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LM7705

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Low Noise Negative Bias Generator

Data sheet
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Low Noise Negative Bias Generator

LM7705

ACTIVE
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Product details

Parameters

Vin (Min) (V) 3 Vin (Max) (V) 5.25 Vout (Min) (V) -0.232 Vout (Max) (V) -0.232 Iout (Max) (A) 0.026 Regulated outputs (#) 1 Switching frequency (Min) (kHz) 92 Switching frequency (Max) (kHz) 92 Iq (Typ) (mA) 0.078 Features Enable, Synchronous Rectification Operating temperature range (C) -40 to 125 Type Charge Pump, Converter Rating Catalog open-in-new Find other Charge pumps (inductorless)

Package | Pins | Size

VSSOP (DGK) 8 15 mm² 3 x 4.9 open-in-new Find other Charge pumps (inductorless)

Features

  • Regulated Output Voltage −0.232 V
  • Output Voltage Tolerance 5%
  • Output Voltage Ripple 4 mVPP
  • Supply Voltage 3 V to 5.25 V
  • Conversion Efficiency Up to 98%
  • Quiescent Current 78 µA
  • Shutdown Current 20 nA
  • Turnon Time 500 µs
  • Operating Temperature Range −40°C to 125°C
  • 8-Pin VSSOP Package

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Description

The LM7705 device is a switched capacitor voltage inverter with a low noise, −0.23 V fixed negative voltage regulator. This device is designed to be used with low voltage amplifiers to enable the amplifiers output to swing to zero volts. The −0.23 V is used to supply the negative supply pin of an amplifier while maintaining less then 5.5 V across the amplifier. Rail-to-Rail output amplifiers cannot output zero volts when operating from a single-supply voltage and can result in error accumulation due to amplifier output saturation voltage being amplified by following gain stages. A small negative supply voltage will prevent the amplifiers output from saturating at zero volts and will help maintain an accurate zero through a signal processing chain. Additionally, when an amplifier is used to drive an input of the ADC, the amplifier can output a zero voltage signal and the full input range of an ADC can be used. The LM7705 device has a shutdown pin to minimize standby power consumption.

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Technical documentation

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Type Title Date
* Data sheet LM7705 Low-Noise Negative Bias Generator datasheet (Rev. D) May 08, 2018
Application note Charge pump circuit (–0.3V) for negative amplifier supply Jun. 16, 2019
Application note Attenuator Amplifier Design to Maximize the Input Voltage of Differential ADCs Jun. 14, 2018
Application note A Topical Index of TI Low Power Buck DC/DC Application Notes Jan. 17, 2018
Technical article Unique active mux capability combines buffer and switch into one solution Oct. 10, 2017
User guide ADS7056EVM-PDK Quick Start Guide Mar. 09, 2017
Technical article Where did the op amp ground pin go? Mar. 18, 2016
Technical article Painting a picture for powering high-performance FPGAs Sep. 05, 2013
Technical article Analog Applications Spotlight: Mark Pieper Jun. 06, 2013
User guide AN-1883 LM7705 Evaluation Board (Rev. B) May 03, 2013

Design & development

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Hardware development

EVALUATION BOARD Download
document-generic User guide
199
Description
The ADS7056 evaluation module (EVM) performance demonstration kit (PDK) is a platform for evaluating the performance of the ADS7056 successive approximation register (SAR) analog-to-digital converter (ADC), which is a single-ended input, 14-bit, 2.5-MSPS device. The ADS7056EVM-PDK (...)
Features
  • Hardware and software required for diagnostic testing, as well as accurate performance evaluation of ADS7056 SAR ADC
  • USB powered; no external power supply required
  • PHI controller provides convenient communication interface to ADS7056 ADC over a USB 2.0 (or higher) for power delivery, as well as (...)
View details
EVALUATION BOARD Download
document-generic User guide
Description

The ADS8168 evaluation module (EVM) performance demonstration kit (PDK) is a platform for evaluating the performance of the ADS8168 successive-approximation register (SAR) analog-to-digital converter (ADC). The ADS8168EVM-PDK includes the ADS8168EVM board, the precision host interface (PHI (...)

Features
  • Includes hardware and software required for diagnostic testing, as well as accurate performance of the ADS8168 ADC
  • No external power supply required
  • Ships with PHI controller that provides a convenient interface to ADS8168EVM over USB 2.0 (or higher) for power delivery, as well as digital input/output
  • (...)
View details
EVALUATION BOARD Download
document-generic User guide
49
Description

This evaluation board is designed to demonstrate the functionality of Texas Instruments LM7705 Low Noise Negative Bias Generator. The board has a dual Operational Amplifier that can be connected to ground or biased with the on board LM7705. In the last case a True zero amplifier is demonstrated.

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Design tools & simulation

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PSPICE-FOR-TI — PSpice® for TI is a design and simulation environment that helps evaluate functionality of analog circuits. This full-featured, design and simulation suite uses an analog analysis engine from Cadence®. Available at no cost, PSpice for TI includes one of the largest model libraries in the (...)
Features
  • Leverages Cadence PSpice Technology
  • Preinstalled library with a suite of digital models to enable worst-case timing analysis
  • Dynamic updates ensure you have access to most current device models
  • Optimized for simulation speed without loss of accuracy
  • Supports simultaneous analysis of multiple products
  • (...)
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Reference designs

REFERENCE DESIGNS Download
Modular battery tester reference design for 50-A, 100-A, and 200-A applications
TIDA-01042 — This reference design provides a modular battery test solution allowing users to have the flexibility to test batteries at different current levels with one design. This design leverages the TIDA-01041 reference design by providing two 100-A battery testers that can work independently or be (...)
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REFERENCE DESIGNS Download
Multi-Rail Power Reference Design for Eliminating EMI Effects in High Performance DAQ Systems
TIDA-01054 — The TIDA-01054 reference design helps eliminate the performance degrading effects of EMI on Data Acquisition (DAQ) systems greater than 16 bits with the help of the LM53635 buck converter. The buck converter enables the designer to place power solutions close to the signal path without the unwanted (...)
document-generic Schematic document-generic User guide
REFERENCE DESIGNS Download
ADC Voltage Reference Buffer Optimization Reference Design for High Performance DAQ Systems
TIDA-01055 — The TIDA-01055 reference design for high performance DAQ Systems optimizes the ADC reference buffer to improve SNR performance and reduce power consumption with the TI OPA837 high-speed op amp. This device is used in a composite buffer configuration and provides a 22% power improvement over (...)
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REFERENCE DESIGNS Download
Reference Design Maximizing Signal Dynamic Range for True 10 Vpp Differential Input to 20 bit ADC
TIDA-01057 — This reference design is designed for high performance data acquisition(DAQ) systems to improve the dynamic range of 20 bit differential input ADCs. Many DAQ systems require the measurement capability at a wide FSR (Full Scale Range) in order to obtain sufficient signal dynamic range. Many earlier (...)
document-generic Schematic document-generic User guide
REFERENCE DESIGNS Download
20-bit 1MSPS DAQ Reference Design Optimizing Power Supply Efficiency While Minimizing EMI
TIDA-01056 — This reference design for high performance data acquisition (DAQ) systems optimizes power stage in order to reduce power consumption and minimize the effect of EMI from switching regulator by using LMS3635-Q1 buck converter.  This reference designs yields 7.2% efficiency improvement at most (...)
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REFERENCE DESIGNS Download
Reference Design Optimizing FPGA Utilization and Data Throughput for Automatic Test Equipment
TIDA-01051 — The TIDA-01051 reference design is used to demonstrate optimized channel density, integration, power consumption, clock distribution and signal chain performance of very high channel count data acquisition (DAQ) systems such as those used in automatic test equipment (ATE). Using serializers, such as (...)
document-generic Schematic document-generic User guide
REFERENCE DESIGNS Download
Optimized Analog Front End DAQ System Reference Design for 18 bit SAR Data Converters
TIDA-01050 — The TIDA-01050 reference design aims to improve the integration, power consumption, performance, and clocking issues typically associated with automatic test equipment. This design is applicable to any ATE system but most applicable to systems requiring a large number of input channels.
document-generic Schematic document-generic User guide
REFERENCE DESIGNS Download
ADC Driver Reference Design Improving Full Scale THD Using Negative Supply
TIDA-01052 — The TIDA-01052 reference design aims to highlight system performance increases seen using a negative voltage rail on the analog front end driver amplifiers rather than ground. This concept is relative to all analog front ends, however this design is aimed specifically at automatic test equipment.
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REFERENCE DESIGNS Download
0-1A, Single-Supply, Low-Side, Current Sensing Solution
TIPD129 — This TI Verified Design implements a single-supply, low-side current sensing solution that can accurately detect load current from 0-1A.  The corresponding linear output range is from 0V to 4.9V. This design relies on the LM7705 inverting charge pump to bias the negative supply of the OPA320 to (...)
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REFERENCE DESIGNS Download
Extending Rail-to-Rail Output Range for Fully Differential Amplifiers to Include True Zero Volts
TIDA-00187 — Operational amplifiers (op amps) have been used for decades in signal conditioning circuits and measurement systems. An op amp that has an output spanning from negative to positive supply rail are generally referred to as rail-to-rail output (RRO) op amps. These devices have been used increasingly (...)
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