DESCRIPCIÓN GENERAL

The AD1582/AD1583/AD1584/AD1585 are low cost, low power, low dropout, precision band gap references. These designs are available as 3-terminal (series) devices and are packaged in the compact SOT-23, 3-lead surface-mount package. The versatility of these references makes them ideal for use in battery-powered 3 V or 5 V systems where there can be wide variations in supply voltage and a need to minimize power dissipation. The superior accuracy and temperature stability of the AD1582/AD1583/AD1584/AD1585 result from the precise matching and thermal tracking of on-chip components. Patented temperature drift curvature correction design techniques minimize the nonlinearities in the voltage output temperature characteristic.

The AD1582/AD1583/AD1584/AD1585 series mode devices source or sink up to 5 mA of load current and operate efficiently with only 200 mV of required headroom supply. These parts draw a maximum 70 μA of quiescent current with only a 1.0 μA/V variation with supply voltage. The advantage of these designs over conventional shunt devices is extraordinary. Valuable supply current is no longer wasted through an input series resistor, and maximum power efficiency is achieved at all input voltage levels.

The AD1582/AD1583/AD1584/AD1585 are available in two grades, A and B, and are provided in a tiny footprint, the SOT-23. All grades are specified over the industrial temperature range of −40°C to +125°C.

 

TEORÍA DE FUNCIONAMIENTO

The AD1582/AD1583/AD1584/AD1585 use the band gap concept to produce stable, low temperature coefficient voltage references suitable for high accuracy data acquisition components and systems. These parts of precision references use the underlying temperature characteristics of a silicon transistor’s base emitter voltage in the forward-biased operating region. Under this condition, all such transistors have a −2 mV/°C temperature coefficient (TC) and a VBE that, when extrapolated to absolute zero, 0 K (with collector current proportional to absolute temperature), approximates the silicon band gap voltage. By summing a voltage that has an equal and opposite temperature coefficient of 2 mV/°C with the VBE of a forward-biased transistor, an almost 0 TC reference can be developed.

 

INFORMACIÓN SOBRE APLICACIONES

The AD1582/AD1583/AD1584/AD1585 are series references that can be used for many applications. To achieve optimum performance with these references, only two external components are required. Shows the AD1582/AD1583/ AD1584/AD1585 configured for operation under all loading conditions. With a simple 4.7 μF capacitor attached to the input and a 1 μF capacitor applied to the output, the devices can achieve specified performance for all input voltage and output current requirements. For best transient response, add a 0.1 μF capacitor in parallel with the 4.7 μF capacitor. While a 1 μF output capacitor can provide stable performance for all loading conditions, the AD1582/AD1583/AD1584/AD1585 can operate under low (−100 μA < IOUT < +100 μA) current conditions with just a 0.2 μF output capacitor. The 4.7 μF capacitor on the input can be reduced to 1 μF in this condition. Unlike conventional shunt reference designs, the AD1582/ AD1583/AD1584/AD1585 provide stable output voltages at constant operating current levels.

 

TEMPERATURE PERFORMANCE

The AD1582/AD1583/AD1584/AD1585 are designed for applications where temperature performance is important. Extensive temperature testing and characterization ensure that device performance is maintained over the specified temperature range.

The error band guaranteed with the AD1582/AD1583/AD1584/ AD1585 is the maximum deviation from the initial value at 25°C.

Therefore, for a given grade of the AD1582/AD1583/AD1584/ AD1585, the designer can easily determine the maximum total error by summing initial accuracy and temperature variation. For example, for the AD1582BRT, the initial tolerance is ±2 mV, and the temperature error band is ±8 mV; therefore, the reference is guaranteed to be 2.5 V ± 10 mV from −40°C to +125°C.

 

DYNAMIC PERFORMANCE

Many ADCs and DACs present transient current loads to the reference and poor reference response can degrade converter performance. The AD1582/AD1583/AD1584/AD1585 provide superior static and dynamic line and load regulation. Because these series references are capable of both sourcing and sinking large current loads, they exhibit excellent settling characteristics.