19-0539; Rev 4; 9/02
Microprocessor Voltage Monitors
with Programmable Voltage Detection
________________General Description
Maxim’s MAX8211 and MAX8212 are CMOS micropower
voltage detectors that warn microprocessors (µPs) of
power failures. Each contains a comparator, a 1.5V
bandgap reference, and an open-drain N-channel output
driver. Two external resistors are used in conjunction with
the internal reference to set the trip voltage to the desired
level. A hysteresis output is also included, allowing the user
to apply positive feedback for noise-free output switching.
The MAX8211 provides a 7mA current-limited output sink
whenever the voltage applied to the threshold pin is less
than the 1.5V internal reference. In the MAX8212, a voltage
greater than 1.5V at the threshold pin turns the output
stage on (no current limit).
The CMOS MAX8211/MAX8212 are plug-in replacements
for the bipolar ICL8211/ICL8212 in applications where the
maximum supply voltage is less than 16.5V. They offer sev-
eral performance advantages, including reduced supply
current, a more tightly controlled bandgap reference, and
more available current from the hysteresis output.
____________________________Features
o
µP Power-Fail Warning
o
Improved 2nd Source for ICL8211/ICL8212
o
Low-Power CMOS Design
o
o
o
o
5µA Quiescent Current
On-Board Hysteresis Output
±40mV Threshold Accuracy (±3.5%)
2.0V to 16.5V Supply-Voltage Range
MAX8211/MAX8212
o
Define Output Current Limit (MAX8211)
o
High Output Current Capability (MAX8212)
_______________Ordering Information
PART
MAX8211CPA
MAX8211CSA
MAX8211CUA
MAX8211CTY
MAX8211EPA
MAX8211ESA
MAX8211EJA
MAX8211ETY
MAX8211MJA
MAX8211MTV
TEMP RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
-55°C to +125°C
PIN-PACKAGE
8 Plastic DIP
8 SO
8 µMAX
8 TO-99
8 Plastic DIP
8 SO
8 CERDIP
8 TO-99
8 CERDIP
8 TO-99
________________________Applications
µP Voltage Monitoring
Undervoltage Detection
Overvoltage Detection
Battery-Backup Switching
Power-Supply Fault Monitoring
Low-Battery Detection
Ordering Information continued on last page.
*Contact
factory for dice specifications.
___________________Pin Configuration
TOP VIEW
___________Typical Operating Circuit
V+
R3
N.C.
HYST
THRESH
OUT
1
2
3
4
8
V+
V+
HYST
N.C.
R2
6
5
N.C.
GND
R1
OUT
µP
NMI
MAX8211
MAX8212
7
MAX8211
THRESH
GND
DIP/SO
Pin Configurations continued at end of data sheet.
LOGIC-SUPPLY UNDERVOLTAGE DETECTOR
(DETAILED CIRCUIT DIAGRAM—FIGURE 5)
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Microprocessor Voltage Monitors
with Programmable Voltage Detection
MAX8211/MAX8212
ABSOLUTE MAXIMUM RATINGS
Supply Voltage .......................................................-0.5V to +18V
Output Voltage .......................................................-0.5V to +18V
Hysteresis...................+0.5V to -18V with respect to (V+ + 0.5V)
Threshold Input Voltage ...............................-0.5V to (V+ + 0.5V)
Current into Any Terminal .................................................±50mA
Continuous Power Dissipation (T
A
= +70°C)
8-Pin Plastic DIP (derate 9.09mW/°C above +70°C) .....727mW
8-Pin SO (derate 5.88mW/°C above +70°C)..................471mW
8-Pin CERDIP (derate 8.00mW/°C above +70°C)..........640mW
8-Pin TO-99 (derate 6.67mW/°C above +70°C).............533mW
Operating Temperature Ranges
MAX821_C_ _ .......................................................0°C to +70°C
MAX821_E_ _.....................................................-40°C to +85°C
MAX821_M_ _ ..................................................-55°C to +125°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V+ = 5V, T
A
= +25°C, unless otherwise noted.)
PARAMETER
Supply Current
SYMBOL
I+
CONDITIONS
2V
≤
V+
≤
16.5V,
GND
≤
V
TH
≤
V+
T
A
= +25°C
Threshold Trip Voltage
V
TH
T
A
= T
MIN
to T
MAX
Threshold Voltage
Disparity between Output
and Hysteresis Output
Guaranteed Operating
Supply Voltage Range
Typical Operating
Supply Voltage Range
Threshold Voltage
Temperature Coefficient
Variation of Threshold
Voltage with Supply Voltage
Threshold Input Current
I
OUT
= 4mA,
I
HYST
= 1mA
T
A
= +25°C
T
A
= T
MIN
to T
MAX
2.0
2.2
1.5
-200
1.0
0.01
10
20
V
OUT
= 16.5V, V
TH
= 1.0V
T
A
= T
MIN
to T
MAX
, V
OUT
= 16.5V, V
TH
= 1.3V
C/E temp. ranges V
OUT
= 5V, V
TH
= 1.0V
Output Leakage Current
I
LOUT
V
OUT
= 5V, V
TH
= 1.3V
V
OUT
= 16.5V, V
TH
= 0.9V
T
A
= T
MIN
to T
MAX
, V
OUT
= 16.5V, V
TH
= 1.3V
M temp. range
V
OUT
= 5V, V
TH
= 0.9V
V
OUT
= 5V, V
TH
= 1.3V
30
10
10
10
1
1
30
µA
T
A
= +25°C
T
A
= T
MIN
to T
MAX
V+ = 16.5V, I
OUT
= 4mA
V+ = 2V, I
OUT
= 500µA
V+ = 16.5V, I
OUT
= 3mA
V+ = 2.2V, I
OUT
= 500µA
1.11
1.05
MAX8211
MAX8212
UNITS
MIN TYP MAX MIN TYP MAX
5
15
20
1.19 1.11
1.25 1.05
5
15
20
1.19
V
1.25
µA
V
THP
±0.1
16.5
16.5
16.5
2.0
2.2
1.5
±0.1
16.5
16.5
16.5
-200
0.2
0.01
10
20
10
mV
V
SUPP
V
SUPP
V
V
ppm/°C
mV
nA
∆V
TH
/∆T See Figure 4
∆V
TH
I
TH
V+ = 4.5V to 5.5V
0V
≤
V
TH
≤
V+, T
A
= +25°C
T
A
= T
MIN
to T
MAX
2
_______________________________________________________________________________________
Microprocessor Voltage Monitors
with Programmable Voltage Detection
MAX8211/MAX8212
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 5V, T
A
= +25°C, unless otherwise noted.)
PARAMETER
Output Saturation Voltage
Maximum Available
Output Current
SYMBOL
V
OL
I
OH
CONDITIONS
I
OUT
= 2mA, V
TH
= 1.0V
I
OUT
= 2mA, V
TH
= 1.3V
C temp. range,
V
OUT
= 5V
V
TH
= 1.0V (Note 1)
V
TH
= 1.3V (Note 2)
0.1
4
7.0
12
35
0.1
µA
T
A
= T
MIN
to T
MAX
, M temp. range,
V+ = 16.5V, V
TH
= 0.9V,
V
HYST
= -16.5V with respect to V+
V
HYS
(MAX)
V
HYS
(MAX)
I
HYST
= 0.5mA, V
TH
= 1.3V,
measured with respect to V+
V
TH
= 1.3V, V
HYS
= 0V
2
-0.1
10
3
3
MAX8211
MAX8212
UNITS
MIN TYP MAX MIN TYP MAX
0.17
0.4
0.17
0.4
V
mA
Hysteresis Leakage
Current
T
A
= T
MIN
to T
MAX
, C/E temp. ranges,
V+ = 16.5V, V
TH
= 1.0V,
V
HYST
= -16.5V with respect to V+
I
LHYS
Hysteresis Saturation
Voltage
Maximum Available
Hysteresis Current
-0.2
2
-0.1
10
-0.2
V
mA
Note 1:
The maximum output current of the MAX8211 is limited by design to 30mA under any operating condition. The output voltage
may be sustained at any voltage up to +16.5V as long as the maximum power dissipation of the device is not exceeded.
Note 2:
The maximum output current of the MAX8212 is not defined, and systems using the MAX8212 must therefore ensure that the
output current does not exceed 50mA and that the maximum power dissipation of the device is not exceeded.
_______________Detailed Description
As shown in the block diagrams of Figures 1 and 2, the
MAX8211 and MAX8212 each contain a 1.15V refer-
ence, a comparator, an open-drain N-channel output
transistor, and an open-drain P-channel hysteresis out-
put. The MAX8211 output N-channel turns on when the
voltage applied to the THRESH pin is less than the
internal reference (1.15V). The sink current is limited to
7mA (typical), allowing direct drive of an LED without a
series resistor. The MAX8212 output turns on when the
voltage applied to THRESH is greater than the internal
reference. It is not current limited, and will typically sink
35mA.
V+
THRESH
P
HYST
OUT
N
1.15V
REFERENCE
Compatibility with ICL8211/ICL8212
The CMOS MAX8211/MAX8212 are plug-in replacements
for the bipolar ICL8211/ICL8212 in most applications.
The use of CMOS technology has several advantages.
The quiescent supply current is much less than in the
bipolar parts. Higher-value resistors can also be used
Figure 1. MAX8211 Block Diagram
________________________________________________________________________________________
3
Microprocessor Voltage Monitors
with Programmable Voltage Detection
MAX8211/MAX8212
V+
V
IN
R2
HYST
R3
HYST
V+
THRESH
P
V+
OUT
V
OUT
MAX8211
MAX8212
OUT
1.15V
REFERENCE
N
R1
THRESH
GND
Figure 2. MAX8212 Block Diagram
Figure 3. Basic Overvoltage/Undervoltage Circuit
in the networks that set up the trip voltage, since the
comparator input (THRESH pin) is a low-leakage
MOSFET transistor. This further reduces system current
drain. The tolerance of the internal reference has also
been significantly improved, allowing for more precise
voltage detection without the use of potentiometers.
The available current from the HYST output has been
increased from 21µA to 10mA, making the hysteresis
feature easier to use. The disparity between the HYST
output and the voltage required at THRESH to switch
the OUT pin has also been reduced in the MAX8211
from 8mV to 0.1mV to eliminate output “chatter” or
oscillation.
Most voltage detection circuits operate with supplies of
15V or less; in these applications, the MAX8211/
MAX8212 will replace ICL8211/ICL8212s with the per-
formance advantages described above. However, note
that the CMOS parts have an absolute maximum sup-
ply-voltage rating of 18V, and should never be used in
applications where this rating could be exceeded.
Exercise caution when replacing ICL8211/ICL8212s in
closed-loop applications such as programmable
zeners. Although neither the ICL8211/ICL8212 nor the
MAX8211/MAX8212 are internally compensated, the
CMOS parts have higher gain and may not be stable
for the external compensation-capacitor values used in
lower-gain ICL8211/ICL8212 circuits.
__________Applications Information
Basic Voltage Detectors
Figure 3 shows the basic circuit for both undervoltage
detection (MAX8211) and overvoltage detection
(MAX8212). For applications where no hysteresis is
needed, R3 should be omitted. The ratio of R1 to R2 is
then chosen such that, for the desired trip voltage at V
IN
,
1.15V is applied to the THRESH pin. Since the com-
parator inputs are very low-leakage MOSFET transis-
tors, the MAX8211/MAX8212 can use much higher
resistors values in the attenuator network than can the
bipolar ICL8211/ICL8212. See Table 1 for switching
delays.
Table 1. Switching Delays
TYPICAL DELAYS
t
(on)
t
(off)
MAX8211
40µs
1.5ms
MAX8212
250µs
3ms
Voltage Detectors with Hysteresis
To ensure noise-free output switching, hysteresis is
frequently used in voltage detectors. For both the
MAX8211 and MAX8212 the HYST output is on for
threshold voltages greater than 1.15V. R3 (Figure 3)
controls the amount of current (positive feedback) sup-
plied from the HYST output to the mid-point of the resis-
tor divider, and hence the magnitude of the hysteresis,
or dead-band.
4
_______________________________________________________________________________________
Microprocessor Voltage Monitors
with Programmable Voltage Detection
MAX8211/MAX8212
V
IN
MAX8211,8212-FIG 4
1.250
1.230
1.210
1.190
V
TH
(V)
1.170
1.150
1.130
1.110
1.090
1.070
1.050
-55
-25
25
T
A
(°C)
75
V+ = 2V
V+ = 16.5V
R3
48.7kΩ
1%
HYST
R2
2.2MΩ
1%
THRESH
R1
750kΩ
1%
V+
MAX8211
OUT
V
OUT
(LOW FOR
V
IN
< 4.5V)
GND
125
Figure 4. MAX8211/MAX8212 Threshold Trip Voltage vs.
Ambient Temperature
Figure 5. MAX8211 Logic-Supply Low-Voltage Detector
Calculate resistor values for Figure 3 as follows:
1) Choose a value for R1. Typical values are in
the 10kΩ to 10MΩ range.
2) Calculate R2 for the desired upper trip point
V
U
using the formula:
R2 = R1
×
(VU
−
VTH )
(VU
−
1.15V)
=
R1
×
VTH
1.15V
Calculate resistor values for Figure 5 as follows:
1) Choose a value for R1. Typical values are in
the 10kΩ to 10MΩ range.
2) Calculate R2:
R2
=
R1
×
(VL
−
VTH )
(VL
−
1.15V)
=
R1
×
VTH
1.15V
3) Calculate R3:
R3
=
R1
×
(VU
−
VL )
1.15V
3) Calculate R3 for the desired amount of
hysteresis, where V
L
is the lower trip point:
R3
=
R2
×
(V
+ −
VTH )
(V +
−
1.15V)
=
R2
×
(VU
−
VL )
(VU
−
VL )
Low-Voltage Detector for Logic Supply
The circuit of Figure 5 will detect when a 5.0V (nominal)
supply goes below 4.5V, which is the V
MIN
normally
specified in logic systems. The selected resistor values
ensure that false undervoltage alarms will not be gener-
ated, even with worst-case threshold trip values and
resistor tolerances. R3 provides approximately 75mV of
hysteresis.
or, if
V
+
= V
IN
:
(VL
−
VTH )
(VL
−
1.15V)
=
R2
×
(VU
−
VL )
(VU
−
VL )
R3
=
R2
×
Figure 5 shows an alternate circuit, suitable only when the
voltage being detected is also the power-supply voltage
for the MAX8211 or MAX8212.
________________________________________________________________________________________
5
京公网安备 11010802033920号
EEWORLD
