![](http://datasheet.mmic.net.cn/370000/TPS2045P_datasheet_16739722/TPS2045P_3.png)
TPS2045, TPS2055
CURRENT-LIMITED POWER-DISTRIBUTION SWITCHES
SLVS182 – APRIL 1999
3
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
detailed description
power switch
The power switch is an N-channel MOSFET with a maximum on-state resistance of 135 m
(V
I(IN)
= 5 V).
Configured as a high-side switch, the power switch prevents current flow from OUT to IN and IN to OUT when
disabled. The power switch can supply a minimum of 250 mA per switch.
charge pump
An internal charge pump supplies power to the driver circuit and provides the necessary voltage to pull the gate
of the MOSFET above the source. The charge pump operates from input voltages as low as 2.7 V and requires
very little supply current.
driver
The driver controls the gate voltage of the power switch. To limit large current surges and reduce the associated
electromagnetic interference (EMI) produced, the driver incorporates circuitry that controls the rise times and
fall times of the output voltage. The rise and fall times are typically in the 2-ms to 4-ms range.
enable (EN or EN)
The logic enable disables the power switch and the bias for the charge pump, driver, and other circuitry to reduce
the supply current to less than 10
μ
A when a logic high is present on EN (TPS2045) or a logic low is present
on EN (TPS2055). A logic zero input on EN or a logic high on EN restores bias to the drive and control circuits
and turns the power on. The enable input is compatible with both TTL and CMOS logic levels.
overcurrent (OC)
The OC open-drain output is asserted (active low) when an overcurrent or overtemperature condition is
encountered. The output will remain asserted until the overcurrent or overtemperature condition is removed.
current sense
A sense FET monitors the current supplied to the load. The sense FET 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 voltage and drives the power FET 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.
thermal sense
An internal thermal-sense circuit shuts off the power switch when the junction temperature rises to
approximately 140
°
C. Hysteresis is built into the thermal sense circuit. After the device has cooled
approximately 20
°
C, the switch turns back on. The switch continues to cycle off and on until the fault is removed.
undervoltage lockout
A voltage sense circuit monitors the input voltage. When the input voltage is below approximately 2 V, a control
signal turns off the power switch.