MAX5925 MAXIM [Maxim Integrated Products], MAX5925 Datasheet - Page 12

• Manufacturer Part Number: MAX5925
• 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. Load
probing is active only when no external R
detected. As the device begins load probing, SC_DET
is connected to V
on-resistance of R
load with a probe current limited at ≈200mA.
If the load voltage does not reach V
within t
up mode is terminated according to the selected fault-
management mode (see the Fault Management section
and Figure 5). If no fault condition is present,
PGOOD/PGOOD asserts at the end of the startup peri-
od (see the Turn-On Waveforms in the Typical
Operating Characteristics ).
Load probing can only be, and must be, employed
when not using an external R
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
Figure 5. Startup Waveform
Figure 6. Load-Probe Resistance vs. Supply Voltage
12
I
PROBE
I
LOAD
V
OUT
______________________________________________________________________________________
LP
, a short-circuit fault is detected and the start-
= (V
SR = dV
14
12
10
8
6
4
dt
CC
I PROBE
2
t
PROBE
- V
CC
C
LP
L
< t
= SMALL
4
OUT
LP
through an internal switch with an
(Figure 6). V
I
INRUSH
)/(R
6
SR = dV
V
LP
dt
CC
8
SENSE
(V)
V
(0.2V typ)
+ R
LP,TH
10
SC
CC
.
C
V
)
CC
12
L
then charges the
= SMALL
Load Probing
LP,TH
C
= V
L
= LARGE
S
14
(Figure 1)
(0.2V typ)
SENSE
V
I
LOAD
OUT
is
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 quick
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.
Figure 7. Slow Comparator Response to an Overcurrent Fault
PGOOD**
PGOOD*
V
I
LOAD
(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
when it detects a large high-current event such as a
short circuit.
V
GATE
OUT
**MAX5924A, MAX5924C, MAX5925A, MAX5925C, AND MAX5926 ONLY.
*MAX5924B, MAX5924D, MAX5925B, MAX5925D, AND MAX5926 ONLY.
I
LIM
3.0V TO 6.7V
t
CBS
V
THPGOOD
Normal Operation