Single-Channel Power Distribution Switch
TJ2110
Function Description
Supply Filtering
A 0.1uF to 1uF bypass capacitor from IN pin to GND pin is recommended to control power supply
transients. Without this bypass capacitor, an output short can cause ringing from supply lead inductance
on the input and damage the internal control circuitry.
Input or output transients must never exceed the absolute maximum supply voltage (VINmax = 6V)
Power Dissipation
The device’s junction temperature depends on several factors such as the load, PCB layout, ambient
temperature, and package type. Equations that can be used to calculate power dissipation of each
channel and junction temperature are found below:
2
PD=RDS(ON)
x
IOUT
Total power dissipation of the device will be the summation of PD for both channels. To relate this to
junction temperature, the following equation can be used:
TJ=PD x θJA +TA
Where:
TJ = Junction temperature
TA = Ambient temperature
θJA= Thermal resistance of the package
Enable/Shutdown
The EN control pin must be driven to a logic high or logic low for a clearly defined signal input. Floating
these control lines may cause unpredictable operation.
Fault Flag
The FLG signal is open-drained output of N-channel MOSFET, the FLG output is pulled low to signal the
following fault conditions: input under voltage, output current limit, and thermal shutdown.
Soft-Start Condition
The TJ2110 has high impedance when off, which gradually shifts to low impedance as the chip turns on.
This prevents an inrush current from causing voltage drops that result from charging a capacitive load and
can pull the USB voltage bus below specified levels. This satisfies the USB voltage droop requirements
for bus-powered applications.
The TJ2110 can provide inrush current limiting for applications with large load capacitances where CL
>10uF.
Current Sense
A sense MOSFET monitors the current supplied to the load. The sense MOSFET measures current more
efficiently than conventional resistance methods. When an overload or short circuit is encountered, the
current-sense circuitry sends a control signal to the driver. The driver in turn reduces the gate-source
voltage and drives the power MOSFET into its saturation region, which switches the output into a
constant-current mode and holds the current constant while varying the voltage on the load.
Over-Current and Short-Circuit Protection
The TJ2110 features an over-current protection circuitry to protect the device against overload conditions.
The current limit threshold is preset internally. It protects the output MOSFET switches from damage due
to undesirable short circuit conditions of excess inrush current often encountered during hot plug-in. The
low limit of the current limit threshold of the TJ2110 allows a minimum current of 1.0A through the
Jun. 2012 – R1.3
- 13 -
HTC
HTC [ HTC KOREA TAEJIN TECHNOLOGY CO. ]
