Datasheet LTC1841, LTC1842, LTC1843 (Analog Devices) - 8

LTC1841/LTC1842/LTC1843
U U W U APPLICATIONS INFORMATION
7 5V VHB 6 R1 = V + LTC1843 IREF REF (2)(IREF) 3 IN A+ 1M + R1 LTC1843 OUT A 1 OUT A HYST ( VHB 2 ) 5 1.182V – R2 = IREF V– – R2 5V 2 TO 8V 5 HYST 1841/43 F04 R2 10k 6 REF
Figure 4. Programmable Hysteresis
R3 R1 2.4M 430Ω V – C1 2 1841/43 F03a 1µF 15%. If hysteresis is not wanted, the HYST pin should be shorted to REF. Acceptable values for IREF range are from 0.1µA to 5µA. If 2.4M is chosen for R2, then the value of
Figure 3a. Power Supply Transient Test Circuit
R1 is equal to the value of VHB.
Window Detector
The LTC1843 is ideal for use as a micropower window 8V detector as shown in Figure 5. The values of R1, R2 and R3 V + are selected for a 4.5V undervoltage threshold and a 5.5V 5V overvoltage threshold. R4 and R5 set the hysteresis volt- DIV VREF age. The following design procedure can be used to select 2mV/ the component values: OUT 5V VIN 2ms/DIV 1841/1843 F03b 7 R3 V +
Figure 3b. Power Supply Transient Rejection
1M LTC1843 1M 3 IN A+ + OUT A 1
Hysteresis
– R2 5 HYST Hysteresis can be added to the LTC1842/LTC1843 by 62.2k 6 REF connecting a resistor (R1) between the REF and HYST pins R5 + and a second resistor (R2) from HYST to V – (Figure 4). 10k OUT B 8 4 IN B– The difference between the upper and lower threshold – voltages, or hysteresis voltage band (V R1 R4 HB), is equal to twice V 294k 2.4M OTH = 5.5V the voltage difference between the REF and HYST pins. VUTH = 4.5V V – As more hysteresis is added, the upper threshold in- 2 1841/43 F05 creases the same amount as the low threshold decreases. The maximum voltage allowed between REF and HYST pins is 50mV, producing a maximum hysteresis voltage
Figure 5. Dual Level Detector
band of 100mV. The hysteresis band may vary by up to 8