MAX1838EEE+ Maxim Integrated Products, MAX1838EEE+ Datasheet - Page 10

• Manufacturer Part Number: MAX1838EEE+
• Description: IC SW USB DUAL W/FB 16-QSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX1838EEE+

• Applications: USB, Peripherals
• Voltage - Supply: 4 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -

between IN and AUX. However, a fault does not trigger
since the fault blanking-time is longer than the supply
switchover time.
AUX provides the power for the MAX1838 internal con-
trol circuitry. Limit the input-voltage slew rate to less
than 0.2V/µs to prevent erroneous FAULT indications.
To limit the input voltage drop during momentary output
short-circuit conditions, connect a capacitor from both
AUX and IN to ground. A 0.1µF ceramic capacitor is
required for local decoupling; however, higher capaci-
tor values will further reduce the voltage drop at the
input (Figure 2). When driving inductive loads, a larger
capacitance prevents voltage spikes from exceeding
the MAX1838’s absolute maximum ratings.
Dual USB Switch with Fault Blanking
and Autoreset
10
Table 2. MAX1838 Current Limiting and Fault Behavior
If a short circuit is present
(V
If an overload current is present
(V
If thermal fault condition is present
OUT
OUT
______________________________________________________________________________________
< 1V)
> 1V)
CONDITION
Applications Information
Input Power Source
Input Capacitor
• If a short circuit is detected at the output, the channel turns off, the blanking timer
• If the short circuit persists during the fault-blanking period, the output pulses at 0.35A
• If the short circuit persists after the fault-blanking period, FAULT goes low, autoreset
• Output current regulates at I
• Continuous current at I
• If overcurrent is still present at 20ms, FAULT goes low, autoreset mode is enabled, and
• FAULT immediately goes low (the blanking timer does not apply to thermal faults), and
begins, and FAULT stays high.
RMS
the next ramped current pulse soft-starts the output. The FAULT flag stays high.
mode is enabled, and the output sources 25mA. If the voltage on that output is above
0.5V for 20ms, the channel resets, the output turns on, and FAULT goes high (see
Short-Circuit Response in the Typical Operating Characteristics.)
or the 20ms continuous current-limit timeout period is reached.
the output sources 25mA. If the voltage on that output is above 0.5V for 20ms, the
channel resets, the output turns on, and FAULT goes high.
the channel turns off. When the junction cools by 15
removed, autoreset mode is enabled, the output sources 25mA, and FAULT remains
low. If the voltage on that output is above 0.5V for 20ms, the channel resets, the output
turns on, and FAULT goes high.
. When the short is removed before the 15ms short-circuit blanking timeout period,
LIM
An output capacitor helps prevent parasitic inductance
from pulling OUT negative during turn-off. When start-
ing up into very large capacitive loads, the switch puls-
es the output current at 0.35A
voltage rises above 1V, then the capacitor continues to
charge at the full 0.9A current limit. There is no limit to
the size of output capacitor, but to prevent a startup
fault assertion, the capacitor must charge up within the
fault-blanking delay period. Typically starting up into a
330µF or smaller capacitor does not trigger a fault out-
put. In addition to bulk capacitance, small value (0.1µF
or greater) ceramic capacitors improve the output’s
resilience to electrostatic discharge (ESD).
A wide variety of devices (mice, keyboards, cameras,
and printers) can load the USB port. These devices
commonly connect to the port with cables, which can
add an inductive component to the load. This induc-
tance causes the output voltage at the USB port to ring
persists until the overload is removed, a thermal fault occurs,
LIM
MAX1838 BEHAVIOR
, the blanking timer turns on, and FAULT stays high.
o
C, the thermal fault condition is
Driving Inductive Loads
Output Capacitor
RMS
until the output
-