max5976a Maxim Integrated Products, Inc., max5976a Datasheet - Page 7

• Manufacturer Part Number: max5976a
• Description: 2.7v To 18v, 7a, Hot-swap Solution
• Manufacturer: Maxim Integrated Products, Inc.

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.
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.
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
IN
Enable Logic and
to fully enhance the
X
X
0
1
Charge Pump
MAX5976A
MAX5976B
UVLO
ACTIVE-
ENABLE
HIGH
ON1
and 18V.
OUT
OFF
OFF
OFF
ON
ON1
falls
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.
The devices feature an open-drain, power-good output
that asserts after 16ms (typ), indicating that OUT has
reached (0.9 x V
The devices include a linear regulator that outputs
2.6V at REG. REG provides power to the internal circuit
blocks of the ICs and must not be loaded externally. REG
requires a 1FF capacitor to ground for proper operation.
FAULT is an open-drain output that pulls low when a cur-
rent limit or an overtemperature fault shutdown occurs.
FAULT remains low until the next startup cycle. FAULT is
capable of sinking up to 5mA when asserted.
The devices enter a thermal shutdown mode in the event
of overheating caused by excessive power dissipation
or high ambient temperature. When the junction tem-
perature exceeds T
protection circuitry turns off the internal power MOSFET.
The devices recover from thermal shutdown mode once
the junction temperature drops by 20NC (typ).
IN
) voltage.
J
Fault Status Output (FAULT)
Circuit-Breaker Comparator
= +150NC (typ), the internal thermal
Thermal Protection
Autoretry/Latch-Off
Power-Good Delay
REG
7