LMZ23605TZ National Semiconductor, LMZ23605TZ Datasheet - Page 16

• Manufacturer Part Number: LMZ23605TZ
• Description: POWER MODULE, 36V, 5A, 7TO-PMOD
• Manufacturer: National Semiconductor

Specifications of LMZ23605TZ

• Primary Input Voltage: 36V
• No. Of Outputs: 1
• Output Voltage: 6V
• Output Current: 5A
• Voltage Regulator Case Style: TO-PMOD
• No. Of Pins: 7
• Operating Temperature Range: -40°C To +125°C
• Rohs Compliant: Yes

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C
None of the required C
in the module. A minimum value of 200 μF is required based
on the values of internal compensation in the error amplifier.
Low ESR tantalum, organic semiconductor or specialty poly-
mer capacitor types are recommended for obtaining lowest
ripple. The output capacitor C
pacitors in parallel placed in close proximity to the module.
The output capacitor assembly must also meet the worst case
minimum ripple current rating of 0.5 * I
equation (14) below. Beyond that, additional capacitance will
reduce output ripple so long as the ESR is low enough to per-
mit it. Loop response verification is also valuable to confirm
closed loop behavior.
For applications with dynamic load steps; the following equa-
tion provides a good first pass approximation of C
transient requirements. Where V
output design.
C
Solving:
C
Note that the stability requirement for 200 µF minimum output
capacitance will take precedence.
One recommended output capacitor combination is a 220uF,
7 milliohm ESR specialty polymer cap in parallel with a 100
uF 6.3V X5R ceramic. This combination provides excellent
performance that may exceed the requirements of certain ap-
plications. Additionally some small ceramic capacitors can be
used for high frequency EMI suppression.
C
The LMZ23605 module contains a small amount of internal
ceramic input capacitors. Additional input capacitance is re-
quired external to the module to handle the input ripple current
of the application. The input capacitor can be several capac-
itors 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 require-
ments rather than by capacitance value. Input ripple current
rating is dictated by the equation:
I(C
where D
O
O
O
IN
≥
≥
IN(RMS)
SELECTION
SELECTION
I
O-Tran
4.5A / ((0.1V – .007*4.5) * ( 800000 / 3.3)
≊
)
*/((V
≊
V
O
1 /2 * I
/ V
O-Tran
Tracking option input detail
IN
O
– ESR * I
* SQRT (D / 1-D) (8)
O
output capacitance is contained with-
FIGURE 2.
O-Tran
O
may consist of several ca-
O-Tran
)*(Fsw / V
LR P-P
is 100mV on a 3.3V
, as calculated in
O
)(6)
≥
271μF (7)
O
30116915
for load
16
(As a point of reference, the worst case ripple current will oc-
cur when the module is presented with full load current and
when V
Recommended minimum input capacitance is 22uF 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
the following equation may be used.
C
If ΔV
this equals 120 mV and f
C
≥
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
LMZ23605 typical applications schematic and evaluation
board include a 150 μF 50V aluminum capacitor for this func-
tion. 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 char-
acteristic curves such that less common applications can be
derived through interpolation. In all designs, the junction tem-
perature must be kept below the rated maximum of 125°C.
For the design case of V
T
from case to ambient of less than:
θ
Given the typical thermal resistance from junction to case to
be 1.9 °C/W. Use the 85°C power dissipation curves in the
Typical Performance Characteristics section to estimate the
P
it is 5.5W. (Note that for package dissipations above 5W air
flow or external heat sinking may be required.)
θ
To reach θ
effectively. With no airflow and no external heat-sink, a good
estimate of the required board area covered by 2 oz. copper
on both the top and bottom metal layers is:
Board_Area_cm
As a result, approximately 93 square cm of 2 oz copper on
top and bottom layers is required for the PCB design. The
PCB copper heat sink must be connected to the exposed pad.
Approximately sixty, 10mil (254 μm) thermal vias spaced 39
mils (1.0 mm) apart connect the top copper to the bottom
copper. For an example of a high thermal performance PCB
layout for SIMPLE SWITCHER© power modules, refer to
AN-2085, AN-2125, AN-2020 and AN-2026.
CA
CA
AMB(MAX)
IC-LOSS
IN
IN
10.2μF
≥
< (T
≥
= (125 – 85) / 5.5W – 1.9 = 5.37 (11)
IN
5A * 3.3V/12V * (1– 3.3V/12V) / (812000 * 0.12 V)
I
O
is 1% of V
IN
J-MAX
* D * (1–D) / f
for the application being designed. In this application
= 2 * V
= 85°C, the module must see a thermal resistance
CA
– T
= 5.37., the PCB is required to dissipate heat
A-MAX
2
O
IN
= 500°C x cm
).
for a 12V input to 3.3V output application
) / P
SW-CCM
SW
IN
IC-LOSS
= 24V, V
= 812 kHz.
* ΔV
2
/W / θ
- θ
IN
JC
(9)
O
IN
(10)
CA
= 3.3V, I
) be maintained then
(12)
O
= 5A, and