MAX1922(2002) View Datasheet(PDF) - Maxim Integrated
Part Name
Description
Manufacturer
MAX1922 Datasheet PDF : 8 Pages
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1A Current-Limited Switch for 2 USB Ports
PIN
1
2, 3
4
5
6, 7, 8
Pin Description
NAME
GND
IN
EN
OC
OUT
FUNCTION
Ground
Input. P-channel MOSFET source—connect all IN pins together and bypass with a 1µF capacitor ground.
Active-Low Switch Enable Input. A logic-low turns on the switch.
Overcurrent-Indicator Output. This open-drain output goes low when the device is in thermal shutdown or
undervoltage lockout, or during a sustained (10ms) current-limit condition.
Switch Output. P-channel MOSFET drain—connect all OUT pins together and bypass with a 0.1µF
capacitor to ground.
IN
OC
N
EN
P
OUT
MAX1922
P
REPLICA
AMPLIFIER
ON
P
ON
10ms
TIMER
HOT
CURRENT-LIMIT
AMPLIFIER
1.24V
GND
CONTROL
CIRCUITRY
Figure 1. Functional Diagram
Detailed Description
The MAX1922 P-channel MOSFET power switch limits
output current to 1.4A min and 2.1A max. When the out-
put current increases beyond the current limit (ILIMIT),
the current also increases through the replica switch
(IOUT / 13000). The current-limit error amplifier com-
pares the voltage to the internal 1.24V reference and
regulates the current back to the ILIMIT (Figure 1).
These switches are not bidirectional; therefore, the
input voltage must be higher than the output voltage.
Continuous Short-Circuit Protection
The MAX1922 is a short-circuit-protected switch. In the
event of an output short-circuit condition, the current
through the switch is foldback-current-limited to 1A
continuous.
Thermal Shutdown
The MAX1922 has a thermal shutdown feature. The
switch turns off and the OC output goes low immediate-
ly (no overcurrent blanking) when the junction tempera-
ture exceeds +165°C. When the MAX1922 cools 20°C,
the switch turns back on. If the fault short-circuit condi-
tion is not removed, the switch will cycle on and off,
resulting in a pulsed output.
OC Indicator
The MAX1922 provides an overcurrent output (OC). A
100kΩ pullup resistor from OC to IN provides a logic
control signal. This open-drain output goes low when
any of the following conditions occur:
• The input voltage is below the 2.4V undervoltage
lockout (UVLO) threshold.
• The die temperature exceeds the thermal shutdown
temperature limit of +165°C.
• The device is in current limit for greater than 10ms.
OC Blanking
The MAX1922 features 10ms overcurrent blanking.
Blanking allows brief current-limit faults, including
momentary short-circuit faults that occur when hot-
swapping a capacitive load, and ensures that no OC is
issued during power-up. When a load transient causes
the device to enter current limit, an internal counter
starts. If the load fault persists beyond the 10ms over-
current blanking timeout, the OC output asserts low.
Ensure that the MAX1922 input is adequately bypassed
to prevent input glitches from triggering spurious OC
outputs. Input voltage glitches less than 150mV will not
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