SNVS610P December 2009 – April 2019 LMZ10504
PRODUCTION DATA.
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 capacitor 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 (CO) based on PWM ripple voltage. The second equation determines CO based on the load transient characteristics. Select the largest capacitance value of the two.
The minimum capacitance, given the maximum output voltage ripple (ΔVOUT) requirement, is determined by the following equation:
where
RESR is the total output capacitor ESR, L is the inductance value of the internal power inductor, where L = 1.5 µH, and fSW = 1 MHz. Therefore, per the design example:
The minimum output capacitance requirement due to the PWM ripple voltage is:
Three mΩ is a typical RESR value for ceramic capacitors.
Equation 17 provides a good first pass capacitance requirement for a load transient:
where
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 3 lists some examples of commercially available capacitors that can be used with the LMZ10504.
CO (µF) | VOLTAGE (V), RESR (mΩ) | MAKE | MANUFACTURER | PART NUMBER | CASE SIZE |
---|---|---|---|---|---|
22 | 6.3, < 5 | Ceramic, X5R | TDK | C3216X5R0J226M | 1206 |
47 | 6.3, < 5 | Ceramic, X5R | TDK | C3216X5R0J476M | 1206 |
47 | 6.3, < 5 | Ceramic, X5R | TDK | C3225X5R0J476M | 1210 |
47 | 10.0, < 5 | Ceramic, X5R | TDK | C3225X5R1A476M | 1210 |
100 | 6.3, < 5 | Ceramic, X5R | TDK | C3225X5R0J107M | 1210 |
100 | 6.3, 50 | Tantalum | AVX | TPSD157M006#0050 | D, 7.5 × 4.3 × 2.9 mm |
100 | 6.3, 25 | Organic Polymer | Sanyo | 6TPE100MPB2 | B2, 3.5 × 2.8 × 1.9 mm |
150 | 6.3, 18 | Organic Polymer | Sanyo | 6TPE150MIC2 | C2, 6.0 × 3.2 × 1.8 mm |
330 | 6.3, 18 | Organic Polymer | Sanyo | 6TPE330MIL | D3L, 7.3 × 4.3 × 2.8 mm |
470 | 6.3, 23 | Niobium Oxide | AVX | NOME37M006#0023 | E, 7.3 × 4.3 × 4.1 mm |