Datasheet LTC1540 (Analog Devices) - 8
| Manufacturer | Analog Devices |
| Description | Nanopower Comparator with Reference |
| Pages / Page | 14 / 8 — APPLICATIONS INFORMATION. Hysteresis. Figure 5. Programmable Hysteresis. … |
| File Format / Size | PDF / 209 Kb |
| Document Language | English |
APPLICATIONS INFORMATION. Hysteresis. Figure 5. Programmable Hysteresis. TYPICAL APPLICATIONS. Level Detector
Model Line for this Datasheet
- LTC1540CDD#PBF LTC1540CDD#PBF LTC1540CDD#TRPBF LTC1540CDD#TRPBF LTC1540CMS8#PBF LTC1540CMS8#PBF LTC1540CMS8#TRPBF LTC1540CMS8#TRPBF LTC1540CS8#PBF LTC1540CS8#PBF LTC1540CS8#TRPBF LTC1540CS8#TRPBF LTC1540IDD#PBF LTC1540IDD#PBF LTC1540IDD#TRPBF LTC1540IDD#TRPBF LTC1540IMS8#PBF LTC1540IMS8#PBF LTC1540IMS8#TRPBF LTC1540IMS8#TRPBF LTC1540IS8#PBF LTC1540IS8#PBF LTC1540IS8#TRPBF LTC1540IS8#TRPBF
Text Version of Document
LTC1540
APPLICATIONS INFORMATION Hysteresis
15%. If hysteresis is not wanted, the HYST pin should Hysteresis can be added to the LTC1540 by connecting a be shorted to REF. Acceptable values for IREF range from resistor (R1) between the REF and HYST pins and a second 0.1µA to 5µA. If 2.4M is chosen for R2, then the value of resistor (R2) from HYST to V– (Figure 5). R1 (kΩ) is equal to the value of VHB (mV). The difference between the upper and lower threshold volt- VHB ages, or hysteresis voltage band (V 6 R1 = HB), is equal to twice I REF REF (2)(IREF) the voltage difference between the REF and HYST pins. R1 LTC1540 ( VHB 2 ) 5 1.182V – When more hysteresis is added, the upper threshold in- HYST R2 = IREF creases the same amount as the low threshold decreases. R2 V– 2 The maximum voltage allowed between REF and HYST pins is 50mV, producing a maximum hysteresis voltage 1540 • F05 band of 100mV. The hysteresis band may vary by up to
Figure 5. Programmable Hysteresis TYPICAL APPLICATIONS Level Detector
R1 = VREF = 1.182V = 1.18M The LTC1540 is ideal for use as a nanopower level detector IBIAS 1µA as shown in Figure 6. R1 and R2 form a voltage divider VIN from VIN to the noninverting comparator input. R3 and R2 = R1 – 1 V R4 set the hysteresis voltage, and R5 and C1 bypass the V HB REF + 2 reference output. The following design procedure can be used to select the component values: 4.65V – 1 1. Choose the VIN voltage trip level, in this example 4.65V. R2 = 1.18M 1.182V + 15mV 2. Calculate the required resistive divider ratio. 2 Ratio = V R2 = 3.40M REF/ VIN Ratio = 1.182V/4.65V = 0.254 VIN 5V 3. Choose the required hysteresis voltage band at the input 7 R2 V 3.4M V+ LTC1540 HBIN, in this example 60mV. Calculate the hysteresis 1% 3 IN+ voltage band referred to the comparator input V + HB. 8 R1 OUT V 1.18M 4 IN– HB = (VHBIN)(Ratio) 1% – VHB = (60mV)(0.254) 5 HYST V R3 HB = 15.24mV 15k 1% 6 REF 4. Choose the values for R3 and R4 to set the hysteresis. R4 R5 R4 = 2.4M 2.4M 430Ω 1% 5% V– GND 2 1 R3 (kΩ) = 15k, V C1 HB (mV) = 15mV 1µF 5. Choose the values for R1 and R2 to set the trip point. 1540 F06
Figure 6. Glitch-Free Level Detector with Hysteresis
1540fb 8 For more information www.linear.com/LTC1540
APPLICATIONS INFORMATION Hysteresis
15%. If hysteresis is not wanted, the HYST pin should Hysteresis can be added to the LTC1540 by connecting a be shorted to REF. Acceptable values for IREF range from resistor (R1) between the REF and HYST pins and a second 0.1µA to 5µA. If 2.4M is chosen for R2, then the value of resistor (R2) from HYST to V– (Figure 5). R1 (kΩ) is equal to the value of VHB (mV). The difference between the upper and lower threshold volt- VHB ages, or hysteresis voltage band (V 6 R1 = HB), is equal to twice I REF REF (2)(IREF) the voltage difference between the REF and HYST pins. R1 LTC1540 ( VHB 2 ) 5 1.182V – When more hysteresis is added, the upper threshold in- HYST R2 = IREF creases the same amount as the low threshold decreases. R2 V– 2 The maximum voltage allowed between REF and HYST pins is 50mV, producing a maximum hysteresis voltage 1540 • F05 band of 100mV. The hysteresis band may vary by up to
Figure 5. Programmable Hysteresis TYPICAL APPLICATIONS Level Detector
R1 = VREF = 1.182V = 1.18M The LTC1540 is ideal for use as a nanopower level detector IBIAS 1µA as shown in Figure 6. R1 and R2 form a voltage divider VIN from VIN to the noninverting comparator input. R3 and R2 = R1 – 1 V R4 set the hysteresis voltage, and R5 and C1 bypass the V HB REF + 2 reference output. The following design procedure can be used to select the component values: 4.65V – 1 1. Choose the VIN voltage trip level, in this example 4.65V. R2 = 1.18M 1.182V + 15mV 2. Calculate the required resistive divider ratio. 2 Ratio = V R2 = 3.40M REF/ VIN Ratio = 1.182V/4.65V = 0.254 VIN 5V 3. Choose the required hysteresis voltage band at the input 7 R2 V 3.4M V+ LTC1540 HBIN, in this example 60mV. Calculate the hysteresis 1% 3 IN+ voltage band referred to the comparator input V + HB. 8 R1 OUT V 1.18M 4 IN– HB = (VHBIN)(Ratio) 1% – VHB = (60mV)(0.254) 5 HYST V R3 HB = 15.24mV 15k 1% 6 REF 4. Choose the values for R3 and R4 to set the hysteresis. R4 R5 R4 = 2.4M 2.4M 430Ω 1% 5% V– GND 2 1 R3 (kΩ) = 15k, V C1 HB (mV) = 15mV 1µF 5. Choose the values for R1 and R2 to set the trip point. 1540 F06
Figure 6. Glitch-Free Level Detector with Hysteresis
1540fb 8 For more information www.linear.com/LTC1540
