September 2001

5

MIC834

MIC834

Micrel

INP

OUT

VDD

GND

MIC834

470k

R1

R2

4

2

1

5

Figure 1. Example Circuit

Input Transients

The MIC834 is inherently immune to very short negative-

going “glitches.” Very brief transients may exceed the V

IN(lo)

threshold without tripping the output.

As shown in Figure 2, the narrower the transient, the deeper

the threshold overdrive that will be ignored by the MIC834.

The graph represents the typical allowable transient duration

for a given amount of threshold overdrive that will not gener-

ate an output.

0

20

40

60

80

100

120

140

1

10

100

1000

RESET COMP. OVERDRIVE, V

Input Transient

Response

Figure 2. Input Transient Response

Applications Information

Output

Since the MIC834 output is an open-drain MOSFET, most

applications will require a pull-up resistor. The value of the

resistor should not be too large or leakage effects may

dominate. 470k

Ω is the maximum recommended value. Note

that the output may be pulled up as high as 6V regardless of

the IC’s supply voltage. See “Electrical Characteristics.”

Programming the Threshold

The voltage threshold is calculated using:

VV

R1 R2

R2

IN(lo)

REF

=

+









where:

V

1.240V

In order to provide the additional criteria needed to solve for

the resistor values, the resistors can be selected such that

they have a given total value, that is, R1 + R2 = R

value such as 1M

Ω for R

it draws minimum current but has no significant effect on

accuracy.

When working with large resistors, a small amount of leakage

current can cause voltage offsets that degrade system accu-

racy. The maximum recommended total resistance from V

IN

to ground is 3M

Ω. The accuracy of the resistors can be

chosen based upon the accuracy required by the system. The

inputs may be subjected to voltages as high as 6V steady-

state without adverse effects of any kind regardless of the

IC’s supply voltage. This applies even if the supply voltage is

zero. This permits the situation in which the IC’s supply is

turned off, but voltage is still present on the inputs. See

“Electrical Characteristics.”