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TS9001-2 データシート(PDF) 6 Page - Touchstone Semiconductor Inc |
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TS9001-2 データシート(HTML) 6 Page - Touchstone Semiconductor Inc |
6 / 8 page TS9001 Page 6 TS9001DS r1p0 RTFDS out of the region where oscillation occurs. Figure 2 illustrates the case in which an IN- input is a fixed voltage and an IN+ is varied. If the input signals were reversed, the figure would be the same with an inverted output. To save cost and external pcb area, an internal 4mV hysteresis circuit was added to the TS9001-1/2. Adding Hysteresis to the TS9001-1 Push-pull Output Option The TS9001-1 exhibits an internal hysteresis band (VHYSB) of 4mV. Additional hysteresis can be generated with three external resistors using positive feedback as shown in Figure 3. Unfortunately, this method also reduces the hysteresis response time. The procedure to calculate the resistor values for the TS9001-1 is as follows: 1) Setting R2. As the leakage current at the IN pin is less than 2nA, the current through R2 should be at least 0.2μA to minimize offset voltage errors caused by the input leakage current. The current through R2 at the trip point is (VREF - VOUT)/R2. In solving for R2, there are two formulas – one each for the two possible output states: R2 = VREF/IR2 or R2 = (VCC - VREF)/IR2 From the results of the two formulae, the smaller of the two resulting resistor values is chosen. For example, when using the TS9001-1 (VREF = 1.252V) at a VCC = 3.3V and if IR2 = 0.2μA is chosen, then the formulae above produce two resistor values: 6.26MΩ and 10.24MΩ - the 6.2MΩ standard value for R2 is selected. 2) Next, the desired hysteresis band (VHYSB) is set. In this example, VHYSB is set to 100mV. 3) Resistor R1 is calculated according to the following equation: R1 = R2 x (VHYSB/VCC) and substituting the values selected in 1) and 2) above yields: R1 = 6.2MΩ x (100mV/3.3V) = 187.88kΩ. The 187kΩ standard value for R1 is chosen. 4) The trip point for VIN rising (VTHR) is chosen such that VTHR > VREF x (R1 + R2)/R2 (VTHF is the trip point for VIN falling). This is the threshold voltage at which the comparator switches its output from low to high as VIN rises above the trip point. In this example, VTHR is set to 3V. 5) With the VTHR from Step 4 above, resistor R3 is then computed as follows: R3 = 1/[VTHR/(VREF x R1) - (1/R1) - (1/R2)] R3 = 1/[3V/(1.252V x 187kΩ) - (1/187kΩ) - (1/6.2MΩ)] = 136.9kΩ In this example, a 137kΩ, 1% standard value resistor is selected for R3.. Figure 3 : Using Three Resistors Introduces Additional Hysteresis in the TS9001-1. Figure 2 : TS9001 Threshold Hysteresis Band |
同様の部品番号 - TS9001-2 |
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同様の説明 - TS9001-2 |
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