MIC2776N-BM5 TR Micrel Inc, MIC2776N-BM5 TR Datasheet - Page 7

• Manufacturer Part Number: MIC2776N-BM5 TR
• Description: IC SUPERVISOR ADJ MCRPWR SOT23-5
• Manufacturer: Micrel Inc
• Type: Simple Reset/Power-On Resetr

Specifications of MIC2776N-BM5 TR

• Number Of Voltages Monitored: 1
• Output: Open Drain or Open Collector
• Reset: Active Low
• Reset Timeout: 140 ms Minimum
• Voltage - Threshold: Adjustable/Selectable
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: SOT-23-5, SC-74A, SOT-25
• Threshold Voltage: 0.3V
• No. Of Supervisors / Monitors: 1
• Supply Voltage Range: 1.5V To 5.5V
• Reset Type: Manual, Active-Low
• Supply Current: 3µA
• Delay Time: 280ms
• Digital Ic Case Style: SOT-23
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: MIC2776N-BM5TR

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 MIC2776N’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 MIC2776 is inherently immune to very short negative-
going “glitches.” Very brief transients may exceed the voltage
threshold without tripping the output.
As shown in Figure 3, the narrower the transient, the deeper the
threshold overdrive that will be ignored by the MIC2776. The
graph represents the typical allowable transient duration for a
given amount of threshold overdrive that will not generate a reset.
November 2005
Figure 2. Interfacing to Bidirectional Reset Pin
1.0V 5%
2.5V 5%
Figure 3. Typical INPUT Transient Response
V
V
V
CORE
I/O
CC
Figure 1. MIC2776 Example Design
Manual
Reset
R1
R2
RESET COMP. OVERDRIVE, V
R1
676k
1%
R2
324k
1%
40
35
30
25
20
15
10
5
0
0
VDD
IN
/MR
MIC2776N
Transient Response
VDD
IN
/MR
MIC2776
/RST
GND
Typical INPUT
100
/RST
GND
200
100k
MICROPROCESSOR
MICROPROCESSOR
REF
VCC
/RESET
VCORE
/RESET
–V
VI/O
300
IN
(mV)
GND
GND
7
Ensuring Proper Operation at Low Supply
At levels of V
driver cannot turn on sufficiently to produce a valid logic-low
on the /RST output. In this situation, other circuits driven by
/RST could be allowed to float, causing undesired opera-
tion. (In most cases, however, it is expected that the circuits
driven by the MIC2776L will be similarly inoperative at V
≤ 1.2V.)
If a given application requires that /RST be valid below V
1.2V, this can be accomplished by adding a pull-down resis-
tor to the /RST output. A value of 100kΩ is recommended as
this is usually an acceptable compromise of leakage current
and pull-down current. The resistor’s value is not critical,
however. See Figure 4.
The statements above also apply to the MIC2776H’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
Figure 4. MIC2776L Valid /Reset Below 1.2V
CC
Figure 5. MIC2776H Valid Reset Below 1.2V
V
CC
Manual
Reset
Manual
Reset
R1
R2
DD
R1
R2
below 1.2V, the MIC2776L’s /RST output
VDD
IN
/MR
MIC2776H
VDD
IN
/MR
MIC2776L
GND
RST
/RST
GND
100k
Rpull-up
100k
Rpull-down
MICROPROCESSOR
MICROPROCESSOR
VCC
/RESET
VCC
RESET
GND
GND
MIC2776
DD
DD
DD
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