Overview:
The AD1580 is a low cost, two terminated (shunt), precision bandgap reference. It provides an accurate 1.225 V output at 50 mA and an input current of 10 mA. The higher accuracy and stability of the AD1580 is made possible by precise matching and on-chip tracking of components. Proprietary curvature correction design techniques have been used to minimize the non-linear output temperature characteristics of the voltage. The AD1580 is stable with any capacitive load value. The low minimum operating current makes the AD1580 ideal for use in battery-powered 3 V or 5 V systems. However, the wide operating current range means that the AD1580 is extremely versatile and suitable for use in a variety of high current applications. The AD1580 is available in two grades, A and B, both of which are offered in a SOT-23 package, the smallest surface mount package available on the market. Both grades are specified over an industrial temperature range of -40°C to 85°C

target application
1. Portable, Battery-Powered Devices: Cell Phones, Notebooks, PDAs, GPS and DMMs.
2. Computer workstations are suitable for a wide range of RAMDACs with video.
3. Smart Industrial Transmitter
4. PCMCIA card.
5. car.
6. 3V/5V 8-12 bit data converter.

Information provided by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed for the use of the analog device, nor does it infringe any patent or other third party rights which may arise from its use. No license is granted to imply or otherwise under any patent or patent rights of Analog Devices.

Notes
1 Measured with no load capacitance.
2 Output hysteresis is defined as the temperature drift to +85°C and then to 40°C after a 25°C output voltage change
3 The operating temperature range refers to the extreme temperatures at which the device will continue to function. Certain parts may deviate from the specified performance.

Specifications are subject to change without notice.

Packaging Brand Information:
Four flag fields identify device generic, class and date handling. The first field is product identification. A "0" is identified as common to the AD1580. The second field indicates at the device level, a number or letter in the third field "A" or "B" indicates a calendar year; "5" for 1995, "A" for 2001. In the fourth field, the letters AZ represent the two-week window calendar year; the first two weeks with an "A" begin January.

Operating principle:
The AD1580 uses a "bandgap" concept to generate a stable, low temperature coefficient voltage reference suitable for high precision data acquisition components and systems. The device allows the physical properties of the underlying silicon to operate in a forward-biased region using the transistor's base-emitter voltage. All of these transistors have a temperature coefficient of about a -2/°C millivolt, which is not suitable for use directly as a low TC reference, but the extrapolated temperature characteristics of any of these devices show that an absolute zero collector (current proportional to absolute temperature) shows that its The bandgap voltage of silicon is reduced in VBE. Therefore, if the sum of the anti-coefficients of voltage and temperature can be developed with VBE, a zero class formulation results. Figure 6 The AD1580 circuit provides such a compensation voltage V1 by driving the two transistors at different currents resulting in a difference in density and sound VBE (DVBE - which has an active match). The sum and VBE of V1 provide a stable voltage reference.

Application for AD1580:
The AD1580 is simple to use in almost any application. To use the AD1580 as a conventional shunt regulator (Figure 7A), an external series resistor is connected between the supply voltage and the AD1580. For a given supply voltage, the series resistor RS determines the reverse current flow through the AD1580. The value of Rs must be chosen to accommodate the expected changes with supply voltage, VS, load current IL, and AD1580 reverse voltage, VR, while maintaining acceptable reverse current, IR, through the AD1580. The lowest value of RS should be chosen when VS is at its lowest and IL and VR are maximized while maintaining the lowest acceptable reverse current. The RS value should be large enough to limit IR to 10 mA when VS is at its maximum and IL and VR are at its minimum. The formula for the chosen RS is as follows: RS = (Ratio - VR)/(IR + IL) Figure 7b shows a typical connection with the AD1580BRT operating at a minimum of 100 mA and can deliver ±1 mA to its load, Also accommodates ±10% power supply variation.

Temperature performance:
The AD1580 is designed for reference applications where stable temperature performance is important. Extensive temperature testing and characterization ensures that the performance of the device does not exceed the specified temperature range. There is some confusion over the definition and specification of the temperature reference voltage error in the region. Historically, references have used characteristics with a maximum deviation of degrees Celsius per degree, i.e. 50 parts per million/°C. However, due to nonlinearity which originates in standard temperature characteristics, the Zener cites (such as the "S" type of feature), most manufacturers now use the ceiling error band method to specify equipment. This technique involves measurements at three or more outputs to guarantee that the voltage at different temperatures will drop within a given error range. This proprietary curvature correction design technique is used to minimize the nonlinearity of the AD1580 allowing temperature performance to warrant the use of the maximum deviation method. This approach is put one more than a designer using it just guarantees a maximum error band over the entire temperature change. Figure 8 shows the typical output voltage drift of the AD1580 and illustrates the methodology. The maximum slope from the initial two diagonals draws the output value at 25°C to the output value at 85°C and -40°C depending on the performance of the high-end equipment. For a given AD1580 class the designer can easily determine the maximum total error from the initial error plus temperature variation. For example, with an AD1580BRT initial tolerance of ±1 mV, a temperature coefficient of ±50 ppm/°C corresponds to an error band of ±4 mV (50'10-6'1.225 V at 65°C), so the unit is guaranteed to be 1.225 Volts ±5 mV over the entire operating temperature range. Reproduction of these results requires a high combination of test accuracy and stable temperature control systems. Evaluation of the AD1580 will yield a curve similar to that in Figures 1 and 8.

Voltage vs. Output Nonlinear Temperature:
When using data converters it is important to understand that temperature drift can affect the overall converter performance. Nonlinearity in the reference output drift represents additional error and is not easy to calibrate out of the system. This feature (9) is the feature of the measured drift from normalizing to the end point, the average drift. A residual drift error of about 500 ppm shows that the AD1580 is compatible with systems requiring 10-bit accurate temperature performance.