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TPS2045A Datasheet(PDF) 8 Page - Texas Instruments |
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TPS2045A Datasheet(HTML) 8 Page - Texas Instruments |
8 / 37 page www.ti.com DETAILED DESCRIPTION POWER SWITCH CHARGE PUMP DRIVER ENABLE (ENx, ENx) OVERCURRENT (OCx) CURRENT SENSE THERMAL SENSE UNDERVOLTAGE LOCKOUT TPS2045A ,, TPS2046A TPS2047A, TPS2048A, TPS2055A TPS2056A, TPS2057A, TPS2058A SLVS251C – SEPTEMBER 2000 – REVISED JANUARY 2008 The power switch is an N-channel MOSFET with a maximum on-state resistance of 135 m Ω (VI(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. 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. 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. 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. 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. 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. 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. 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. 8 Submit Documentation Feedback Copyright © 2000–2008, Texas Instruments Incorporated Product Folder Link(s): TPS2045A TPS2046A TPS2047A TPS2048A TPS2055A TPS2056A TPS2057A TPS2058A |
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