PRM48BF480T400A00 Datasheet, PDF (19/22 Pages) Vicor Corporation – Regulator

PRM48BF480T400A00
(Formerly VIP0001TFJ)
Open Loop Gain vs. Frequency
80
60 ^I _{Compensation Gain}
Application's op-amp G·BW
40
E
F
PRM Open Loop Min Load
A
B
20
PRM Open Loop Max Load
0
J
F_CMIN F_CMAX
K
L
-20
C
-40
G
Frequency, Log scale
(y-intercept is application specific)
Figure 27 – Reference asymptotic Bode plot for the considered system
10.2.6 High Frequency Pole Design (C2):
Using Equation [3], C2 should be selected so that F_P2 is at
least one decade above F_CMAX and prior to the gain
bandwidth product of the operational amplifier (10MHz for
this example). For applications with a higher desired
crossover frequency the use of a high gain bandwidth
product amplifier may be necessary to ensure that the real
pole can be set at least one decade above the maximum
crossover frequency.
10.2.7 Verifying Stability:
The preferred method for verifying stability is to use a
network analyzer, measuring the closed loop response
across various lines and load conditions.
In the absence of a network analyzer, a load step transient
response can be used in order to estimate stability.
Figure 28 illustrates an example of a load step response.
Equation [4] can be used to predict the phase margin
based on the ratio of the “kick” to “droop” (as defined in
Fig. 28).
Figure 28 – load step response example and “droop”
vs. “kick” definition
V•I CHIP CORP. (A VICOR COMPANY) 25 FRONTAGE RD. ANDOVER, MA 01810 800-735-6200
Rev. 1.1
12 / 2010
Page 19 of 22