MAX1922 Maxim, MAX1922 Datasheet - Page 6

• Manufacturer Part Number: MAX1922
• Description: The MAX1922 current-limited 70mΩ switch with built-in fault blanking provides an accurate, preset 1
• Manufacturer: Maxim

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 (I
the current also increases through the replica switch
(I
pares the voltage to the internal 1.24V reference and
regulates the current back to the I
These switches are not bidirectional; therefore, the
input voltage must be higher than the output voltage.
1A Current-Limited Switch for 2 USB Ports
Figure 1. Functional Diagram
6
OUT
OC
TDFN
1, 3, 9
EN
IN
8, 10
2, 4,
PACKAGE
—
_______________________________________________________________________________________
6
5
7
/ 13000). The current-limit error amplifier com-
N
6, 7,
2, 3
SO
—
1
4
5
8
NAME
GND
OUT
OC
EN
EP
IN
CIRCUITRY
CONTROL
P
P
10ms
TIMER
Detailed Description
REPLICA
AMPLIFIER
Ground
Inp ut. p - channel M O S FE T sour ce— connect al l IN p i ns tog ether and b yp ass w i th a 1µF cap aci tor g r ound .
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.
TDFN Only. Exposed paddle. Connect to the GND plane for optimum thermal dissipation. This does not
remove the requirement for a proper ground.
HOT
ON
ON
CURRENT-LIMIT
AMPLIFIER
LIMIT
1.24V
MAX1922
(Figure 1).
P
LIMIT
GND
OUT
),
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.
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 cycles on and off, result-
ing in a pulsed output.
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
• The die temperature exceeds the thermal shutdown
• The device is in current limit for greater than 10ms.
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
lockout (UVLO) threshold.
temperature limit of +165°C.
FUNCTION
Continuous Short-Circuit Protection
Pin Description
Thermal Shutdown
OC Indicator
OC Blanking