Datasheet

www.ti.com
C2 +
C1
2p R2 C1
ǒ
f
DROOPZ
* 1
Ǔ
(21)
G − Gain − dB
Phase − °
f − Frequency − Hz
60
0
10
20
40
50
30
−20
−10
0
60
80
20
40
−20
100 1 k 10 k 100 k 1 M
Phase
Gain
V
IN
= 12 V
V
OUT
= 1.5 V
Setting the Output Voltage Droop
R
DROOP
+
5000 V
DROOP
I
OUT
R
CS
R
BIAS
R1 ) R
BIAS
(22)
TPS40130
SLUS602B – JUNE 2004 – REVISED SEPTEMBER 2005
When attempting closing the feedback loop at frequency that is close to the theoretical limit, use the above
considerations as a first approximation and perform on bench measurements of closed loop parameters as
effects of switching frequency proximity and finite bandwidth of voltage and current amplifiers may substantially
alter them as it is shown in Figure 8 .
GAIN AND PHASE
vs
FREQUENCY
Figure 8.
In many applications the output voltage of the converter intentionally allowed to droop as load current increases.
This approach also called active load line programming and allows for better use of regulation window and
reduces the amount of the output capacitors required to handle a load current step. A resistor from the VREF pin
to the DROOP pin sets the desired value of the output voltage droop. See Equation 22 .
where
• V
DROOP
is the value of droop at maximum load current (I
LOAD
)
• R
CS
is a value of the current sense resistor used or the DCR value of the output inductor
18
Submit Documentation Feedback