TLV3501A-Q1 Datasheet, PDF (9/18 Pages) Texas Instruments – 4.5-ns Rail-to-Rail, High-Speed Comparator in Microsize Packages

TLV3501-Q1
www.ti.com
SBOS533A – SEPTEMBER 2010 – REVISED SEPTEMBER 2010
Input Over-Voltage Protection
Device inputs are protected by electrostatic discharge (ESD) diodes that conduct if the input voltages exceed the
power supplies by more than approximately 300 mV. Momentary voltages greater than 300 mV beyond the
power supply can be tolerated if the input current is limited to 10 mA. This limiting is easily accomplished with a
small input resistor in series with the comparator, as shown in Figure 17.
V_S
V_IN
V_REF
0.1 mF
2.2 mF
TLV3501-Q1
V_OUT
Figure 17. Input Current Protection for Voltages Exceeding the Supply Voltage
Relaxation Oscillator
The TLV3501-Q1 can easily be configured as a simple and inexpensive relaxation oscillator. In Figure 18, the R₂
network sets the trip threshold at 1/3 and 2/3 of the supply. Because this is a high-speed circuit, the resistor
values are rather low to minimize the effect of parasitic capacitance. The positive input alternates between 1/3 of
V+ and 2/3 of V+ depending on whether the output is low or high. The time to charge (or discharge) is 0.69R₁C.
Therefore, the period is 1.38R₁C. For 62 pF and 1 kΩ as shown in Figure 18, the output is calculated to be 10.9
MHz. An implementation of this circuit oscillated at 9.6 MHz. Parasitic capacitance and component tolerances
explain the difference between theory and actual performance.
V_C
2/3 (V+)
1/3 (V+)
t
C
62 pF
V_S = ^V+
5 V R₁
1 kW
1.38R₁C
V_OUT
R₂
5 kW
V+
R₂
5 kW
R₂
5 kW
t
f = 10MHz
Figure 18. Relaxation Oscillator
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