Consider the case of VIN = 0. The output of comparator 4 is also at ground, "shorting" the capacitor and holding

it at 0V. This implies that the outputs of comparators 1, 2, and 3 are also at 0V. When an input signal is applied,

the output of open drain comparator 4 goes High-Z and C charges exponentially through R. This is indicated in

the graph. The output voltages of comparators 1, 2, and 3 switch to the high state in sequence when VC rises

above the reference voltages V1, V2 and V3. A small amount of hysteresis has been provided by the 10kΩ and

10MΩ resistors to insure fast switching when the RC time constant is chosen to give long delay times. A good

starting point is R = 100kΩ and C = 0.01µF to 1µF.

All outputs will immediately go low when VIN falls to 0V, due to the comparator output going low and immediately

discharging the capacitor.

Comparator 4 must be a open-drain type output (TLV1822-EP), whereas comparators 1 though 3 may be either

open drain or push-pull output, depending on system requirements. RPU is not required for push-pull output

devices.

6.2.5 Logic Level Shifter

The output of the TLV1822-EP is the uncommitted drain of the output transistor. Many open-drain outputs can be

tied together to provide an output OR'ing function if desired.

+

±

R1

VCC

Logic

Out

VLOGIC

0

RPULLUP

VLOGIC

Logic

In

10 kŸ

R2

10 kŸ

VCC

VCC

0

Open

Drain

Output

Figure 6-14. Universal Logic Level Shifter

The two 10kΩ resistors bias the input to half of the input logic supply level to set the threshold in the mid-point

of the input logic levels. Only one shared output pull-up resistor is needed and may be connected to any pull-up

voltage between 0V and 5.5V. The pullup voltage should match the driven logic input "high" level.

6.2.6 One-Shot Multivibrator

+

±

R1

1 0Ÿ

R2

1 0Ÿ

R4

D1

1N4148

C1

100 pF

D2

1N4148

C2

t0

+VIN

+V

t0

t1

V2

V1

PW

0

+V

Figure 6-15. One-Shot Multivibrator

A monostable multivibrator has one stable state in which it can remain indefinitely. It can be triggered externally

to another quasi-stable state. A monostable multivibrator can thus be used to generate a pulse of desired width.

The desired pulse width is set by adjusting the values of C2 and R4. The resistor divider of R1 and R2 can be

used to determine the magnitude of the input trigger pulse. The output will change state when V1 < V2. Diode

TLV1812-EP, TLV1822-EP

SNOSDJ3 – MAY 2024

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