ZHCSQI6A May   2022  – July 2022

PRODUCTION DATA

1. 特性
2. 应用
3. 说明
4. Revision History
5. 说明（续）
6. Device Options
7. Pin Configuration and Functions
8. Specifications
9. Detailed Description
1. 9.1 Overview
2. 9.2 Functional Block Diagram
3. 9.3 Feature Description
4. 9.4 Device Functional Modes
5. 9.5 Programming
6. 9.6 Register Map
10. 10Application and Implementation
1. 10.1 Application Information
2. 10.2 Typical Application
3. 10.3 Best Design Practices
4. 10.4 Power Supply Recommendations
5. 10.5 Layout
11. 11Device and Documentation Support
1. 11.1 Device Support
2. 11.2 Documentation Support
3. 11.3 接收文档更新通知
4. 11.4 支持资源
6. 11.6 Electrostatic Discharge Caution
7. 11.7 术语表
12. 12Mechanical, Packaging, and Orderable Information

• RXS|16

#### 10.2.2.4 Selecting the Output Capacitors

In practice, the total output capacitance is typically comprised of a combination of different capacitors, in which larger capacitors provide the load current at lower frequencies and smaller capacitors provide the load current at higher frequencies. The value, type, and location of the output capacitors are critical for correct operation. Low-ESR multilayer ceramic capacitors with an X7R dielectric (or similar) are recommended for best performance.

The TPS6287x-Q1 devices feature a butterfly layout with two GND pins on opposite sides of the package. This allows the output capacitors to be placed symmetrically on the PCB such that the electromagnetic fields generated cancel each other out, thereby reducing EMI.

The transient response of the converter is limited by one of two criteria:

• The slew rate of the current through the inductor, in which case, the feedback loop of the converter saturates.
• The maximum allowed ratio of converter bandwidth to switching frequency, in which the converter remains in regulation (that is, its loop does not saturate). A minimum ratio of four is recommended for typical applications.

Which of the above criteria applies in any given application depends on the operating conditions and component values used. Therefore, it is recommended that the user calculate the output capacitance for both cases, and select the higher of the two values.

If the converter remains in regulation, the minimum output required capacitance is given by:

Equation 13. ${\mathrm{C}}_{\mathrm{O}\mathrm{U}\mathrm{T}\left(\mathrm{m}\mathrm{i}\mathrm{n}\right)\left(\mathrm{r}\mathrm{e}\mathrm{g}\right)}=\left(\frac{\mathrm{\tau }×\left(1+{\mathrm{g}}_{\mathrm{m}}×{\mathrm{R}}_{\mathrm{Z}}\right)}{2×\mathrm{\pi }×\mathrm{L}×\frac{{\mathrm{f}}_{\mathrm{S}\mathrm{W}}}{4}}\right)\left(1+\sqrt{{{\mathrm{T}\mathrm{O}\mathrm{L}}_{\mathrm{\tau }}}^{2}+{{\mathrm{T}\mathrm{O}\mathrm{L}}_{\mathrm{I}\mathrm{N}\mathrm{D}}}^{2}+{{\mathrm{T}\mathrm{O}\mathrm{L}}_{\mathrm{f}\mathrm{S}\mathrm{W}}}^{2}}\right)$
Equation 14.

If the converter loop saturates, the minimum output capacitance is given by:

Equation 15.
Equation 16.

In this case, choose COUT(min) = 203 µF as the larger of the two values for the output capacitance.

When calculating worst-case component values, use the value calculated above as the minimum output capacitance required. For ceramic capacitors, the maximum capacitance when considering tolerance, DC bias, temperature, and aging effects is typically two times the minimum capacitance. In this case, the maximum capacitance is 406 μF.

Table 10-4 List of Recommended Output Capacitors
Capacitance Dimensions Voltage Rating Manufacturer, Part Number(1)
mm (Inch)
22 μF ±20% 2012 (0805) 6.3 V TDK, CGA4J1X7T0J226M125AC
22 μF ±10% 2012 (0805) 6.3 V Murata, GCM31CR71A226KE02
47 μF ±20% 3216 (1206) 4 V TDK, CGA5L1X7T0G476M160AC
47 μF ±20% 2012 (1210) 6.3 V Murata, GCM32ER70J476ME19
100 μF ±20% 3225 (1210) 4 V TDK, CGA6P1X7T0G107M250AC
100 μF ±20% 3216 (1210) 6.3 V Murata, GRT32EC70J107ME13