MAX5924 MAXIM [Maxim Integrated Products], MAX5924 Datasheet - Page 12

• Manufacturer Part Number: MAX5924
• Description: 1V to 13.2V, n-Channel Hot-Swap Controllers Require No Sense Resistor
• Manufacturer: MAXIM [Maxim Integrated Products]

1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
Figure 8a. Gate Discharge Current vs. MOSFET Gate-to-Source
Voltage
If the slow comparator detects an overload condition while
in normal operation (after startup is complete), it turns off
the external MOSFET by discharging the gate capaci-
tance with I
depends on the external MOSFET gate-to-source volt-
age, V
ately following a fault and decreases as the MOSFET
gate is discharged (Figure 8a).
The fast comparator is used for serious current overloads
or short circuits. If the load current reaches the fast com-
parator threshold, the device quickly forces the MOSFET
off. The fast comparator has a response time of 280ns,
and discharges GATE with I
The MAX5924A, MAX5924B, MAX5925A, and MAX5925B
latch the external MOSFET off when an overcurrent fault
is detected. Following an overcurrent fault, the
MAX5924C, MAX5924D, MAX5925C, and MAX5925D
enter autoretry mode. The MAX5926 can be configured
for either latched or autoretry mode (see Table 1).
In autoretry, a fault turns the external MOSFET off then
automatically restarts the device after the autoretry
delay, t
EN1 low to restart the device. In latched mode, pull EN
or EN1 low for at least 100µs to clear a latched fault
and restart the device.
12
Latched and Autoretry Fault Management
______________________________________________________________________________________
GS
RETRY
. The discharge current is strongest immedi-
60
50
40
30
20
10
0
0
GATE,PD
. During the autoretry delay, pull EN or
V
CC
1
= 13.2V
2
. The magnitude of I
3
V
GS
GATE,PD
(V)
4
5
(Figure 8a).
Fast Comparator
6
7
GATE,PD
The power-good output(s) are open-drain output(s) that
deassert:
PGOOD/PGOOD asserts only if the part is in normal
mode and no faults are present.
UVLO circuitry prevents the MAX5924/MAX5925/
MAX5926 from turning on the external MOSFET until V
exceeds the UVLO threshold, V
protects the external MOSFET from insufficient gate-drive
voltage, and t
plugged into the backplane and V
powering the hot-swapped system. Any input voltage
transient at V
the UVLO deglitch period, t
tiates a startup sequence. Device operation is protected
from momentary input-voltage steps extending below the
UVLO threshold for a deglitch period, t
power-good output(s) may momentarily deassert if the
magnitude of a negative step in V
mately 0.5V, and V
unaffected and the power-good output(s) assert(s) within
200µs as shown in Figure 8b. This figure also shows that
if the UVLO condition exceeds t
power-good output(s) again deassert(s) and the load is
disconnected.
Table
Mode (MAX5926)
• When V
• During t
• When V
• During load probing
• When disabled (EN = GND (MAX5924/MAX5925),
• During fault management
• During t
EN1 = GND or EN2 = high (MAX5926))
MAX5924B, MAX5925A, MAX5925B, or MAX5926
(LATCH = low)).
LATCH
High
Low
1. Selecting Fault Management
CC
GS
D,UVLO
CC
RETRY
D,UVLO
< V
< V
below the UVLO threshold for more than
Undervoltage Lockout (UVLO)
Autoretry mode
Latched mode
THPGOOD
UVLO
CC
or when latched off (MAX5924A,
drops below V
ensures that the board is fully
FAULT MANAGEMENT
DG
Power-Good Outputs
, resets the device and ini-
UVLO
DG
CC
CC
, for t
UVLO
= 900µs (typ), the
exceeds approxi-
DG.
is stable prior to
D,UVLO
. Operation is
However, the
. UVLO
CC