Datasheet

-60
-40
-20
0
20
40
60
80
10 100 100 0 10000 100000 1000000
Frequency - Hz
Gain - dB
-45
0
45
90
135
180
Phase - °
PHASE
GAIN
TPS40195
www.ti.com SLUS720E –FEBRUARY 2007–REVISED JULY 2012
4. Place the second pole near the ESR zero of the output capacitors of 318 kHz. f
P2
= 318 kHz
5. The high frequency gain must be such that the over all system has 0 dB at the required crossover frequency.
This gain is -1 times the sum of the modulator gain and the gain of the output stage at the crossover
frequency of 50 kHz.
Using these values and the above equations calculate the set point and the Rs and Cs around the compensation
network using the following procedure.
1. Set R
Z1
= 51 kΩ
2. Calculate R
SET
using Equation 43. For this module R
SET
= a standard 1% value = 24.9 kΩ.
3. Using Equation 48 and f
Z1
= 1.8 kHz, C
PZ1
can be calculated to be 1500 pF, F
P1
and Equation 46 yields R
P1
to be 363 Ω and the standard value 357 Ω is used.
4. From Figure 25, the required gain is calculated at 15.8 dB. Equation 45 sets the value for R
PZ2
. A resistor for
R
PZ2
with value of 12.7 kΩ is used. C
Z2
is calculated using Equation 49 and the desired frequency for the
second zero, C
Z2
= 1475 pF. A 2200 pF capacitor is used.
5. C
P2
is calculated using the second pole frequency and Equation 47, C
P2
= 37 pF. A 33-pf capacitor is used.
Figure 28. Final Bode Plot
Copyright © 2007–2012, Texas Instruments Incorporated 29