SBOS410H June   2007  – June 2016 REF5010 , REF5020 , REF5025 , REF5030 , REF5040 , REF5045 , REF5050

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Device Comparison Table
  6. Pin Configuration and Functions
  7. Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. Parameter Measurement Information
    1. 8.1 Solder Heat Shift
  9. Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Temperature Monitoring
      2. 9.3.2 Temperature Drift
      3. 9.3.3 Thermal Hysteresis
      4. 9.3.4 Noise Performance
      5. 9.3.5 Output Adjustment Using the TRIM/NR Pin
    4. 9.4 Device Functional Modes
      1. 9.4.1 Basic Connections
      2. 9.4.2 Supply Voltage
      3. 9.4.3 Negative Reference Voltage
  10. 10Applications and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Applications
      1. 10.2.1 16-bit, 250-KSPS Data Acquisition System
        1. 10.2.1.1 Design Requirements
        2. 10.2.1.2 Detailed Design Procedure
        3. 10.2.1.3 Application Curve
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
    3. 12.3 Power Dissipation
  13. 13Device and Documentation Support
    1. 13.1 Documentation Support
      1. 13.1.1 Related Documentation
    2. 13.2 Related Links
    3. 13.3 Community Resources
    4. 13.4 Trademarks
    5. 13.5 Electrostatic Discharge Caution
    6. 13.6 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

9 Detailed Description

9.1 Overview

The REF50xx is family of low-noise, precision bandgap voltage references that are specifically designed for excellent initial voltage accuracy and drift. See the Functional Block Diagram for a simplified block diagram of the REF50xx.

9.2 Functional Block Diagram

REF5010 REF5020 REF5025 REF5030 REF5040 REF5045 REF5050 ai_fbd_bos410.gif

9.3 Feature Description

9.3.1 Temperature Monitoring

The temperature output terminal (TEMP, pin 3) provides a temperature-dependent voltage output with approximately 60-kΩ source impedance. As illustrated in Figure 8, the output voltage follows the nominal relationship:

Equation 1. VTEMP PIN = 509 mV + 2.64 × T(°C)

This pin indicates general chip temperature, accurate to approximately ±15°C. Although not generally suitable for accurate temperature measurements, this pin can be used to indicate temperature changes or for temperature compensation of analog circuitry. A temperature change of 30°C corresponds to an approximate 79-mV change in voltage at the TEMP pin.

The TEMP pin has high-output impedance (see the Functional Block Diagram). Loading this pin with a low-impedance circuit induces a measurement error; however, this pin does not have any effect on VOUT accuracy.

To avoid errors caused by low-impedance loading, buffer the TEMP pin output with a suitable low-temperature drift op amp, such as the OPA333, OPA335, or OPA376, as shown in Figure 37.

REF5010 REF5020 REF5025 REF5030 REF5040 REF5045 REF5050 ai_temp_buf_bos401.gif Figure 37. Buffering the TEMP Pin Output

9.3.2 Temperature Drift

The REF50xx is designed for minimal drift error, which is defined as the change in output voltage over temperature. The drift is calculated using the box method, as described in Equation 2.

Equation 2. REF5010 REF5020 REF5025 REF5030 REF5040 REF5045 REF5050 q_drift_bos410.gif

The REF50xx features a maximum drift coefficient of 3 ppm/°C for the high-grade version, and 8 ppm/°C for the standard-grade.

9.3.3 Thermal Hysteresis

Thermal hysteresis for the REF50xx is defined as the change in output voltage after operating the device at 25°C, cycling the device through the specified temperature range, and returning to 25°C. Thermal hysteresis can be expressed as Equation 3:

Equation 3. REF5010 REF5020 REF5025 REF5030 REF5040 REF5045 REF5050 q_hysteresis_bos410.gif

where

  • VHYST = thermal hysteresis (in units of ppm).
  • VNOM = the specified output voltage.
  • VPRE = output voltage measured at 25°C pretemperature cycling.
  • VPOST = output voltage measured after the device has been cycled from 25°C through the specified temperature range of –40°C to 125°C and returned to 25°C.

9.3.4 Noise Performance

Typical 0.1-Hz to 10-Hz voltage noise for each member of the REF50xx family is specified in the Electrical Characteristics table. The noise voltage increases with output voltage and operating temperature. Additional filtering can be used to improve output noise levels, although take care to ensure the output impedance does not degrade performance.

For additional information about how to minimize noise and maximize performance in mixed-signal applications such as data converters, refer to the series of Analog Applications Journal articles entitled, How a Voltage Reference Affects ADC Performance. This three-part series is available for download from the TI website under three literature numbers: SLYT331, SLYT339, and SLYT355 for Part I, Part II, and Part III, respectively.

REF5010 REF5020 REF5025 REF5030 REF5040 REF5045 REF5050 ai_noise_redux_bos410.gif Figure 38. Noise Reduction Using the TRIM/NR Pin

9.3.5 Output Adjustment Using the TRIM/NR Pin

The REF50xx provides a very accurate, factory-trimmed voltage output. However, VOUT can be adjusted using the trim and noise reduction pin (TRIM/NR, pin 5). Figure 39 shows a typical circuit that allows an output adjustment of ±15mV

REF5010 REF5020 REF5025 REF5030 REF5040 REF5045 REF5050 ai_vout_trim_bos410.gif Figure 39. VOUT Adjustment Using the TRIM/NR Pin

The REF50xx allows access to the bandgap through the TRIM/NR pin. Placing a capacitor from the TRIM/NR pin to GND (Figure 38) in combination with the internal R3 and R4 resistors creates a low-pass filter. A capacitance of 1μF creates a low-pass filter with the corner frequency from 10 Hz to 20 Hz. Such a filter decreases the overall noise measured on the VOUT pin by half. Higher capacitance results in a lower filter cutoff frequency, further reducing output noise. Using this capacitor increases start-up time.

9.4 Device Functional Modes

9.4.1 Basic Connections

Figure 40 shows the typical connections for the REF50xx. TI recommends a supply bypass capacitor ranging from 1 μF to 10 μF. A 1-μF to 50-μF output capacitor (CL) must be connected from VOUT to GND. The equivalent series resistance (ESR) value of CL must be less than or equal to 1.5 Ω to ensure output stability. To minimize noise, the recommended ESR of CL is from 1 Ω and 1.5 Ω.

REF5010 REF5020 REF5025 REF5030 REF5040 REF5045 REF5050 ai_basic_conn_bos410.gif Figure 40. Basic Connections

9.4.2 Supply Voltage

The REF50xx family of voltage references features extremely low dropout voltage. With the exception of the REF5020, which has a minimum supply requirement of 2.7 V, these references can be operated with a supply of 200 mV more than the output voltage in an unloaded condition. For loaded conditions, a typical dropout voltage versus load plot is provided in Figure 6 in the Typical Characteristics.

9.4.3 Negative Reference Voltage

For applications requiring a negative and positive reference voltage, the REF50xx and OPA735 can be used to provide a dual-supply reference from a 5-V supply. Figure 41 shows the REF5025 used to provide a 2.5-V supply reference voltage. The low drift performance of the REF50xx complements the low offset voltage and zero drift of the OPA735 to provide an accurate solution for split-supply applications. Take care to match the temperature coefficients of R1 and R2.

REF5010 REF5020 REF5025 REF5030 REF5040 REF5045 REF5050 ai_pos_neg_vref_bos401.gif Figure 41. The REF5025 and OPA735 Create Positive and Negative Reference Voltages