max5938 Maxim Integrated Products, Inc., max5938 Datasheet - Page 17

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

Figure 16 is a functional diagram exhibiting the elements
of the MAX5938 involved in the step immunity function.
This functional diagram shows the parallel relationship
between V
nent establishing the DC level prior to a step. While it is
referred to as a V
finite voltage ramp that is of interest.
Given a positive V
approximate response of V
where τ
lent time constant of the load that must be found empir-
ically (see Appendix B).
Similarly, the response of STEP_MON to a V
V
where τ
For proper step detection, V
STEP
V
the application). V
Figure 16. MAX5938 Step Immunity Functional Diagram
-48V Hot-Swap Controller with V
STEP_MON
OUT
V
V
IN
OUT
TH
STEP
reaching V
STEP
C
prior to V
(t) = (dV/dt) x τ
= C
OUT
(t) = (dV/dt) x τ
C
= R
R
LOAD
STEP_MON
V
STEP_MON
STEP_MON
and V
I
LOAD
x R
CB
STEP_MON
IN
IN
STEP_MON
OUT
______________________________________________________________________________________
STEP
(over all V
x R
step, it is the dynamic response to a
STEP-MON
ramp with a ramp rate of dV/dt, the
DS(ON)
reaching V
C
No R
STEP_MON
x (1-e
STEP
OUT
x C
GND
I
STEP
V
must be set below STEP
IN
EE
and τL,eqv is the equiva-
. Each has an I*R compo-
STEP_MON
STEP_MON
to V
ramp rates anticipated in
(-t / τL,eqv)
x (1-e
SC
IN
NOTE: V
SENSE
R
GATE
DS,ON
(-t / τSTEP)
or within 1.4ms of
is:
SC
.
) + R
, V
STEP
must exceed
I
STEP_OS
V
V
CB
SC
CB
IN
, V
TH
MAX5938
STEPTH
ramp is:
DS(ON)
) + 10µA
V
OUT
, V
, and Overvoltage Protection
STEP_MON
STEP_DET
TH
SC TRIP
, AND V
t
CB_DLY
with an adequate margin, ∆V
the tolerance of both I
R
∆V
The margin of V
set when R
Setting the Circuit-Breaker and Short-Circuit Thresholds
section. This margin may be lower at one of the temper-
ature extremes and if so, that value should be used in
the following discussion. These margins will be called
∆V
excursion required to trip the respective fault.
To set τ
ramp rate, find the ratio of ∆V
choose τ
And since R
C
After the first-pass component selection, if sufficient
timing margin exists (see Appendix B), it is possible but
not necessary to lower R
reduce the sensitivity of STEP_MON to V
OUT
STEP_MON
STEP_MON
ARE REFERENCED TO V
STEP_MON
CB
CB TRIP
and ∆V
STEP
τ
STEP
STEP
CB_ADJ
= τ
is typically set to 100kΩ, which gives a
for a worst-case high of 0.36V.
SC
to block all V
so:
= 1.2 x τ
STEP_MON
IN
STEP
EE
OUT
CYCLE
FAULT
GATE
and they represent the minimum V
MGT
LOW
.
, with respect to V
was selected as described in the
Step Immunity,
/ 100kΩ.
STEP_OS
C
x ∆V
C
= 100kΩ. This results in
STEP_MON
LOAD
STEP_MON
CB
STEP_MON
STEP_MON
(±8%) and R
and V
ESR
C
ESL
, to accommodate
SC
SC
below 100kΩ to
IN
/ ∆V
and V
faults for any
to ∆V
noise.
CB
STEP_MON
LOAD
CB
CB
, was
OUT
and
17
.