TPS65145PWPR datasheet(16/32 Pages) TI

16 / 32 page

CC = 4.7 nF

fz +

VIN

COMP

15 k

Ω

1 nF

Load Step

TPS65140, TPS65141

TPS65145

SLVS497E – SEPTEMBER 2003 – REVISED NOVEMBER 2012

www.ti.com

Figure 16. Load Step Caused By A Too Large Feedforward Capacitor Value

Compensation

The regulator loop can be compensated by adjusting the external components connected to the COMP pin. The

COMP pin is connected to the output of the internal transconductance error amplifier. A typical compensation

scheme is shown in Figure 17.

Figure 17. Compensation Network

The compensation capacitor Cc adjusts the low frequency gain, and the resistor value adjusts the high frequency

gain. The following formula calculates at what frequency the resistor increases the high frequency gain.

Lower input voltages require a higher gain and a lower compensation capacitor value. A good start is Cc = 1 nF

for a 3.3-V input and Cc = 2.2 nF for a 5-V input. If the device operates over the entire input voltage range from

2.7 V to 5.8 V, a larger compensation capacitor up to 10 nF is recommended. Figure 18 shows the load transient

with a larger compensation capacitor, and Figure 19 shows a smaller compensation capacitor.

Figure 18. CC = 4. 7 nF

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TPS65145PWPR Datasheet(PDF) 16 Page - Texas Instruments