Understanding and Implementing Hysteresis in Comparator Circuits

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Comparator circuits with hysteresis play a crucial role in signal processing applications. This article explores the theory behind comparator functions, hysteresis adjustment, and practical implementation using the TLV1701-Q1 series. Learn how to set up non-inverting and inverting comparators with hysteresis, optimize resistor values, and enhance accuracy through simulation. Find guidelines for applying hysteresis effectively in push-pull comparator circuits.


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  1. Comparators with Hysteresis E2E: TLV1702-Q1 hysteresis adjustment Zak Kaye Thomas Kuehl 1

  2. The Comparator function + + 5 V Rp 10 k V1 and V2 are two input voltages applied to +IN and -IN inputs Either one may be a dc level, or a changing ac signal Vout can be one of two levels; VH high (1), or VL low (0) VH V+ and VL 0 V, or GND Non-inverting condition If V1 > V2, Vout will be high If V1 < V2, Vout will be low Inverting condition If V2 > V1, Vout will be low If V2 < V1, Vout will be high V+ Vout -IN Vout Vin 2.5 V V2 +IN 100 uA + + 0.1 V V1 2

  3. Setting up a comparator circuit to use hysteresis Non-inverting comparator, open-collector Goals VHYST 100 mV, Vref 2.5 V Let Vcc = 5 V, VO(max) = 5 V, VO(min) = 50 mV R1 = 100 K, Rpull-up = 10 k Then R2 = 104 5.0 2.5 1 R1 = = 100 k Vcc Vref 1 105 105 105+105 = 50 k R1 R2 R1+R2 = R3 = ??(???) ??(???) VHYST 5.0 0.05 0.10 1 = 5 104 R4 = R3 1 Equations simplified by setting Rpull-up < 0.1*R4 Threshold voltage errors are in low percent range R4 = 2.43 MEG 3

  4. Setting up a comparator circuit to use hysteresis TLV1701 Non-inverting comparator, open-collector, 100 mV HHYST VH = 2.55 V VL = 2.45 V VHYST = 100 mV TINA-TI simulation and verification Hysteresis accuracy improves with Rpull-up < 0.1 R4 Equations can be used for push-pull output too! 4

  5. Setting up a comparator circuit to use hysteresis TLV1701 Inverting comparator, open-collector Let Goals Vcc = 5 V, VO(max) = 5.0 V, VO(min) = 0.05 V VHYST = 50 mV, Vref = 2.5 V R1 = 10 k, Rpull-up = 10 k Then R2 = 104 5.0 2.5 1 ?1 = = 10 k ??? ???? 1 ??(???) ??(???) VHYST ?1 ?2 ?1+?2 R3 = 1 104 104 104+104 5.0 0.05 0.05 R3 = 1 = 490 k 5

  6. Setting up a comparator circuit to use hysteresis Inverting comparator, open-collector, 50 mV VHYST VH = 2.52 V VL = 2.47 V VHYST = 49.5 mV TINA-TI simulation and verification Hysteresis accuracy improves with Rpull-up < 0.1 R3 Equations can be used for push-pull output too! 6

  7. Setting up a comparator circuit to use hysteresis Some guidelines when applying hysteresis Push-pull comparators with hysteresis applied The resistor values directly affect the reference voltage and the VH and VL levels. Their tolerances are an important factor in hysteresis accuracy Keeping Rpull-up 10 % of the feedback resistor value for open-drain/ collector outputs assures more accurate VHand VL voltage levels The inverting and non-inverting equations can be used for push-pull output comparators Use the datasheet Output Voltage vs Output Current curves to establish VO(max)and VO(min)from the VOH and VOL levels 7

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