In this episode Shahriar explores the world of Delta-Sigma modulators with emphasis on a Delta-Sigma Analog to Digital Converter (ADC). The basic concepts of analog to digital conversion is presented, particularly with respect to quantization noise spectral shape and power density. Next, oversampling ADCs are presented to demonstrate the possibility of increasing SQNR (ENOB) through manipulation of quantization noise spectrum.
Due to the practical limitations of high oversampling ratios, delta-sigma modulations is explored. The principle operation behind delta-sigma ADCs is presented with detailed explanation on noise shaping, filtering and decimation. The signal and noise transfer functions for a 1st order and 2nd order delta-sigma ADC are derived. Finally, as a practical example, a 2nd order delta-sigma ADC based on a 1-bit quantizer is presented. The ADC uses two Miller integrator op-amps, one comparator and a D-Type flip-flop. The complete measurement of this delta-sigma ADC is presented. The impact of over sampling ration, op-amp linearity and input signal bandwidth is presented. The slides for this video can be downloaded from The Signal Path website.
Theory, Design and Characterization of Delta-Sigma Analog to Digital Converters - [Link]
by Avago Technologies:
Analog isolation is still widely used in motor drives, power monitoring, etc whereby applications typically use inexpensive analog voltage control for speed, intensity or other adjustments.
The HCNR201/200 analog optocoupler is commonly added to isolate the analog signal in the front end module of an application circuitry. The optocoupler will be placed between the analog input and the A/D converter to provide isolation of the analog input from the mixed signal ADC and other digital circuitries. The HCNR201/200 is an excellent solution for many of the analog isolation problems.
Fast analog isolation with linear optocouplers - [Link]
An SMPS application using PIC16F785 from Microchip. [via]
In this application note, we will examine a typical buck topology intelligent SMPS design using the PIC16F785.
The design presented here shows an alternative single-chip approach to adding intelligence to SMPS designs. The basic design is really unchanged. There are current and voltage feedback loops, a counter-based PWM is used to generate the reference voltage to the voltage loop, and the microcontroller uses the reference voltage to modify the operation of the system in response to conditions sensed through the ADC.
App note: Switching power supply design with the PIC16F785 - [Link]
by prem_ranjan @ open-electronics.org:
We have designed an Oscilloscope using PC and Arduino Board. The signal is first of all fed to the Arduino Board where the analog signal is converted to a digital signal by the ADC which is then serially outputted to the PC and is read by the MATLAB software via the COM ports. Here the signal is read in the form of digital data but then is converted to analog one by using the resolution of the ADC used by the Arduino Board. The MATLAB software was then used to plot the signals.
A PC and an Arduino: here’s your DIY Oscilloscope - [Link]
TMP75B 1.8-V Digital Temperature Sensor with Two-Wire Interface and Alert. by ti.com:
The TMP75B is an integrated digital temperature sensor with a 12-bit analog-to-digital converter (ADC) that can operate at a 1.8-V supply, and is pin and register compatible with the industry-standard LM75 and TMP75. This device is available in an SOIC-8 package and requires no external components to sense the temperature. The TMP75B is capable of reading temperatures with a resolution of 0.0625°C and is specified over a temperature range of –55°C to +125°C.
The TMP75B features SMBus and two-wire interface compatibility, and allows up to eight devices on the same bus with the SMBus overtemperature alert function. The programmable temperature limits and the ALERT pin allow the sensor to operate as a stand-alone thermostat, or an overtemperature alarm for power throttling or system shutdown.
TMP75B – 1.8V Capable Digital Temperature Sensor - [Link]
Electronic scales are widely used in kitchens and bathrooms because they can quickly make accurate weight measurements.
A load sensor called a load cell is used for weight measurement. Because the output voltage of this sensor is very small, it is amplified by an operational amplifier (op-amp) and input to an A/D converter. A microcontroller (MCU) converts the signal to weight based on the conversion results of the A/D converter and displays it.
Renesas offers a lineup of microcontroller products for meeting their customers’ needs, such as the RL78/L1x, 78K0/Lx3, and R8C/Lx series with built in LCD driver for designing small and inexpensive models. For highly precise measuring, they offer the 78K0/Lx3, the H8/38086R group, the RX21A group, and other with built-in high precision ΔΣ (delta-sigma) A/D converter.
Renesas MCU for Electronic Scales - [Link]
The LTC2338 fully differential 1Msps SAR ADC family offers a wide ±10.24V true bipolar input range for high voltage industrial applications. The proprietary internal reference buffer maintains less than 1LSB error during sudden bursts of conversions, enabling true one-shot operation after lengthy idle periods. The internal reference can be overdriven to interface to a range of signal levels that swing above and below ground. The LTC2338 family eliminates complicated circuitry required to interface true bipolar signals to ADCs, and provides a compact solution for easy interfacing to 1.8V to 5V serial logic. The LTC2328 offers similar performance with a pseudo-differential input.
LTC2338-18 – 18-Bit, 1Msps, ±10.24V True Bipolar, Fully Differential Input ADC with 100dB SNR - [Link]
This Instructable will teach you how to use the Arduino Analog ports. johnag @ instructables.com writes:
Digital Voltmeters (DVMs) are a special case of Analog to Digital converters- A/DCs.- they measure voltage – and are usually a function of a general purpose instrument called a Digital Multimeter( DMMs), commonly used to measure voltages in labs and in the field. DMMs display the measured voltage using LCDs or LEDs to display the result in a floating point format. They are an instrument of choice for voltage measurements in all kinds of situations. This instructable will show you how to use the Arduino as a DC DVM (Direct Current Digital Volt Meter).
Make a Mini Arduino programmable 4 channel DC-DVM - [Link]
by Claude Haridge:
Microcontroller-based products sometimes require rotary switches. As many microcontrollers have an onboard ADC, it is easy to replace the rotary switch with a low cost potentiometer, when a rotary switch is too expensive or unavailable.
Although digitizing a potentiometer setting to act like a switch requires only a few instructions, an immediate problem is that instabilities in value occur at the switching threshold between one value and the next due to electrical or mechanical noise. The solution is to introduce upper and lower hysteresis thresholds about each transition so that the potentiometer needs to move beyond a threshold before another switch state is validated. For every updated switch state, another pair of thresholds replaces the previous. In this manner, the hysteresis provides clean switching between states.
Replace a rotary switch with a potentiometer - [Link]
By Stephen Evanczuk
For circuits relying on lithium-ion cells, determining the amount of charge remaining in a cell requires specialized techniques that can complicate the design of energy-harvesting applications. Engineers can implement these techniques with MCUs and ADCs normally used in these applications, but at the cost of increased complexity. Instead, engineers can easily add this functionality to existing designs using dedicated “fuel-gauge” ICs available from manufacturers including Linear Technology, Maxim Integrated, STMicroelectronics, and Texas Instruments.
Determining the state of charge (SOC) in lithium-ion batteries is essential yet challenging due to the great variability in capacity not only across different cells, but also in the same cell. As a Li-ion cell ages, it loses its ability to store charge. Consequently, even if fully charged, an older cell would deliver usable voltage for a shorter period of time than a newer cell. With any Li-ion cell, SOC varies greatly depending on the temperature and discharge rate, resulting in a unique family of curves for any particular cell (Figure 1).
Fuel-Gauge ICs Simplify Li-Ion Cell Charge Monitoring - [Link]