LTM4636
10
4636f
Decoupling requireMenTs
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
C
IN
External Input Capacitor Requirement
(V
IN
= 4.70V to 16V, V
OUT
= 1.5V)
I
OUT
= 40A, 6
×
22µF Ceramic X7R Capacitors
(See Table 4)
100
µF
C
OUT
External Output Capacitor Requirement
(V
IN
= 4.70V to 16V, V
OUT
= 1.5V)
I
OUT
= 40A (See Table 4)
1000
µF
T
A
= 25°C. Use Figure 1 configuration.
Power Module Description
The LTM4636 is a high efficiency regulator that can provide
a 40A output with few external input and output capacitors.
This module provides precisely regulated output voltages
programmable via external resistors from 0.6V DC to 3.3V
DC over a 4.70V to 15V input range. The Typical Applica-
tion schematic is shown in Figure 20.
The LTM4636 has an integrated constant-frequency cur-
rent mode regulator, power MOSFETs, 0.18µH inductor,
protection circuitry, 5V regulator and other supporting
discrete components. The switching frequency range is
from 250kHz to 770kHz, and the typical operating frequency
is 400kHz. For switching noise-sensitive applications, it
can be externally synchronized from 250kHz to 800kHz,
subject to minimum on-time limitations and limiting the
inductor ripple current to less than 40% of maximum
output current.
A single resistor is used to program the frequency. See
the Applications Information section.
With current mode control and internal feedback loop
compensation, the LTM4636 module has sufficient stabil-
ity margins and good transient performance with a wide
range of output capacitors, even with all ceramic output
capacitors. An option has been provided for external loop
compensation. LTpowerCAD
®
can be used to optimize
the external compensation option. See the Applications
Information section.
Current mode control provides cycle-by-cycle fast current
limit in an overcurrent condition. An internal overvoltage
operaTion
monitor feedback pin referred will attempt to protect the
output voltage in the event of an overvoltage >10%. The
top MOSFET is turned off and the bottom MOSFET is
turned on until the output is cleared.
Pulling the RUNC pin below 1.1V forces the regulator con-
troller into a shutdown state. The TRACK/SS pin is used for
programming the output voltage ramp and voltage tracking
during start-up. See the Applications Information section.
The LTM4636 is internally compensated to be stable over
all operating conditions. Table 5 provides a guideline for
input and output capacitances for several operating condi-
tions. LTpowerCAD is available for transient and stability
analysis. This tool can be used to optimize the regulators
loop response.
A remote sense amplifier is provided for accurately sensing
output voltages at the load point.
Multiphase operation can be easily employed with the
internal clock source or a synchronization clock applied
to the MODE/PLLIN input using an external clock source,
and connecting the CLKOUT pins. See the Applications
Information section. Review Figure 4.
High efficiency at light loads can be accomplished with
selectable Burst Mode operation using the MODE_PLLIN
pin. These light load features will accommodate battery
operation. Efficiency graphs are provided for light load op-
eration in the Typical Performance Characteristics section.
A TEMP
+
and TEMP
–
pins are provided to allow the internal
device temperature to be monitored using an onboard
diode connected NPN transistor.
