Features: Series Reference (2.5 V, 3 V, 4.096 V, 5 V); Low Quiescent Current: 70 µA Max; Current Output Capability: ±5 mA; Wide Supply Range: VIN = VOUT + 200 mV to 12 V ; Broadband Noise (10 Hz to 10 kHz): 50 μV rms; Specified Temperature Range: –40°C to + 125 °C; Compact Surface Mount SOT-23 Assembly.

Applications: Portable battery powered equipment; for example, notebook computers, mobile phones, pagers, PDAs, GPS and digital multimeters; computer workstations; suitable for various video ramdacs; smart industrial transmitters; PCMCIA cards; automobiles; hard disk drives; 3V/5V, 8-bit/12-bit data converter.

General Instructions

The ad1582/ad1583/ad1584/ad1585 is a low-cost, low-power, low-power, high-precision bandgap reference. These designs are available as 3-terminal (series) devices and packaged in compact SOT-23, 3-lead surface mount packages. The versatility of these references makes them ideal for use in battery-operated 3 V or 5 V systems, where variations in supply voltage and the need to minimize power consumption can be made. The precise matching and thermal tracking of the AD1582 /AD1583/AD1584/AD1585 chip assemblies provide high accuracy and temperature stability. The patented temperature drift curvature correction design technology minimizes the nonlinearity of the voltage output temperature characteristic.

The AD1582/AD1583/AD1584/AD1585 family of mode devices can source or sink up to 5mA of load current and require only 200mV of headroom supply to operate efficiently. These parts have a maximum quiescent current of 70µA, varying only 1.0µA/V with supply voltage. The advantages of these designs are extraordinary compared to traditional parallel devices. Valuable supply current is no longer wasted through the input series resistance and maximum power efficiency is achieved at all input voltage levels.

The AD1582/AD1583/AD1584/AD1585 can be divided into two grades, A and B, with a small footprint, namely SOT2 3. All grades are specified over the industrial temperature range -40°C to +125°C.

the term

Temperature Coefficient (tcvo)

Change in output voltage as operating temperature changes, normalized by output voltage at 25°C, in ppm/°C. The equation is as follows:

where: Vo(25°C) = V at 25°C. o;VO(T1)=V@Temp1. V=V@Temp2. oO(T2)o

Line Regulation (Δvo/Δvin) Definition

The change in output voltage due to a specific change in input voltage. It includes self-heating effects. Line regulation is expressed in percent per volt, parts per million per volt, or microvolts per volt of input voltage change.

Load regulation (Δvo/Δiload)

The change in output voltage due to a specific change in load current. It includes self-heating effects. Load regulation is expressed in microvolts per milliamp, millionths per milliamp, or DC output resistance in ohms.

Long-term stability (Δvo)

Typical shift in output voltage on a part sample subjected to a 1000-hour operational life test at 125°C at 25°C.

where: V at 25°C when Vo(t)0)=0. o; Vo(t)1) = V at 25°C after 1000 hours of operation at 125°C. o

Thermal Hysteresis (vo_hys)

Change in output voltage of the device after cycling the temperature from +25°C to -40°C to +85°C and back to +25°C. This is a typical value for a sample of parts through a loop like this:

Where: Vo(25°C) = VAT 25°C. o; V otak = VO at 25°C, back to +25°C after temperature cycling from +25°C to -40°C to +85°C.

Operating temperature

In extreme temperature conditions, the device can still function. Outside the specified temperature range, parts can deviate from the specified performance.

theory of operation

The AD1582/AD1583/AD1584/AD1585 use the concept of a bandgap to generate stable, low temperature coefficient voltages for reference in high precision data acquisition components and systems. These parts of the precision reference use the basic temperature characteristics of the base-emitter voltage of silicon transistors in the forward-biased operating region. In this case, all such transistors have -2 mV/°C R3 temperature coefficient (tc) and v, which when extrapolated to absolute zero, 0 k (collector current proportional to absolute temperature) approximates the silicon ribbon gap voltage. By adding voltages with equal and opposite temperatures - yes + calculating a true coefficient transistor of 2mv/°C with a forward biased vbe, an almost 0 TC reference can be developed. Figure 9 in the AD1582/AD1583/AD1584/AD1585 simplified circuit diagram.

As shown in Figure 9, this compensation voltage v1 is obtained by driving two transistors at different current densities and amplifying the resulting vbe difference (∏vbe with positive tc). The sum of vbe and v1 (vbg) is then buffered and amplified to produce stable reference voltage outputs of 2.5v, 3v, 4.096v and 5v.

application information

The AD1582/AD1583/AD1584/AD1585 are a series of references that can be used in many applications. For optimum performance using these references, only two external components are required. Figure 10 shows the AD1582/AD1583/AD1584/AD1585 configured to operate under all load conditions. By connecting a simple 4.7µF capacitor to the input and a 1µF capacitor to the output, the device achieves the specified performance for all input voltage and output current requirements. For the best transient response, connect a 0.1µf capacitor in parallel with a 4.7µf capacitor. While the 1µF output capacitor provides stable performance for all load conditions, the AD1582/AD1583/AD1584/AD1585 can operate at low levels. (-100μA

temperature performance

The AD1582/AD1583/AD1584/AD1585 are designed for applications where temperature performance is important. Extensive temperature testing and characterization ensures device performance remains within specified temperature ranges.

The guaranteed error band 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 finding the 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 voltage is guaranteed to be 2.5 V ±10 mV from -40°C to +125°C.

Figure 11 shows the typical output voltage drift of the AD1582/AD1583/AD1584/AD1585 and illustrates the method. The box in Figure 11 is defined on the x-axis by the operating temperature limit. It is limited on the y-axis by the maximum and minimum output voltages observed over the operating temperature range. The slope of the diagonal line drawn from the initial output value at 25°C to the output value at +125°C and -40°C determines the performance level of the device.

Reproducing these results requires a test system with stable temperature control with high accuracy. Evaluation of the AD1582/AD1583/AD1584/AD1585 produces curves similar to Figure 5 and Figure 11, but the output readings can vary depending on the test method and test equipment used.

Voltage Output Nonlinearity vs. Temperature

When using voltage references for data converters, it is important to understand the effect of temperature drift on converter performance. The nonlinearity of the reference output drift represents an additional error that cannot be easily calibrated out of the overall system. To better understand the effect of this drift on the data converter, see Figure 12, where the measured drift characteristics are normalized to the endpoint average drift. The residual drift error of the AD1582/AD1583/AD1584/AD1585 is approximately 200 ppm demon-strategy These parts are compatible with systems requiring 12-bit accurate temperature performance.

Output voltage hysteresis

Manufacturers of high-performance industrial equipment can require the AD1582/AD1583/AD1584/AD1585 to maintain a consistent output voltage error of 25°C over the full temperature range from the reference temperature. All references have a feature called output voltage hysteresis; however, the AD1582/AD1583/AD1584/AD1585 are designed to minimize this feature. This phenomenon can be quantified by measuring the change in output voltage at ±25°C after temperature changes from ±125°C to +25°C and from 40°C to ±25°C. Figure 13 shows the distribution of the AD1582/AD1583/AD1584/AD1585 output voltage hysteresis.

Supply Current and Temperature

The quiescent current of the AD1582/AD1583/AD1584/AD1585 varies slightly over temperature and input supply range. Figure 14 shows the AD1582/AD1583/AD1584/AD1585 references over temperature and supply voltage. As shown in Figure 14, the AD1582/AD1583/AD1584/AD1585 supply current increases by only 1 μA/V, making the device very attractive in applications where supply voltages vary widely and power dissipation needs to be minimized .

Supply voltage

One of the desirable features of the AD1582/AD1583/AD1584/AD1585 is low supply voltage headroom. These parts can operate from supply voltages as low as over 200 mV and as high as 12 V. However, if a negative voltage is inadvertently applied to V relative to ground, or if any negative transient >5 V is coupled to V, the device may be damaged.

AC performance

To apply the ad1582/ad1583/ad1584/ad1585, it is important to understand the effects of dynamic output impedance and power supply rejection. In Figure 15, the voltage divider consists of the AD1582/AD1583/AD1584/AD1585 output impedance and the external source impedance. Figure 16 shows the effect of changing the load capacitor on the reference output. When characterizing the AC performance of a series voltage reference, the power supply rejection ratio (psrr) should be determined. Figure 17 shows the test circuit used to measure PSRR, and Figure 18 shows the ability of the AD1582/AD1583/AD1584/AD1585 to attenuate line voltage ripple.

Noise performance and reduction

The noise generated by the ad1582/ad1583/ad1584/ad1585 is typically less than 70µv pp over the 0.1Hz to 10Hz frequency band. Figure 19 shows the 0.1 Hz to 10 Hz noise of a typical AD1582/AD1583/AD1584/AD1585. Noise measurements are made using a high gain bandpass filter. Noise in the 10 Hz to 10 kHz range is about 50 microvolts rms. Figure 20 shows the wideband noise for a typical AD1582/AD1583/AD1584/AD1585. If further noise reduction is required, add a 1-pole low-pass filter between the output pin and ground. A time constant of 0.2ms has a -3db point at about 800hz and reduces high frequency noise to about 16v rms. However, it should be noted that while additional filtering on the output can improve the noise performance of the AD1582/AD1583/AD1584/AD1585, the increased output impedance will degrade the AC performance of the reference.

opening time

Many low-power meter manufacturers are concerned with the energization characteristics of the components used in their systems. Quick turn-on components often save power by enabling end users to turn off power when not needed. The power-on settling time is the time it takes for the output voltage to reach its final value within a specified error range after power is applied (cold start). The two main factors that affect this are the settling time of the active circuit and the time it takes for thermal gradients on the chip to settle. Figure 21 shows the power-on stability and transient response test circuit. Figure 22 shows the turn-on characteristics of the AD1582/AD1583/AD1584/AD1585. These characteristics result from cold crank operation and represent the true turn-on waveform after power-up. Figure 23 shows the fine sedimentation characteristics of the AD1582/AD1583/AD1584/AD1585. Typically, the reference settles to within 0.1% of its final value within about 100 microseconds.

When V is slightly below the minimum specified level, the device can momentarily draw excessive supply current. The power supply resistance must be low enough to ensure reliable turn-on. Fast power edges minimize this effect.

Dynamic performance

Many ADCs and DACs provide transient current loads to the reference, and poor reference response can degrade converter performance. The AD1582/AD1583/AD1584/AD1585 provide excellent static and dynamic line and load regulation. Since these series references can both generate and sink high current loads, they have excellent settling characteristics.

Figure 24 shows the line transient response of the AD1582/AD1583/AD1584/AD1585. The circuit used to make this measurement is shown in Figure 21, where the input supply voltage was switched from 5 V to 10 V, and the input and output capacitors were both 0.22 μF.

Figure 25 and Figure 26 show the load transient settling characteristics of the AD1582/AD1583/AD1584/AD1585 with applied load current steps of 0 to +5 mA and 0 to -1 mA. Input supply voltage remains constant at 5v; input decoupling capacitors and output load capacitors are 4.7µf and 1µf, respectively; output current switches. For both positive and negative current loads, the reference response settles quickly and shows an initial voltage peak of less than 10 mV.