LTM4614IV#PBF Linear Technology, LTM4614IV#PBF Datasheet - Page 9
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LTM4614IV#PBF
Manufacturer Part Number
LTM4614IV#PBF
Description
IC UMODULE DC/DC DUAL 4A 144LGA
Manufacturer
Linear Technology
Series
µModuler
Type
Point of Load (POL) Non-Isolatedr
Datasheet
1.LTM4614EVPBF.pdf
(20 pages)
Specifications of LTM4614IV#PBF
Design Resources
LTM4614 Spice Model
Output
0.8 ~ 5 V
Number Of Outputs
2
Power (watts)
12W
Mounting Type
Surface Mount
Voltage - Input
2.38 ~ 5.5 V
Package / Case
144-LGA
1st Output
0.8 ~ 5 VDC @ 4A
2nd Output
0.8 ~ 5 VDC @ 4A
Size / Dimension
0.59" L x 0.59" W x 0.11" H (15mm x 15mm x 2.8mm)
Power (watts) - Rated
12W
Operating Temperature
-40°C ~ 125°C
Efficiency
95%
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
3rd Output
-
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
APPLICATIONS INFORMATION
Dual Switching Regulator
A typical LTM4614 application circuit is shown in Figure 12.
External component selection is primarily determined by
the maximum load current and output voltage. Refer to
Table 4 for specifi c external capacitor requirements for a
particular application.
V
There are restrictions in the maximum V
down ratio than can be achieved for a given input voltage
on the two switching regulators. The LTM4614 is 100%
duty cycle, but the V
a function the load current. A typical 0.5V minimum is
suffi cient.
Output Voltage Programming
Each regulator channel has an internal 0.8V reference
voltage. As shown in the Block Diagram, a 4.99k internal
feedback resistor connects the V
The output voltage will default to 0.8V with no feedback
resistor. Adding a resistor R
programs the output voltage:
Table 1. FB Resistor Table vs Various Output Voltages
Input Capacitors
The LTM4614 module should be connected to a low AC
impedance DC source. One 4.7μF ceramic capacitor is
included inside the module for each regulator channel.
Additional input capacitors are needed if a large load step
is required up to the full 4A level and for RMS ripple cur-
rent requirements. A 47μF bulk capacitor can be used for
more input bulk capacitance. This 47μF capacitor is only
needed if the input source impedance is compromised by
long inductive leads or traces.
IN
V
R
V
OUT
to V
FB
OUT
OUT
= 0.8V •
Open
0.8V
Step-Down Ratios
4.99k + R
1.2V
10k
IN
R
to V
FB
5.76k
1.5V
OUT
FB
FB
minimum dropout will be
from the FB pin to GND
OUT
3.92k
1.8V
and FB pins together.
IN
and V
2.37k
2.5V
OUT
1.62k
3.3V
step-
For a buck converter, the switching duty cycle can be
estimated as:
Without considering the inductor current ripple, the RMS
current of the input capacitor can be estimated as:
In the above equation, η% is the estimated effi ciency of
the power module. The bulk capacitor can be a switcher-
rated electrolytic aluminum OS-CON capacitor for bulk
input capacitance due to high inductance traces or leads.
If a low inductance plane is used to power the device,
then no input capacitance is required. The internal 4.7μF
ceramics on each channel input are typically rated for 1A of
RMS ripple current up to 85°C operation. The worst-case
ripple current for the 4A maximum current is 2A or less.
An additional 10μF or 22μF ceramic capacitor can be used
to supplement the internal capacitor with an additional 1A
to 2A ripple current rating.
Output Capacitors
The LTM4614 switchers are designed for low output volt-
age ripple on each channel. The bulk output capacitors are
chosen with low enough effective series resistance (ESR)
to meet the output voltage ripple and transient require-
ments. The output capacitors can be a low ESR tantalum
capacitor, low ESR polymer capacitor or ceramic capacitor.
The typical output capacitance range is 66μF to 100μF .
Additional output fi ltering may be required by the system
designer, if further reduction of output ripple or dynamic
transient spike is required. Table 4 shows a matrix of dif-
ferent output voltages and output capacitors to minimize
the voltage droop and overshoot during a 2A/μs transient.
The table optimizes total equivalent ESR and total bulk
capacitance to maximize transient performance.
D =
I
CIN(RMS)
V
V
OUT
IN
=
I
OUT(MAX)
η%
• D • 1– D
(
)
LTM4614
4614fa
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