AP2171DSG-13 Diodes Zetex, AP2171DSG-13 Datasheet - Page 10

• Manufacturer Part Number: AP2171DSG-13
• Manufacturer: Diodes Zetex

Specifications of AP2171DSG-13

• Lead Free Status / RoHS Status: Supplier Unconfirmed

Application Note
The AP2161D and AP2171D are integrated high-side
power switches optimized for Universal Serial Bus (USB)
that require protection functions. The power switches are
equipped with a driver that controls the gate voltage and
incorporates slew-rate limitation. This, along with the
various protection features and special functions, makes
these power switches ideal for hot-swap or hot-plug
applications.
Protection Features:
Under-voltage Lockout (UVLO)
Under-voltage lockout function (UVLO) guarantees that
the internal power switch is initially off during start-up.
The UVLO functions only when the switch is enabled.
Even if the switch is enabled, the switch is not turned ON
until the power supply has reached at least 1.9V.
Whenever the input voltage falls below approximately
Note that when the output has been shorted to GND at
extremely low temperature (< -30
electrolytic capacitor on the output pin is recommended. A
correct capacitor type with capacitor voltage rating and
temperature characteristics must be properly chosen so
that capacitance value does not drop too low at the
extremely low temperature operation.
capacitor should have temperature characteristics of less
than 10% variation of capacitance change when operated
at extremely low temp.
electrolytic capacitor type is Panasonic FC series.
Thermal Protection
Thermal protection prevents the IC from damage when
the die temperature exceeds safe margins. This mainly
occurs when heavy-overload or short-circuit faults are
AP2161D/2171D
Document number: DS32250 Rev. 2 - 2
S.NO
1
2
3
Conditions
Short circuit condition at
start-up
Short-circuit or over-
current condition
Gradual increase from
nominal operating current
to I
LIMIT
Our recommended aluminum
o
C), a minimum 120-μF
Explanation
Output is shorted before
input voltage is applied or
before the part is enabled
Short-Circuit or Overload
condition that occurs when
the part is enabled.
Load increases gradually
until the current-limit
threshold.(I
A recommended
TRIG
)
1A SINGLE CHANNEL CURRENT-LIMITED POWER
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1.9V, the power switch is turned off. This facilitates the
design of hot-insertion systems where it is not possible to
turn off the power switch before input power is removed.
Over-current and Short Circuit Protection
An internal sensing FET is employed to check for over-
current conditions. Unlike current-sense resistors, sense
FETs do not increase the series resistance of the current
path. When an over-current condition is detected, the
device maintains a constant output current and reduces
the output voltage accordingly. Complete shutdown
occurs only if the fault stays long enough to activate
thermal limiting.
The different overload conditions and the corresponding
response of the AP2161D/2171D are outlined below:
present
AP2161D/AP2171D implements thermal sensing to
monitor the operating junction temperature of the power
distribution switch. Once the die temperature rises to
approximately 140°C, the Thermal protection feature gets
activated as follows: The internal thermal sense circuitry
turns the power switch off and the FLG output is asserted
thus preventing the power switch from damage.
Hysteresis in the thermal sense circuit allows the device
to cool down to approximately 25°C before the output is
turned back on. The built-in thermal hysteresis feature
avoids undesirable oscillations of the thermal protection
circuit. The switch continues to cycle in this manner until
the load fault is removed, resulting in a pulsed output.
The FLG open-drain output is asserted when an over-
current occurs with 7-ms deglitch.
Behavior of the AP2161D/2171D
The IC senses the short circuit and immediately
clamps output current to a certain safe level namely
I
The current rises until I
threshold has been reached, the device switches into
its current limiting mode and is set at I
• At the instance the overload occurs, higher current
• After the current limit function has tripped (reached
LIMIT.
may flow for a very short period of time before the
current limit function can react.
the
switches into current limiting mode and the current
is clamped at I
SWITCH WITH OUTPUT DISCHARGE
over-current
for
AP2161D/AP2171D
extended
LIMIT
.
trip
TRIG
periods
or thermal limit. Once the
threshold),
LIMIT
of
© Diodes Incorporated
September 2010
the
.
time.
device
The