19-2946; Rev 0; 9/03
-48V Hot-Swap Controllers with External
and High Gate Pulldown Current
R
SENSE
General Description
Features
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.
ꢀ 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
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.
ꢀ 450mA GATE Pulldown Current During Short-
Circuit Condition
ꢀ Exponential GATE Pulldown Current
ꢀ Withstands -100V Input Transients with No
External Components
ꢀ Programmable Inrush and Short-Circuit Current
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.
Limits
ꢀ Operates from -20V to -80V
ꢀ Programmable Overvoltage Protection
ꢀ Programmable Undervoltage Lockout
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.
with Built-In Glitch Filter
ꢀ Overcurrent Fault Integrator
ꢀ Powers Up into a Shorted Load
ꢀ Power-Good Control Output
ꢀ Thermal Shutdown Protects External MOSFET
The MAX5921/MAX5939 are available in an 8-pin SO
package and operate in the extended -40°C to +85°C
temperature range.
Ordering Information
PART
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
8 SO
Applications
MAX5921AESA
MAX5921BESA
Telecom Line Cards
8 SO
Network Switches/Routers
Central-Office Line Cards
Server Line Cards
Ordering Information continued at end of data sheet.
Pin Configuration
Base-Station Line Cards
TOP VIEW
PWRGD
1
2
3
4
8
7
6
5
V
DD
(PWRGD)
OV
DRAIN
GATE
Typical Operating Circuit and Selector Guide appear at end
of data sheet.
MAX5921
MAX5939
UV
V
SENSE
EE
SO
() 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.