Datasheet

SLUU194 − May 2004
10
Using the TPS51020
4.5 Load Transient
Figures 8 and 9 show the load transient waveforms for each channel. When load is stepped from 0 A to 5 A,
the undershoot voltage is less than 60 mV and the settling time is less than 30 µs. When load is stepped down
from 5 A to 0 A, the overshoot voltage is less than 50 mV and the settling time is less than 50 µs.
Figure 8. Channel 1 Load Transient Waveform
V
O2
50 mV/div
I
OUT1
(2 A/div)
t − Time − 50 µs/div
t − Time − 25 µs/div
Figure 9. Channel 2 Load Transient Waveform
V
O2
50 mV/div
I
OUT1
(2 A/div)
4.6 Loop Characteristics
Figures 10 and 11 show the bode plot of each channel. The crossover frequency is approximately 14 kHz and
the phase margin is 32° for Channel 1 when the output is 5 V and 6 A. Channel 2 shows a 15-kHz crossover
frequency and a 41° phase margin.
100 1 k 10 k 100 k
−40
−20
−30
−10
10
30
20
0
20
60
40
80
120
160
140
100
180
40
Figure 10. Channel 1 Bode Plot
f − Frequency − Hz
GAIN AND PHASE
vs
FREQUENCY
Gain − dB
PHASE
GAIN
V
O1
= 5 V
I
OUT1
= 6 A
I
OUT2
= 0 A
V
IN
= 12 V
Phase − 5
Figure 11. Channel 2 Bode Plot
GAIN AND PHASE
vs
FREQUENCY
50
−20
−30
−10
10
30
20
40
0
20
60
40
80
120
160
140
180
100
100 1 k 10 k 100 k
PHASE
GAIN
f − Frequency − Hz
V
O2
= 3.3 V
I
OUT1
= 0 A
I
OUT2
= 6 A
V
IN
= 12 V
Gain − dB
Phase − 5