MAX5976BETE+ Maxim Integrated Products, MAX5976BETE+ Datasheet - Page 7

• Manufacturer Part Number: MAX5976BETE+
• Description: Hot Swap & Power Distribution 2.7-18V Hot-Swap Controller
• Manufacturer: Maxim Integrated Products

Specifications of MAX5976BETE+

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

The MAX5976A/MAX5976B enable the output as shown
in Table 1. The ICs turn on the output only when V
is high (V
low. The devices turn off the output when V
below 1.21V - V
above V
provides the flexibility to set the undervoltage lockout
threshold to any desired level between V
See Figure 1 and Setting the Undervoltage Threshold in
the Applications Information section.
Once the MAX5976A/MAX5976B output is enabled, the
device provides controlled application of power to a load.
The voltage at OUT will begin to rise at approximately
18kV/s until the programmed circuit-breaker current level
is reached, at which time the MAX5976A/MAX5976B will
actively limit inrush current at the circuit-breaker setting.
Table 1. Output Enable Truth Table
X = Don’t care.
V
Figure 1. Undervoltage Threshold Setting
ON1_TH
V
ANALOG INPUT
V
ON1
ON1
PRECISION
- V
V
< (V
ON_HYS
IN
> V
ON1
PRESDET
IH
= 1.21V (typ).
X
X
R1
R2
ON1
. A resistive divider from IN to ON1 and ground
ON1_TH
ON1
ON2
ON1_TH
)
Undervoltage Lockout Threshold
> 1.21V) while ON2 and PRESDET are
HYS
or whenever ON2 or PRESDET are
Detailed Description
ON2
1.21V
LOGIC INPUTS
X
X
0
1
2.7V to 18V, 7A, Hot-Swap Solution
PRESDET
Enable Logic and
X
X
0
1
MAX5976A
MAX5976B
UVLO
ACTIVE-
ENABLE
HIGH
Startup
ON1
and 18V.
OUT
OFF
OFF
OFF
ON
ON1
falls
Because of this, the inrush current can be easily pro-
grammed by appropriate selection of R
mode of operation will continue for up to 16ms; after the
startup time elapses, the output will either have risen to
the IN potential, or if the device is still in current limit, it
will shut down and assert the FAULT output low.
The resulting dV
mined according to the following equation:
In this equation, I
device during the output ramp time that does not charge
C
This ensures that the output capacitance can be fully
charged before the 16ms startup timer elapses.
An open-drain power-good output goes high-impedance
16ms (typ) after the output has risen to more than 90% of
the input voltage to indicate a successful startup.
An integrated charge pump provides the gate-drive volt-
age for the internal power MOSFET. The charge pump
generates +5V potential above V
internal power MOSFET.
The current through the internal power MOSFET is com-
pared to a circuit-breaker threshold. An external resistor
between CB and ground sets this threshold.
The circuit-breaker comparator is designed so that the
load current can exceed the threshold for some amount
of time before tripping. The time delay varies inversely
with the overdrive above the threshold. The greater the
overcurrent condition, the faster the response time allow-
ing the devices to tolerate load transients and noise near
the circuit-breaker threshold.
The ICs also feature catastrophic short-circuit protec-
tion. During normal operation, if OUT is shorted directly
to ground, a fast protection circuit forces the gate of the
internal MOSFET to discharge quickly and disconnect
the output from the input.
During a fault condition, the devices turn off the inter-
nal MOSFET disconnecting the output from the input.
The MAX5976A enters an autoretry mode with a fixed
250ms lockout time before reconnect can occur. The
MAX5676B latches off and remains off until the enable
logic is cycled off and on.
OUT
. Make certain that R
V
dV
IN
OUT
x C
OUT
LOAD
OUT
/dt ≈ (I
Circuit-Breaker Comparator
/dt during startup can be deter-
/(I
is any current drawn by a load
CB
CB
CB
- I
- I
is chosen such that:
LOAD
LOAD
Autoretry/Latch-Off
IN
) < 16ms
to fully enhance the
)/C
Charge Pump
OUT
CB.
This startup
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