Texas Instruments TPS7B4258QDDARQ1

The TPS7B4258-Q1 is a monolithic, integrated, low-dropout (LDO) voltage tracker. The device is available in an 8-pin HSOIC package. The TPS7B4258-Q1 is designed to reliably provide power to off-board sensors via wire harness, even in harsh automotive environments. In such severe operating conditions, the cables in the harness are potentially exposed to various fault conditions, increasing risk of failure. Such conditions include short to ground, short to battery, and overtemperature. The TPS7B4258-Q1 comes with integrated protection features against each of these fault conditions, as well as protection against reverse polarity. The device incorporates a topology containing two back-to-back P-channel metal-oxide semiconductor field-effect transistors (MOSFETs). This PMOS topology eliminates the need for an external diode that is otherwise required to prevent the flow of reverse current. The high 150mA current rating of the device potentially allows a single tracker to power multiple off-board sensors simultaneously. The device is designed to handle a 45V (absolute maximum) input voltage and survive the automotive load dump transient conditions.

The TPS7B4258-Q1 provides a protective buffer for the ADC and MCU against fault conditions, while securely transferring power to the off-board sensors. A reference voltage applied at the adjustable input pin (ADJ/EN) is tracked with a very tight 6mV (max) tolerance at the FB pin. This tolerance holds true for all variations across the specified line, load, and temperature values. For ratiometric sensors whose output is sampled by the ADC, this tight tracking tolerance is particularly benficial. This tolerance makes sure that the error between the ADC full-scale reference and the sensor power supply voltage is minimal. The ratiometricity of the sensor measurement is thereby maintained.

Output voltage becomes equal to the voltage at the ADJ/EN pin (± the tracking tolerance) by tying the FB pin directly to the OUT pin. If the ADC full-scale reference voltage equals the sensor supply voltage, connect the reference voltage directly to the ADJ/EN pin. If the sensor supply is lower than the reference, use a resistive divider at the ADJ/EN pin. This divider helps scale down the reference voltage to match the sensor supply voltage. If the sensor supply is higher than the reference, use a resistive divider between the FB and OUT pins. This divider helps scale up the ADC full-scale reference voltage and match the sensor supply voltage.

By setting the ADJ/EN input pin low, the TPS7B4258-Q1 switches to standby mode. In this mode, the quiescent current consumption of the LDO reduces to less than 3.8µA.