MAX5920AESA Maxim Integrated Products, MAX5920AESA Datasheet - Page 10

• Manufacturer Part Number: MAX5920AESA
• Description: Hot Swap & Power Distribution
• Manufacturer: Maxim Integrated Products

Specifications of MAX5920AESA

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

If the voltage between V
rent-limit trip voltage (V
the GATE pin and regulates the current through the
external MOSFET so V
drawn by the load drops below V
GATE pin voltage rises again. However, if the load cur-
rent is at the regulation limit of V
of t
the MAX5920A/MAX5920B to turn off the external MOS-
FET.
After an overcurrent fault condition, the circuit breaker
is reset by pulling the UV pin low and then pulling UV
high or by cycling power to the MAX5920A/MAX5920B.
Unless power is cycled to the MAX5920A/MAX5920B,
the device waits until t
on the gate of the external FET.
The MAX5920_ feature an overcurrent fault integrator.
When an overcurrent condition exists, an internal digital
counter increments its count. When the counter reaches
500µs (the maximum current-limit duration) for the
MAX5920_, an overcurrent fault is generated. If the
overcurrent fault does not last 500µs, then the counter
begins decrementing at a rate 128 (maximum current-
limit duty cycle) times slower than the counter was
incrementing. Repeated overcurrent conditions will gen-
erate a fault if duty cycle of the overcurrent condition is
greater than 1/128.
The MAX5920A/MAX5920B accomplish load-current
regulation by pulling current from the GATE pin when-
ever V
Characteristics). This decreases the gate-to-source
-48V Hot-Swap Controller
with External R
Figure 6b. Input Inrush Current
10
PHLCL
______________________________________________________________________________________
SENSE
, the electronic circuit breaker trips, causing
CONTACT
BOUNCE
- V
EE
Overcurrent Fault Integrator
4ms/div
> V
SENSE
OFF
EE
CL
Load-Current Regulation
CL
), the MAX5920_ pulls down
and SENSE reaches the cur-
has elapsed before turning
- V
(see Typical Operating
CL
EE
CL
/ R
< V
/ R
SENSE
SENSE
CL
SENSE
INRUSH
CURRENT
1A/div
GATE - V
10V/div
DRAIN
50V/div
V
50V/div
EE
. If the current
for a period
EE
limit, the
voltage of the external MOSFET, thereby reducing the
load current. When V
MAX5920A/MAX5920B pull the GATE pin high by a
45µA (I
In the event of a permanent short-circuit condition, the
MAX5920A/MAX5920B limit the current drawn by the
load to V
the circuit breaker trips. Once the circuit breaker trips,
the GATE of the external FET is pulled low by 50mA
(I
The MAX5920A/MAX5920B guard against input voltage
steps on the input supply. A rapid increase in the input
supply voltage (V
step equal to I = C
voltage slew rate (∆V
V
MAX5920A/MAX5920B current limit activates, pulling
down the gate voltage and limiting the load current to
V
a slower rate than the input voltage. As the drain voltage
starts to slew down, the drain-to-gate feedback capacitor
C2 pushes back on the gate, reducing the gate-to-
source voltage (V
nal MOSFET. Once the input supply reaches its final
value, the DRAIN slew rate (and therefore the inrush cur-
rent) is limited by the capacitor C2 just as it is limited in
the startup condition. To ensure correct operation,
R
than the sum of the load current and the dynamic current
into the load capacitance in the slewing mode.
If the load current plus the capacitive charging current is
below the current limit, the circuit breaker does not trip.
Figure 7a. Startup Into a Short Circuit
PD
CL
SENSE
CL
) turning off power to the load.
/ R
/ R
SENSE
PU
must be chosen to provide a current limit larger
SENSE
CL
) current.
/ R
. The DRAIN voltage (V
Immunity to Input Voltage Steps
SENSE
during an input voltage step, the
DD
GS
L
CONTACT
BOUNCE
x ∆V
) and the current through the exter-
Driving into a Shorted Load
IN
- V
4ms/div
for a period of t
/ ∆T). If the load current exceeds
EE
IN
SENSE
increasing) causes a current
/ ∆T, proportional to the input
- V
DRAIN
PHLCL
EE
INRUSH
CURRENT
2A/div
GATE - V
4V/div
V
50V/div
EE
) then slews at
< V
, after which
EE
CL
, the