MIC2774N-28YM5 TR Micrel Inc, MIC2774N-28YM5 TR Datasheet - Page 7

• Manufacturer Part Number: MIC2774N-28YM5 TR
• Description: Dual Ultra-Low-V Supervisor
• Manufacturer: Micrel Inc
• Type: Multi-Voltage Supervisorr

Specifications of MIC2774N-28YM5 TR

• Active-high: Manual Reset, SOT23-5 ( )
• Number Of Voltages Monitored: 2
• Output: Open Drain or Open Collector
• Reset: Active Low
• Reset Timeout: 140 ms Minimum
• Voltage - Threshold: 2.81V, Adj
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: SOT-23-5, SC-74A, SOT-25
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 576-2677-2; MIC2774N-28YM5 TR; MIC2774N-28YM5TR; MIC2774N-28YM5TR

Interfacing to Processors With Bidirectional Reset Pins
Some microprocessors have reset signal pins that are bi-
directional, rather than input only. The Motorola 68HC11
family is one example. Because the MIC2774N’s output is
open-drain, it can be connected directly to the processor’s
reset pin using only the pull-up resistor normally required.
See Figure 2.
Transient response
The MIC2774 is inherently immune to very short negative-
going “glitches.” Very brief transients may exceed the voltage
thresholds without tripping the output.
As shown in Figure 3a and 3b, in general the narrower the
transient, the deeper the threshold overdrive that will be
ignored by the MIC2774. The graphs represent the typical
allowable transient duration for a given amount of threshold
overdrive that will not generate a reset.
October 2005
Figure 2. Interfacing to Bidirectional Reset Pin
Figure 3a. Typical INPUT Transient Response
1.0V 5%
2.5V 5%
V
V
V
CORE
CC
I/O
Figure 1. MIC2774 Example Design
Manual
Reset
eset
ese
R1
R2
R1
676k
1%
R2
324k
1%
1%
40
35
30
25
20
15
10
RESET COMP. OVERDRIVE, V
5
0
0
MIC2774N-X
MIC2774N-X
MIC2774N- X
VDD
VDD
IN
/MR
T rans ient R es pons e
VDD
VDD
IN
/MR
/MR
MIC2774L-23
GND
/RST
/RST
100
T ypic al IN
GND
GND
/RST
/RST
100k
200
REF
MICROPROCESSOR
–V
VCC
/RESET
/RESET
MICROPROCESSOR
IN
VCORE
/RESET
/RESET
VI/O
(mV)
300
OCESSOR
OCESSO
OCESSOR
OCESSO
GND
GND
7
Ensuring Proper Operation at Low Supply
At levels of V
not turn on suffi ciently to produce a valid logic-low on /RST.
In this situation, circuits driven by /RST could be allowed to
fl oat, causing undesired operation. (In most cases, however,
it is expected that the circuits driven by the MIC2774L will be
similarly inoperative at V
If a given application requires that /RST be valid below V
= 1.2V, this can be accomplished by adding a pull-down re-
sistor to the /RST output. A value of 100kΩ is recommended
as this is usually an acceptable compromise of quiescent
current and pull-down current. The resistor’s value is not
critical, however. See Figure 4.
The statements above also apply to the MIC2774H’s RST
output. That is, to ensure valid RST signal levels at V
1.2V, a pull-up resistor (as opposed to a pull-down) should
be added to the RST output. A value of 100kΩ is typical for
this application as well. See Figure 5.
V
CC
Figure 3b. Typical V
V
Figure 4. MIC2774L Valid /RST Below 1.2V
Figure 5. MIC2774H Valid RST Below 1.2V
CC
Manual
Reset
eset
ese
Manual
Reset
eset
ese
DD
R1
R2
100
R1
R2
80
60
40
20
RESET COMP. OVERDRIVE, V
below 1.2V, the MIC2774’s reset output can-
0
0
MIC2774H-X
MIC2774H-X
MIC2774H- X
VDD
VDD
IN
/MR
/MR
T rans ient R es pons e
VDD
VDD
IN
/MR
/MR
500
MIC2774L-X
MIC2774L-X
MIC2774L- X
T ypic al V
DD
GND
GND
RST
RST
1000
GND
GND
/RST
/RST
DD
≤ 1.2V.)
DD
Transient Response
1500
100k
Rpull-up
REF
100k
Rpull-do
Rpull-do
Rpull-d wn
–V
DD
2000
VCC
/RESET
/RESET
MICROPROCESSOR
(mV)
VCC
RESET
MICROPROCESSOR
OCESSOR
OCESSO
GND
OCESSOR
OCESSO
GND
M9999-102605
DD
DD
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