ap2141d Diodes, Inc., ap2141d Datasheet - Page 10

• Manufacturer Part Number: ap2141d
• Description: 0.5a Single Channel Current-limited Power Switch With Output Discharge
• Manufacturer: Diodes, Inc.

Application Note
The AP2141D and AP2151D are integrated high-side power switches optimized for Universal Serial Bus (USB)
that requires 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 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 overcurrent 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 AP2141D/2151D are outlined below:
Note that when the output has been shorted to GND at extremely low temperature (< -20
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. A recommended capacitor should have temperature characteristics of less
than 10% variation of capacitance change when operated at extremely low temp. Our recommended aluminum
electrolytic capacitor type is Panasonic FC series.
AP2141D/2151D
Document number: DS32242 Rev. 1 - 2
S.NO
1
2
3
Conditions
Short circuit condition
at start-up
Short-circuit or
Overcurrent condition
Gradual increase from
nominal operating
current to I
LIMIT
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
TRIG
0.5A SINGLE CHANNEL CURRENT-LIMITED POWER
)
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Behavior of the AP2141D/2151D
The IC senses the short circuit and immediately
clamps output current to a certain safe level
namely I
The current rises until I
Once the threshold has been reached, the
device switches into its current limiting mode
and is set at I
• At the instance the overload occurs, higher
• After the current limit function has tripped
current may flow for a very short period of
time before the current limit function can
react.
(reached the over-current trip threshold), the
device switches into current limiting mode
and the current is clamped at I
SWITCH WITH OUTPUT DISCHARGE
LIMIT.
AP2141D/AP2151D
LIMIT
.
TRIG
o
C), a minimum 120-μF
or thermal limit.
LIMIT
© Diodes Incorporated
.
June 2010