概要

The ADR380 and ADR381 are precision 2.048 V and 2.500 V band gap voltage references featuring high accuracy, high stability, and low power consumption in a tiny footprint. Patented temperature drift curvature correction techniques minimize nonlinearity of the voltage change with temperature. The wide operating range and low power consumption make them ideal for 3 V to 5 V battery-powered applications.

The ADR380 and ADR381 are micropower, low dropout voltage (LDV) devices that provide a stable output voltage from supplies as low as 300 mV above the output voltage. They are specified over the industrial (−40°C to +85°C) temperature range. The ADR380/ADR381 are available in the tiny 3-lead SOT-23 package.

 

特徴

Initial accuracy: ±5 mV/±6 mV maximum

Initial accuracy error: ±0.24%/±0.24%

Low TCVOUT: 25 ppm/°C maximum

Load regulation: 70 ppm/mA

Line regulation: 25 ppm/V

Wide operating ranges

2.4 V to 18 V for ADR380

2.8 V to 18 V for ADR381

Low power: 120 μA maximum

High output current: 5 mA

Wide temperature range: −40°C to +85°C

Tiny 3-lead SOT-23 package with standard pinout

 

アプリケーション

バッテリー駆動の計測器

Portable medical instruments

Data acquisition systems

Industrial process control systems

Hard disk drives

自動車

 

動作理論

Band gap references are the high performance solution for low supply voltage and low power voltage reference applications, and the ADR380/ADR381 are no exception. However, the uniqueness of this product lies in its architecture. As shown in Figure 26, the ideal zero TC band gap voltage is referenced to the output, not to ground. The band gap cell consists of the PNP pair Q51 and Q52, running at unequal current densities. The difference in VBE results in a voltage with a positive TC that is amplified  by the ratio of 2 × R58/R54. This PTAT voltage, combined with the VBE of Q51 and Q52, produce the stable band gap voltage. Reduction in the band gap curvature is performed by the ratio of the two resistors, R44 and R59. Precision laser trimming and other patented circuit techniques are used to further enhance the drift performance.

 

デバイスの消費電力に関する考察

The ADR380/ADR381 are capable of delivering load currents to 5 mA with an input voltage that ranges from 2.8 V (ADR381 only) to 15 V. When this device is used in applications with large input voltages, take care to avoid exceeding the specified maximum power dissipation or junction temperature that may result in premature device failure.

 

INPUT CAPACITOR

An input capacitor is not required on the ADR380/ADR381. There is no limit for the value of the capacitor used on the input, but a capacitor on the input improves transient response in applications where the load current suddenly increases.

 

OUTPUT CAPACITOR

The ADR380/ADR381 do not need an output capacitor for stability under any load condition. Using an output capacitor, typically 0.1 μF, removes any very low level noise voltage and does not affect the operation of the part. The only parameter that degrades by applying an output capacitor is turn-on time. (This varies depending on the size of the capacitor.) Load transient response is also improved with an output capacitor, which acts as a source of stored energy for a sudden increase in load current.

 

アプリケーション情報

Two ADR380s or ADR381s are used; the outputs of the individual references are simply cascaded to reduce the supply current. Such configuration provides two output voltages: VOUT1 and VOUT2. VOUT1 is the terminal voltage of U1, while VOUT2 is the sum of this voltage and the terminal voltage of U2. U1 and U2 can be chosen for the two different voltages that supply the required outputs.

 

PRECISION HIGH CURRENT VOLTAGE SOURCE

In some cases, the user may want higher output current delivered to a load and still achieve better than 0.5% accuracy from the ADR380/ADR381. The accuracy for a reference is normally specified on the data sheet with no load. However, the output voltage changes with load current.