MAX8664 Maxim Integrated Products, MAX8664 Datasheet - Page 10

• Manufacturer Part Number: MAX8664
• Description: Step-Down Controller
• Manufacturer: Maxim Integrated Products

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The threshold that trips overcurrent protection is set by a
resistor connected from ILIM_ to the drain of the high-
side MOSFET(s). ILIM_ sinks 50µA (typ) through this
resistor. When the drain-source voltage exceeds the volt-
age drop across this resistor during the high-side
MOSFET(s) on-time, an overcurrent fault is triggered. To
prevent glitches from falsely tripping the overcurrent pro-
tection, connect a filter capacitor (0.01µF typically) in
parallel with the overcurrent-setting resistor.
During an overvoltage event on one or both of its out-
puts, the MAX8664 latches off the controller. This
occurs when the feedback voltage exceeds its normal
regulation voltage by 150mV for 10µs. In this state, the
low-side MOSFET(s) are on and the high-side MOS-
FET(s) are off to discharge the output. To clear the
latch, cycle EN or the input power.
Thermal-overload protection limits total power dissipa-
tion in the MAX8664. When the junction temperature
exceeds +160°C, an internal thermal sensor shuts down
the device, pulling DH_ and DL_ low for both controllers.
To restart the controller, cycle EN or input power.
Table 1. Fault Shutdown Modes for Circuits of Figures 2–5
Low-Cost, Dual-Output, Step-Down
Controller with Fast Transient Response
10
Figure 2,
Figure 5
(Independent)
Figure 3
(Tracking)
Figure 4
(Sequenced)
CIRCUIT
______________________________________________________________________________________
Output Overvoltage Protection (OVP)
Controller 2 remains on.
PWRGD is pulled low.
Controller 2 shuts down.
PWRGD is pulled low.
Controller 2 shuts down.
PWRGD is pulled low.
Thermal-Overload Protection
CONTROLLER 1 FAULT
MAX8664A (INDEPENDENT)
Controller 1 remains on.
PWRGD remains high.
Controller 1 remains on.
PWRGD remains high.
Controller 1 remains on.
PWRGD remains high.
CONTROLLER 2 FAULT
PWRGD is an open-drain output that is pulled low when
the output voltage rises above the PWRGD upper
threshold or falls below the PWRGD falling threshold.
PWRGD is held low in shutdown, when V
UVLO threshold, during soft-start, and during fault con-
ditions. PWRGD does not reflect the status of controller
2 in the MAX8664A, or when REFIN2 is connected to an
external reference with either version. See Table 1 for
PWRGD operation of the circuits of Figures 2–5 during
fault conditions. For logic-level output voltages, con-
nect an external pullup resistor between PWRGD and
the logic power supply. A 100kΩ resistor works well in
most applications.
When an overvoltage or overcurrent fault occurs on one
controller of the MAX8664A, the second controller con-
tinues to operate. With the MAX8664B, a fault in one
controller latches off both controllers automatically, and
PWRGD is pulled low. See Table 1 for the fault-shut-
down modes of the circuits shown in Figures 2–5.
Controller 2 is shut down.
PWRGD is pulled low.
Controller 2 is shut down.
PWRGD is pulled low.
Controller 2 is shut down.
PWRGD is pulled low.
CONTROLLER 1 FAULT
Power-Good Output (PWRGD)
MAX8664B (JOINT)
Fault-Shutdown Modes
Controller 1 is shut down.
PWRGD is pulled low.
Controller 1 is shut down.
PWRGD is pulled low.
Controller 1 is shut down.
PWRGD is pulled low.
CONTROLLER 2 FAULT
CC
is below the