MAX5944
Dual FireWire Current Limiter and Low-Drop
ORing Switch Controller
8 _______________________________________________________________________________________
Pin Description
PIN NAME FUNCTION
1 INA
Channel A Input Power and Current-Sense Positive Input. Connect INA to the other end of the current-
sense resistor and to the power source (see the Typical Operating Circuit).
2 ONA
Channel A On/Off Control Input. ONA sets the undervoltage lockout threshold and resets the part after a
fault latch. Drive ONA high to enable the device. Drive ON_ low to disable the device. Connect ONA to INA
for the default undervoltage lockout threshold. Connect a resistor-divider from INA to ONA and to GND to
program the desired undervoltage lockout threshold.
3
FAULTA
Channel A Current-Fault Status Output. FAULTA is an open-drain output. FAULTA goes low after a current-
limit fault has exceeded the 2ms (typ) current-limit timeout period (see the
FAULT_
section).
4 ONQ1
ORing Switch Manual Turn-On Input. Drive ONQ1 low to enable power-supply ORing for channels A and B.
Drive ONQ1 high to set GATE1A to GATE1B high to allow reverse-current flow. ONQ1 is disabled for the
respective channel when V
IN
is below the UVLO threshold, V
ON_
is below the undervoltage lockout
threshold and after a current-limit fault.
5 OUTB Channel B Output-Voltage Sense. Connect to the output.
6
GATE2B
Channel B Current-Limiter Switch Gate-Drive Output. Referenced to OUTB. Connect GATE2B to the gate of
the 2nd n-channel MOSFET. GATE2B is a charge pump with a 50µA pullup current to 5.5V (typ) above
OUTB when active (see the Typical Operating Circuit).
7
GATE1B
Channel B ORing Switch Gate-Drive Output. Referenced to SENSEB. Connect GATE1B to the gate of the
1st n-channel MOSFET. GATE1B is a charge pump with a 50µA pullup current to 5.5V (typ) above SENSEB
when active (see the Typical Operating Circuit).
8
SENSEB
Channel B Current-Sense Negative Input. Connect current-sense resistor, R
SENSE
, from INB to SENSEB.
9 INB
Channel B Input Power and Current-Sense Positive Input. Connect INB to the other end of the current-
sense resistor and to the power source.
10 ONB
Channel B On/Off Control Input. ONB sets the undervoltage lockout threshold and resets the part after a
fault latch. Drive ONB high to enable the device. Drive ON_ low to disable the device. Connect ONB to INB
for the default undervoltage lockout threshold. Connect a resistor-divider from INB to ONB and to GND to
program the desired undervoltage lockout threshold.
11
FAULTB
Channel B Current-Fault Status Output. FAULTB is an open-drain output. FAULTB goes low after a current-
limit fault has exceeded the 2ms (typ) current-limit timeout period (see the
FAULT_
section).
12 GND Ground
13 OUTA Channel A Output-Voltage Sense. Connect to the output.
14
GATE2A
Channel A Current-Limiter Switch Gate-Drive Output. Referenced to OUTA. Connect GATE2A to the gate of
the 2nd n-channel MOSFET. GATE2A is a charge pump with a 50µA pullup current to 5.5V (typ) above
OUTA when active.
15
GATE1A
Channel A ORing Switch Gate-Drive Output. Referenced to SENSEA. Connect GATE1A to the gate of the
1st n-channel MOSFET. GATE1A is a charge pump with a 50µA pullup current to 5.5V (typ) above SENSEA
when active.
16
SENSEA
Channel A Current-Sense Negative Input. Connect current-sense resistor, R
SENSEA
, from INA to SENSEA
(see the Typical Operating Circuit).
