DS1834A [DALLAS]
Dual EconoReset with Pushbutton; 双EconoReset带有按钮
| 型号： | DS1834A |
| 厂家： | 
DALLAS SEMICONDUCTOR |
| 描述： | Dual EconoReset with Pushbutton |
| 文件： | 总7页 (文件大小：109K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
DS1834/A/D
Dual EconoReset with Pushbutton
www.dalsemi.com
FEATURES
PIN ASSIGNMENT
ꢀ 5V power-on reset
3.3VIN
5VIN
5V RST
5V TOL
GND
1
2
3
4
8
7
6
5
ꢀ 3.3V power-on reset
3.3V RST
3.3V TOL
PBRST
ꢀ Internal power is drawn from higher of either
the 5VIN input or the 3.3VIN input
ꢀ Excellent for systems designed to operate
with dual power supplies
DS1834 8-Pin DIP (300-mil)
ꢀ Asserts resets during power transients
ꢀ Pushbutton reset input for system override
ꢀ Maintains reset for 350 ms after VCC returns
to an in-tolerance condition
ꢀ Reduces need for discrete components
ꢀ Precision temperature-compensated voltage
reference and voltage sensor
3.3VIN
1
2
3
4
8
7
6
5
5VIN
5V RST
5V TOL
GND
3.3V RST
3.3V TOL
PBRST
DS1834 8-Pin SOIC (150-mil)
ꢀ 8-pin DIP, 8-pin SOIC, and 8-pin µ-SOP
available
ꢀ CMOS output for low current operation on
the DS1834 and DS1834D
5VIN
5V RST (*RST)
5V TOL
3.3VIN
1
2
3
4
8
7
6
5
3.3V RST (*RST)
3.3V TOL
PBRST
GND
DS1834 8-Pin µ-SOP (118-mil)
ꢀ Operating temperature of -40°C to +85°C
PIN DESCRIPTION
5VIN
- 5V Power Supply Input
5VRST (*RST) - 5V Reset Output
5V TOL
GND
- Selects 5V Input Tolerance
- Ground
PBRST
- Pushbutton Reset
3.3V TOL
- Selects 3.3V Input Tolerance
3.3V RST (*RST) - 3.3V Reset Output
3.3VIN
- 3.3V Power Supply Input
*DS1834D Active High Reset
DESCRIPTION
The DS1834 Dual EconoResets monitors three vital system conditions: 5-volt supply, 3.3-volt supply,
and an external override. First a precision temperature reference and comparator circuit monitor the status
of the 5-volt supply and the 3.3-volt supply. When an out-of-tolerance condition is detected, an internal
power-fail signal is generated which forces the reset of the affected supply to an active state.
Lastly, the DS1834 supports an external reset via an internally debounced pushbutton input. When the
pushbutton is pulled low both resets will be asserted for approximately 350 ms after the pushbutton is
released.
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071700
DS1834/A/D
OPERATION
Power Monitor
The DS1834 provides the functions of detecting out-of-tolerance conditions on a 3.3-volt and 5-volt
power supply and warning a processor-based system of impending power failure. When an input is
detected as out of tolerance on either voltage input the RST for that supply will be forced active. When
that input returns to a valid state the RST will remain active for about 350 ms and then return to an
inactive state until the next input out-of-tolerance condition.
On power-up both resets are kept active for approximately 350 ms after the power supply inputs have
reached the selected tolerance. This allows the power supply and system power to stabilize before RST is
released.
All internal operating current for the DS1834 will be drawn from the input with the highest voltage level.
The outputs will draw current only from the controlling input (5V IN or 3.3V IN).
DS1834 BLOCK DIAGRAM Figure 1
DS1834A BLOCK DIAGRAM OUTPUT Figure 2
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DS1834/A/D
Tolerance Select
The DS1834 provides two TOL inputs for individual customization of the DS1834 to specific application
requirements. If the TOL for the 5-volt supply is tied to the 5-volt input a 10% tolerance is selected for
the 5 volt supply. If the TOL for the 3.3-volt supply is tied to the 3.3-volt input, a 20% tolerance is
selected for the 3.3-volt supply. If TOL inputs are tied to ground, the 5-volt input will be set at a 5%
tolerance and the 3.3-volt input would be set to a 10% tolerance.
Pushbutton Reset
The DS1834 provides a pushbutton switch for manual reset control. When at least one of the DS1834
resets are not in a reset cycle, a pushbutton reset can be generated by pulling the PBRST pin low for at
least 2 ms. When the pushbutton is held low, both resets are forced active and will remain active for about
350 ms after the pushbutton is released. The pushbutton input is pulled high through an internal
40 kΩ=pull-up resistor and debounced via internal circuitry. See Figure 3 for an application example and
Figure 4 for the timing diagram.
PUSHBUTTON RESET Figure 3
TIMING DIAGRAM: PUSHBUTTON RESET Figure 4
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DS1834/A/D
OUTPUT VALID CONDITIONS
All versions of the DS1834 can maintain valid outputs as long as one input remains above 1.2 volts.
However, the RST outputs on the DS1834 use a push-pull output structure which can maintain a valid
output below 1.2 volts. To sink current below 1.2 volts a resistor can be connected from RST to GND
(see Figure 5). This arrangement will maintain a valid value on the RST outputs even if all inputs are at 0
volts. During both power-up and power-down this arrangement will draw current when RST is in the high
state. A value of about 100 kΩ=should be adequate to maintain a valid condition.
The DS1834A requires pull-up resistors on the outputs to maintain a valid output. The value of the
resistors is not critical in most cases but must be set low enough to pull the output to a high state. A
common value used is 10 kΩs (see Figure 6 and Figure 7).
APPLICATION DIAGRAM:
RST VALID TO 0 VOLTS VCC ON THE DS1834 Figure 5
APPLICATION DIAGRAM: DS1834A NMOS OUTPUTS Figure 6
Note: If outputs are pulled-up to different voltages the outputs can not be connected to form a wired
"AND".
APPLICATION DIAGRAM: DS1834A WIRED "AND" OUTPUT Figure 7
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DS1834/A/D
TIMING DIAGRAM: POWER-DOWN Figure 8
TIMING DIAGRAM: POWER-UP Figure 9
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DS1834/A/D
ABSOLUTE MAXIMUM RATINGS*
Voltage on VIN Pin Relative to Ground
Voltage on RST (5V) Pin Relative to Ground
-0.5V to +7.0V
-0.5V to +0.5VIN + 0.5V (DS1834 & DS1834D)
Voltage on RST (3.3V) Pin Relative to Ground -0.5V to +3.3VIN + 0.5V (DS1834 & DS1834D)
Voltage on PBRST & RST (DS1834A) Pin
Relative to Ground
Operating Temperature
Storage Temperature
Soldering Temperature
-0.5 to the greater of 0.5VIN + 0.5V or 3VIN + 0.5V
-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
(-40°C to +85°C)
PARAMETER
SYMBOL
MIN
1.2
1.2
2
TYP
MAX
5.5
UNITS NOTES
5VIN (Supply Voltage)
3VIN (Supply Voltage)
VIN
V
V
V
1
1
1
VIN
5.5
VIH
VIN(MAX)
+0.3
PBRST Input High Level
PBRST Input Low Level
VIN(MAX)
-0.4
V
V
1, 3
1
VIL
-0.3
0.5
DC ELECTRICAL CHARACTERISTICS
(-40°C to +85°C; VCC=1.2V to 5.5V)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS NOTES
Output Voltage
VOH
VIN
V
1
-0.1V
Input Leakage
IIL
IOH
-1.0
+10
+1.0
µA
µA
mA
µA
µA
V
4
5
5
6
7
1
1
1
1
Output Current @ 2.4V
350
Output Current @ 0.4V
IOL
ICC
50
35
Operating Current @ Ο 5.5VIN
Operating Current @ Ο 3.6VIN
5VIN Trip Point (TOL=GND)
5VIN Trip Point (TOL=5VIN)
3.3VIN Trip Point (TOL=GND)
3.3VIN Trip Point (TOL=3.3VIN)
Output Capacitance
ICC
VINTP
VINTP
VINTP
VINTP
COUT
4.50
4.25
2.80
2.47
4.63
4.38
2.88
2.55
4.75
4.49
2.97
2.64
10
V
V
V
pF
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DS1834/A/D
AC ELECTRICAL CHARACTERISTICS
(-40°C to +85°C; VCC=1.2V to 5.5V)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS NOTES
tPB
2
ms
PBRST = VIL
tPDLY
2
ms
PBRST Stable Low to Reset
Active
Reset Active Time
tRST
tRPD
200
350
500
2
ms
µs
µs
8
9
VCC Detect to RST (or RST)
VCC Slew Rate (VINTP(MAX) to
tF
300
0
VINTP(MIN)
VCC Slew Rate (VINTP(MIN) to
VINTP(MAX)
)
tR
ns
)
tRPU
200
350
500
ms
VCC Detect to RST (or RST)
NOTES:
1. All voltages are referenced to ground.
2. Measured with both 3.3VIN and 5VIN =2.7V.
3. Measured with both 3.3VIN and 5VIN ꢀ=2.7V.
4. PBRST is internally pulled up to VIN(MAX) input with an internal impedance of approximately 40 kΩ.
5. Measured with either 3.3VIN or 5VIN =2.7V (valid for DS1834 and DS1834D only).
6. Measured with outputs open and both 3.3VIN and 5VIN ꢀ=5.5V.
7. Measured with outputs open and both 3.3VIN and 5VIN ꢀ=3.6V.
8. Noise immunity - pulses < 2 µs @ VCCTP minimum will not generate a reset.
9. tR =5 µs.
MARKING:
DS1834
DS1834
DS1834
834
DS1834A
DS1834A
DS1834A
834A
DS1834D
DS1834D
DS1834D
834D
8-pin DIP
8-pin SOIC
8-pin ꢁ-SOP
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