TLV3502-Q1
SBOS507 –FEBRUARY 2010
www.ti.com
Input Over-Voltage Protection
Device inputs are protected by ESD diodes that will 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 3.
VS
µ
µ
2.2 F
0.1
F
R
VIN
VOUT
TLV3501
VREF
Figure 3. Input Current Protection for Voltages Exceeding the Supply Voltage
Relaxation Oscillator
The TLV350x can easily be configured as a simple and inexpensive relaxation oscillator. In Figure 4, the R2
network sets the trip threshold at 1/3 and 2/3 of the supply. Since 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 4, the output is calculated to be
10.9MHz. An implementation of this circuit oscillated at 9.6 MHz. Parasitic capacitance and component
tolerances explain the difference between theory and actual performance.
VC
2/3 (V+)
1/3 (V+)
t
V+
R1
1.38R1C
VS = 5V
1k
C
62pF
Ω
VOUT
t
R2
R2
Ω
5k
f = 10MHz
Ω
5k
V+
R2
Ω
5k
Figure 4. Relaxation Oscillator
High-Speed Window Comparator
A window comparator circuit is used to determine when a signal is between two voltages. The TLV3502 can
readily be used to create a high-speed window comparator. VHI is the upper voltage threshold, and VLO is the
lower voltage threshold. When VIN is between these two thresholds, the output in Figure 5 is high. Figure 6
shows a simple means of obtaining an active low output. Note that the reference levels are connected differently
between Figure 5 and Figure 6. The operating voltage range of either circuit is 2.7 V to 5.5 V.
8
Submit Documentation Feedback
Copyright © 2010, Texas Instruments Incorporated
Product Folder Link(s): TLV3502-Q1
TI [ TEXAS INSTRUMENTS ]
