TI TPS78918DBVR

The TPS789xx family of low-dropout (LDO) voltage regulators offers the benefits of low-dropout voltage, ultralow-power operation, low-output noise, and miniaturized packaging. These regulators feature low-dropout voltages and ultralow quiescent current compared to conventional LDO regulators. An internal resistor, in conjunction with an external bypass capacitor, creates a low-pass filter to reduce the noise. The TPS78930 exhibits only 56 μν RMS of output voltage noise using 0.01 μF bypass and 10 μF output capacitors. Offered in a 5-terminal small outline integrated-circuit SOT-23 package, the TPS789xx series devices are ideal for micropower operations, low output noise, and where board space is limited.

The usual PNP pass transistor has been replaced by a PMOS pass element. Because the PMOS pass element behaves as a low-value resistor, the dropout voltage is very low, typically 115 mV at 100 mA of load current (TPS78930), and is directly proportional to the load current. The quiescent current is ultralow (17 μA typically) and is stable over the entire range of output load current (0 mA to 100 mA). Intended for use in portable systems such as laptops and cellular phones, the ultralow-dropout voltage feature and ultralow-power operation result in a significant increase in system battery operating life.

The TPS789xx also features a logic-enabled sleep mode to shut down the regulator, reducing quiescent current to 1 μA typical at TJ = 25°C. The TPS789xx is offered in 1.5 V, 1.8 V, 2.5 V, 2.8 V, and 3.0 V.

The TPS789xx uses a PMOS pass element to dramatically reduce both dropout voltage and supply current over more conventional PNP-pass-element LDO designs. The PMOS pass element is a voltage-controlled device and, unlike a PNP transistor, it does not require increased drive current as output current increases. Supply current in the TPS789xx is essentially constant from no load to maximum load.

The TPS789xx family of low-dropout (LDO) regulators have been optimized for use in battery-operated equipment. They feature extremely low dropout voltages, low output noise, low quiescent current (17 μA typically), and enable inputs to reduce supply currents to 1 μA when the regulators are turned off.

The internal voltage reference is a key source of noise in a LDO regulator. The TPS789xx has a BYPASS pin which is connected to the voltage reference through a 150-kΩ internal resistor. The 150-kΩ internal resistor, in conjunction with an external bypass capacitor connected to the BYPASS pin, creates a low pass filter to reduce the voltage reference noise and, therefore, the noise at the regulator output. Note that the output will start up slower as the bypass capacitance increases due to the RC time constant at the bypass pin that is created by the internal 150-kΩ resistor and external capacitor.

Current limiting and thermal protection prevent damage by excessive output current and/or power dissipation. The device switches into a constant-current mode at approximately 350 mA; further load reduces the output voltage instead of increasing the output current. The thermal protection shuts the regulator off if the junction temperature rises above approximately 165°C. Recovery is automatic when the junction temperature drops approximately 25°C below the high temperature trip point. The PMOS pass element includes a back gate diode that conducts reverse current when the input voltage level drops below the output voltage level.

A voltage of 1.7 V or greater on the EN input will disable the TPS789xx internal circuitry, reducing the supply current to 1 μA. A voltage of less than 0.9 V on the EN input will enable the TPS789xx and will enable normal operation to resume. The EN input does not include any deliberate hysteresis, and it exhibits an actual switching threshold of approximately 1.5 V.

• 1 μA Quiescent Current in Standby Mode
• Dropout Voltage Typically 115 mV at 100 mA (TPS78930)
• Over Current Limitation
• -40°C to 125°C Operating Junction Temperature Range
• 5-Pin SOT-23 (DBV) Package