max5943beeet Maxim Integrated Products, Inc., max5943beeet Datasheet - Page 10

• Manufacturer Part Number: max5943beeet
• Description: Max5943 Firewire Current Limiter And Low-drop Oring Switch Controller
• Manufacturer: Maxim Integrated Products, Inc.

FireWire Current Limiter and Low-Drop
ORing Switch Controller
Figure 1. MAX5943 Functional Diagram
The MAX5943 performs hot-swapping, power-supply
ORing, and current limiting for FireWire power-supply
applications. The MAX5943 incorporates two MOSFET
drivers (GATE1 and GATE2) to control two external
n-channel power MOSFETs to perform low-voltage-drop
power-supply ORing (GATE1) and hot swapping and
current limiting (GATE2) from the input power supply to
the load. A sense resistor provides accurate current-
limiting/circuit-breaker function. GATE1 and GATE2
provide true load disconnect to prevent current flowing
from either direction between IN and OUT.
The MAX5943 remains in low-current shutdown mode
when V
shutdown mode disables the MAX5943, resulting in
less than 10µA supply current. Shutdown places all
10
______________________________________________________________________________________
ON
is below the 0.4V threshold. Low-current
OR_ADJ
ONQ1
ILIM
ON
POWER
SOURCE
( ) MAX5943A ONLY.
0.4V
Detailed Description
1.24V
6.5V
+
-
CIRCUIT-BREAKER
MAX5943A–MAX5943E
(CURRENT-LIMIT)
(FAST CURRENT-
UVLO COMPARATOR
COMPARATOR
ON COMPARATOR
THRESHOLD)
THRESHOLD
THRESHOLD
R
+
-
+
-
SENSE
LIMIT
OR
SHUTDOWN
MODE
+
+
+
-
-
-
SENSE
SENSE GATE1
CP1
logic inputs in a high-impedance state allowing the
inputs to be connected to IN without drawing additional
current from the supply.
When the input supply voltage (V
V
turns on, sourcing 45µA current from GATE2 (current
regulation) to enhance Q2 slowly. For the MAX5943A, if
the voltage across the current-sense resistor, V
greater than the programmed current-limit threshold,
the MAX5943A regulates the GATE2 voltage to limit the
load current at the current-limit level so that V
to V
GATE2 rises to approximately 5.5V above OUT. Since
the MAX5943B–MAX5943E do not regulate the load
current, a capacitor can be added from GATE2 to GND
to limit inrush current during startup (see the
Applications Information section).
ON
CHARGE
PUMPS
GATE1
DRIVE
GATE
TH
CP2
Q1
is above the V
. In normal operation, V
GATE1
GATE2
GATE2
Q2
GATE2
DRIVE
MANAGEMENT
AUTORETRY
AUTORETRY
ON_REF
LATCH OR
TIMEOUT
TIMEOUT
PERIOD
FAULT
FAULT
OUT
OUT
X128
GND
threshold, the MAX5943
IS
drops below V
IN
) is above 7.5V and
TIM
LATCH
FAULT
IS
is equal
TH
IS
and
, is