MAX5943DEEE+ Maxim Integrated Products, MAX5943DEEE+ Datasheet - Page 16

• Manufacturer Part Number: MAX5943DEEE+
• Description: IC FIREWIRE CURR LIMITER 16-QSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX5943DEEE+

• Applications: FireWire® Apps
• Fet Type: N-Channel
• Number Of Outputs: 2
• Internal Switch(s): No
• Delay Time - Off: 100ns
• Voltage - Supply: 7.5 V ~ 37 V
• Current - Supply: 1.3mA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Delay Time - On: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

FireWire Current Limiter and Low-Drop
ORing Switch Controller
Select external MOSFETs according to the application
current level. The MOSFETs’ on-resistance (R
should be chosen low enough to have minimum voltage
drop at full load to limit the MOSFET power dissipation.
High R
a pulsating load. Determine the device power rating to
accommodate startup, a short-circuit condition, and
when the device is in autoretry mode.
During normal operation, the external MOSFETs dissipate
little power. The power dissipated in normal operation is:
The most power dissipation occurs during a short-circuit
event, resulting in high power dissipated in Q2 (Figure
11) during the timeout period for the MAX5943A, where
the power dissipated across Q2 is:
Figure 12. UL-Recognized Single-Port FireWire Protective Circuit
16
GND
V
J1
J2
IN
1μF
C1
______________________________________________________________________________________
GND
DS(ON)
TP1
V
TP2
IN
0.01μF
0.020Ω
200kΩ
0.25W
P
C2
1%
Q2
R2
R1
also causes large output ripple if there is
= (V
P = I
Si2318DS
V
PULLUP
TP5
ON
TP6
N1
IN
LOAD
- V
100kΩ
Si7222DN
IS
R8
2
N2A
100kΩ
x R
– V
R5
Q1
DS(ON)
FAULT
TP4
) x I
MOSFET Selection
N2B
MAX5943AEEE
1kΩ
R3
LIMIT
U1
Q1A
DS(ON)
DMMT3906
)
Q1B
For the MAX5943B–MAX5943E, a short-circuit event
results in high power dissipated in both Q1 and Q2 dur-
ing the timeout period (Figure 13) where the total power
dissipated in either MOSFET is:
where:
and
Figure 11. Power Dissipated Across MOSFETs During a Short-
Circuit Fault for MAX5943A
1kΩ
100kΩ
R4
R6
V
IN
R
EQ
IN
+
C3
1μF
= R
V
IS
SENSE
P = I
-
SENSE GATE1
C4
0.1μF
I
SC
MAX5943A
SC
+R
= V
+
2
V
DS(ON1)
x R
R7
100kΩ
Q1
IN
-
FERRITE
/R
250Ω
DS(ON)
L1
EQ
+
GATE2
+ R
V
PORT 0
Q2
TP3
-
DS(ON2)
1
2
OUT
PORT 0
3
4
5
6
J3