Datasheet MIC812U, MIC811U Datasheet (MICREL)

1

The MIC811/MIC812 are inexpensive microprocessor
supervisory circuits that monitor power supplies in
microprocessor based systems.

The function of these devices is to assert a reset if
either the power supply drops below a designated reset
threshold level or MR is forced low. Several different
reset threshold levels are available to accomodate 3V,

3.3V or 5V powered systems.

The MIC811 has an active low RESET output, while the
MIC812 offers an active high RESET output. The reset
output is guaranteed to remain asserted for a minimum
of 140ms after VCChas risen above the designated
reset threshold level. The MIC811/MIC812 come in a 4­pin SOT-143 package.

1

2

4 V

CC

GND

MIC812

RESET 3

MR

1

2

4

V

CC

GND

MIC811

RESET 3

MR

Top View

Part Package Temp. Range

MIC811_U 4-Lead SOT-143 -40°C to +85°C

MIC812_U 4-Lead SOT-143 -40°C to +85°C

Place the device suffix of desired reset threshold voltage from table above in
blank to complete the part number.

·

Portable Equipment

·

Intelligent Instruments

·

Critical Microprocessor Power Monitoring

·

Printers/Computers

·

Controllers

·

RESET Remains Valid with V

CC

as Low

as 1.4V

·

Precision Voltage Monitor for 3V, 3.3V
or 5V Power Supplies

·

Available in 4-Pin SOT-143 Package

·

<15µA Supply Current

·

140ms Minimum Reset Pulse Width

·

Manual Reset Input

V

CC

RESET

µP

RESET

V

CC

MIC811

V

CC

MR

Typical Operating Circuit

Features

Description Pin Configuration

Ordering Information

Typical Applications

Reset Threshold Device

Voltage (V) Suffix

4.63 L

4.38 M

4.00 J

3.08 T

2.93 S

2.63 R

MIC811/MIC812 Microprocessor Reset Circuits

MIC811/MIC812

Microprocessor Reset Circuits

MIC811/MIC812 Microprocessor Reset Circuits

2

Electrical Characteristics

VCC= 5V for MIC81-L/M/J, VCC= 3.3V for MIC81-S/T, VCC= 3V for MIC81-R, TA= Operating Temperature Range, unless
otherwise noted.

Parameter Conditions Min Typ Max Units

Operating Voltage Range, V

CC

TA= 0°C to 70°C 1.4 5.5 V
TA= -40°C to 85°C 1.6 5.5

Supply Current, I

CC

MIC811L/M/J, MIC812L/M/J 9 15 µA

VCC< 3.6V, MIC811R/S/T, MIC812R/S/T 6 10

Reset Voltage Threshold, V

TH

MIC811L, MIC812L 4.50 4.63 4.75 V
MIC811M, MIC812M 4.25 4.38 4.50
MIC811J, MIC812J 3.89 4.00 4.10
MIC811T, MIC812T 3.00 3.08 3.15
MIC811S, MIC812S 2.85 2.93 3.00
MIC811R, MIC812R 2.55 2.63 2.70

Reset Timeout Period 140 240 560 ms

RESET Output Voltage, V

OH

I

Source

= 800µA, MIC811L/M/J

VCC- 1.5V

V

I

Source

= 500µA, MIC811R/S/T 0.8 X

V

CC

RESET Output Voltage, V

OL

VCC=VTHMin., I

Sink

=3.2mA, MIC811L/M/J

0.4 V

VCC=VTHMin., I

Sink

=1.2mA, MIC811R/S/T

0.3

VCC>1.4V, I

Sink

=50µA,

TA= 0°C to 70°C 0.3

VCC>1.6V, I

Sink

=50µA,

TA= -40°C to 85°C 0.3

RESET Output Voltage, V

OH

1.8V < V

CC

< VTHMin., 0.8 X

V

CC

V

I

Source

= 150µA

RESET Output Voltage, V

OL

I

Sink

=3.2mA, MIC812L/M/J 0.4 V

I

Sink

=1.2mA, MIC812R/S/T 0.3

MR Minimum Pulse Width 10 µs
MR to Reset Delay 0.5 µs

MR Input Threshold, V

IH

VCC>

VTHMax., MIC81_L/M/J 2.3 V

MIC81_R/S/T 0.7 X

V

CC

MR Input Threshold, V

IL

VCC>

VTHMax., MIC81_L/M_ 0.8 V

MIC81_R/S/T 0.25 X

V

CC

MR Pull-Up Resistance

10 20 30 kΩ

MR Glitch Immunity

100 ns

Absolute Maximum Ratings

Terminal Voltage

VCC. . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6.0V

MR . . . . . . . . . . . . . . . . . . . . . -0.3V to (VCC+ 0.3V)

Input Current, VCC, MR . . . . . . . . . . . . . . . . . . . . 20mA

Output Current, RESET, RESET . . . . . . . . . . . . . .20mA

Rate of Rise, V

CC

. . . . . . . . . . . . . . . . . . . . . . 100V/µs

Operating Temperature Range

MIC81

--

U . . . . . . . . . . . . . . . . . . . . . . . . -40°C to 85°C

Storage Temperature Range . . . . . . . . . . . . . -65°C to 150°C

Lead Temperature (Soldering - 10 sec.) . . . . . . . . . . . 300°C

Power Dissipation (TA= +70°C) . . . . . . . . . . . . . . . . 320mW

Stresses above those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent device failure. Functionality at or above these limits is not implied. Exposure to absolute
maximum ratings for extended periods may affect device reliability. Operating ranges define those limits between which the functionality of the device is guaranteed.

Pin Functions

Description

IC Ground Pin.

RESET goes low if VCCfalls below the reset threshold and remains
asserted for one reset timeout period (140ms min.) after VCCexceeds
the reset threshold.

RESET goes high if VCCfalls below the reset threshold and remains
asserted for one reset timeout period (140ms min.) after VCCexceeds
the reset threshold.

Manual reset input. A logic low on MR forces a reset. The reset will
remain asserted as long as MR is held low and for one reset timeout
period (140ms min.) after MR goes high. This input can be shorted to
ground via a switch or driven from CMOS or TTL logic. Float if unused.

Power supply input, 3V, 3.3V or 5V.

Pin No.

Pin Name MIC811 MIC812

GND 11

RESET 2 N/A

RESET N/A 2

MR 33

V

CC

44

MIC811/MIC812 Microprocessor Reset Circuits

3

MIC811/MIC812 Microprocessor Reset Circuits

4

+

-

Reset

Threshold (V)

VCC(4)

RESET (2)
RESET (MIC812)

GND (1)

RESET

GENERATOR

MR (3)

Figure 1. MIC811/812 Block Diagram

Block Diagram

Microprocessor Reset

The RESET pin is asserted whenever V

CC

falls below
the reset threshold voltage or if MR (manual reset) is
forced low. The reset pin remains asserted for a period
of 240ms after VCChas risen above the reset threshold
voltage or MR has returned high. The reset function
ensures the microprocessor is properly reset and powers
up into a known condition after a power failure. RESET
will remain valid with VCCas low as 1.4V.

VCCTransients

The MIC811/MIC812 are relatively immune to negative­going VCCglitches below the reset threshold. Typically,
a negative-going transient 125mV below the reset

threshold with a duration of 50µs (25µs for

MIC81_R/S/T) or less will not cause an unwanted reset.

Interfacing to Bidirectional Reset Pins

The MIC811/MIC812 can interface with µPs with
bidirectional reset pins by connecting a 4.7KΩ resistor in
series with the MIC811/MIC812 output and the µP reset

pin.

RESET Valid to 0V

A resistor can be added from the RESET pin to ground
to ensure the RESET output remains low with V

CC

down to 0V. A 100KΩ resistor connected from RESET

to ground is recommended. The size of the resistor
should be large enough to not load the RESET output
and small enough to pull-down any stray leakage
currents.

Circuit Description

Figure 2. Reset Timing Diagram

Figure 3. RESET Valid to VCC= 0V.

V

CC

MR

RESET

t1t1

V

thr

MIC811/MIC812 Microprocessor Reset Circuits

5

V

CC

RESET

µP

RESET

V

CC

MIC811

V

CC

100K

MIC811/MIC812 Microprocessor Reset Circuits

6

MIC Direct

Industry P/N Replacement

MAX811JEUS-T MIC811JU

MAX811LEUS-T MIC811LU

MAX811MEUS-T MIC811MU

MAX811REUS-T MIC811RU

MAX811SEUS-T MIC811SU

MAX811TEUS-T MIC811TU

MAX812JEUS-T MIC812JU

MAX812LEUS-T MIC812LU

MAX812MEUS-T MIC812MU

MAX812REUS-T MIC812RU

MAX812SEUS-T MIC812SU

MAX812TEUS-T MIC812TU

Alternate Source Cross Reference Guide

Packaging Information

0.0059

0.0035

0.010

0.005

0-8¼

0.080

0.070

0.120

0.105

0.040

0.031

0.004

0.001

0.021

0.015

0.055

0.047

0.098

0.083

0.079

0.071

0.037

0.030

U Package, 4-Pin SOT-143 Small-Outline Transistor Package

Device Marking Information

Lot Code

KJXX = MIC811J

KLXX = MIC811L

KMXX = MIC811M

KRXX = MIC811R

KSXX = MIC811S

KTXX = MIC811T

LJXX = MIC812J

LLXX = MIC812L

LMXX = MIC812M

LRXX = MIC812R

LSXX = MIC812S

LTXX = MIC812T

Dimensions are in inches.

MIC811/MIC812 Microprocessor Reset Circuits

7

MIC811/MIC812 Microprocessor Reset Circuits

8

Packaging Information

4.0–0.1

4.0–0.1

2.0–0.05

3.5–0.05

8.0–0.3

1.75–0.1

fl1.5–0.1

fl1.1–0.1

2.7–0.1

3.1–0.1

1.2–0.1

Tape and Reel Information

Dimensions are in millimeters.