LTM4605IV#PBF Linear Technology, LTM4605IV#PBF Datasheet - Page 14

• Manufacturer Part Number: LTM4605IV#PBF
• Description: IC DC/DC UMODULE 5A 141-LGA
• Manufacturer: Linear Technology
• Series: µModuler
• Type: Point of Load (POL) Non-Isolatedr

Specifications of LTM4605IV#PBF

• Design Resources: LTM4605 Spice Model
• Output: 0.8 ~ 16 V
• Number Of Outputs: 1
• Power (watts): 80W
• Mounting Type: Surface Mount
• Voltage - Input: 4.5 ~ 20V
• Package / Case: 141-LGA
• 1st Output: 0.8 ~ 16 VDC @ 5A
• Size / Dimension: 0.59" L x 0.59" W x 0.11" H (15mm x 15mm x 2.8mm)
• Power (watts) - Rated: 80W
• Operating Temperature: -40°C ~ 85°C
• Efficiency: 98%
• Dc To Dc Converter Type: Non-Inverting/Inverting/Step Up/Step Down
• Pin Count: 141
• Input Voltage: 20V
• Output Voltage: 0.8 to 16V
• Switching Freq: 170 TO 440KHz
• Output Current: 12/5A
• Package Type: LGA
• Output Type: Adjustable
• Switching Regulator: Yes
• Load Regulation: 0.5%
• Line Regulation: 0.02%
• Mounting: Surface Mount
• Input Voltage (min): 4.5V
• Operating Temperature Classification: Industrial
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• 3rd Output: -
• 2nd Output: -
• Lead Free Status / Rohs Status: Compliant

APPLICATIONS INFORMATION
LTM4605
To set the output voltage at 12V, the resistor R
pin to ground should be chosen as:
To choose a proper inductor, we need to know the current
ripples at different input voltages. The inductor should
be chosen by considering the worst case in the practi-
cal operating region. If the maximum output power P is
150W at buck mode, we can get the current ripple ratio
of the current ripple ΔI
I
Figure 3 shows the current ripple ratio at different input
voltages based on the inductor values: 1.5μH, 2.5μH,
3.3μH and 4.7μH. If we need 30% ripple current ratio at
all inputs, the 3.3μH inductor can be selected.
At buck mode, sensing resistor selection is based on
the maximum output current and the allowed maximum
sensing threshold 130mV.
14
Figure 3. Current Ripple Ratio at Different Inputs for Buck Mode
L
as follows:
R
R
ΔI
I
FB
SENSE
L
L
=
=
V
0.8V • 100k
(V
OUT
=
0.8
0.6
0.4
0.2
IN
0
V
2 • (P / V
12
IN
− 0.8V
– V
V
ƒ = 400kHz
OUT
• L • f • P
2 • 130mV
OUT
= 12V
14
INPUT VOLTAGE V
OUT
L
) • V
≈ 7.15k
to the maximum inductor current
) − ΔI
OUT
2
16
L
IN
(V)
18
1.5μH
2.5μH
4.7μH
3.3μH
4605 F03
20
FB
from V
FB
Consider the safety margin about 30%, we can choose
the sensing resistor as 8mΩ.
For the input capacitor, use a low ESR sized capacitor to
handle the maximum RMS current. Input capacitors are
required to be placed adjacent to the module. In Figure 14,
the 10μF ceramic input capacitors are selected for their
ability to handle the large RMS current into the converter.
The 100μF bulk capacitor is only needed if the input source
impedance is compromised by long inductive leads or
traces.
For the output capacitor, the output voltage ripple and
transient requirements require low ESR capacitors. If
assuming that the ESR dominates the output ripple, the
output ripple is as follows:
If a total low ESR of about 5mΩ is chosen for output
capacitors, the maximum output ripple of 17.5mV occurs
at the input voltage of 20V with the current ripple at 3.5A.
Boost Mode Operation
For boost mode operation, use input voltage V
12V, V
Set the PLLFLTR pin and R
If the maximum output power P is 60W at boost mode
and the module effi ciency η is about 95%, we can get
the current ripple ratio of the current ripple ΔI
maximum inductor current I
Figure 4. shows the current ripple ratio at different input
voltages based on the inductor values: 1.5μH, 2.5μH,
3.3μH and 4.7μH. If we need 30% ripple current ratio at
all inputs, the 3.3μH inductor can be selected.
ΔV
ΔI
I
L
L
OUT(P-P)
OUT
=
(V
= 12V and f = 400kHz.
OUT
V
OUT
= ESR • ΔI
− V
• L • f • P
IN
) • V
L
IN
FB
2
η
L
as in buck mode.
as follows:
IN
L
= 5V to
to the
4605fc