Monday, April 03, 2017

Digital Potentiometer - AD5242 - Analog Devices

AD5241 and AD5242 provide a single-/dual-channel, 256-position, digitally controlled variable resistor (VR) device. They have 2-Wire I2C Compatible Digital Interface.

Digital Potentiometer - AD5242 - Analog Devices

They are Analog Semiconductor Replacements for Electromechanical Devices like potentiometer, trimmer or variable resistor.

The Advantage of the latter is low cost and easy to configure and use. The Advantage of the Digital Version is "No moving Parts". hence not limited to things like "10000 operations". Another clear advantage is precision and vibration resistant.

See an Application of this Digipot in a TinyOS hardware magnetometer.. 

Digital Potentiometer AD5242 Magnetometer Application

The temperature stability of 30 ppm/°C and low noise settings is also achieved with SiCr thin film resistor technology. They range from 10K, 100K and 1M Ω End-to-End Terminal Resistances.

Digipots are not for high currents or power, even high voltage and very low resistance values are not for these devices. These are signal control devices. Use it for analog circuits and instrumentation and signal control too.

MAX5160 Digital Potentiometers - Maxim

They are linear-taper digital potentiometers perform the same function as a mechanical potentiometer or a variable resistor.

MAX5160 Digital Potentiometers - Maxim

Three resistance values are available for each part type: 50kΩ,100kΩ, and 200kΩ. A nominal resistor temperature coefficient of 50ppm/°C end-to-end and only 5ppm/°C ratiometric.

MAX5160 Digital Potentiometers - Maxim

This has 32 Tap Positions, 400Ω Wiper Resistance, 3-Wire Serial Data Input . Power-On Reset: Wiper Goes to Midscale (position 16).

See an application circuit of this chip - A solid-state industrial potentiometer simulates an equivalent mechanical potentiometer, and fits in the same space. 

Industrial 0V to +10V Digital Potentiometer

The key to this circuit is a low-power digital potentiometer IC, 100kΩ version (U3). Configured as a voltage divider, this IC provides an output of 32 discrete voltage steps between its minimum and maximum settings (0V and 5V). A low-power linear regulator (U1) provides a +5V supply rail for U2, U3, and a resistor ladder internal to U3 (whose maximum rating is +5V).

Saturday, April 01, 2017

AD8436 - Low Cost RMS to DC Convertor

This chip from Analog Devices  computes a precise dc equivalent of the rms value ac waveforms, including complex patterns such as those generated by switchmode power supplies and triacs.

AD8436 - Low Cost RMS to DC Convertor

There is an evaluation board available to study its performance.

AD8436 - Low Cost RMS to DC Convertor

Delivers true RMS or average rectified value of an AC input and Fast is settling at all input levels.It is an Accurate conversion with crest factors up to 10.

AD8436 - Low Cost RMS to DC Convertor

Typical application for frequencies as low as power line, and above. The recommended averaging, crest factor and LPF capacitor values are 10 μF, 0.1 μF and 3.3 μF.

Other Features
  • Accuracy: ±10 µV ± 0.5% of reading 
  • 100 µV rms to 3 V rms (8.5 V p-p) full-scale input
  • 1 MHz for -3 dB (300 mV) 
  • 65 kHz for additional 1% error 
  • Zero converter dc output offset 
  • Low power: 300 µA typical at ±2.4 V

Sunday, March 05, 2017

TPS65070 Handheld Gadget Power Chip

One chip that takes care of all Power requirements in a Portable Electronic Gadget. Power Management Multi-Channel IC (PMIC) Solutions - PMIC Solutions with and without Battery Charger.

TPS65070 Handheld Gadget Power Chip

A battery charger for single Li-Ion or Li-Polymer cell. The voltages needed for an embedded system. Includes PWM mode using I2C. wLED Boost Converter, Touch Screen Interface. 10 Bit A/D Converter too.

TPS65070 Handheld Gadget Power Chip

Charger/Power Path Management:
  • 2A Output Current on the Power Path
  • Linear Charger; 1.5A Maximum Charge
  • I Limit - 100mA/500mA/ 800mA/1300mA
  • Thermal Regulation, Safety Timers
  • Temperature Sense Input
Battery charging, gauging and protection

"As different battery technologies like Lithium Iron Phosphate (LiFePO4) and Super Capacitor are becoming more popular, TI .........."

Figure below shows a complete application diagram that details how to connect the TPS65070 to power an OMAP-L132/L138 application processor.

TEAC USB Interface

The TPS65070 is a single-chip with multiple voltage outputs. Here it provides the different voltages required by the DSP chip. It is a convenient, integrated solution to provide the power to the main chip instead of using separate regulators.

Saturday, March 04, 2017

LT1510 - CC CV Battery Charger

A Circuit for charging NiCd, NiMH and Lithium-Ion Batteries.PWM 500kHz with Soft Start and Shutdown Control.

Linear Technology - LT1510 - CV CC Battery Charger

The LT1510 can charge batteries ranging from 2V to 20V. Ground sensing of current is not required and the battery’s negative terminal can be tied directly to ground. A saturating switch running at 200kHz (500kHz for LT1510-5) giveshigh charging efficiency and small inductor size

LT1510 - CC CV Battery Charger

Notes -

Some things to know in battery charging. A battery that has drained will almost appear like a short circuit to the charger. A battery is never fully drained, if you want a nice battery life. Overcharging a battery can damage it and is not safe too. We have to charge it with an optimum current, upto a Top up charge voltage only. Then a trickle to compensate for internal leakage on no-load. Float charging and Cyclic charging are some popular methods.

It can charge lithium-ion (Li-Ion), nickel-metal-hydride (NiMH) and nickel-cadmium (NiCd). These require constant-current and constant-voltage charging. A 2A peak current switch for Boost Charging may be helpful for charging Lead Acid Batteries too. A 0.1 ohm current sense shunt makes charging current programmable.

3.6v and 3.7v Lithium Battery Charger

The charger is based on the LT1510IN Constant-Voltage/ Constant-Current battery charger IC from Linear Technology. It can be configured to charge NiCd, NiMH or Lithium-Ion (and Lithium-Polymer) batteries at up to 1.5 Amps.

Thursday, March 02, 2017

Fast-Charge Controllers - MAX712 and MAX713

Uses MAX712/MAX713 fast charge controllers. PCB Design too. The only difference between them is the battery-fully-charged sensing method. The MAX713 is designed for NiCd batteries, while the 712 is for NiMh batteries.

Fast, smart and universal NiCd/NiMh battery charger

This is a project by Roberto Barrios at his Ham Projects EB4EQA Site.

Application Note - The MAX712 terminates fast charge by detecting zero voltage slope, while the MAX713 uses a negative voltage-slope detection scheme.

Fast-Charge Controllers - MAX712

The MAX712/MAX713 are powered by the DC source via an on-board +5V shunt regulator. They draw a maximum of 5µA from the battery when not charging.

Fast-Charge Controllers - MAX712 and MAX713

Some Specs
  • Charge 1 to 16 Series Cells
  • Supply Battery's Load While Charging (Linear Mode)
  • Fast Charge from C/4 to 4C Rate
  • C/16 Trickle-Charge Rate
  • Automatically Switch from Fast to Trickle Charge