When you open a datasheet, which sections are the most important to review first?

A practical way to make a quick suitability check is to review these six items first:
1. Application / Intended series application
2. Composition of part number / Part number structure
3. Rating / Rated conditions and measurement conditions (temperature range, surge conditions, rated ripple current conditions)
4. Leakage current / Leakage current conditions (test time and applied voltage)
5. Standard ratings / Electrical characteristics table and part number cross-reference
6. Frequency correction factor / Ripple current frequency correction factor

Typical locations in the datasheet:
• 1. Application
• 2. Composition of part number (Table 1 to Table 4)
• 3. Rating (Section 3.1 to 3.3)
• 3.4 Standard ratings (Table 5)
• 3.5 Frequency correction factor of allowable ripple current

How should Rated Voltage (Vr) be interpreted? Is it enough for the operating voltage to simply stay below it?

Do not look only at the average operating voltage. The highest possible voltage and any instantaneous spikes must also be considered. Vr is the basis for continuous operation. If the datasheet also specifies a Surge Voltage (Vs), or defines surge by a multiplier, make sure that any instantaneous voltage peak also remains within that specification.

Typical locations in the datasheet:
• 2.1 Rated voltage code: Table 1 Rated voltage and surge voltage
• 3.2 Surge voltage (if defined by a multiplier, for example Rated Voltage × multiplier, refer to the datasheet)

How should capacitance and the capacitance code be interpreted? Is larger capacitance always better?

Capacitance is one of the required selection criteria, but in power supply and filtering applications it is usually necessary to review ESR and allowable ripple current (Ir) at the same time. Datasheets often use a capacitance code to represent capacitance. First decode the capacitance code, then go back to the electrical characteristics table to confirm the overall performance.

Typical locations in the datasheet:
• 2.2 Capacitance code: Table 2 Rated capacitance
• 3.4 Standard ratings: Table 5 (Capacitance, ESR, Rated ripple current, etc.)

How should capacitance tolerance be interpreted? What does the tolerance code in the part number mean?

The tolerance code indicates the allowable capacitance range, for example ±20%. When reading a part number, first decode the tolerance code and then confirm whether the tolerance is acceptable for the intended application.

Typical locations in the datasheet:
• 2.3 Capacitance tolerance code: Table 3 Capacitance tolerance

How should the ESR column be interpreted?

ESR or impedance varies with frequency and temperature, so the datasheet specifies the measurement conditions that define the comparison basis. An ESR or impedance value is valid only under the frequency and temperature conditions specified in the datasheet. When comparing different products, including competing products, first make sure the comparison item and the measurement conditions are the same.

Typical locations in the datasheet:
• 3.4 Standard ratings: Table 5 (ESR column and measurement condition notes)

How should Rated Ripple Current (Ir) be interpreted? What is the simplest way to use it?

Rated Ripple Current (Ir) is the maximum allowable AC ripple current. The simplest rule is to keep the actual ripple current less than or equal to the rated value. Also note that Ir is usually specified under particular frequency and temperature conditions, such as 100 kHz, 105°C, and RMS.

Typical locations in the datasheet:
• 3.3 Rated ripple current (measurement conditions, for example 100 kHz, 105°C, RMS)
• 3.4 Standard ratings: Table 5 (Rated Ripple Current)
• 3.5 Frequency correction factor

How should the size code and outer dimensions be interpreted? How do you make sure the part fits mechanically and can be soldered properly?

The size code should be checked against the dimensional table to confirm outer dimensions such as diameter and case length, and to make sure the part is compatible with the PCB hole pattern or pad layout, assembly height, and manufacturing process conditions.

Typical locations in the datasheet:
• 2.4 Size code: Table 4 Dimensions of radial type capacitors
• Outer dimensions (if a separate dimensional table is provided, for example Table 7)

Final reminder

The table numbers and page locations above reflect a common document structure. Always refer to the actual section names and numbering in the datasheet or specification sheet of the selected series.