AN-2084 Datasheet, PDF (1/10 Pages) National Semiconductor (TI) – LMZ1420xEXT/ LMZ1200xEXT Evaluation Board

User's Guide
SNVA456A – August 2010 – Revised April 2013
AN-2084 LMZ1420xEXT / LMZ1200xEXT Evaluation Board
1 Introduction
The LMZ1420xEXT and LMZ1200xEXT SIMPLE SWITCHER® power modules are easy-to-use DC-DC
solution capable of driving up to a 3A load with exceptional power conversion efficiency, output voltage
accuracy, line and load regulation. They are available in an innovative package that enhances thermal
performance and allows for hand or machine soldering.
The LMZ14203EXT/2EXT/1EXT can accept an input voltage rail between 6V and 42V and the
LMZ12003EXT/2EXT/1EXT can accept an input voltage rail between 4.5V and 20V. The devices can
deliver an adjustable and highly accurate output voltage as low as 0.8V and as high as 6V. The control
structure is constant on-time with input voltage feed forward. This creates a nearly constant switching
frequency across the input voltage range. The control loop operates well with low ESR output capacitors
such as ceramics. An output feed-forward capacitor across the upper feedback resistor trims for optimum
transient response. The precision enable input allows for programmable UVLO of the input supply. The
external soft-start capacitor facilitates controlled startup output rise time. The LMZ1420xEXT and
LMZ1200xEXT family is a reliable and robust solution with the following features: lossless cycle-by-cycle
valley current limit to protect for over current or short-circuit fault, thermal shutdown, input under-voltage
lock-out, and will start up into a pre-biased output. The LMZ1420xEXT and LMZ1200xEXT families are
shock and vibration certified and rated for operation down to –55°C.
2 Board Specifications
• LMZ1420xEXT V_IN = 6V to 42V
• LMZ1420xEXT enable UVLO = 8V
• LMZ1420xEXT V_OUT = 3.3V
• LMZ1200xEXT V_IN = 4.5V to 20V
• LMZ1200xEXT enable UVLO = 4.5V
• LMZ1200xEXT V_OUT = 1.8V
• Operates at full load up to 80°C ambient at 12V input
• θ_JA = 20°C / W, θ_JC = 1.9°C / W
• Designed on four layers, all four layers are 1 oz. copper weight
• The two internal ground planes are identical
• Measures 1.705 in. x 3.03 in. (4.33 cm x 7.7cm) and is 62mil (.062”) thick of FR4 laminate material
For additional circuit modifications refer to the Design Consideration section of the LMZ1420xEXT or
LMZ1200xEXT data sheet. For negative output voltage connections see AN-2027.
3 Additional Footprints
Additional component mounting pads are available to experiment with alternative Cin and Cout
combinations or a zener clamp on the enable input. See Figure 6 for corresponding schematic locations.
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SNVA456A – August 2010 – Revised April 2013
AN-2084 LMZ1420xEXT / LMZ1200xEXT Evaluation Board
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