AN3552, Analog Comparator Tips And Tricks For The
eliminator. This is implemented using the analogcomparator, which recovers the original data from the input data stream. A low-pass filter comprised ofAnalog Comparator Tips and Tricks for the MC9S08QG MCU, Rev. 08Freescale Semiconductor
Function DescriptionR1 and C1 track the DC average of the incoming serial data stream with a time constant chosen to be muchlonger than the serial data rate. The time constant must not be very high, so that the capacitor will chargeto the DC value of the input data stream quickly. This averaged voltage on C1 becomes the reference valueat the non-inverting terminal of the comparator. The serial data stream is applied directly to the invertingterminal of the comparator. The transitions of the input data stream above and below the average valuescause the comparator output to swing between the VDD and ground reference.Figure 10. DC Offset Elimination CircuitEqn. 4Fc 1/(2*Π*R1*C1)Consider the input data is streaming at a rate of 1 kbps. Choose an RC time constant such that it is greaterthan (10 times approximately) the period of input data bit. Consider the low pass filter frequency is 150 Hz,which gives R1 10k and C1 0.1 μF, using Equation 4 for the low pass filter cutoff frequency.To get optimum performance, positive feedback to the comparator as explained in function 2 (hysteresis)can be provided. The thresholds can be fixed based on the input noise level.Figure 11 shows different waveforms involved in the application for the example considered. Channel 1(blue trace) shows a 1 kHz 2 Vp-p digital signal with a 1 V DC offset at the inverting terminal. Channel 2(red trace) is the averaged value at the non-inverting terminal. Channel 3 (green trace) is the recovereddigital data (inverted), with rail-to-rail transitions and the offset removed.Analog Comparator Tips and Tricks for the MC9S08QG MCU, Rev. 0Freescale Semiconductor9
Function DescriptionFigure 11. DC Offset Elimination WaveformsThe code for this example is shown in A.1, “CODE 1: Basic Initialization Program (for Functions 1, 2,4–7).” For this example, the MCU init function must have ACMPSC ACBGS 0 and SPMSC1 BGBE 0 to use the external reference.2.5Function 5: Voltage DoublerA voltage multiplier is an electrical circuit that converts AC electrical power from a lower voltage to ahigher DC voltage by means of capacitors and diodes combined into a network. The Voltage Doubler isthe basic stage of the voltage multiplier. This is implemented by using the on-chip analog comparator as asquare wave generator, from which the doubler action is achieved by using diode and capacitorcombinations, as shown in Figure 12.Analog Comparator Tips and Tricks for the MC9S08QG MCU, Rev. 010Freescale Semiconductor
Function DescriptionFigure 12. Voltage Doubler CircuitConfigure the comparator as a Schmitt trigger, as explained in Section 2.2, “Function 2: HysteresisImplementation.” This network generates the square wave. The values of R1, R2 and R3 can be found bythe same procedure explained in function 2. Remember, for a square wave generation, the higher (Vth) andlower (Vtl) thresholds must be equidistant from the value VDD/2. For a VDD of 3.3 V, one of thecombinations is, Vth 1.9 V and Vtl 1.4 V.Let us retain the values of hysteresis resistors explained in function 2, R1 R2 6.8k and R3 18k.The period of the square wave is decided by the R4 and C3 combination. Their values are calculated usingEquation 5.F 1/(2*R4*C3*ln (Vth/Vtl))Eqn. 5Consider a period of 1 ms or frequency (F) 1 kHz. Selecting the value of R4 15k, the value of capacitorC3 0.1 uF, from Equation 5.The values of RL and C2 must be such that this time constant is greater than 10 times the oscillating period,so that the output will be with minimum ripple.Let us consider the period of 1 ms, RL 4.7k and C2 10 μF is one choice. C1 is usually chosen to be sameas C2 value. The diode used is chosen to be 1N4148.Initially, when output is low, the capacitor C1 gets charged to VDD through D1. When the ou
through a software switch. When the ACBGS bit of the ACMPSC register is set, it connects the internal bandgap reference to the non-inverting terminal of the analog comparator. Figure 2. Voltage Monitoring Circuit Using Internal Reference Consider the normal battery voltage Vb 5 V and battery low threshold
CMOS COMPARATOR 1. Comparator Design Specifications Vo (Vin - Vin-) VOH VOL (Vin - Vin-) VOH VOL VIL VIH (Vin - Vin-) VOH VOL VIL VIH VOS (b) (c) (a) Figure 1. Comparator Transfer Characteristics. A comparator is a circuit that has binary output. Ideally
V VV. Comparator. X o K Lower-gain Amplifier-Based Comparator. V DD V B1 M 1 M 2 V B2 M 3 M 4 V IN V IN M 9 C L C L V OUT V OUT Amplifier-Based Comparator with Regenerative Feedback. Amplifier-Based Comparator with Regenerative Feedback. At the start of the comparison process, an amplifier-based comparator behaves as a linear amplifier.
amplifiers and the higher the comparator's parasitic input capacitances. As an alternative to the traditional methods, we propose using calibration as an extra design variable for dealing with comparator offset in pipeline ADCs, with the target of simplifying comparator design and relaxing the OS and driving requirements of MDAC op-amps.
In this paper, the 8-bit comparator circuit designs that use as the higher number of bits are proposed. The comparative design and analysis of 4-bit comparator and 8-bit comparator using GDI logic. For com
The comparator is shipped fully assembled. It is ready to use after unpacking and installing the glass screen included. 1. Remove the comparator from the shipping container. The glass screen is packed in a separate box. Place the comparator on a bench and remove the packing materials. 2. Refer to Figure 1.
1.2.1 A high-speed CMOS comparator with 8-bit resolution A high-speed CMOS comparator is shown in figure 1.2. The comparator consists of three blocks, an input stage, a flip-flop and SR latch. The architecture uses two non-overlapping clocks ( 1and 2). The circuit operates in two m
Abstract—This brief presents a digital background calibration technique that embraces comparator decision time to calibrate interstage gain errors and capacitor mismatches in pipelined analog-to-digital converters (ADCs). It does not modify the orig-inal analog signal path except for the addition of a comparator
Invitation to Tender TfL/90711 – Bridge Design Consultancy Services Page 9 Closing date for return of ITT responses. 25 February 2013 at 12 noon ITT Evaluation 5 working days Notification of ITT results w/c 11 March 2013 Contract Award w/c 11 March 2013 Please note that TfL reserves the right to change the above dates and timings 13. DURATION OF CONTRACT The Contract will be awarded for 6 .
