TPS2047A_14 Datasheet, PDF (8/38 Pages) Texas Instruments – CURRENT-LIMITED POWER-DISTRIBUTION SWITCHES

TPS2045A, TPS2046A
TPS2047A, TPS2048A, TPS2055A
TPS2056A, TPS2057A, TPS2058A
SLVS251C – SEPTEMBER 2000 – REVISED JANUARY 2008
DETAILED DESCRIPTION
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POWER SWITCH
The power switch is an N-channel MOSFET with a maximum on-state resistance of 135 mΩ (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 supplies 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 (ENx, ENx)
The logic enable disables the power switch and the bias for the charge pump, driver, and other circuitry to reduce
the supply current. The supply current is reduced to less than 10 µA on the single and dual devices (20 µA on
the triple and quad devices) when a logic high is present on ENx (TPS204xA ¹) or a logic low is present on ENx
(TPS205xA¹). A logic zero input on ENx or a logic high on ENx 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 (OCx)
The OCx open-drain output is asserted (active low) when an overcurrent or over temperature condition is
encountered. The output will remain asserted until the overcurrent or over temperature 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
The TPS204xA and TPS205xA implement a dual-threshold thermal trip to allow fully independent operation of
the power distribution switches. In an overcurrent or short-circuit condition the junction temperature rises. When
the die temperature rises to approximately 140°C, the internal thermal sense circuitry checks to determine which
power switch is in an overcurrent condition and turns off that switch, thus isolating the fault without interrupting
operation of the adjacent power switch. Hysteresis is built into the thermal sense, and after the device has cooled
approximately 20 degrees, the switch turns back on. The switch continues to cycle off and on until the fault is
removed. The (OCx) open-drain output is asserted (active low) when over temperature or overcurrent occurs.
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.
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