SBOS456H September   2008  – February 2015 REF5020A-Q1 , REF5025A-Q1 , REF5030A-Q1 , REF5040A-Q1 , REF5045A-Q1 , REF5050A-Q1

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Simplified Schematic
  5. Revision History
  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: Per Device
    6. 7.6 Electrical Characteristics: All Devices
    7. 7.7 Typical Characteristics
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Supply Voltage
      2. 8.3.2 Using the TRIM/NR Pin
      3. 8.3.3 Temperature Drift
      4. 8.3.4 Temperature Monitoring
    4. 8.4 Device Functional Modes
  9. Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Thermal Hysteresis
    2. 9.2 Typical Applications
      1. 9.2.1 Standalone Applications
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1 Power Dissipation
          2. 9.2.1.2.2 Noise Performance
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Negative-Reference Voltage Applications
      3. 9.2.3 Data-Acquisition Applications
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Related Links
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

パッケージ・オプション

メカニカル・データ(パッケージ|ピン)
サーマルパッド・メカニカル・データ
発注情報

8 Detailed Description

8.1 Overview

The REF50xxA-Q1 family of devices is a low-noise, precision-bandgap voltage reference that is specifically designed for excellent initial voltage accuracy and drift. See the Functional Block Diagram section for a simplified block diagram of the REF50xxA-Q1 family of devices.

8.2 Functional Block Diagram

REF5020A-Q1 REF5025A-Q1 REF5030A-Q1 REF5040A-Q1 REF5045A-Q1 REF5050A-Q1 ai_fbd_bos456.gif

8.3 Feature Description

8.3.1 Supply Voltage

The REF50xxA-Q1 family of voltage references features extremely low dropout voltage. With the exception of the REF5020A-Q1 device, which has a minimum supply requirement of 2.7 V, these references can operate with a supply of 200 mV above the output voltage in an unloaded condition. For loaded conditions, Figure 6 in the Typical Characteristics section shows a typical dropout voltage versus load plot.

8.3.2 Using the TRIM/NR Pin

The REF50xxA-Q1 family of devices provides a very accurate voltage output. However, VOUT can be adjusted to reduce noise and shift the output voltage from the nominal value by configuring the trim and noise reduction pin (TRIM/NR, pin 5). The TRIM/NR pin provides a ±15-mV adjustment of the device bandgap, which produces a ±15-mV change on the VOUT pin. Figure 25 shows a typical circuit using the TRIM/NR pin to adjust VOUT. When using this technique, the temperature coefficients of the resistors can degrade the temperature drift at the output.

REF5020A-Q1 REF5025A-Q1 REF5030A-Q1 REF5040A-Q1 REF5045A-Q1 REF5050A-Q1 ai_vout_trim_bos456.gifFigure 25. VOUT Adjustment Using TRIM/NR Pin

The REF50xxA-Q1 family of devices allows access to the bandgap through the TRIM/NR pin. Placing a capacitor from the TRIM/NR pin to GND (as shown in Figure 26) in combination with the internal 1-kΩ resistor creates a low-pass filter that lowers the overall noise measured on the VOUT pin. A capacitance of 1 μF is suggested for a low-pass filter with a corner frequency of 14.5 Hz. Higher capacitance results in a lower cutoff frequency.

REF5020A-Q1 REF5025A-Q1 REF5030A-Q1 REF5040A-Q1 REF5045A-Q1 REF5050A-Q1 ai_noise_redux_bos456.gifFigure 26. Noise Reduction Using TRIM/NR Pin

8.3.3 Temperature Drift

The REF50xxA-Q1 family of devices 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. Use Equation 1 to calculate the drift.

Equation 1. REF5020A-Q1 REF5025A-Q1 REF5030A-Q1 REF5040A-Q1 REF5045A-Q1 REF5050A-Q1 q_drift_bos456.gif

The REF50xxA-Q1 family of devices features a maximum drift coefficient of 8 ppm/°C for the standard-grade.

8.3.4 Temperature Monitoring

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

Equation 2. VTEMP PIN = 509 mV + 2.64 × T(°C)

This pin indicates general chip temperature, accurate to approximately ±15°C. Although this pin is not generally suitable for accurate temperature measurements, it 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 section). Loading this pin with a low-impedance circuit induces a measurement error; however, it 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 27.

REF5020A-Q1 REF5025A-Q1 REF5030A-Q1 REF5040A-Q1 REF5045A-Q1 REF5050A-Q1 ai_temp_buf_bos456.gif
1. Low drift op amp, such as the OPA333, OPA335, or OPA376 device.
Figure 27. Buffering the TEMP Pin Output

8.4 Device Functional Modes

The REF50xxA-Q1 family of devices can only operate in an on or off mode. As long as a sufficient input supply voltage is made available to device, the device performs in standard operation. The device cannot be placed in a low power or shutdown mode.