max5938 Maxim Integrated Products, Inc., max5938 Datasheet - Page 9

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

LP is shut off. The MAX5938A times out for 16 x t
retry the load-probe test. The MAX5938L latches the fault
condition indefinitely until ON and OFF are cycled low for
1.5ms or the power is recycled. See the Applications
Information for recommendations on selecting R
the load-probe current level.
Upon successful completion of the load-probe test, the
MAX5938 enters the power-up GATE cycle and begins
ramping the GATE voltage with a 52µA current source.
This current source is restricted if V
down faster than the default 9V/ms slew rate. The V
slew rate can be reduced to below 9V/ms by adding
C
enhances the power MOSFET in a controlled manner
and ramping V
inrush current from the backplane. The MAX5938 con-
tinues to charge up the GATE until one of two events
occurs: a normal power-up GATE cycle is completed or
a power-up-to-fault-management fault is detected (see
-48V Hot-Swap Controller with V
Figure 2. GATE Voltage Clamp During Power-Up
Figure 4. MAX5938 Normal Startup (POL_SEL = Floating)
SLEW
from GATE to V
C
IN
= 100µF
OUT
_______________________________________________________________________________________
at a user-settable rate controls the
40ms/div
4ms/div
No R
OUT
. Charging up GATE
OUT
SENSE
begins to ramp
V
20V/div
V
1V/div
V
50V/div
V
10V/div
V
50V/div
V
50V/div
I
2A/div
IN
IN
GATE
IN
GATE
OUT
PGOOD
LP
LP
, and Overvoltage Protection
to set
then
OUT
the GATE Cycles section in Appendix A). In a normal
power-up GATE cycle, the voltage at V
to V
breaker threshold voltage, V
ing GATE voltage is rapidly pulled up to full
enhancement. PGOOD is asserted 1.26ms after GATE
is fully enhanced (see Figure 4). If the voltage at V
remains above 74% of the programmed V
GATE reaches 90% of full enhancement), then a power-
up-to-fault-management fault has occurred). GATE is
rapidly pulled to V
and disconnecting the load. PGOOD remains deassert-
ed and the MAX5938 enters the fault management
mode (Figure 5).
When the power MOSFET is fully enhanced, the
MAX5938 monitors the drain voltage (V
breaker and short-circuit faults. The MAX5938 makes
use of the power MOSFET’s R
sense resistance to detect excessive current through
Figure 3. Load-Probe Test During Initial Power-Up
Figure 5. MAX5938 Startup into Fault Condition (POL_SEL =
Floating)
EE
) ramps to below 74% of the programmed circuit-
GND
GND
GND
IN
EE
Step Immunity,
40ms/div
, turning off the power MOSFET
40ms/div
CB
C
R
LP
. At this time, the remain-
LOAD
DS(ON)
= 75kΩ
= 100µF
OUT
OUT
as the current-
V
20V/div
V
50V/div
V
10V/div
V
50V/div
V
50V/div
I
2A/div
IN
V
20V/div
V
200mV/div
EE
IN
GATE
OUT
PGOOD
LP
OUT
) for circuit-
(referenced
CB
(when
OUT
9