PTC and NTC Thermistors - Murata

While PTC Ohms increments on Temperature rise, the NTC is the opposite its Ohmic Resistance drops with rise in temperature. Both types are very useful in Power Electronics and Electrical Immunity of Telecommunication Units.

PTC and NTC Thermistors - Murata

Another application in in control systems, Temperature Measurement and Control. Watchdog Controllers to prevent a Burn-out of system, this happens when a software based electronic control system breaksdown or hangs.

Murata's PTC Thermistors called POSISTOR detect overheating to protect a circuit from drawing more than rated current in a equipment. This prevents a fire hazard and most important protects devices and units.

The NTC Thermistor are used in inrush current limiting and also temperature compensation in electronic products.

Protecting the MOSFET of DC-DC Converters from Overheating

When the MOSFET temperature goes beyond the design limit the PTC thermistor which is thermally coupled to the device builds up its Ohmic Value, thereby the Emitter-Base Voltage rises to bias the NPN, which drinks away the bias meant for Mosfet. That works as the Foldback protection.

Silicon PTC Thermistors - RTI Electronics

Extensively used in temperature compensating and sensing applications. Circuit design applications include power supplies and Over-Temperature protection.

Silicon PTC Thermistors - RTI Electronics

Positive Temperature Coefficient (PTC) thermistors - the resistance increments with temperature rise. An example application for 'Standard PTC Thermistors' of say 1 Ohm is Thermal runaway prevention in stacked power semiconductors. The Thermistor Thermally connected to the device/heatsink case, when device gets heated the current flow drops, as thermistor resistance increases, thereby balancing load. This Silicon PTC can also be used but in the bias or drive circuit as the resistance is more.

Thermistors offer a regulation or monitor of temperature over a narrow range at a lower cost. Thermistors with minimum analog circuitry can replace bimetallic thermostats in most situations.

RTD and Thermocouples offer wider range and a more consistent output for Recording and Measurement. Thermistors are ideal for closed loop controls for protecting electrical equipment by limiting or cutting off the input power.

General Notes - PTC Thermistors - PTC Thermistor

RTI Electronics designs, manufactures and sells thermistor, magnetic and film capacitor products. They also manufacture a full line of Magnetics, including Current Transformers & Sensors, Inductors & Power Transformers.

RTI Electronics, Inc. 1800 E. Via Burton St. Anaheim, CA 92806-1213

SM Series High-Value Resistors - Ohmcraft

SM Chip Resistors go to values in giga-ohms. The Technology - Micropenned serpentine patterned resistors, engineered for ultra precision.

SM Series High-Value Resistors - Ohmcraft

These are surface mount resistors, the Resistive Element is Thick Film on Alumina Substrate. We can get Voltage Ratings upto 600 Volts and 50 Gigohms Values. Low noise high stability resistors.

From - Ohmcraft - Micropen Technologies Corporation

93 Paper Mill St., Honeoye Falls, NY 14472

Precision Resistors - UNS 4-T220 - Riedon

These Precision Shunt Resistors are designed for systems which have a fast changing electrical load. It has a Heatsink and is encapsulated in epoxy. The substrate is Alumina for Good Heat Transfer but with Electrical Insulation. It is a Resistor formed by a NiCr Foil. (Like Nichrome).

Precision Resistors - UNS 4-T220 - Riedon

Specifications

• Resistance from 0.2 Ohm to 80 Ohms
• Power Rating to 15 Watts
• Resistance Tolerances to ±0.01%
• TCR to ±1ppm/K
• Load Stability to 0.01%

Here are some documents that will build your awareness on how Resistors work and their Thermal behavior. These are from a firm called Riedon who design manufacture custom resistors and special resistors used in tight design requirements.

Riedon's Technical Information

Resistors are probably the most common and well known of all electrical components. Applying a resistor to a circuit normally requires (1) calculating the nominal values needed in the circuit application (resistance, power rating, etc.) then (2) developing acceptable tolerances for the resistor that ensure it will function properly in all extremes of the application.

Read up the "Temperature dependence and TC" - The absolute ohmic value of a resistor is temperature-dependent. Also the "Definition of terms in the specifications of Resistors."

Interface - @riedonresistors

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

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.

LT1510 - CC CV Battery Charger

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.

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 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