LTM4632
15
4632fb
For more information www.linear.com/LTM4632
APPLICATIONS INFORMATION
For example, R
TR(TOP)
= 60.4k and R
TR(BOT)
= 60.4k is a
good combination for Coincident tracking for V
OUT(MA)
=
1.5V and V
OUT(SL)
= 1.2V application.
Power Good
The PGOOD pins are open drain pins that can be used to
monitor valid output voltage regulation. This pin monitors
a ±8% window around the regulation point. A resistor can
be pulled up to a particular supply voltage for monitoring.
To prevent unwanted PGOOD glitches during transients
or dynamic V
OUT
changes, the LTM4632’s PGOOD falling
edge includes a blanking delay of approximately 40us.
Stability Compensation
The LTM4632 module internal compensation loop is
de-signed and optimized for low ESR ceramic output
capacitors only application. Table 5 is provided for most
application requirements. The LTpowerCAD Design Tool is
available to download for control loop analysis for further
optimization.
RUN Enable
Pulling the RUN pin to ground forces the LTM4632 into
its shutdown state, turning off both power MOSFETs and
most of its internal control circuitry. Tying the RUN pin
voltage above 1.28V will turn on the entire chip.
Low Input Application
The LTM4632 is capable to run from 3.3V input when
the V
IN
pin is tied to INTV
CC
pin. See Figure 21 for the
application circuit. Please note the INTV
CC
pin has 3.6V
abs max voltage rating.
Pre-Biased Output Start-Up (Channel 1)
There may be situations that require the power supply to
start up with a pre-bias on the output capacitors. In this
case, it is desirable to start up without discharging that
output pre-bias. The LTM4632 channel 1 can safely power
up into a pre-biased output without discharging it.
The LTM4632 accomplishes this by forcing discontinuous
mode (DCM) operation until the TRACK/SS1 pin voltage
reaches 80% of the 0.6V reference voltage for channel 1.
This will prevent the BG from turning on during the pre-
biased output start-up which would discharge the output.
Do not pre-bias LTM4632 with a voltage higher than INTV
CC
(3.3V) voltage.
Overtemperature Protection
The internal overtemperature protection monitors the junc
-
tion temperature of the module. If
the junction temperature
reaches approximately 170°C, both power switches will be
turned off until the temperature drops about 10°C cooler.
Input Overvoltage Protection
In order to protect the internal power MOSFET devices
against transient voltage spikes, the LTM4632 constantly
monitors each V
IN
pin for an overvoltage condition. When
V
IN
rises above 17.5V, the regulator suspends operation
by shutting off both power MOSFETs on the correspond-
ing channel. Once V
IN
drops below 16.5V, the regulator
immediately resumes normal operation. The regulator
executes its soft-start function when exiting an overvolt
-
age condition.
Thermal Considerations and Output Current Derating
The thermal resistances reported in the Pin Configura
-
tion section of the data sheet are consistent with those
parameters defined by JESD51-9 and are intended for
use with finite element analysis (FEA) software modeling
tools that leverage the outcome of thermal modeling,
simulation, and correlation to hardware evaluation per-
formed on a µModule package mounted to a hardware test
board—also defined by JESD51-9 (“Test Boards for Area
Array Surface Mount Package Thermal Measurements”).
The motivation for providing these thermal coefficients in
found in JESD51-12 (“Guidelines for Reporting and Using
Electronic Package Thermal Information”).
Many designers may opt to use laboratory equipment
and a test vehicle such as the demo board to anticipate
the µModule regulator’s thermal performance in their ap
-
plication at various electrical and environmental operating
conditions to compliment any FEA activities
.
Without FEA
software, the thermal resistances reported in the Pin Con
-
figuration section are in-and-of themselves not relevant to
providing guidance of thermal performance; instead, the
