DS1231N-35 [DALLAS]
Power Supply Support Circuit, Fixed, 1 Channel, CMOS, PDIP8, 0.300 INCH, DIP-8;
| 型号： | DS1231N-35 |
| 厂家： | 
DALLAS SEMICONDUCTOR |
| 描述： | Power Supply Support Circuit, Fixed, 1 Channel, CMOS, PDIP8, 0.300 INCH, DIP-8 光电二极管 |
| 文件： | 总9页 (文件大小：70K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
DS1231/S
DS1231/S
Power Monitor Chip
FEATURES
PIN ASSIGNMENT
• Warns processor of an impending power failure
1
2
3
4
8
7
VCC
NMI
IN
MODE
TOL
• Provides time for an orderly shutdown
• Prevents processor from destroying nonvolatile
memory during power transients
RST
RST
6
5
GND
• Automatically restarts processor after power is
restored
DS1231 8–Pin DIP
(300 MIL)
See Mech. Drawings
Section
• Suitable for linear or switching power supplies
• Adjusts to hold time of the power supply
NC
16
15
NC
IN
1
2
3
VCC
NC
• Supplies necessary signals for processor interface
NC
14
13
MODE
NMI
NC
4
5
• Accurate 5% or 10% V monitoring
CC
NC
12
6
7
TOL
• Replaces power-up reset circuitry
• No external capacitors required
11
10
RST
NC
NC
9
GND
8
RST
• Optional 16-pin SOIC surface mount package
DS1231S 16–Pin SOIC
(300 MIL)
See Mech. Drawings
Section
PIN DESCRIPTION
IN
–
–
–
–
–
–
–
–
–
Input
MODE
TOL
GND
RST
RST
NMI
Selects input pin characteristics
Selects 5% or 10% V detect
Ground
Reset (Active High)
Reset (Active Low, open drain)
Non–Maskable Interrupt
+5V Supply
CC
V
CC
NC
No Connections
DESCRIPTION
The DS1231 Power Monitor Chip uses a precise tem-
perature-compensatedreference circuit whichprovides
an orderly shutdown and an automatic restart of a pro-
cessor-basedsystem. Asignalwarningofanimpending
power failure is generated well before regulated DC
voltages go out of specification by monitoring high volt-
age inputs to the power supply regulators. If line isola-
tion is required a UL-approved opto-isolator can be di-
rectly interfaced to the DS1231. The time for processor
shutdown is directly proportional to the available
hold-up time of the power supply. Just before the
hold-up time is exhausted, the Power Monitor uncondi-
tionally halts the processor to prevent spurious cycles
by enabling Reset as V falls below a selectable 5 or
CC
10 percent threshold. When power returns, the proces-
sor is held inactive until well after power conditions have
stabilized, safeguarding any nonvolatile memory in the
system from inadvertent data changes.
022698 1/9
DS1231/S
modes of operation the input pin has hysteresis for
noise immunity (Figure 3).
OPERATION
The DS1231 Power Monitor detects out-of-tolerance
power supply conditions and warns a processor-based
system of impending power failure. The main elements
of the DS1231 are illustrated in Figure 1. As shown, the
DS1231 actually has two comparators, one for monitor-
APPLICATION – MODE PIN
CONNECTED TO VCC
When the Mode pin is connected to V , pin 1 is a high
CC
ing the input (Pin 1) and one for monitoring V (Pin 8).
CC
impedance input. The voltage sense point and the level
of voltage at the sense point are dependent upon the
application (Figure 4). The sense point may be devel-
oped from the AC power line by rectifying and filtering
the AC. Alternatively, a DC voltage level may be se-
lected which is closer to the AC power input than the
regulated +5-volt supply, so that ample time is provided
for warning before regulation is lost.
The V
comparator outputs the signals RST (Pin 5)
CC
and RST (Pin 6) when V falls below a preset trip level
as defined by TOL (Pin 3).
CC
When TOL is connected to ground, the RST and RST
signals will become active as V
volts. WhenTOLisconnectedtoV , theRSTandRST
signalsbecomeactiveasV goesbelow4.5volts. The
goes below 4.75
CC
CC
CC
RST and RST signals are excellent control signals for a
microprocessor, as processing is stopped at the last
Proper operation of the DS1231 requires a maximum
voltage of 5 volts at the input (Pin 1), which must be
derived from the maximum voltage at the sense point.
This is accomplished with a simple voltage divider net-
possible moments of valid V . On power-up, RST and
CC
RSTarekeptactiveforaminimumof150mstoallowthe
power supply to stabilize (see Figure 2).
work of R1 and R2. Since the IN trip point V - is 2.3
TP
volts(usingthe-20device),andthemaximumallowable
voltage on pin 1 is 5 volts, the dynamic range of voltage
at the sense point is set by the ratio of 2.3/5.0=.46 min.
This ratio determines the maximum deviation between
the maximum voltage at the sense point and the actual
voltage which will generate NMI.
The comparator monitoring the input pin produces the
NMI signal (Pin 7) when the input threshold voltage
(V ) falls to a level as determined by Mode (Pin 2).
TP
When the Mode pin is connected to V , detection oc-
CC
curs at V -. In this mode Pin 1 is an extremely high im-
TP
pedance input allowing for a simple resistor voltage di-
vider network to interface with high voltage signals.
When the Mode pin is connected to ground, detection
Having established the desired ratio, and confirming
that the ratio is greater than .46 and less than 1, the
proper values for R1 and R2 can be determined by the
equation as shown in Figure 4. A simple approach to
solving this equation is to select a value for R2 which is
high enough impedance to keep power consumption
low, and solve for R1. Figure 5 illustrates how the
DS1231 can be interfaced to the AC power line when
occurs at V +. In this mode Pin 1 sources 30 µA of cur-
TP
rent allowing for connection to switched inputs, such as
a UL-approved opto-isolator. The flexibility of the input
pinallowsfordetectionofpowerlossattheearliestpoint
in a power supply system, maximizing the amount of
time allotted between NMI and RST. On power-up, NMI
is released as soon as the input threshold voltage (V
)
TP
the mode pin is connected to V
.
CC
is achieved and V
is within nominal limits. In both
CC
022698 2/9
DS1231/S
POWER MONITOR BLOCK DIAGRAM Figure 1
MODE
NMI
2
7
30mA
IN
1
4
NMI
MODE
SELECTION
GND
RST
RST
6
5
V
CC
8
3
V
CC
DIGITAL
SAMPLER
DIGITAL
DELAY
TOLERANCE
BIAS
TOL
T.C. REFERENCE
POWER-UP RESET Figure 2
MICROPROCESSOR
DS1231
IN
V
CC
+5V
NC
MODE
TOL
NMI
RST
GND
RST
RST
8051
µP
(-5% V
THRESHOLD)
CC
022698 3/9
DS1231/S
INPUT PIN HYSTERESIS Figure 3
NMI
MODE = GND, V = +5V
CC
V
OH
–20
–35
–50
V
TP-
2.3
2.5
2.15
2.5
2.0
2.5
V
+
TP
V
OL
V
NOTE: HYSTERESIS TOLERANCE IS +60 mV
V
V
TP
+
IN
TP-
NMI
MODE = V , V = +5V
CC CC
V
OH
V
OL
V
IN
V
V
TP
+
TP-
APPLICATION WITH MODE PIN CONNECTED TO VCC Figure 4
VOLTAGE SENSE POINT
DS1231
R1
R2
IN
V
CC
+5V
MODE
TOL
NMI
RST
+5V
TO mP
GND
RST
(-5% V
THRESHOLD)
CC
V SENSE
VTP *
R1 ) R2
V MAX +
X 5.0
V SENSE +
X 2.3
R2
EXAMPLE: V SENSE = 8 VOLTS AT TRIP POINT AND A
MAXIMUM VOLTAGE OF 17.5V WITH R2 = 10K
R1 ) 10K
R1 = 25K
THEN 8 +
X 2.3
10K
NOTE: RST requires a pull–up resister.
022698 4/9
DS1231/S
the trip point. This is particularly true if power consump-
tionon the high voltage side of the opto-isolator is not an
issue. However, if power consumption is a concern,
then it is desirable to make the value of R1 high. As the
value of R1 increases, the effect of the LED current in
theopto-isolatorstartstoaffecttheINtrippoint. Thiscan
be seen from the equation shown in Figure 6. R1 must
also be low enough to allow the opto-isolator to sink the
30 µA of collector current required by pin 1 and still have
enough resistance to keep the maximum current
through the opto-isolator’s LED within data sheet limits.
Figure 7illustrateshowtheDS1231canbeinterfacedto
the AC power line when the mode pin is grounded.
APPLICATION – MODE PIN CONNECTED TO
GROUND
When the Mode pin is connected to ground, pin 1 is a
current source of 30 µA with a V + of 2.5 volts. Pin 1 is
TP
held below the trip point by a switching device like an
opto-isolator as shown in Figure 6. Determination of the
sense point has the same criteria as discussed in the
previousapplication. However, determining component
values is significantly different. In this mode, the maxi-
mum dynamic range of the sense point versus desired
trip voltage is primarily determined by the selection of a
zener diode. As an example, if the maximum voltage at
the sense point is 200V and the desired trip point is
150V, then a zener diode of 150V will approximately set
AC VOLTAGE MONITOR WITH TRANSFORMER ISOLATION Figure 5
VOLTAGE SENSE POINT
DS1231
-10% V
THRESHOLD
CC
+5V
DC
IN
V
CC
MODE
TOL
GND
NMI
RST
+5V
DC
TO µ P
RST
NOTE: RST requires a pull–up resister.
022698 5/9
DS1231/S
APPLICATION WITH MODE PIN GROUNDED Figure 6
VOLTAGE SENSE POINT
-5% V
THRESHOLD
CC
R1
DS1231
+5V
DC
IN
V
IF
CC
IC
MODE
TOL
GND
NMI
RST
TO µ P
RST
IC
CTR
VOLTAGE SENSE POINT (TRIP VALUE) + VZ )
X R1
IC
IF
CTR +
CTR + CURRENT TRANSFER RATIO
VZ + ZENNER VOLTAGE
EXAMPLE:
CTR = 0.2 IC = 30 µA IF = 150 µA
VOLTAGE SENSE POINT = 105 AND
VZ = 100 VOLTS
30
0.2
THEN 105 + 100 )
x R1
R1 + 33K
NOTE: RST requires a pull–up resister.
AC VOLTAGE MONITOR WITH OPTO-ISOLATION Figure 7
DS1231
-5% V
THRESHOLD
CC
+5V
DC
IN
V
CC
MODE
NMI
RST
AC LINE
INPUT
TO µ P
TOL
GND
RST
NOTE: RST requires a pull–up resister.
022698 6/9
DS1231/S
ABSOLUTE MAXIMUM RATINGS*
Voltage on V Pin Relative to Ground
-0.5V to +7.0V
CC
Voltage on I/O Relative to Ground
-0.5V to V + 0.5V
CC
Operating Temperature
0°C to 70°C
Operating Temperature (Industrial Version)
Storage Temperature
Soldering Temperature
–40°C to +85°C
-55°C to +125°C
260°C for 10 seconds
* This is a stress rating only and functional operation of the device at these or any other conditions above those
indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods of time may affect reliability.
RECOMMENDED DC OPERATING CONDITIONS
(0°C to 70°C)
PARAMETER
Supply Voltage
Input Pin 1
SYMBOL
MIN
TYP
MAX
UNITS
NOTES
V
CC
4.5
5.0
5.5
V
V
1
1
V
IN
V
CC
DC ELECTRICAL CHARACTERISTICS
(0°C to 70°C; VCC = 4.5 to 5.5V)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
V
NOTES
Low Level @ RST
V
OL
0.4
1
1, 6
2
Output Voltage @ –500 µA
Input Leakage
V
OH
V
–0.5V
V –0.1V
CC
V
CC
I
IL
-10
1.0
2.0
+10
µA
Output Current @2.4V
Output Current @0.4V
Operating Current
I
2.0
3.0
0.5
25
mA
mA
mA
µA
5
OH
I
OL
I
2.0
50
3
CC
Input Pin 1 (Mode=GND)
I
I
15
C
Input Pin 1 (Mode=V
)
0.1
µA
CC
C
IN Trip Piont (Mode=GND)
IN Trip Point (Mode=V
V
V
See Figure 3
1
1
1
1
TP
)
CC
TP
V
V
Trip Point (TOL=GND)
V
V
4.50
4.25
4.62
4.37
4.74
4.49
V
V
CC
CCTP
Trip Point (TOL=V
)
CC
CC
CCTP
CAPACITANCE
PARAMETER
(TA = 25°C)
SYMBOL
MIN
TYP
MAX
UNITS
pF
NOTES
Input Capacitance
Output Capacitance
C
5
7
IN
C
pF
OUT
022698 7/9
DS1231/S
AC ELECTRICAL CHARACTERISTICS
(0°C to 70°C; VCC = 5V + 10%)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
µs
NOTES
V
V
V
V
V
V
to NMI Delay
t
1.1
TP
IPD
Slew Rate 4.75-4.25V
Detect to RST and RST
Detect to NMI
t
F
300
µs
CC
CC
CC
CC
CC
t
100
200
ns
RPD
t
µs
4
4
IPU
Detect to RST and RST
Slew Rate 4.25-4.75V
t
150
0
500
1000
ms
ns
RPU
t
R
NOTES:
1. All voltages referenced to ground.
2. V = +5.0 volts with outputs open.
CC
3. Measured with outputs open.
4. t = 5 µs.
R
5. RST is an open drain output and requires a pull–up resister.
6. RST remains within 0.5V of V on power–down until V drops below 2.0V. RST remains within 0.5V of
CC
CC
GND on power–down until V drops below 2.0V.
CC
TIMING DIAGRAM: POWER-UP
V
TP
MODE=V
CC
INPUT PIN 1
MODE=GND
t
R
4.75V
4.5V
4.25V
V
CC
t
IPU
V
OH
NMI
t
RPU
RST
V
V
OH
OL
RST
022698 8/9
DS1231/S
TIMING DIAGRAM: POWER-DOWN
V
TP
INPUT PIN 1
MODE=V
CC
INPUT PIN 1
MODE=GND
V
TP
t
IPD
NMI
V
OL
t
F
V
CC
4.75V
V
CCTP
4.25V
t
RPD
RST
RST
RST SLEWS WITH V
CC
V
V
OH
OL
022698 9/9
相关型号：
©2020 ICPDF网 联系我们和版权申明