LTM8026 LINER [Linear Technology], LTM8026 Datasheet - Page 12

• Manufacturer Part Number: LTM8026
• Description: 36VIN, 5A, 2-Quadrant CVCC Step-Down
• Manufacturer: LINER [Linear Technology]

LTM8052
operaTion
When the LTM8052 is sinking current, it maintains its
output voltage regulation by power conversion, not power
dissipation. This means that the energy provided to the
LTM8052 is in turn delivered to its input power bus. There
must be something on this power bus to accept or use
the energy, or the LTM8052’s input voltage will rise. Left
unchecked, the energy can raise the input voltage above
the absolute maximum voltage and damage the LTM8052.
Please see the Input Precautions section for further details.
For applications where only sourcing current (one quadrant
operation) is desired, use LTM8026.
The LTM8052 operates in forced continuous mode. This
means that the part will not skip cycles when the load
applications where the synchronization function is used,
or any time discontinuous switching is undesirable. The
LTM8052 will not operate in forced continuous mode
when an input UVLO, output OVLO or minimum duty cycle
current mode controller, power switches, power inductor,
mode control to accurately regulate the inductor current,
independent from the output voltage. This is an ideal solu-
tion for applications requiring a regulated current source.
The control loop will regulate the current in the internal
inductor. Once the output has reached the regulation
voltage determined by the resistor from the ADJ pin to
ground, the inductor current will be reduced by the volt-
age regulation loop.
approaches zero amps. This may be particularly useful in
violation occurs.
As shown in the Block Diagram, the LTM8052 contains a
and a modest amount of input and output capacitance.
The LTM8052 utilizes fixed frequency, average current
12
The output current loop has two control inputs, deter-
mined 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 LTM8052, 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. As
shown in the Typical Performance Characteristics section,
the positive and negative currents are not symmetric. The
negative current limit is offset by approximately 2A.
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 LTM8052 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 LTM8052 may also be synchronized to an
external clock through the use of the SYNC pin.
IN
to set a hysteresis. During start-
8052fa