MAX4370ESA+ Maxim Integrated Products, MAX4370ESA+ Datasheet - Page 12

• Manufacturer Part Number: MAX4370ESA+
• Description: IC CNTRLR HOT-SWAP 8-SOIC
• Manufacturer: Maxim Integrated Products
• Type: Hot-Swap Controllerr

Specifications of MAX4370ESA+

• 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: 8-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Current-Regulating Hot-Swap Controller with
DualSpeed/BiLevel Fault Protection
Case A: Slow Turn-On (without overcurrent)
There are two ways to turn on the MOSFET without
reaching the fast comparator current limit:
1) If the board capacitance (C
2) If the capacitance at GATE is high, the MOSFET
In both cases, the turn-on (t
the charge required to enhance the MOSFET—effec -
tively, the small gate-charging current limits the output
voltage dv/dt. This time can be extended by connect-
ing an external capacitor between GATE and GND, as
shown in Figure 7. The turn-on time is dominated by the
external gate capacitance if its value is considerably
higher than MOSFET gate capacitance. Table 4 shows
the timing required to enhance the recommended
MOSFET with or without an external capacitor at GATE;
Figures 2 and 3 show the related waveforms and timing
diagrams (see Start-Up Time with C
Start-Up Time with External C
Operating Characteristics ). Remember that a high gate
capacitance also increases the turn-off time.
When using the MAX4370 without an external gate
capacitor, R
source oscillations that can occur when C
while C
Case B: Fast Turn-On (with current limit)
In applications where the board capacitor (C
V
across R
threshold (V
Table 4. MOSFET Turn-On Time (start-up without current limit)
(C
Electrical characteristics as specified by the manufacturer’s data sheet:
FDS6670A: C
IRF7401: C
MMSF5N03HD: C
12
OUT
Fairchild FDS6670A
International Rectifier
IRF7401
Motorola
MMSF5N03HD
BOARD
inrush current is low.
turns on slowly.
______________________________________________________________________________________
is high, the inrush current causes a voltage drop
BOARD
DEVICE
= 0, turn-on with no load current, turn-off with 2A fault current)
ISS
SENSE
ISS
FC,TH
S
= 1600pF, Q
is not necessary. R
is low.
= 3200pF, Q
ISS
that exceeds the fast comparator
= 1200pF, Q
= 200mV). In this case, the current
T(MAX)
C
T(MAX)
(nF)
GATE
22
22
22
0
0
0
ON
T(MAX)
= 48nC, R
) is determined only by
= 50nC, R
GATE
BOARD
S
= 21nC, R
prevents MOSFET
BOARD
V
DS(ON)
220µs
2.3ms
175µs
1.9ms
101µs
IN
in the Typical
2ms
DS(ON)
= 3V
) is low, the
GATE
MOSFET TURN-ON (t
DS(ON)
= 22mΩ
BOARD
= 0 and
= 8.2mΩ
is high
= 40mΩ
V
) at
160µs
130µs
1.8ms
1.8ms
IN
74µs
2ms
= 5V
charging C
turn-on time is determined by:
where the maximum load current I
R
grams for a turn-on transient with current regulation (see
Start-Up Time with C
Operating Characteristics ). When operating under this
condition, an external gate capacitor is not required.
Adding an external capacitor at GATE reduces the regu-
lated current ripple but increases the turn-off time by
increasing the gate delay (t
Figure 7. Operation with External Gate Capacitor
SENSE
ON
R
V
PULL-UP
IN
)
190µs
3.2ms
160µs
3.5ms
3.2ms
73µs
V
. Figure 2 shows the waveforms and timing dia-
C
= 12V
IN
SPD
*OPTIONAL (SEE TEXT)
BOARD
t
ON
CSPD
STAT
ON
= C
V
V
IN
can be considered constant and the
540µs
540µs
470µs
IN
70µs
75µs
33µs
BOARD
= 3V
R
BOARD
SENSE
MOSFET TURN-OFF (t
MAX4370
GND
d
· V
) (Figure 3).
VSEN
IN
= 470µF in the Typical
V
130µs
1.1ms
130µs
1.1ms
/ I
IN
67µs
GATE
1ms
M1
FAST,SET
= 5V
FAST,SET
CTIM
R
S
*
V
OUT
OFF
C
V
C
= V
GATE
TIM
C
1.95ms
1.95ms
IN
145µs
160µs
BOARD
85µs
)
2ms
= 12V
FC,TH
/