max5938 Maxim Integrated Products, Inc., max5938 Datasheet - Page 10

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

the load. The short-circuit threshold voltage, V
twice V
resistance between CB_ADJ and V
nal 2kΩ precision-trimmed resistor and an internal 50µA
current source at CB_ADJ, which results in the mini-
mum or default V
nected to V
compensated (increasing with temperature) to track the
normalized temperature coefficient of R
power MOSFETs.
When the load current is increased during full enhance-
ment, this causes V
than V
rejection timer. At the end of the glitch rejection period,
if V
pulled to V
part enters fault management. Alternatively, during full
enhancement when V
glitch rejection timer. GATE is immediately pulled to
V
management.
The V
through a large step increase in V
plane inrush current and without shutting down the load.
Without V
fully enhanced), a step increase in V
high inrush current and a large step in V
trip the circuit breaker.
With V
the step before a short circuit is detected at V
alters the MAX5938 response to V
V
STEP_MON and a 10µA current source at STEP_MON
-48V Hot-Swap Controller with V
No R
10
Figure 6. MAX5938 Response to a Step Input with No Fault
(V
EE
SC
OUT
OUT
, PGOOD is deasserted, and the part enters fault
______________________________________________________________________________________
due to the step. The 1.25V voltage threshold at
IN
< 0.75V
IN
SC
CB
step immunity provides a means for transitioning
still exceeds V
40V
IN
, and starts the 1.2ms circuit-breaker glitch
step immunity, the STEP_MON input detects
(V
EE
SENSE
step immunity (when the power MOSFET is
CB
SC
EE
(330ns), PGOOD is deasserted, and the
)
. The current source is temperature
= 2 x V
SC
OUT
of 100mV when CB_ADJ is con-
OUT
2ms/div
to exceed V
CB
CB
, and Overvoltage Protection
) and is set by adjusting the
, the GATE is immediately
exceeds V
C
R
LOAD
LOAD
IN
= 100Ω
= 100µF
EE
CB
with minimal back-
. There is an inter-
IN
DS(ON)
OUT
but remains less
SC
OUT
will result in a
V
5V/div
V
10V/div
V
20V/div
V
20V/div
I
1A/div
IN
, there is no
IN
GATE
OUT
PGOOD
, which can
exceeding
for typical
OUT
SC
and
, is
allow the user to set the sensitivity of the step detection
with an external resistor to V
between GND and the STEP_MON input, which in con-
junction with the resistor, sets the STEP_MON time
constant.
When a step is detected by the STEP_MON input rising
above its threshold (STEP
management is blocked and remains blocked as long
as STEP
the MAX5938 takes no action until V
V
rejection period. When either of these conditions
occurs, a step GATE cycle begins and the GATE is
immediately brought to V
MOSFET to minimize the resulting inrush current surge
from the backplane. PGOOD remains asserted. GATE
is held at V
ramp up, enhancing the power MOSFET in a controlled
manner as in the power-up GATE cycle. This provides a
controlled inrush current to charge the load capaci-
tance to the new supply voltage (see the GATE Cycles
section in Appendix A).
As in the case of the power-up GATE cycle, if V
drops to less than 74% of the programmed V
pendent of the state of STEP_MON, the GATE voltage is
rapidly pulled to full enhancement. PGOOD remains
asserted throughout the step (Figure 6). Otherwise, if the
STEP_MON input has decayed below its threshold but
V
(when GATE reaches 90% of full enhancement), a step-
to-fault-management fault has occurred. GATE is rapidly
pulled to V
connecting the load; PGOOD is deasserted and the
MAX5938 enters the fault management mode (Figure 7).
Figure 7. MAX5938 Response to a Step Input Ending in a Fault
(V
SC
OUT
OUT
or above V
> 0.75V
remains above 74% of the programmed V
40V
20V
TH
EE
EE
is exceeded. When STEP
CB
, turning off the power MOSFET and dis-
for 350µs, and after about 1ms, begins to
IN
)
CB
for the 1.2ms circuit-breaker glitch
Step Immunity,
4ms/div
EE
, which turns off the power
TH
EE
C
R
), the overcurrent fault
LOAD
LOAD
. A capacitor is placed
= 100µF
= 20Ω
OUT
TH
V
20V/div
V
10V/div
V
50V/div
V
50V/div
I
5A/div
IN
IN
GATE
OUT
PGOOD
is exceeded,
rises above
CB
, inde-
OUT
CB