max5938 Maxim Integrated Products, Inc., max5938 Datasheet - Page 24

• Manufacturer Part Number: max5938
• Description: Max5938 -48v Hot-swap Controller With Vin Step Immunity, No Rsense, And Overvoltage Protection
• Manufacturer: Maxim Integrated Products, Inc.

At any time (t) the ∆V
If V
time constant of the load is found from:
As mentioned earlier, several measurements of ∆V
at times t1, t2, t3, and t4 should be made during the
ramp. Each of these may result in slightly different val-
ues of τ
In making the measurements, the V
should be such that ∆V
selected ∆V
ramp rates: ∆V
The values of τ
rates due to measurement error, nonlinear dynamics in
the load, and due to the fact that Equation 1 is a simpli-
fication from a higher order dynamic system. The
resulting range of τ
date the performance of the final design.
-48V Hot-Swap Controller with V
No R
24
Figure 24. V
OUT
______________________________________________________________________________________
∆V
(t) is measured at time t, then the equivalent
τ
L,eqv
L,eqv
OUT
OUT
SENSE
1.4
1.2
1.0
0.8
0.6
0.4
0.2
SC
0
and all values should then be averaged.
= -t / ln(1 – ∆V
(t) / [(dV/dt) x τ
SC
V
Response to V
. The ramp tests should include three
0
A = V
B = ∆V
C = ∆V
L,eqv
OUT
/ τ
4
RESPONSE TO V
IN
L,eqv
STEP_MON
OUT
(GND - V
C
OUT
8
, 2 x ∆V
may vary over the range of slew
t
STEP
12
OUT
t
values should be used to vali-
, and Overvoltage Protection
CB
EE
fraction of ∆V
)
16
TIME (µs)
IN
OUT
F
C
SC
20
reaches 2 or 3 times the
Ramp of 30V/ms
] = (1-e
IN
24
RAMP OF 30V/ms
/ τ
/ [(dV/dt) x τ
D = ∆V
E = ∆V
F = ∆V
D
E
C
28
, and 4 x ∆V
CB
SC
STEP,TH
IN
32
(-t / τL,eqv)
t
OUT
SC
A
C
ramp duration
36
B
(max) is:
40
C
])
)
SC
/ τ
OUT
C
.
Having τ
analysis using Equation 1 and Equation 2 can verify the
step monitor function by displaying the relative timing
of t
V
A simple Excel spreadsheet for this purpose can be
supplied by Maxim upon request. Figures 23, 24, and
25 graphically verify a particular solution over 3
decades of V
fies that this solution will block all circuit-breaker and
short-circuit faults for even the lowest V
cause V
Figure 25. V
STEP_MON
CB
, t
OUT
STEP
C
, τ
OUT
, and V
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
to exceed V
, and t
L,eqv
0
IN
IN
V
Response to V
0
A = V
B = ∆V
C = ∆V
OUT
ramp rates. In addition, Figure 25 veri-
D
, R
SC
IN
RESPONSE TO V
SC
STEP_MON
OUT
(GND - V
C
100
Step Immunity,
STEP
voltage thresholds are exceeded.
, which are the times when V
CB
EE
200
)
, and C
TIME (µs)
.
IN
t
STEP
F
Ramp of 3V/ms
IN
300
RAMP OF 3V/ms
D = ∆V
E = ∆V
F = ∆V
STEP
E
CB
SC
STEP,TH
400
A
IN
in a graphical
B
ramp that will
500
CB
,