LMZ1050X Datasheet, PDF (1/12 Pages) National Semiconductor (TI) – The LMZ1050x can accept an input voltage rail between

LMZ1050x Evaluation Board
National Semiconductor
Application Note 2022
Ricardo Capetillo
August 12, 2010
Introduction
The LMZ1050x SIMPLE SWITCHER® power module is a
complete, easy-to-use DC-DC solution capable of driving up
to 3A, 4A, or 5A load with exceptional power conversion effi-
ciency, output voltage accuracy, line and load regulation. The
LMZ1050x is available in an innovative package that en-
hances thermal performance and allows for hand or machine
soldering.
The LMZ1050x can accept an input voltage rail between
2.95V and 5.5V and deliver an adjustable and highly accurate
output voltage as low as 0.8V. One megahertz fixed frequen-
cy PWM switching provides a predictable EMI characteristic.
Two external compensation components can be adjusted to
set the fastest response time, while allowing the option to use
ceramic and/or electrolytic output capacitors. Externally pro-
grammable soft-start capacitor facilitates controlled startup.
The LMZ1050x is a reliable and robust solution with the fol-
lowing features: lossless cycle-by-cycle peak current limit to
protect for over current or short-circuit fault, thermal shut-
down, input under-voltage lock-out, and pre-biased startup.
Board Specifications
• V_IN = 2.95V to 5.5V
• V_OUT = 2.5V (default output voltage setting, refer to Table
2 for other output settings)
• ±2.5% feedback voltage accuracy at 2.5V output
(Including line and load regulation from T_J = -40°C to 125°
C)
• ±1.63% feedback voltage accuracy over temperature
• I_OUT = 0A to 3A, 4A, and 5A
• θ_JA = 20°C / W, θ_JC = 1.9°C / W
• Designed on four layers, the top and bottom layers are
1oz. copper and the two inner layers are 1/2 oz. copper
weight
• Measures 2.25 in. x 2.25 in. (5.8 cm x 5.8 cm) and is 62mil
(.062”) thick on a FR4 laminate
Evaluation Board Design Concept
The evaluation board is designed to demonstrate low con-
ducted noise on the input and output lines, as seen in Figure
11 and Figure 14. Four input capacitors (C_in1 - C _in4) and three
output capacitors (C_o1 - C_o3) are populated for this purpose.
All the input and output filter capacitors are not necessary to
comply with radiation standards. For a circuit example that
passes radiated emissions standards (EN55022, class B)
please refer to Figure 19. Additionally, C_in5 is present to re-
duce the resonance of the input line produced by the induc-
tance and resistance in the cables connecting the bench
power supply to the evaluation board and the input capacitors.
Additional Component Footprints
When the tracking feature of the LMZ1050x is used, remove
the soft-start capacitor C_SS and use a resistor divider on des-
ignators R_trkb and R_trkt. The ground and V_trk post have been
provided for easy connection.
The LMZ1050x eval board incorporates a precision enable
circuit which is pulled high by a 100 kΩ pull up resistor to VIN.
This allows the user to pull low on the enable pin to ground.
The top enable resistor is R_ent and the bottom enable resistor
is R_enb. Refer to the Design Guideline and Operating Descrip-
tion section of the LMZ1050x data sheet for detailed design
implementation.
Select FPGAs specify input inrush currents for particular pow-
er-up sequences and others require sequencing rails to avoid
start-up or latch-up problems. To prevent early turn-on of the
LMZ1050x in systems with multiple power rails, precision en-
able and tracking are useful as the main input voltage rail rises
at power-up.
© 2010 National Semiconductor Corporation 301113
www.national.com