Datasheet
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OUTPUT CAPACITOR SELECTION, SM1, SM2 CONVERTERS
I
RMSCout
+
1 *
V
OUT
V
IN
2 L f
1
3
Ǹ
(13)
V
RMSCout
+
1 *
V
OUT
V
IN
L f
ǒ
1
8 Cout f
) ESR
Ǔ
(14)
TPS65810
TPS65811
SLVS658B – MARCH 2006 – REVISED FEBRUARY 2007
Table 16. Inductors for Typical Operation Conditions (continued)
DEVICE INDUCTOR VALUE TYPE COMPONENT SUPPLIER
DCDC2 converter 3.3 µ H CDRH2D18/HPNP-3R3 Sumida
3.3 µ H VLF4012AT-3R3M1R3 TDK
2.2 µ H VLCF4020-2R2 TDK
DCDC1 converter 3.3 µ H CDRH3D14/HPNP-3R2 Sumida
3.3 µ H CDRH4D28C-3R2 Sumida
3.3 µ H MSS5131-332 Coilcraft
2.2 µ H VLCF4020-2R2 TDK
The advanced Fast Response voltage mode control scheme of the SM1, SM2 converters implemented in the
TPS65020 allow the use of small ceramic capacitors with a typical value of 10 µ F for a 3.3- µ H inductor, without
having large output voltage under and overshoots during heavy load transients.
Ceramic capacitors having low ESR values have low output voltage ripple, and recommended values and
manufacturers are listed in Table 1 . Often, due to the low ESR, the ripple current rating of the ceramic capacitor
is adequate to meet the inductor ’ s currents requirements.
The RMS ripple current is calculated as:
At nominal load current, the inductive converters operate in PWM mode. The overall output voltage ripple is the
sum of the voltage spike caused by the output capacitor ESR plus the voltage ripple caused by charging and
discharging the output capacitor: The output voltage ripple is maximum at the highest input voltage Vin.
At light load currents, the converters operate in PFM and the output voltage ripple is dependent on the output
capacitor value. The output voltage ripple is set by the internal PFM output voltage comparator delay and the
external capacitor. The typical output voltage ripple is less than 1% of the nominal output voltage.
Table 17. Input/Output Capacitors for Typical Operation Conditions
CAPACITOR VALUE CASE SIZE COMPONENT SUPPLIER COMMENTS
22 µ F 1260 TDK C3216X5R0J226M Ceramic
22 µ F 1260 Taiyo Yuden JMK316BJ226ML Ceramic
10 µ F 0805 Taiyo Yuden JMK212BJ106M Ceramic
10 µ F 0805 TDK C2012X5R0J106M Ceramic
22 µ F 0805 TDK C2012X5R0J226MT Ceramic
22 µ F 0805 Taiyo Yuden JMK212BJ226MG Ceramic
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