ZHCSHU5A July 2017 – March 2018 TPSM82480
PRODUCTION DATA.
The recommended minimum output capacitance is 4 x 22 µF, that can be ceramic capacitors exclusively. A larger value of COUT might be needed for VOUT ≤ 1.8V, to improve transient response performance, as well as for VOUT> 3.3 V to compensate for voltage bias effects of the ceramic capacitors. The usage of an additional feed forward capacitor can help reducing amount of output capacitance that is needed to achieve a certain transient response target (see Table 3).
The TPSM82480 provides a wide output voltage range of 0.6 V to 5.5 V. While stability is a critical criteria for the output filter selection, the output capacitor value also determines transient response behavior, ripple and accuracy of VOUT. The internal compensation is designed for an output capacitance range from about 50 µF to 150 µF effectively. Since ceramic capacitors are used preferably, this translates into nominal values of 4 x 22 µF to 4 x 47 µF and mainly depends on the output voltage. The following values are recommended:
| VOUT ≤ 1.0V | 1.0V ≤ VOUT ≤ 3.3V | VOUT ≥ 3.3V | |||
|---|---|---|---|---|---|
| 2x22µF | |||||
| 4x22µF | √ | ||||
| 4x47µF | √ | √ | √ | ||
| 6x47µF | |||||
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Beyond the recommendations in Table 2, other values can be chosen and might be suitable depending on VOUT and actual effective capacitance. In such case, stability needs to be checked within the actual environment.
Even if the output capacitance is sufficient for stability, a different value might be desirable to improve the transient response behavior. Table 3 can be used to determine capacitor values for specific transient response targets:
| Output Voltage [V] | Load Step [A] | Output Capacitor Value(1) | Feedforward Capacitor(1) | Typical Transient Response Accuracy | |
|---|---|---|---|---|---|
| ±mV | ±% | ||||
| 1.0 | 0 - 3 | 4 x 47µF | - | 50 | 5 |
| 3 - 6 | 50 | 5 | |||
| 1.8 | 0 - 3 | 4 x 22µF | 36pF | 50 | 3 |
| 3 - 6 | 50 | 3 | |||
| 2.5 | 0 - 3 | 4 x 22µF | 36pF | 62 | 2.5 |
| 3 - 6 | 50 | 2 | |||
| 3.3 | 0 - 3 | 4 x 47µF | 36pF | 100 | 3 |
| 3 - 6 | 80 | 2.5 | |||
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The architecture of the TPSM82480 allows the use of tiny ceramic output capacitors with low equivalent series resistance (ESR). These capacitors provide low output voltage ripple and are recommended. To keep its low resistance up to high frequencies and to get narrow capacitance variation with temperature, it is recommended to use X5R or X7R dielectrics. Using even higher values than demanded for stability and transient response has further advantages like smaller voltage ripple and tighter dc output accuracy in Power Save Mode.