Datasheet
T
CA
<
125°C ± 50°C
5.3 W
- 1.0
°C
W
< 13.15
°C
W
T
CA
<
T
J-MAX
± T
A-MAX
P
IC_LOSS
- T
JC
C
IN
8
350 kHz x 200mV
8 28µF
10A x x 1 -
3.3V
12V
3.3V
12V
¹
·
©
§
¹
·
©
§
C
IN
8
I
OUT
x D x (1 - D)
f
SW
x 'V
IN
I
CIN-RMS
= I
OUT
x
D(1-D)
LMZ22010
SNVS687G –MARCH 2011–REVISED OCTOBER 2013
www.ti.com
Note that the stability requirement for minimum output capacitance must always be met.
One recommended output capacitor combination is two 330μF, 15 mOhm ESR tantalum polymer capacitors
connected in parallel with a 47 uF 6.3V X5R ceramic. This combination provides excellent performance that may
exceed the requirements of certain applications. Additionally some small 47nF ceramic capacitors can be used
for high frequency EMI suppression.
C
IN
SELECTION
The LMZ22010 module contains two internal ceramic input capacitors. Additional input capacitance is required
external to the module to handle the input ripple current of the application. The input capacitor can be several
capacitors in parallel. This input capacitance should be located in very close proximity to the module. Input
capacitor selection is generally directed to satisfy the input ripple current requirements rather than by
capacitance value. Input ripple current rating is dictated by the equation:
(10)
where D ≊ V
OUT
/ V
IN
(As a point of reference, the worst case ripple current will occur when the module is presented with full load
current and when V
IN
= 2 * V
OUT
).
Recommended minimum input capacitance is 30 uF X7R (or X5R) ceramic with a voltage rating at least 25%
higher than the maximum applied input voltage for the application. It is also recommended that attention be paid
to the voltage and temperature derating of the capacitor selected. It should be noted that ripple current rating of
ceramic capacitors may be missing from the capacitor data sheet and you may have to contact the capacitor
manufacturer for this parameter.
If the system design requires a certain minimum value of peak-to-peak input ripple voltage (ΔV
IN
) to be
maintained then the following equation may be used.
(11)
If ΔV
IN
is 200 mV or 1.66% of V
IN
for a 12V input to 3.3V output application and f
SW
= 350 kHz then:
(12)
Additional bulk capacitance with higher ESR may be required to damp any resonant effects of the input
capacitance and parasitic inductance of the incoming supply lines. The LMZ22010 typical applications schematic
and evaluation board include a 150 μF 50V aluminum capacitor for this function. There are many situations
where this capacitor is not necessary.
POWER DISSIPATION AND BOARD THERMAL REQUIREMENTS
When calculating module dissipation use the maximum input voltage and the average output current for the
application. Many common operating conditions are provided in the characteristic curves such that less common
applications can be derived through interpolation. In all designs, the junction temperature must be kept below the
rated maximum of 125°C.
For the design case of V
IN
= 12V, V
OUT
= 3.3V, I
OUT
= 10A, and T
A-MAX
= 50°C, the module must see a thermal
resistance from case to ambient (θ
CA
) of less than:
(13)
Given the typical thermal resistance from junction to case (θ
JC
) to be 1.0 °C/W. Use the 85°C power dissipation
curves in the Typical Performance Characteristics section to estimate the P
IC-LOSS
for the application being
designed. In this application it is 5.3W.
(14)
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