LTC1540 APPLICATIONS INFORMATION REFERENCE OUTPUT 7 REF V+ LTC1540 R1 3 IN+ LTC1540 + 8 OUT 4 IN– C1 – V– 5V 5 HYST TO 8V 1540 • F01 R2 10k Figure 1. Damping the Reference Output 6 REF R3 R1 2.4M 430Ω V– GND 1000 C1 2 1 1µF 100 1540 • F03a Figure 3a. Power Supply Transient Test Circuit 10 RESISTOR VALUE (kΩ) 1 8V V+ 0.1 5V 0.001 0.01 0.1 1 10 CAPACITOR VALUE (µF) VREF 1540 • F02 2mV/DIV Figure 2. Damping Resistance vs Bypass Capacitor Value Figure 3 shows the bypassed reference output with a square OUT wave applied to the V+ pin. Resistors R2 and R3 set 10mV 1540 F03b 2ms/DIV of hysteresis voltage band while R1 damps the reference response. Note that the comparator output doesn’t trip. Figure 3b. Power Supply Transient RejectionLow Voltage Operation: V+ = 1.6V 5 The guaranteed minimum operating voltage is 2V (or V– = GND = 0V ±1V). As the total supply voltage is reduced below 2V, IN+ = 0V 4 IN– = REF = HYST the performance degrades and the supply current falls. TA = 25°C At low supply voltages, the comparator’s output drive is 3 reduced and the propagation delay increases. The VREF and VOS are also slightly worse. The useful input voltage 2 range extends from the negative supply to 0.9V below SUPPLY CURRENT (µA) the positive supply. Test your prototype over the full 1 temperature and supply voltage range if operation be- low 2V is anticipated. Because of the increase in sup- 0 0 0.5 1.0 1.5 2.0 2.5 ply current, operation below 1.5V is not recommended SUPPLY VOLTAGE (V) (Figure 4). 1540 F04 Figure 4. Supply Current vs Supply Voltage 1540fb For more information www.linear.com/LTC1540 7