19-2946; Rev 1; 2/06
-48V Hot-Swap Controllers with External
RSENSE and High Gate Pulldown Current
The MAX5921/MAX5939 hot-swap controllers allow a cir-
cuit card to be safely hot plugged into a live backplane.
The MAX5921/MAX5939 operate from -20V to -80V and
are well suited for -48V power systems. These devices
are pin compatible with both the LT1640 and LT4250 and
provide improved features over these devices.
The MAX5921/MAX5939 provide a controlled turn-on to
circuit cards preventing damage to board connectors,
board components, and preventing glitches on the
power-supply rail. The MAX5921/MAX5939 provide
undervoltage, overvoltage, and overcurrent protection.
These devices ensure that the input voltage is stable
and within tolerance before applying power to the load.
Both the MAX5921 and MAX5939 protect a system
against overcurrent and short-circuit conditions by turn-
ing off the external MOSFET in the event of a fault con-
dition. The MAX5921/MAX5939 protect against input
voltage steps by limiting the load current to a safe level
without turning off power to the load.
The device features an open-drain power-good status
output, PWRGD or PWRGD for enabling downstream
converters (see Selector Guide). A built-in thermal shut-
down feature is also included to protect the external
MOSFET in case of overheating. The MAX5939 features
a latched fault output. The MAX5921 contains built-in
autoretry circuitry after a fault condition.
The MAX5921/MAX5939 are available in an 8-pin SO
package and operate in the extended -40°C to +85°C
Telecom Line Cards
Central-Office Line Cards
Server Line Cards
Base-Station Line Cards
♦ Allows Safe Board Insertion and Removal
from a Live -48V Backplane
♦ Pin-Compatible with LT1640 and LT4250
♦ Circuit Breaker Immunity to Input Voltage Steps
and Current Spikes
♦ 450mA GATE Pulldown Current During Short-
♦ Exponential GATE Pulldown Current
♦ Withstands -100V Input Transients with No
♦ Programmable Inrush and Short-Circuit Current
♦ Operates from -20V to -80V
♦ Programmable Overvoltage Protection
♦ Programmable Undervoltage Lockout
with Built-In Glitch Filter
♦ Overcurrent Fault Integrator
♦ Powers Up into a Shorted Load
♦ Power-Good Control Output
♦ Thermal Shutdown Protects External MOSFET
-40°C to +85°C
-40°C to +85°C
Ordering Information continued at end of data sheet.
Typical Operating Circuit and Selector Guide appear at end
of data sheet.
() FOR MAX5921B/F AND MAX5939B/F.
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.