FEATURES

Output Current: 1.5A

Dropout Voltage: 310mV

Precision Current Limit with Foldback

Low Output Noise: 60µVRMS (10Hz to 100kHz)

Low Quiescent Current: 1.1mA

Precision Positive or Negative Shutdown Logic

Fast Transient Response

Wide Input Voltage Range: –1.8V to –30V

Adjustable Output Voltage Range: –1.22V to –29.3V

Fixed Output Voltages: –2.5V, –3V, –3.3V, –5V, –12V, –15V

Controlled Quiescent Current in Dropout

<1µA Quiescent Current in Shutdown

Stable with 10µF Output Capacitor

Stable with Ceramic, Tantalum or Aluminum Capacitors

Thermal Limit with Hysteresis

Reverse Output Protection

5-Lead TO-220 and DD-Pak, Thermally Enhanced 12-Lead MSOP and 8-Lead 3mm × 3mm × 75mm DFN Packages

 

APPLICATIONS

Post-Regulator for Switching Supplies

Negative Logic Supplies

Low Noise Instrumentation

Industrial Supplies

Negative Complement to the LT1963A

 

DESCRIPTION

The LT®3015 series are low noise, low dropout, negative linear regulators with fast transient response. The devices supply up to 1.5A of output current at a typical dropout voltage of 310mV. Operating quiescent current is typically 1.1mA and drops to < 1µA in shutdown. Quiescent current is also well controlled in dropout. In addition to fast transient response, the LT3015 series exhibit very low output noise, making them ideal for noise sensitive applications.

The LT3015 regulators are stable with a minimum 10µF output capacitor. Moreover, the regulator can use small ceramic capacitors without the necessary addition of ESR as is common with other regulators. Internal protection circuitry includes reverse output protection, precision current limit with fold back and thermal limit with hysteresis.

The LT3015 regulators are available in fixed output volt ages of –2.5V, –3V, –3.3V, –5V, –12V and –15V and as an adjustable device with a –1.22V reference voltage. Pack ages include the 5-lead TO-220 and DD-Pak, a thermally enhanced 12-lead MSOP and the low profile (0.75 mm) 8-lead 3mm × 3mm DFN.

 

APPLICATIONS INFORMATION

The LT3015 series are 1.5A negative low dropout linear regulators featuring precision current limit and precision bi-directional shutdown. The device supplies up to 1.5A of output load current at a typical dropout voltage of 310mV. Moreover, the low 1.1mA operating quiescent current drops to less than 1µA in shutdown. In addition to low quiescent current, the LT3015 incorporates several protection features that make it ideal for battery powered applications. In dual supply applications where the regulator’s load is returned to a positive supply, OUT can be pulled above GND by 30V and still allow the LT3015 to start up and operate.

The LT3015 adjustable version has an output voltage range of –1.22V to –29.3V. Output voltage is set by the ratio of two external resistors. The device regulates the output to maintain the ADJ pin voltage to –1.22V referred to ground. The current in R1 equals –1.22V/R1 and the current in R2 equals the current in R1 plus the ADJ pin bias current. The ADJ pin bias current, 30nA at 25°C, flows into the ADJ pin. Calculate the output voltage using the formul. The value of R1 should be less than 50k to minimize errors in the output voltage created by the ADJ pin bias current. Note that in shutdown, the output is off and the divider current is zero. Curves of ADJ Pin Voltage vs Temperature, ADJ Pin Bias Current vs Temperature and ADJ Pin Bias Cur rent vs Input Voltage appear in the Typical Performance Characteristics section.
The adjustable device is tested and specified with the ADJ pin tied to the OUT pin for a –1.22V output voltage. Specifications for output voltages greater than –1.22V are proportional to the ratio of the desired VOUT to –1.22V (VOUT/–1.22V). For example, load regulation for an out put current change of –1mA to –1.5A is typically 2mV at VOUT = –1.22V. At VOUT = –5V, load regulation equals:

(–5V/–1.22V) • (2mV) = 8.2mV