DA7218 Datasheet, PDF (168/173 Pages) Dialog Semiconductor – Ultra-Low Power Stereo Codec

DA7218
Ultra-Low Power Stereo Codec
B.9 Capacitor Selection
Ceramic capacitors are manufactured with a variety of dielectrics, each with a different behavior over
temperature and applied voltage. Capacitors must have a dielectric adequate to ensure the minimum
capacitance over the necessary temperature range, dc bias conditions and low Equivalent Series
Resistance (ESR). X5R or X7R dielectrics with a voltage rating of 6.3 V or 10 V are recommended
for best performance. Y5V and Z5U dielectrics are not recommended for use because of their poor
temperature and dc bias characteristics.
The worst-case capacitance accounting for capacitor variation over temperature, component
tolerance, and voltage is calculated using the following equation:
𝐶_{𝐸𝐹𝐹} = 𝐶_{𝑂𝑈𝑇} 𝑥 (1 − 𝑇𝐸𝑀𝑃𝐶𝑂) 𝑥 (1 − 𝑇𝑂𝐿)
Where: CEFF is the effective capacitance at the operating voltage. TEMPCO is the worst-case
capacitor temperature coefficient. TOL is the worst-case component tolerance. These figures can be
found in the manufacturer’s datasheet.
In the example below, the worst-case temperature coefficient (TEMPCO) over −55 °C to +85 °C is
assumed to be 15 %. The tolerance of the capacitor (TOL) is assumed to be 10 %, and COUT is
0.65 μF at 1.8 V.
Substituting these values in the equation yields
𝐶_{𝐸𝐹𝐹} = 0.65𝜇𝐹 𝑥 (1 − 0.15) 𝑥 (1 − 0.1) = 0.497 𝜇𝐹
Table 278: Recommended Capacitor Types
Application
Value
Size
Temp.
Char.
VDD,VDD_IO,
VDD_MIC,
VDDDIG,
DACREF,
VMID,VREF,
HPCFP/HPCFN,
HPCSP,
HPCSN,
MICBIAS1,
MICBIAS2
12x 1 µF
0201
X5R +/-
15 %
Tolerance
Rated
Voltage
Type
+/-10 %
6.3 V
Murata GRM033R60J105M
Datasheet
CFR0011-120-00
Revision 2.5
168 of 173
01 Sep 2016
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