MAX5943CEEE+ Maxim Integrated Products, MAX5943CEEE+ Datasheet - Page 11

• Manufacturer Part Number: MAX5943CEEE+
• Description: IC FIREWIRE CURR LIMITER 16-QSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX5943CEEE+

• 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

The MAX5943 current-limit/circuit-breaker timeout is
programmable by connecting an external resistor from
TIM to GND. The MAX5943A has a default 2ms current-
limit timeout. The MAX5943B, MAX5943C, MAX5943D,
and MAX5943E have 0.5ms, 1ms, 2ms, and 4ms
default circuit-breaker timeouts, respectively.
GATE1 controls the MAX5943 ORing function. Initially,
GATE1 is off (ONQ1 = low) and the load current con-
ducts through the body diode of Q1. GATE1 rises to
5.5V above SENSE when V
enhancing Q1 and reducing the voltage drop, power
dissipation, and heat generation in the power-supply
path. When a voltage greater than V
OUT, the higher voltage source commences, providing
current to the load. The MAX5943 rapidly turns off
GATE1 upon V
blocking the higher voltage from back-driving V
GATE1 also turns off when the load current drops,
causing V
The MAX5943A limits the load current by monitoring the
voltage across R
current to the load as necessary to keep V
grammable current-limit threshold voltage (V
maximum current limit (I
sense resistor between IN and SENSE, where I
V
GATE2 rises to V
(see the Typical Operating Circuit) .
When the load current attempts to draw more than
I
regulates the current through Q2 causing OUT to act as
a constant-current source. The output current is limited
to the programmed I
persists after the current-limit timeout (t
expired, GATE2’s strong pulldown current (I
quickly turns off GATE2 to disconnect the load from the
power supply. FAULT then asserts low (Figure 2a). If the
current-limit duration is less than t
V
gross overload, the load current overshoots and causes
V
voltage (V
stronger GATE2 pulldown currents (I
to quickly bring the load current back down to the pro-
grammed current limit.
LIMIT
TH
G2
IS
/R
to exceed the fast pulldown current-limit threshold
(Figure 2b). During an output short circuit or a
, the MAX5943A’s GATE2 pulldown current (I
SENSE
IS
THF
. When the load current is less than I
to fall below the V
Current Limiting/Circuit Breaker
). The MAX5943A responds with much
IS
SENSE
G2
falling below V
______________________________________________________________________________________
Current Limiting (MAX5943A Only)
(5.5V) to fully enhance MOSFET Q2
LIMIT
FireWire Current Limiter and Low-Drop
at all times and by regulating the
LIMIT
. If the current-limit condition
) by placing the appropriate
IS
OR
exceeds V
hysteresis.
OR
ILIM
G2DP
IN
- hysteresis, thus
, GATE2 pulls to
ILIM
is connected at
and/or I
OR
) period has
IS
TH
to its pro-
, thereby
). Set the
G2 OFF
LIMIT
G2DF
LIMIT
G2D
IN
=
)
)
)
.
,
ORing Switch Controller
Figure 2. MAX5943A Current-Limit Timing Diagram
V
V
V
V
V
V
GATE1
GATE2
GATE1
GATE2
FAULT
FAULT
V
V
I
I
OUT
OUT
OUT
OUT
I
LIMIT
x R
LOAD
I
< t
LIMIT
(a)
ILIM
(b)
x R
LOAD
t
ILIM
I
LIMIT
I
LIMIT
V
IN
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