MIC841/2
Micrel
MIC841/2
Comparator with Reference
Advance Information
General Description
The MIC841 and MIC842 are micropower, precision voltage
comparator with an on-chip voltage reference.
Both devices are intended for voltage monitoring applica-
tions, external resistors are used to set the voltage monitor
threshold and when the threshold is crossed the outputs
switch polarity.
The MIC842 incorporates a voltage reference and compara-
tor with fixed internal hysteresis; two external resistors are
used to set the switching threshold voltage. The MIC841
provides a similar function with user adjustable hysteresis,
this part requires three external resistors to set the upper and
lower thresholds (the difference between the threshold volt-
ages being the hysteresis voltage).
Both the MIC841 and MIC842 are available with push-pull
outputs and active-high or active-low inputs. The active-low
part is also available with an open-drain output.
Supply current is extremely low (1.5µA, typical), making it
ideal for portable applications.
The MIC841/2 is supplied in Micrel’s Teeny™ 5-lead SC-70
package.
Features
• Optimized for PDAs, cellular telephones, pagers,
and other battery-powered devices
• Input and output can be pulled up to 6V
regardless of supply voltage
• High
±1.25%
voltage threshold accuracy
• Built in hysteresis for noise suppression
• Extremely low 1.5µA typical supply current
• Immune to brief input transients
• 5-lead SC-70 package
Applications
•
•
•
•
•
•
PDAs
Pagers
Cordless phones
Consumer electronics
Embedded controllers
Personal electronics
Ordering Information
Part Number
MIC841HBC5
MIC841LBC5
MIC841NBC5
MIC842HBC5
MIC842LBC5
MIC842NBC5
Marking
B13
B14
B15
B16
B17
B18
Hysteresis
Adjustment
External
External
External
Internal
Internal
Internal
Output
Stage
Push Pull
Push Pull
Open Drain
Push Pull
Push Pull
Open Drain
Output
Function
Active High
Active Low
Active Low
Active High
Active Low
Active Low
Temperature Range
—40°C to +85°C
—40°C to +85°C
—40°C to +85°C
—40°C to +85°C
—40°C to +85°C
—40°C to +85°C
Package
SC70-5
SC70-5
SC70-5
SC70-5
SC70-5
SC70-5
Typical Application
V
IN
V
DD
MIC841
R1
5
3
V
IN
V
DD
4
VDD
LTH
HTH
OUT
GND
V
OUT
V
LTH
> V
HTH
V
REF
= 1.24V
1.5V
≤
V
DD
≤
5.5V
MIC842
R1
5
R2
1
2
VDD
INP
OUT
GND
4
V
OUT
V
REF
= 1.24V
1.5V
≤
V
DD
≤
5.5V
1
2
R3
R2
Threshold detection with hysteresis set by a third
external resistor
Teeny™ is a trademark of Micrel, Inc.
Threshold detector with internal fixed hysteresis
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
December 2000
1
MIC841/2
MIC841/2
Micrel
Pin Configuration
LTH GND HTH
3
2
1
Bxx
4
5
OUT
VDD
MIC841
SC-70-5 (C5)
Pin Description MIC841
Pin Number
1
Pin Name
HTH
Pin Function
High-Voltage Threshold (Input): Analog input to a comparator. This is the
voltage input assigned to detect a high-voltage condition when the level on
this pin exceeds V
REF
, OUT is asserted and the condition is latched until
V
LTH
< V
REF
.
Ground
Low-Voltage Threshold (Input): Analog input to a comparator. This is the
voltage input assigned to detect a low voltage condition. When the level on
this pin falls below V
REF
, OUT is de-asserted and the condition is latched
until V
HTH
> V
REF
.
Output: Active-high, open-drain output. This output is deasserted and
latched when V
LTH
<V
REF
, indicating a low voltage condition. This state
remains latched until V
HTH
> V
REF
.
Power Supply (Input): Independent supply input for internal circuitry.
2
3
GND
LTH
4
OUT
5
VDD
NC GND INP
3
2
1
Bxx
4
5
OUT
VDD
MIC842
SC-70-5 (C5)
Pin Description MIC842
Pin Number
1
2
3
4
Pin Name
INP
GND
NC
OUT
Pin Function
Input: Analog input to the comparator. When V
INP
> V
REF
+ V
HYST
, V
OUT
is
asserted to a logic-high level output.
Ground
No Connect
Output: Active-high, open-drain output. This output is de-asserted when
V
INP
< V
REF
, indicating a low voltage input. The output is asserted when
V
INP
> V
REF
+ V
HYST.
Power Supply (Input): Independent supply input for internal circuitry.
5
VDD
MIC841/2
2
December 2000
MIC841/2
Micrel
Absolute Maximum Ratings
(Note 1)
Supply Voltage (V
DD
) ..................................... –0.3V to +7V
Input Voltage (V
INP
) ...................................................... +7V
Output Current (I
OUT
) ................................................. 20mA
Storage Temperature (T
S
) ....................... –65°C to +150°C
ESD Rating,
Note 3
...................................................... 1kV
Operating Ratings
(Note 2)
Supply Voltage (V
DD
) .................................. +1.5V to +5.5V
Input Voltage (V
INP
) ......................................... –0.3V to 6V
Ambient Temperature Range (T
A
) ............. –40°C to +85°C
Junction Temperature (T
J
) ....................... Internally Limited
Package Thermal Resistance (θ
JA
) ...................... 450°C/W
Electrical Characteristics
1.5V
≤
V
DD
≤
5.5V; T
A
= +25°C,
bold
values indicate –40°C
≤
T
A
≤
+85°C; unless noted
Symbol
I
DD
I
INP
V
REF
V
HYST
t
D
V
OUT
Parameter
Supply Current
Input Leakage Current
Reference Voltage
0°C to 85°C
–40°C to 85°C
Hysteresis Voltage,
Note 4
Propagation Delay
842 only
V
INP
= 1.352V to 1.128V
V
INP
= 1.143V to 1.367V
Output Voltage-Low,
Note 5
OUT de-asserted, I
SINK
= 1.6mA, V
DD
≥
1.6V
OUT de-asserted, I
SINK
= 100µA, V
DD
≥
1.2V,
Note 1.
Note 2.
Note 3.
Note 4.
Note 5.
Exceeding the absolute maximum rating may damage the device.
The device is not guaranteed to function outside its operating rating.
Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
V
HTH
= V
REF
+ V
HYST
.
V
DD
operating range is 1.5V to 5.5V. Output is guaranteed to be held low down to V
DD
= 1.2V.
Condition
output not asserted
Min
Typ
1.5
0.005
Max
3
10
1.256
1.259
35
Units
µA
nA
V
V
mV
µs
µs
1.225
1.221
8
1.240
1.240
20
12
8
0.05
0.005
0.3
0.4
V
V
December 2000
3
MIC841/2
MIC841/2
Micrel
Block Diagrams
V
DD
5
V
IN
V
DD
5
VDD
VDD
V
IN
Low-Voltage
Detect
INP
High-Voltage
Detect
OUT
4
LTH
V
LTH
3
V
TH
1
R Q
High-Voltage
Detect
4
OUT
HTH
V
HTH
1
S Q
1.24V
Bandgap
Reference
MIC842H
1.24V
Bandgap
Reference
MIC841H
2
2
GND
GND
V
DD
5
VDD
V
IN
V
DD
5
V
IN
Low-Voltage
Detect
LTH
V
LTH
3
VDD
INP
High-Voltage
Detect
OUT
4
R Q
High-Voltage
Detect
4
OUT
V
TH
1
HTH
V
HTH
1
S Q
1.24V
Bandgap
Reference
1.24V
Bandgap
Reference
MIC841L
2
MIC842L
2
GND
GND
V
DD
5
VDD
V
IN
V
DD
5
V
IN
Low-Voltage
Detect
LTH
V
LTH
3
VDD
OUT
R Q
High-Voltage
Detect
S Q
4
INP
V
TH
1
High-Voltage
Detect
OUT
4
HTH
V
HTH
1
1.24V
Bandgap
Reference
1.24V
Bandgap
Reference
MIC841N
2
MIC842N
2
GND
GND
MIC841/2
4
December 2000
MIC841/2
Micrel
1M
Ω
V
IN(hi)
=
3.6V
=
1.24
R3
R3
=
344k
Ω
Once R3 is determined, the equation for V
IN(lo)
can be used
to determine R2. A single lithium-ion cell, for example, should
not be discharged below 2.5V. Many applications limit the
drain to 3.1V. Using 3.1V for the V
IN(lo)
threshold allows
calculation of the two remaining resistor values.
Applications Information
Output
The the MIC841N and MIC842N outputs are an open-drain
MOSFET so most applications will require a pull-up resistor.
The value of the resistor should not be too large or leakage
effects may dominate. 470kΩ 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 Charac-
teristics.”
When working with large resistors on the input to the devices
a small amount of leakage current can cause voltage offsets
that degrade system accuracy. The maximum recommended
total resistance from V
IN
to ground is 3MΩ. The accuracy of
the resistors can be chosen based upon the accuracy re-
quired 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.”
Programming the MIC841 Thresholds
The low-voltage threshold is calculated using:
R1
+
R2
+
R3
V
IN(lo)
=
V
REF
R2
+
R3
The high-voltage threshold is calculated using:
R1
+
R2
+
R3
V
IN(hi)
=
V
REF
R3
where, for both equations:
V
REF
=
1.240V
1M
Ω
V
IN(lo)
=
3.1V
=
1.24
R2
+
344k
R2
=
56k
Ω
1M
Ω −
(
R2
−
R3
)
=
R1
R1
=
600k
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
supply voltage. This applys even if the supply voltage is zero.
This permits the situation in which the IC supply is turned off,
but voltage is still present on the inputs. See “Electrical
Characteritics.”
Programming the MIC842 Thresholds
The voltage threshold is calculated using:
R1
+
R2
V
IN(lo)
=
V
REF
R2
where:
V
REF
=
1.240V
V
IN
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 + R3 = R
TOTAL
.
A value such as 1MΩ for R
TOTAL
is a reasonable value
because it draws minimum current but has no significant
effect on accuracy.
V
IN
V
DD
MIC842
R1
5
470k
4
VDD
INP
OUT
GND
V
OUT
1
2
R2
R1
604k
1%
56k
1%
340k
1%
MIC841
5
3
1
VDD
LTH
HTH
OUT
GND
4
470k
V
OUT
Figure 2. Example Circuit
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
TOTAL
. A
value such as 1MΩ for R
TOTAL
is a reasonable value because
it draws minimum current but has no significant effect on
accuracy.
Input Transients
The MIC841/2 is inherently immune to very short negative-
going “glitches.” Very brief transients may exceed the V
IN(lo)
threshold without tripping the output.
2
R2
R3
Figure 1. Example Circuit
Once the desired trip points are determined, set the V
IN(hi)
threshold first.
For example, use a total of 1MΩ = R1 + R2 + R3. For a typical
single-cell lithium ion battery, 3.6V is a good “high threshold”
because at 3.6V the battery is moderately charged. Solving
for R3:
December 2000
5
MIC841/2
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
