MAX5924 MAXIM [Maxim Integrated Products], MAX5924 Datasheet - Page 16

• 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 15. Kelvin Connection for the Current-Sense Resistor
In applications where the external MOSFET’s on-resis-
tance is used as a sense resistor to determine overcur-
rent conditions, a 3300ppm/°C temperature coefficient
is desirable to compensate for the R
ture coefficient. Use the MAX5926’s TC input to select
the circuit-breaker programming current’s temperature
coefficient, TC
ature coefficient is preset to 0ppm/°C, and the
MAX5925’s is preset to 3300ppm/°C.
Setting TC
threshold to track and compensate for the increase in the
MOSFET’s R
MOSFETs have a temperature coefficient within a
3000ppm/°C to 7000ppm/°C range. Refer to the MOSFET
data sheet for a device-specific temperature coefficent.
R
therefore be expressed as functions of temperature. At
a given temperature, the MAX5925/MAX5926 indicate
an overcurrent condition when:
where V
graphically portrays operating conditions for a MOSFET
with a 4500ppm/°C temperature coefficient.
Table
16
Sense Resistors
MOSFETs
DS(ON)
COMPONENT
I
Circuit-Breaker Temperature Coefficient
TRIPSLOW
______________________________________________________________________________________
CB,OS
4. Component Manufacturers
and I
ICB
DS(ON)
x R
CB
ICB
to 3300ppm/°C allows the circuit-breaker
is the worst-case offset voltage. Figure 14
HIGH-CURRENT PATH
DS(ON)
are temperature dependent, and can
(see Table 2). The MAX5924 temper-
with increasing temperature. Most
International Rectifier
MAX5924
MAX5925
MAX5926
(T) ≥ I
MANUFACTURER
Dale-Vishay
Fairchild
CB
R
IRC
CB
(T) x R
SENSE RESISTOR
DS(ON)
CB
+
|
V
CB,OS
tempera-
402-564-3131
828-264-8861
888-522-5372
310-233-3331
|
PHONE
Select the external n-channel MOSFET according to the
application’s current and voltage level. Table 3 lists some
recommended components. Choose the MOSFET’s
on-resistance, R
voltage drop at full load to limit the MOSFET power dis-
sipation. High R
loss and output ripple if the board has pulsing loads or
triggers an external undervoltage reset monitor at full
load. Determine the device power-rating requirement to
accommodate a short circuit on the board at startup
with the device configured in autoretry mode.
Using the MAX5924/MAX5925/MAX5926 in latched mode
allows the consideration of MOSFETs with higher R
and lower power ratings. A MOSFET can typically with-
stand single-shot pulses with higher dissipation than the
specified package rating. Low MOSFET gate capaci-
tance is not necessary since the inrush current limiting is
achieved by limiting the gate dv/dt. Table 4 lists some
recommended manufacturers and components.
Be sure to select a MOSFET with an appropriate gate
drive (see the Typical Operating Characteristics).
Typically, for V
a 2.5V V
Select the sense resistor in conjunction with R
the slow and fast circuit-breaker thresholds (see the
Selecting a Circuit-Breaker Threshold section). The
sense-resistor power dissipation depends on the device
configuration. If latched mode is selected, P
(I
P
Choose a sense-resistor power rating of twice the
P
ensure that the sense resistor has an adequate I
to survive instantaneous short-circuit conditions.
OVERLOAD
RSENSE
RSENSE
GS
www.vishay.com
www.irctt.com
www.fairchildsemi.com
www.irf.com
for long-term reliable operation. In addition,
= (I
MOSFET.
)
2
CC
OVERLOAD
x R
Applications Information
DS(ON)
DS(ON)
less than 3V or greater than 12V, select
SENSE
, low enough to have a minimum
; if autoretry is selected, then
can cause undesired power
)
2
WEBSITE
Component Selection
x R
Optional Sense Resistor
SENSE
n-Channel MOSFET
x (t
ON
RSENSE
/t
CB
2
RETRY
T rating
DS(ON)
to set
=
).