DS1231S-20 [ROCHESTER]
1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO16, 0.300 INCH, SOIC-16;
| 型号： | DS1231S-20 |
| 厂家： | 
Rochester Electronics |
| 描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO16, 0.300 INCH, SOIC-16 光电二极管 |
| 文件： | 总10页 (文件大小：915K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
DS1231/S
Power Monitor Chip
www.dalsemi.com
FEATURES
PIN ASSIGNMENT
§ Warns processor of an impending power
failure
VCC
IN
1
2
3
4
8
NMI
RST
RST
MODE
TOL
7
6
5
§ Provides time for an orderly shutdown
§ Prevents processor from destroying
nonvolatile memory during power transients
§ Automatically restarts processor after power
is restored
GND
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
§ Supplies necessary signals for processor
interface
§ Accurate 5% or 10% VCC monitoring
§ Replaces power-up reset circuitry
§ No external capacitors required
§ Optional 16-pin SOIC surface-mount package
NC
IN
1
2
16
15
NC
VCC
NC
MODE
NC
3
4
5
6
7
8
14
13
12
11
10
9
NC
NMI
NC
TOL
RST
NC
NC
GND
RST
DS1231S 16-Pin SOIC (300-mil)
See Mech. Drawings Section
PIN DESCRIPTION
IN
- Input
MODE
TOL
GND
RST
- Selects input pin characteristics
- Selects 5% or 10% VCC detect
- Ground
- Reset (Active High)
RST
- Reset (Active Low, open drain)
NMI
VCC
NC
- Non-Maskable Interrupt
- +5V Supply
- No Connections
DESCRIPTION
The DS1231 Power Monitor Chip uses a precise temperature-compensated reference circuit which
provides an orderly shutdown and an automatic restart of a processor-based system. A signal warning of
an impending power failure is generated well before regulated DC voltages go out of specification by
monitoring high voltage inputs to the power supply regulators. If line isolation is required a UL-approved
opto-isolator can be directly 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 unconditionally halts the processor to prevent spurious cycles by enabling Reset as
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DS1231/S
VCC falls below a selectable 5 or 10 percent threshold. When power returns, the processor is held inactive
until well after power conditions have stabilized, safeguarding any nonvolatile memory in the system
from inadvertent data changes.
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 monitoring the input (Pin 1) and one for
monitoring VCC (Pin 8). The VCC comparator outputs the signals RST (Pin 5) and RST (Pin 6) when VCC
falls below a preset trip level as defined by TOL (Pin 3).
When TOL is connected to ground, the RST and RST signals will become active as VCC goes below 4.75
volts. When TOL is connected to VCC, the RST and RST signals become active as VCC goes below 4.5
volts. The RST and RST signals are excellent control signals for a microprocessor, as processing is
stopped at the last possible moments of valid V . On power-up, RST and RST are kept active for a
CC
minimum of 150 ms to allow the power supply to stabilize (see Figure 2).
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). When the Mode pin is connected to V ,
TP
CC
detection occurs at V -. In this mode Pin 1 is an extremely high impedance input allowing for a simple
TP
resistor voltage divider network to interface with high voltage signals. When the Mode pin is connected
to ground, detection occurs at VTP+. In this mode Pin 1 sources 30 mA of current allowing for connection
to switched inputs, such as a UL-approved opto-isolator. The flexibility of the input pin allows for
detection of power loss at the earliest point 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
(VTP) is achieved and VCC is within nominal limits. In both modes of operation the input pin has
hysteresis for noise immunity (Figure 3).
APPLICATION - MODE PIN CONNECTED TO VCC
When the Mode pin is connected to VCC, pin 1 is a high 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
developed from the AC power line by rectifying and filtering the AC. Alternatively, a DC voltage level
may be selected 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.
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 network of R1 and R2. Since the IN trip point V - is 2.3 volts (using the -20 device), and the
TP
maximum allowable 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 .
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 the mode pin is connected to VCC.
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DS1231/S
POWER MONITOR BLOCK DIAGRAM Figure 1
POWER-UP RESET Figure 2
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DS1231/S
INPUT PIN HYSTERESIS Figure 3
-20
2.3
2.5
-35
2.15
2.5
-50
2.0
2.5
VTP-
VTP+
NOTE: HYSTERESIS TOLERANCE IS ±60 mV
APPLICATION WITH MODE PIN CONNECTED TO VCC Figure 4
R1+ R2
V SENSE
V SENSE =
X 2.3
V MAX =
X 5.0
R2
VTP -
EXAMPLE: V SENSE = 8 VOLTS AT TRIP POINT AND A
MAXIMUM VOLTAGE OF 17.5V WITH R2 = 10k
R1+10k
THEN 8 =
X 2.3
R1 = 25k
10k
NOTE: RST requires a pull-up resister.
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DS1231/S
APPLICATION - MODE PIN CONNECTED TO GROUND
When the Mode pin is connected to ground, pin 1 is a current source of 30 mA with a V + of 2.5 volts.
TP
Pin 1 is 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 previous application. However,
determining component values is significantly different. In this mode, the maximum 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 the trip point. This is particularly true if power consumption
on 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 the opto-isolator starts to affect the IN trip point. This can be seen from the equation shown in
Figure 6. R1 must also be low enough to allow the opto-isolator to sink the 30 mA 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 7 illustrates how the DS1231 can be interfaced to the AC
power line when the mode pin is grounded.
AC VOLTAGE MONITOR WITH TRANSFORMER ISOLATION Figure 5
NOTE: RST requires a pull-up resister.
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DS1231/S
APPLICATION WITH MODE PIN GROUNDED Figure 6
IC
VOLTAGE SENSE POINT (TRIP VALUE) = VZ +
IC
X R1
CTR
CTR =
CTR = CURRENT TRANSFER RATIO
IF
VZ = ZENER VOLTAGE
EXAMPLE: CTR = 0.2 IC = 30 mA IF = 150 mA
VOLTAGE SENSE POINT = 105 AND
VZ = 100 VOLTS
30
THEN 105 = 100 +
X R1
R1 = 33k
0.2
NOTE: RST requires a pull-up resister.
AC VOLTAGE MONITOR WITH OPTO-ISOLATION Figure 7
NOTE: RST requires a pull-up resister.
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DS1231/S
ABSOLUTE MAXIMUM RATINGS*
Voltage on VCC Pin Relative to Ground
Voltage on I/O Relative to Ground
Operating Temperature
-0.5V to +7.0V
-0.5V to VCC + 0.5V
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
5.5
UNITS NOTES
VCC
VIN
4.5
5.0
V
V
1
1
VCC
DC ELECTRICAL CHARACTERISTICS
(0°C to 70°C; VCC=4.5 to 5.5V)
PARAMETER
SYMBOL MIN
TYP
MAX
UNITS NOTES
Low Level @ RST
VOL
0.4
V
V
1
VOH
VCC
VCC
1, 6
Output Voltage @ -500 mA
-0.5V -0.1V
-10
Input Leakage
IIL
IOH
+10
2
5
mA
mA
mA
mA
mA
mA
Output Current @2.4V
Output Current @0.4V
Operating Current
1.0
2.0
2.0
3.0
0.5
25
IOL
ICC
2.0
50
3
Input Pin 1 (Mode=GND)
Input Pin 1 (Mode=VCC)
IN Trip Point (Mode=GND)
IN Trip Point (Mode=VCC)
VCC Trip Point (TOL=GND)
VCC Trip Point (TOL=VCC)
IC
15
IC
0.1
VTP
VTP
VCCTP
VCCTP
1
1
1
1
See Figure 3
4.50
4.25
4.62
4.74
4.49
V
V
4.37
CAPACITANCE
PARAMETER
(TA=25°C)
UNITS NOTES
SYMBOL MIN
TYP
MAX
Input Capacitance
Output Capacitance
CIN
5
7
pF
pF
COUT
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DS1231/S
AC ELECTRICAL CHARACTERISTICS
(0°C to 70°C; VCC=5V ± 10%)
PARAMETER
SYMBOL MIN
TYP
MAX
UNITS NOTES
tIPD
1.1
ms
VTP to NMI Delay
VCC Slew Rate 4.75-4.25V
tF
300
ms
tRPD
100
200
ns
VCC Detect to RST and RST
VCC Detect to NMI
tIPU
tRPU
tR
4
4
ms
ms
ns
150
0
500
1000
VCC Detect to RST and RST
VCC Slew Rate 4.25-4.75V
NOTES:
1. All voltages referenced to ground.
2. VCC = +5.0 volts with outputs open.
3. Measured with outputs open.
4. tR = 5 ms.
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 VCC drops below 2.0V. RST remains within
CC
0.5V of GND on power-down until VCC drops below 2.0V.
TIMING DIAGRAM: POWER-UP
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DS1231/S
TIMING DIAGRAM: POWER-DOWN
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相关型号：
DS1231S-500+T&R
Power Supply Support Circuit, Fixed, 1 Channel, PDSO16, 0.300 INCH, ROHS COMPLIANT, SOIC-16
MAXIM
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