mic834bm5 Micrel Semiconductor, mic834bm5 Datasheet - Page 5

• Manufacturer Part Number: mic834bm5
• Description: Mic834 Comparator With Reference
• Manufacturer: Micrel Semiconductor

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 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:
where:
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 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
to ground is 3M . 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.”
September 2001
MIC834
V
V
IN(lo)
REF
1.240V
V
REF
R1 R2
R2
TOTAL
is a reasonable value because
TOTAL
. A
IN
5
Input Transients
The MIC834 is inherently immune to very short negative-
going “glitches.” Very brief transients may exceed the V
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.
Figure 2. Input Transient Response
R1
R2
RESET COMP. OVERDRIVE, V
V
Figure 1. Example Circuit
140
120
100
IN
80
60
40
20
0
1
5
1
Input Transient
VDD
INP
10
MIC834
Response
GND
OUT
100
4
2
REF
470k
–V
1000
LTH
V
(mV)
OUT
MIC834
Micrel
IN(lo)