LMZ10503TZX-ADJ/NOPB National Semiconductor, LMZ10503TZX-ADJ/NOPB Datasheet - Page 10

• Manufacturer Part Number: LMZ10503TZX-ADJ/NOPB
• Description: IC BUCK SYNC ADJ 3A TO-PMOD-7
• Manufacturer: National Semiconductor
• Series: SIMPLE SWITCHER®r
• Type: Point of Load (POL) Non-Isolated with UVLOr

Specifications of LMZ10503TZX-ADJ/NOPB

• Output: 0.8 ~ 5 V
• Number Of Outputs: 1
• Power (watts): 15W
• Mounting Type: Surface Mount
• Voltage - Input: 2.95 ~ 5.5 V
• Package / Case: TO-PMOD-7, Power Module
• 1st Output: 0.8 ~ 5 VDC @ 3A
• Size / Dimension: 0.40" L x 0.54" W x 0.18" H (10.16mm x 13.77mm x 4.57mm)
• Power (watts) - Rated: 15W
• Operating Temperature: -40°C ~ 125°C
• Efficiency: 96%
• Approvals: EN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• 3rd Output: -
• 2nd Output: -
• Other names: LMZ10503TZX-ADJ

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A second criteria before finalizing the C
the RMS current capability. The necessary RMS current rat-
ing of the input capacitor to a buck regulator can be estimated
by
With this high AC current present in the input capacitor, the
RMS current rating becomes an important parameter. The
maximum input capacitor ripple voltage and RMS current oc-
cur at 50% duty cycle. Select an input capacitor rated for at
least the maximum calculated I
Additional bulk capacitance with higher ESR may be required
to damp any resonance effects of the input capacitance and
parasitic inductance.
Output Capacitor Selection
In general, 22 µF to 100 µF high quality dielectric (X5R, X7R)
ceramic capacitor rated at twice the maximum output voltage
is sufficient given the optimal high frequency characteristics
and low ESR of ceramic dielectrics. Although, the output ca-
pacitor can also be of electrolytic chemistry for increased
capacitance density.
Two output capacitance equations are required to determine
the minimum output capacitance. One equation determines
the output capacitance (C
The second equation determines C
sient characteristics. Select the largest capacitance value of
the two.
The minimum capacitance, given the maximum output volt-
age ripple (ΔV
ing equation:
Where the peak to peak inductor current ripple (Δi
to:
OUT
) requirement, is determined by the follow-
O
) based on PWM ripple voltage.
Cin(RMS)
O
based on the load tran-
.
in
bypass capacitor is
L
) is equal
10
R
value of the internal power inductor, where L = 2.2 µH, and
f
The minimum output capacitance requirement due to the
PWM ripple voltage is:
Three miliohms is a typical R
The following equation provides a good first pass capacitance
requirement for a load transient:
Where I
I
ΔV
±20 mV.
Therefore the capacitance requirement for the given design
parameters is:
In this particular design the output capacitance is determined
by the load transient requirements.
Table 1
pacitors that can be used with the LMZ10503.
SW
step
ESR
o_tran
= 1 MHz. Therefore, per the design example:
= 10% to 90% of the maximum load), V
is the total output capacitor ESR, L is the inductance
step
is the maximum output voltage deviation, which is
lists some examples of commercially available ca-
is the peak to peak load step (for this example
ESR
value for ceramic capacitors.
FB
= 0.8V, and