link to page 7 link to page 7 Data SheetAD7802.027+VINDNC1.6VOUT 61DNC1.2AD780TRIM 50.83TEMPC1O/P SELECT0.4C22.5V – DNCERROR (mV)GND3.0V – GND480 009 –0.4DNC = DO NOT CONNECT TO THIS PIN 00841- Figure 9. Noise Reduction Circuit –0.8 00841-011 –60–40–20020406080100120140NOISE COMPARISONTEMPERATURE ( ° C) Figure 11. Typical AD780BN Temperature Drift The wideband noise performance of the AD780 can also be expressed in ppm. The typical performance with C1 and C2 is TEMPERATURE OUTPUT PIN 0.6 ppm; without external capacitors, typical performance is The AD780 provides a TEMP output (Pin 3) that varies linearly 1.2 ppm. with temperature. This output can be used to monitor changes This performance is, respectively, 7× and 3× lower than the in system ambient temperature, and to initiate calibration of the specified performance of the LT1019. system, if desired. The voltage VTEMP is 560 mV at 25°C, and the temperature coefficient is approximately 2 mV/°C. NO AMPLIFIER Figure 12 shows the typical VTEMP characteristic curve over 20 µ V10ms temperature taken at the output of the op amp with a 100 noninverting gain of 5. 904.25CIRCUIT CALIBRATED AT 25 ° C REFER TO FIGURE 134.003.75) 3.501010mV PER ° COUT0%3.253.00VOLTAGE (V 2.75 00841-010 10Hz TO 10kHz2.50 Figure 10. Reduced Noise Performance with C1 = 100 µF, C2 = 100 nF 2.25TEMPERATURE PERFORMANCE2.00 00841-012 The AD780 provides superior performance over temperature by –75–50–250255075100125150TEMPERATURE ( ° C) means of a combination of patented circuit design techniques, Figure 12. Temperature Pin Transfer Characteristic precision thin-film resistors, and drift trimming. Temperature performance is specified in terms of ppm/°C; because of Since the TEMP voltage is acquired from the band gap core nonlinearity in the temperature characteristic, the box test circuit, current pul ed from this pin has a significant effect on method is used to test and specify the part. The nonlinearity VOUT. Care must be taken to buffer the TEMP output with a takes the form of the characteristic S-shaped curve shown in suitable op amp, for example, an OP07, AD820, or AD711 (all Figure 11. The box test method forms a rectangular box around of which would result in less than a 100 µV change in VOUT). this curve, enclosing the maximum and minimum output voltages The relationship between ITEMP and VOUT is over the specified temperature range. The specified drift is equal to ∆VOUT = 5.8 mV/µA ITEMP (2.5 V Range) the slope of the diagonal of this box. or ∆VOUT = 6.9 mV/µA ITEMP (3.0 V Range) Rev. I | Page 7 of 12 Document Outline Features Functional Block Diagram General Description Product Highlights Table of Contents Revision History Specifications Absolute Maximum Ratings Thermal Resistance Notes ESD Caution Theory of Operation Applying the AD780 Noise Performance Noise Comparison Temperature Performance Temperature Output Pin Temperature Transducer Circuit Supply Current Over Temperature Turn-On Time Dynamic Performance Line Regulation Precision Reference for High Resolution 5 V Data Converters 4.5 V Reference from 5 V Supply Negative (–2.5 V) Reference Outline Dimensions Ordering Guide