Runic OP Amp RS8551, LDO RS3002 and RS3226 Series Apply in Hand-Held Infrared Thermometer Detector

PublishTime： 2023-01-01 Article Source：RUN-IC News

A hand-held infrared thermometer detector is a kind of non-contact, near-field human temperature detector which is popularly used in many temporary and fast temperature detective needed places. With the development of the current C-Virus situation, a Handheld infrared thermometer is mandatorily required to use when people are in and out of the communities, public places, etc. Runic is a High- tech company with high-performance analog signal chain design capabilities, Runic product lines such as OP Amps, Comparator, Analog Switch, LDO, etc. Can match very well with the demand for Infrared thermometers and medical equipment.

The theory of the Handheld infrared thermometer which uses an Analog thermopile probe’s schematic block diagram is as below:

Fig.1

In the picture, take the battery as 9V for example, it's using a High-voltage LDO RS3002 to transfer the battery voltage to 3V for all the system power supply, including MCU, LEDs, OP Amps, and others. Then use a low-power consumption LDO RS3236 step down 3V to 1.5V, the function of this is to provide a reference voltage for the thermopile and which will expand the temperature detective range. In order to calculate accurately under different environment temperatures, the MCU needs to read the current environment temperature and calculate through reading the voltage point of the NTC resistance and the 100KΩ resistance divide voltage in the thermopile.

As the thermopile’s output resistance is high, so the topology of the amplifier part suit adopts an In-phase amplifier, the magnifying power is more than 100 times, and needs a reserved low-pass filter to reduce the output noise. In order to maximize the resolution of the temperature, the 1/F noise of the OP Amp is need less than 5μVpp and the DC offset voltage is need less than 10μV. The OP Amp RS8551 in the block above is a self-stabilized, zero drift OP Amp developed by Runic technology, which has an Ultra-low offset voltage and is very suitable for DC or low-frequency signal amplify. the main parameters are as below:

●Wide voltage supply: 2.5V~5.5V.

●Ultra-low offset voltage: 1μV Type, 5μV Max.

●Ultra-low temp shift: 5nV/C Type, 50nV/C Max.

●Ultra-low current offset: 50pA.

●Gain Bandwidth: 4.5MHz.

● Quiescent current: 640μA per channel.

● 0.01Hz~10Hz noise: 0.75μVpp.

Runic can also supply the high input voltage LDO and low input voltage LDO with excellent performance—— RS3002 series and RS3226 series.

Main features of RS3002:

●Wide input voltage range: 2.5V~36V, Popular used in the Common 9V battery input application.

●Output current: 150mA.

●Ultra-low quiescent current: 2.5μA.

●low voltage drop: 10mA/mA.

●Ultra-high PSRR: 54dB/1kHz.

●Output voltage density optional: 1% or 2.5%.

●Kinds of fixed-output voltage and many packages such as SOT-23, SOT-89-3, and SOT-23-5 for your choice.

Main features of RS3226:

● Wide input voltage range: 1.7V~7.5V, support 4 cells dry battery input application.

●Internal max output current limit: >500mA.

●Ultra-low quiescent current: 20μA.

●Ultra-low drop voltage :1mV/mA.

●High PSRR: 70dB/Hz.

●Output voltage density optional: 1% or 2.5%.

●Kinds of fixed-output voltage and many packages such as SOT-23, SOT-89-3, SOT-23-5, and UTDFN-1*1-4L for your choice.

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