The MAX5923 is a fully integrated Simple Swapper™
hot-swap switch for positive supply rails. The device
allows the safe insertion and removal of circuit cards
into live backplanes or ports without causing glitches
on the power-supply rail. The device also monitors various
circuit parameters and disconnects the load if a
fault condition occurs, alerting the host with a logiclevel
FAULT-bar output. The MAX5923 operates over the
+16V to +60V input voltage range.
During startup, an integrated 0.45Ω power MOSFET
regulates the current and voltage between the backplane
power source and the load. After startup, the
MOSFET is fully enhanced to reduce its on-resistance.
To ensure robust operation, the MAX5923 contains
built-in safety features that monitor fault conditions and
prevent damage to the internal MOSFET.
The MAX5923 monitors three parameters for fault conditions:
zero current, overcurrent, and thermal overload.
The output overcurrent limit counts the time the MAX5923
spends in an overcurrent condition and shuts down the
pass transistor if the current limit is exceeded for the overcurrent
time limit. The zero-current detection counts the
time the output current is below the zero-current threshold
and shuts down the pass transistor if the counter reaches
the zero-current time limit. The thermal monitoring feature
shuts down the pass transistor if the die temperature
reaches the overtemperature limit. A fault logic output
indicates when an overtemperature or an overcurrent
condition has occurred and a zero-current logic output
indicates if there is a zero-current condition.
An undervoltage detection circuitry keeps the pass transistor
off until the input voltage is above the undervoltage
lockout (UVLO) threshold, which is internally set or can be
set externally with a resistive divider. A power-OK (POK)
output is provided to signal when the output voltage has
reached to within 0.75V of the input voltage. An Enable
input allows the host system to disconnect the system
from the load and/or reset a fault condition by toggling
Enable.
The MAX5923 is available in a 20-pin TSSOP package
and operates in the extended -40°C to +85°C temperature
range.
Applications
- Current Limiter
- Industrial Equipment
- Network Routers and Switches
- Servers
