down
switching DC/DC power supply that can deliver up to 5A of
output current. This µModule regulator provides a precisely
regulated output voltage programmable via one external
resistor from 1.2V to 24V. The input voltage range is 6V
to 36V. Given that the LTM8026 is a step-down converter,
make sure that the input voltage is high enough to support
the desired output voltage and load current.
As shown in the Block Diagram, the LTM8026 contains a
current mode controller, power switches, power inductor,
and a modest amount of input and output capacitance.
The LTM8026 utilizes fixed frequency, average current
mode control to accurately regulate the inductor current,
independently from the output voltage. This is an ideal
solution for applications requiring a regulated current
source. The control loop will regulate the current in the
internal inductor. Once the output has reached the regula-
tion voltage determined by the resistor from the ADJ pin
to ground, the inductor current will be reduced by the
voltage regulation loop.
The current control loop has two reference inputs,
determined by the voltage at the analog control pins, CTL_I
and CTL_T . CTL_I is typically used to set the maximum
allowable current output of the LTM8026, while CTL_T
is typically used with a NTC thermistor to reduce the
output current in response to temperature. The lower of
the two analog voltages on CTL_I and CTL_T determines
the regulated output current. The analog control range of
both the CTL_I and CTL_T pin is from 0V to 1.5V.
12
The RUN pin functions as a precision shutdown pin. When
the voltage at the RUN pin is lower than 1.55V, switch-
ing is terminated. Below the turn-on threshold, the RUN
pin sinks 5.5µA. This current can be used with a resistor
between RUN and V
up, the SS pin is held low until the part is enabled, after
which the capacitor at the soft-start pin is charged with
an 11µA current source.
The LTM8026 is equipped with a thermal shutdown to
protect the device during momentary overload conditions.
It is set above the 125°C absolute maximum internal tem-
perature rating to avoid interfering with normal specified
operation, so internal device temperatures will exceed
the absolute maximum rating when the overtemperature
protection is active. So, continuous or repeated activation
of the thermal shutdown may impair device reliability.
During thermal shutdown, all switching is terminated and
the SS pin is driven low.
The switching frequency is determined by a resistor at
the RT pin. The LTM8026 may also be synchronized to an
external clock through the use of the SYNC pin.
IN
to the set a hysteresis. During start-
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