LTM4601AHVEV#PBF Linear Technology, LTM4601AHVEV#PBF Datasheet - Page 11

• Manufacturer Part Number: LTM4601AHVEV#PBF
• Description: IC DC/DC UMODULE 12A 133-LGA
• Manufacturer: Linear Technology
• Series: µModuler
• Type: Point of Load (POL) Non-Isolatedr

Specifications of LTM4601AHVEV#PBF

• Design Resources: LTM4601AHV Spice Model
• Output: 0.6 ~ 5 V
• Number Of Outputs: 1
• Power (watts): 60W
• Mounting Type: Surface Mount
• Voltage - Input: 4.5 ~ 28 V
• Package / Case: 133-LGA
• 1st Output: 0.6 ~ 5 VDC @ 12A
• Size / Dimension: 0.59" L x 0.59" W x 0.11" H (15mm x 15mm x 2.8mm)
• Power (watts) - Rated: 60W
• Operating Temperature: -40°C ~ 85°C
• Efficiency: 95%
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• 3rd Output: -
• 2nd Output: -

APPLICATIONS INFORMATION
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. C
aluminum capacitor, OS-CON capacitor or high volume
ceramic capacitor. Note the capacitor ripple current ratings
are often based on temperature and hours of life. This
makes it advisable to properly derate the input capacitor,
or choose a capacitor rated at a higher temperature than
required. Always contact the capacitor manufacturer for
derating requirements.
In Figures 19 and 20, the 10μF ceramic capacitors are to-
gether used as a high frequency input decoupling capacitor.
In a typical 12A output application, three very low ESR,
X5R or X7R (extended temperature range), 10μF ceramic
capacitors are recommended. These decoupling capacitors
should be placed directly adjacent to the module input pins
in the PCB layout to minimize the trace inductance and high
frequency AC noise. Each 10μF ceramic is typically good
for 2A to 3A of RMS ripple current. Refer to your ceramics
capacitor catalog for the RMS current ratings.
Multiphase operation with multiple LTM4601AHV devices
in parallel will lower the effective input RMS ripple current
due to the interleaving operation of the regulators. Appli-
cation Note 77 provides a detailed explanation. Refer to
Figure 2 for the input capacitor ripple current requirement
as a function of the number of phases. The fi gure provides
a ratio of RMS ripple current to DC load current as func-
tion of duty cycle and the number of paralleled phases.
D =
I
CIN(RMS)
V
V
OUT
IN
=
I
OUT(MAX)
η%
IN
can be a switcher-rated electrolytic
• D • 1– D
(
)
Pick the corresponding duty cycle and the number of phases
to arrive at the correct ripple current value. For example,
the 2-phase parallel LTM4601AHV design provides 24A
at 2.5V output from a 12V input. The duty cycle is DC =
2.5V/12V = 0.21. The 2-phase curve has a ratio of ~0.25
for a duty cycle of 0.21. This 0.25 ratio of RMS ripple cur-
rent to a DC load current of 24A equals ~6A of input RMS
ripple current for the external input capacitors.
Output Capacitors
The LTM4601AHV is designed for low output voltage ripple.
The bulk output capacitors defi ned as C
with low enough effective series resistance (ESR) to meet
the output voltage ripple and transient requirements. C
can be a low ESR tantalum capacitor, a low ESR polymer
capacitor or a ceramic capacitor. The typical capacitance is
200μF if all ceramic output capacitors are used. Additional
output fi ltering may be required by the system designer,
if further reduction of output ripple or dynamic transient
spike is required. Table 2 shows a matrix of different output
voltages and output capacitors to minimize the voltage
droop and overshoot during a 5A/μs transient. The table
optimizes total equivalent ESR and total bulk capacitance
to maximize transient performance.
Figure 2. Normalized Input RMS Ripple Current
vs Duty Factor for One to Six Modules (Phases)
0.6
0.5
0.4
0.3
0.2
0.1
0
0.1
0.2
0.3
DUTY FACTOR (V
0.4
1-PHASE
2-PHASE
3-PHASE
4-PHASE
6-PHASE
12-PHASE
0.5
LTM4601AHV
OUT
0.6
/V
IN
0.7
)
4601AHV F02
0.8
OUT
0.9
are chosen
11
4601ahvfa
OUT