LMZ1050X NSC | Alldatasheet

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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

  • VIN = 2.95V to 5.5V
  • VOUT = 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 TJ = -40°C to 125°
  • ±1.63% feedback voltage accuracy over temperature
  • IOUT = 0A to 3A, 4A, and 5A
  • θJA = 20°C / W, θJC = 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 (.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 (Cin1 - C in4) and three output capacitors (Co1 - Co3) 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, Cin5 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 CSS and use a resistor divider on des- ignators Rtrkb and Rtrkt. 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 Rent and the bottom enable resistor is Renb. 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 LMZ1050x Evaluation BoardAN-2022

FIGURE 1. Component Schematic for Evaluation Board TABLE 1. Bill of Materials for Evaluation Board, VIN = 3.3V to 5V, VOUT = 2.5V TABLE 2. Output Voltage Setting (Rfbt = 75 kΩ)

1.8 V 59 kΩ

1.2 V 150 kΩ

0.9 V 590 kΩ

FIGURE 2. Complete Evaluation Board Schematic

FIGURE 22. Radiated Emissions (EN55022, Class B)

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