MAX5924 MAXIM [Maxim Integrated Products], MAX5924 Datasheet - Page 11

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

The MAX5924/MAX5925/MAX5926 load-probing circuit-
ry detects short-circuit conditions during startup. As the
device begins load probing, SC_DET is connected to
V
R
current:
If the load voltage does not reach V
within t
nel is turned off according to the selected fault-manage-
ment mode (see the Fault Management section and
Figure 5). PGOOD/PGOOD asserts at the end of the
startup period, t
(see the Turn-On Waveforms in the Typical Operating
Characteristics).
In normal operation, after startup is complete, protec-
tion is provided by turning off the external MOSFET
when a fault condition is encountered. Dual-speed/
bilevel fault protection incorporates two comparators
with different thresholds and response times to monitor
the current:
1) Slow comparator. This comparator has a 1.6ms
2) Fast comparator. This comparator has a fixed
Figure 6. Load-Probe Resistance vs. Supply Voltage
CC
LP
(typ) response time. The slow comparator ignores
low-amplitude momentary current glitches. After an
extended overcurrent condition, a fault is acknowl-
edged and the MOSFET gate is discharged.
response time and a higher threshold voltage. The
fast comparator turns off the MOSFET immediately
(Figure 6). V
I
through an internal switch with an on-resistance of
PROBE
LP
1V to 13.2V, n-Channel Hot-Swap Controllers
, a short-circuit fault is detected and the chan-
= (V
14
12
10
8
6
4
2
CC
CC
START
______________________________________________________________________________________
- V
then charges the load with a probe
4
OUT
, if no fault condition is present
6
)/(R
V
CC
LP
8
(V)
Normal Operation
+ R
10
SC
LP,TH
Load Probing
) (Figure 1)
V
12
CC
= V
S
(0.2V, typ)
14
Require No Sense Resistor
In each case, when a fault is encountered, the power-
good output deasserts and the device drives GATE low.
After a fault, the MAX5924A, MAX5924B, MAX5925A,
and MAX5925B latch GATE low and the MAX5924C,
MAX5924D, MAX5925C, and MAX5925D enter the
autoretry mode. The MAX5926 has selectable latched or
autoretry modes. Figure 7 shows the slow comparator
response to an overcurrent fault.
Bilevel fault protection is disabled during startup when
no R
protection when R
trip levels are higher than normal during startup because
I
The slow comparator is disabled during startup while
the external MOSFET turns on. This allows the
MAX5924/MAX5925/MAX5926 to ignore higher than
normal inrush currents charging the board capacitors
when a card is first plugged in.
Figure 7. Slow Comparator Response to an Overcurrent Fault
CB,SU
PGOOD**
PGOOD*
V
I
after it detects a large amplitude event such as a
short circuit.
LOAD
V
GATE
OUT
SENSE
**MAX5924A, MAX5924C, MAX5925A, MAX5925C, AND MAX5926 ONLY.
*MAX5924B, MAX5924D, MAX5925B, MAX5925D, AND MAX5926 ONLY.
= 2 x I
I
LIM
4.3V TO 6.7V
is detected. The device enables bilevel fault
CB
Bilevel Fault Protection in Startup Mode
t
CBS
(see the Startup Mode section).
SENSE
V
THPGOOD
is detected, but the overcurrent
Bilevel Fault Protection
Slow Comparator
11