Datasheet

500
T
CA
Board Area_cm
2
8
o
C x cm
2
W
.
T
CA
<
T
J(MAX)
- T
A(MAX)
P
IC_LOSS
- T
JC
VIN
EN
GND
FB
LMZ10505EXT
R
fbt
R
comp
C
comp
R
fbb
V
IN
VOUT
LMZ10505EXT
SNVS669G –JUNE 2010–REVISED OCTOBER 2013 www.ti.com
Table 2. LMZ10505EXT Compensation Component Values
(1)
V
IN
(V) C
O
(µF) ESR (mΩ) R
fbt
(kΩ) C
comp
(pF) R
comp
(kΩ)
Min Max
22 2 20 200 27 1.5
47 2 20 124 56 1.4
100 1 10 82.5 120 1
150 1 5 63.4 180 1.21
5.0
150 10 25 63.4 220 16.5
150 26 50 44.2 220 23.7
220 15 30 63.4 220 23.7
220 31 60 76.8 220 57.6
22 2 20 118 39 9.09
47 2 20 76.8 82 8.45
100 1 10 49.9 180 4.12
150 1 5 40.2 330 2.0
3.3
150 10 25 43.2 330 11.5
150 26 50 49.9 270 25.5
220 15 30 40.2 390 15.4
220 31 60 48.7 330 35.7
(1) In the special case where the output voltage is 0.8V, it is recommended to remove R
fbb
and keep R
fbt
, R
comp
, and C
comp
for a type III
compensation.
Estimate Power Dissipation And Board Thermal Requirements
Use the current derating curves in the Typical Performance Characteristics section to obtain an estimate of
power loss (P
IC_LOSS
). For the design case of V
IN
= 5V, V
OUT
= 2.5V, I
OUT
= 5A, T
A(MAX)
= 85°C , and T
J(MAX)
=
125°C, the device must see a thermal resistance from case to ambient (θ
CA
) of less than:
(15)
(16)
Given the typical thermal resistance from junction to case (θ
JC
) to be 1.9°C/W (typ.). Continuously operating at a
T
J
greater than 125°C will have a shorten life span.
To reach θ
CA
= 27.5°C/W, the PCB is required to dissipate heat effectively. With no airflow and no external heat,
a good estimate of the required board area covered by 1oz. copper on both the top and bottom metal layers is:
(17)
(18)
As a result, approximately 18 square cm of 1oz. copper on top and bottom layers is required for the PCB design.
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