SNVS053F June   2000  – September 2016 LM4140

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 ON/OFF Operation
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Input Capacitors
      2. 8.1.2 Output Capacitors
      3. 8.1.3 Tantalum Capacitors
      4. 8.1.4 Aluminum Electrolytic Capacitors
      5. 8.1.5 Multilayer Ceramic Capacitors
      6. 8.1.6 Reverse Current Path
      7. 8.1.7 Output Accuracy
    2. 8.2 Typical Applications
      1. 8.2.1 Precision DAC Reference
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Boosted Output Current
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
      3. 8.2.3 Boosted Output Current With Current Limiter
        1. 8.2.3.1 Design Requirements
        2. 8.2.3.2 Detailed Design Procedure
      4. 8.2.4 Complimentary Outputs
        1. 8.2.4.1 Design Requirements
        2. 8.2.4.2 Detailed Design Procedure
      5. 8.2.5 Voltage Reference With Force and Sense Output
        1. 8.2.5.1 Design Requirements
        2. 8.2.5.2 Detailed Design Procedure
      6. 8.2.6 Precision Programmable Current Source
        1. 8.2.6.1 Design Requirements
        2. 8.2.6.2 Detailed Design Procedure
      7. 8.2.7 Strain Gauge Conditioner for 350-Ω Bridge
        1. 8.2.7.1 Design Requirements
        2. 8.2.7.2 Detailed Design Procedure
      8. 8.2.8 Bipolar Voltage References for Low Power ADC
        1. 8.2.8.1 Design Requirements
        2. 8.2.8.2 Detailed Design Procedure
      9. 8.2.9 Self-Biased Low Power ADC Reference With Trim Current Sources
        1. 8.2.9.1 Design Requirements
        2. 8.2.9.2 Detailed Design Procedure
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Receiving Notification of Documentation Updates
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

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7 Detailed Description

7.1 Overview

The LM4140 device is a high-precision series voltage reference available in 5 difference output voltage options, including the 1.024-V option below the bandgap voltage. The series reference can operate with input voltage as low as VREF + 400 mV over temperature, consuming 400 µA or less over temperature depending on voltage option. While in shutdown, the device consumes 10 nA (typical).

7.2 Functional Block Diagram

LM4140 FBD_SNVS053F.gif

7.3 Feature Description

7.3.1 ON/OFF Operation

The LM4140 is designed to quickly reduce both VREF and IQ to zero when turned off. VREF is restored in less than 200 µs when turned on. During the turnoff, the charge across the output capacitor is discharged to ground through internal circuitry.

The LM4140 is turned off by pulling the enable input low, and turned on by driving the input high. If this feature is not to be used, the enable pin must be tied to the VIN to keep the reference on at all times (the enable pin must not be left floating).

To ensure proper operation, the signal source used to drive the enable pin must be able to swing above and below the specified high and low voltage thresholds which ensure an ON or OFF state (see Electrical Characteristics).

The ON/OFF signal may come from either a totem-pole output, or an open-collector output with pullup resistor to the LM4140 input voltage. This high-level voltage may exceed the LM4140 input voltage, but must remain within the absolute maximum rating for the enable pin.

7.4 Device Functional Modes

Table 1 lists the operational modes of the LM4140.

Table 1. Operational Modes

ENABLE PIN LOGIC STATE DESCRIPTION
EN = VIN 1 Normal operation, device powered up
EN = Ground 0 Device in shutdown