MAX5924 MAXIM [Maxim Integrated Products], MAX5924 Datasheet - Page 10

• 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
The MAX5924/MAX5925/MAX5926 are hot-swap con-
troller ICs designed for applications where a line card is
inserted into a live backplane. Normally, when a line card
is plugged into a live backplane, the card’s discharged
filter capacitors provide a low impedance that can
momentarily cause the main power supply to collapse.
The MAX5924/MAX5925/MAX5926 are designed to
reside either in the backplane or in the removable card
to provide inrush current limiting and short-circuit pro-
tection. This is achieved using an external n-channel
MOSFET and an optional external current-sense resistor.
Several critical parameters can be programmed:
See the Selector Guide for a device-specific list of fac-
tory-preset features and parameters.
The MAX5924/MAX5925/MAX5926 control an external
MOSFET connected in series with the hot-swapped
power supply, V
MOSFET off while the supply voltage, V
undervoltage lockout threshold or when the device is
disabled (see the EN (MAX5924/MAX5925, EN1/ EN2
(MAX5926) section). When V
the MAX5924/MAX5925/MAX5926 are enabled, an
undervoltage lockout timer initiates. V
greater than V
During the first stage of startup, the MAX5924/
MAX5925/MAX5926 detect whether an external sense
resistor is present and autoconfigure accordingly
(Figure 4). Bilevel fault protection temporarily disables,
and load-probing circuitry enables, if no sense resistor
is detected (see the Load Probing section). During load
probing, if V
the device manages the fault according to the selected
fault-management mode (see the Latched and
Autoretry Fault Management section). If V
above V
MAX5926 begin startup (Figure 5). If an external
R
bilevel fault protection enables with a startup circuit-
breaker programming current of I
accommodate the higher-than-normal inrush current
required to charge board capacitance, C
10
SENSE
• Slew rate (inrush current)
• Circuit-breaker threshold
• Turn-on voltage
• Fault-management mode (MAX5926)
• Circuit-breaker temperature coefficient (MAX5926)
______________________________________________________________________________________
is detected, load probing is bypassed and
LP,TH
OUT
UVLO
within t
does not rise above V
S
. These devices hold the external
for t
Detailed Description
D,UVLO
LP
, the MAX5924/MAX5925/
CC
to enter startup.
rises above V
CB,SU
Startup Mode
CC
CC
LP,TH
L
.
, is below the
= 2 x I
must remain
OUT
within t
UVLO
CB
rises
and
LP
to
,
During startup, the MAX5924/MAX5925/MAX5926 gradu-
ally turn on the MOSFET, and V
mined by the selected slew rate, SR (see the Slew Rate
section). The inrush current, I
proportional to the load capacitance, C
where SR is in V/ms and C
Farads. For operation with and without R
V
and the MAX5924/MAX5925/MAX5926 enable standard
bilevel fault protection (see the Bilevel Fault Protection
section).
Figure 4. Startup Flow Chart
Figure 5. Startup Waveform
GS
I
LOAD
V
OUT
*V
exceeds V
OUT
LIMITED STARTUP
MUST REACH V
SLEW-RATE-
SR = dV
OPERATION
NORMAL
PRESENT
dt
R
I
I PROBE
SENSE
INRUSH
t
PROBE
CB,EN
C
LP,TH
L
< t
= SMALL
LP
WITHIN t
I
(A) = C
V
INRUSH
, PGOOD and/or PGOOD assert
CC
AUTODETECT
SUCCESS
RISES ABOVE
R
SR = dV
V
SENSE
UVLO
LP
.
L
dt
L
INRUSH
is the load capacitance in
x 1000 x SR
V
(0.2V typ)
OUT
LP,TH
PROBE*
LOAD
rises at a rate deter-
, is limited to a level
ABSENT
R
SENSE
C
L
L
MANAGEMENT
= SMALL
, and SR:
C
L
= LARGE
FAULT
SENSE
FAILURE
, once
V
I
LOAD
OUT