MAX4273EEE Maxim Integrated Products, MAX4273EEE Datasheet - Page 17

• Manufacturer Part Number: MAX4273EEE
• Description: IC CTRLR 3-12V HOTSWAP 16-QSOP
• Manufacturer: Maxim Integrated Products
• Type: Hot-Swap Controllerr

Specifications of MAX4273EEE

• Applications: General Purpose
• Internal Switch(s): No
• Voltage - Supply: 2.7 V ~ 13.2 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP (0.150", 3.90mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

CTON determines the maximum time allowed to com-
plete turn-on for the MAX4273. The default values for
turn-on time (t
these pins floating; they are 10µs and 320µs, respec-
tively. These are also the minimum values (not con-
trolled and dependent on stray capacitance). Longer
timings are determined by the size of the capacitor
according to Figure 8, and can be determined in Table
5, which lists the startup and retry timing parameters.
Set the t
be enhanced and the load capacitor to be charged com-
pletely .
There are two ways of completing the startup sequence.
Case A describes a startup sequence that does not use
the current-limiting feature and slowly turns on the MOS-
FET by limiting the gate dv/dt. Case B uses the current-
limiting feature and turns on the MOSFET as fast as
possible while still preventing a high inrush current.
Figure 7. Fast Comparator Threshold vs. RTH
Table 5. Startup and Retry Timing Parameters
*MAX4273 retry feature disabled by connecting CTIM to V
with Autoretry, DualSpeed/BiLevel Fault Protection
MAX4271
MAX4272
MAX4273*
PART
3V to 12V Current-Limiting Hot-Swap Controllers
ON
800
700
600
500
400
300
200
100
timer long enough to allow for the MOSFET to
0
0
DEFAULT (µs)
ON
DISABLED FOR
RTH (kΩ) = V
RTH < 200Ω
FAST COMPARATOR THRESHOLD
10
) and t
______________________________________________________________________________________
10
10
10
20
VOLTAGE vs. RTH
TH
INDETERMINATE,
NOT RECOMMENDED FOR
RTH < 5kΩ
30
RETRY
,
FC
RTH (kΩ)
(mV)/10
40
t
t
t
ON
ON
ON
are chosen by leaving
50
(ms) = 0.31 x CTIM (nF)
(ms) = 0.31 x CTIM (nF)
(ms) = 0.31 x CTON (nF)
t
EXTERNALLY SET
ON
60
70
80
IN
.
Case A. Startup Without Current Regulation
There are three ways to turn on the MOSFET without
reaching the fast comparator current limit:
1) If the board capacitance is small, the inrush current
2) If the gate capacitance is high, the MOSFET turns on
3) The fast comparator can be disabled (MAX4273
In all three cases, t
required to enhance the MOSFET. Effectively, the small
gate-charging current limits the output voltage dv/dt.
This time can be extended by connecting an external
capacitor between GATE and GND (MAX4271/
MAX4272) (Figure 9) or between GATE and CEXT
(MAX4273). The turn-on time is dominated by the exter-
nal gate capacitance if this value is considerably higher
than the MOSFET gate capacitance. Table 6 shows the
timing required to enhance the recommended MOSFET
with or without the external capacitor; Figure 3 shows
the related waveforms and timing diagrams. (See Time
to Charge Gate vs. C
C
Remember that a high gate capacitance also increases
the turn-off time (t
MAX4273 fast fault.
If an external gate capacitor is not used, R
essary. R
occur when C
Electrical characteristics as specified by the manufac-
turer’s data sheet are:
FDS6670A: C
8.2mΩ
IRF7401: C
22mΩ
MMSF5N03HD: C
R
DEFAULT (µs)
DS(ON)
BOARD
is low.
slowly.
only).
320
320
= 40mΩ
= 0 in the Typical Operating Characteristics.)
S
ISS
prevents MOSFET self-oscillations that can
ISS
GATE
= 1600pF, Q
t
t
RETRY
RETRY
= 3200pF, Q
ON
ISS
is high while C
No retry available
OFF
(ms) = 32 x t
(ms) =10 x CTIM (nF)
is determined only by the charge
= 1200pF, Q
GATE
t
RETRY
), except in the case of a
EXTERNALLY SET
T
T
(MAX) = 48nC, R
(MAX) = 50nC, R
and Startup Time with
ON
BOARD
= 10 x CTIM (nF)
T
(MAX) = 21nC,
is low.
S
is not nec-
DS(ON)
DS(ON)
17
=
=