Datasheet LTC1443, LTC1444, LTC1445 (Analog Devices) - 10

LTC1443/LTC1444/LTC1445
applicaTions inForMaTion Level Detector
The following design procedure can be used to select the The LTC1444 is ideal for use as a multisupply micropower component values: level detector as shown in Figure 5. 1. Choose the V1 voltage trip level, in this example 4.65V. R1 and R2 form a voltage divider from V1 to the non- 2. Calculate the required resistive divider ratio. inverting comparator A input. R6 and R7 are used to Ratio = V divide down V2, while R8 is the output pull-up resistor REF/ VIN for the comparator outputs. R3 and R4 set the hysteresis Ratio = 1.221V/4.65V = 0.263 voltage and R5 and C1 bypass the reference output. 3. Choose the required hysteresis voltage band at the input, V 5V HBIN, in this example 60mV. Calculate the hysteresis voltage band referred to the comparator input VHB. V2 3 V R6 V+ R8 HB = (VHBIN)(Ratio) 1.82M 2M 1% 1% V IN B+ 7 + HB = (60mV)(0.263) OUT B 1 VHB = 15.78mV V1 IN B– 6 – 4. Choose the values for R3 and R4 to set the hysteresis. R2 R4 = 2.4M 3.40M 1/2LTC1444 1% IN A+ 5 + R3(kΩ) = VHB = 15k OUT A 2 R7 5. Choose the values for R1 and R2 to set the trip point. 4 IN A– 1.21M – 1% R1 = V 14 HYST REF/IBIAS = 1.221V/1µA ≈ 1.21M R1 R3 1.21M 15k, 1% 8 REF   1%   + R4 R5 1.2V – R2 = R ( 1) VIN  − 1 2.4M 430Ω 1% 5% V– VREF + VHB  9  2  C1 1.0µF 144345 F05     R2 = 1.21 ( M) 4.65V  − 1
Figure 5. Glitch-Free Level Detector with Hysteresis
1.221V + 15mV   2  R2 = 3.40M Using the same equations, R6 and R7 are 1.82M and 1.21M, respectively, to set the trip level at 3V for V2. 144345fe 10 Document Outline Features Applications Description Absolute Maximum Ratings Typical Application Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Applications Information Package Description Revision History Typical Application Related Parts