DC1506A Linear Technology, DC1506A Datasheet - Page 6

• Manufacturer Part Number: DC1506A
• Description: LTC4361-1/LTC4361-2 Overvoltage/Overcurrent Protection Controller With Latchoff/Auto-Retry
• Manufacturer: Linear Technology
• Series: -r

Specifications of DC1506A

• Design Resources: DC1506 Design Files DC1506A Schematic
• Main Purpose: Overvoltage/Overcurrent Protection
• Embedded: No
• Utilized Ic / Part: LTC4361
• Primary Attributes: -
• Secondary Attributes: -
• Kit Application Type: Power Management
• Application Sub Type: Overvoltage Protection
• Features: Demonstrates Three Protection Schemes Selected At JP1, Provides Connection For USB Protection
• Lead Free Status / Rohs Status: Not applicable / Not applicable

LTC4361-1/LTC4361-2
OPERATION
Mobile devices like cell phones and MP3/MP4 players have
highly integrated subsystems fabricated from deep submi-
cron CMOS processes. The small form factor is accompanied
by low absolute maximum voltage ratings. The sensitive
electronics are susceptible to damage from transient or DC
overvoltage conditions from the power supply.
Failures or faults in the power adaptor can cause an over-
voltage event. So can hot-plugging an AC adaptor into the
power input of the mobile device (see LTC Application Note
88). Today’s mobile devices derive their power supply or
recharge their internal batteries from multiple alternative
inputs like AC wall adaptors, car battery adaptors and USB
ports. A user may unknowingly plug in the wrong adaptor,
damaging the device with a high or even a negative power
supply voltage.
The LTC4361 protects low voltage electronics from these
overvoltage conditions by controlling a low cost external
N-channel MOSFET confi gured as a pass transistor. At
power-up (V
overvoltage condition causes the delay cycle to continue
until a safe voltage is present. When the delay cycle
completes, an internal high side switch driver slowly
ramps up the MOSFET gate, powering up the output at
a controlled rate and limiting the inrush current to the
output capacitor.
6
IN
> 2.1V), a start-up delay cycle begins. Any
If the voltage at the IN pin exceeds 5.8V (V
GATE is pulled low quickly to protect the load. The
incoming power supply must remain below 5.7V
(V
restart the GATE ramp-up.
A sense resistor placed between IN and SENSE implements
an overcurrent protection with a 50mV trip threshold and
a 10μs glitch fi lter. After an overcurrent, the LTC4361-1
latches off while the LTC4361-2 restarts following a 130ms
delay.
The LTC4361 has a CMOS compatible ON input. When
driven low, the part is enabled. When driven high, the
external N-channel MOSFET is turned off and the supply
current of the LTC4361 drops to 1.5μA. The PWRGD pull-
down releases during this low current sleep mode, UVLO,
overvoltage or overcurrent and the subsequent 130ms
start-up delay. After the start-up delay, GATE starts its
slow ramp-up and ramps higher than V
a 65ms delay cycle. When that completes, PWRGD pulls
low.The LTC4361 has a GATEP pin that drives an optional
external P-channel MOSFET to provide protection against
negative voltages at IN.
IN(OV)
– ∆V
OV
) for the duration of the start-up delay to
GATE(TH)
to trigger
IN(OV)
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),