PT6364 Datasheet, PDF (5/13 Pages) Texas Instruments – 11 A 12-V Input Adjustable Integrated Switching Regulator

Application Notes
PT6360 Series
Operating Features and System Considerations
for the PT6360 Regulator Series
The PT6360 is a series of integrated switching regulators
(ISRs) that operate off a 12-V input to provide step-
down voltage conversion for output loads of up to 11 A.
Power up & Soft-Start Timing
Following either the application of a valid input source
voltage, or the removal of a ground signal to the Inhihit
control pin (with input power applied), the regulator will
initiate a soft-start power up. A soft start slows the rate at
which the output voltage rises and introduces a short time
delay, t_d (approx. 10 ms), into the power-up sequence.
Figure 1-1 shows the power-up characteristic of a PT6363
(2.5-V output) with an 8.3-A load. Note that the initial
step of input current when the input voltage begins to
rise is the input capacitor(s) charging.
Figure 1-1
Vin (5V/Div)
Vo (1V/Div)
t_d
Output Remote Sense
The (+)Sense pin allows the regulator to compensate for
limited amounts of ‘IR’ voltage drop in the positive output
connection resistance. This is the voltage drop incurred
in the PCB trace between Vout (pins 9 & 10) of the regu-
lator and the load some distance away. Connecting (+)Sense
to the positive load terminal improves the voltage regu-
lation at the load, particularly when the load current
fluctuates. Although not recommended, leaving (+)Sense
disconnected will not damage the regulator or the load
circuitry. An internal 10 Ω resistor, connected between
the sense pin and the output, keeps the output voltage in
regulation.
With the sense pin connected, the difference between
the voltage measured between V_out and GND at the
regulator, and that measured from (+)Sense to GND, is
the amount of IR drop being compensated by the regula-
tor. This should be limited to 0.3 V maximum.
Note: The remote sense feature is not designed to compensate
for the forward drop of non-linear or frequency dependent
components that may be placed in series with the converter
output. Examples include OR-ing diodes, filter inductors,
ferrite beads, and fuses. When these components are enclosed
by the remote sense connections they are effectively placed
inside the regulation control loop, which can adversely affect
the stability of the regulator.
Iin (2A/Div)
HORIZ SCALE: 5ms/Div
Over-Current Protection
To protect against load faults, these ISRs incorporate
output over-current protection. Applying a load that
exceeds the over-current threshold (see data sheet speci-
fications) will cause the regulated output to shut down.
Following shutdown the ISR will periodically attempt to
recover by initiating a soft-start power-up. This is often
described as a “hiccup” mode of operation, whereby the
module continues in a cycle of successive shutdown and
power up until the load fault is removed. During this
period, the average current flowing into the fault is
significantly reduced. Once the fault is removed, the
converter automatically recovers and returns to normal
operation.
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