DS1819BR-5T&R [DALLAS]

Power Supply Management Circuit, Fixed, 1 Channel, +3VV, CMOS, PDSO5, SOT-23, 5 PIN;


型号：	DS1819BR-5T&R
厂家：	DALLAS SEMICONDUCTOR
描述：	Power Supply Management Circuit, Fixed, 1 Channel, +3VV, CMOS, PDSO5, SOT-23, 5 PIN 光电二极管
文件：	总8页 (文件大小：110K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

DS1814/DS1819

5-Volt and 3.3-Volt MicroMonitor

www.dalsemi.com

FEATURES

ꢀ Halts and restarts an out-of-control

microprocessor

PIN ASSIGNMENT

ꢀ Holds microprocessor in check during power

transients

ꢀ Automatically restarts microprocessor after

power failure

ꢀ Monitors pushbutton for external override

ꢀ Accurate 5%, 10%, or 20% (3-volt only)

microprocessor power monitoring

ꢀ Eliminates the need for discrete components

ꢀ 20% tolerance for use with 3.0-volt systems

ꢀ Pin- and function-compatible with the

MAX823/24/25 products

SOT-23-5 PACKAGE

See Mech. Drawing

PIN DESCRIPTION

DS181xA

RST

GND

Active Low Reset Output

Ground

ꢀ Low cost SOT-23-5 package

ꢀ Industrial temperature: -40°C to +85°C

PBRST

Pushbutton Reset Input

VCC

Strobe Input

Power Supply

DEVICE

RST

PBRST

DS181xA

DS181xB

DS181xC

x = "DS1814" for 5 volt devices

x = "DS1819" for 3 volt devices

DS181xB

RST

GND

RST

Active Low Reset Output

Ground

Active High Reset Output

VCC

Strobe Input

Power Supply

DS181xC

RST

GND

RST

Active Low Reset Output

Ground

Active High Reset Output

PBRST

VCC

Pushbutton Reset Input

Power Supply

DESCRIPTION

The DS1814 5-Volt MicroMonitor and the DS1819 3.3-Volt MicroMonitor monitor three vital conditions

for a microprocessor: power supply, software execution, and external override. First, a precision

temperature-compensated reference and comparator circuit monitor the status of V_CC. When an out-of-

tolerance condition occurs, an internal power-fail signal is generated which forces the reset(s) to an active

state. When V_CCreturns to an in-tolerance condition, the reset signal is kept in the active state for a

minimum of 140 ms to allow the power supply and processor to stabilize.

1 of 8

111999

DS1814/DS1819

The DS1814/DS1819 ‘A’ and ‘C’ perform pushbutton reset control. They debounce the pushbutton input

and generate an active reset pulse width of 140 ms minimum. The DS1814/9 ‘A’ and ‘B’ versions

perform a watchdog function. The watchdog is an internal timer that forces the reset signals to the active

state if the strobe input does not change state every 1.12 seconds. The watchdog timer function can be

disabled by leaving the watchdog strobe input disconnected.

OPERATION

Power Monitor

The DS1814 detects out-of-tolerance power supply conditions and warns a processor-based system of

impending power failure. When V_CCfalls below a preset level, a comparator outputs the signal RST (or

RST). RST (or RST) are excellent control signals for a microprocessor, as processing is stopped at the

last possible moment of valid V_CC. On power-up, RST (or RST) are kept active for a minimum of 140 ms

to allow the power supply and processor to stabilize.

Pushbutton Reset

The DS1814 ‘A’ and ‘C’ provide an input pin for direct connection to a pushbutton reset (see Figure 2).

The pushbutton reset input requires an active low signal. Internally, this input is debounced and timed

such that a RST (or RST) signal of at least 140 ms minimum will be generated. The 140 ms delay

commences as the pushbutton reset input is released from the low level (see Figure 3).

Watchdog Timer

The DS1814/DS1819 ‘A’ and ‘B’ versions watchdog timer function forces RST (and RST) signal(s)

active when the ST input is not clocked within the 1.12 second watchdog time-out period. Time-out of

the watchdog starts when RST (and RST) become(s) inactive. If a transition occurs on the ST input pin

prior to time-out, the watchdog timer is reset and begins to time out again. If the watchdog timer is

allowed to time out, then the reset output(s) will go active for 140 ms. The watchdog can be disabled by

floating (or tri-stating) the ST input.

The ST input can be derived from many microprocessor outputs. The most typical signals used are the

microprocessor data I/O signals and control signals. When the microprocessor functions normally, these

signals would as a matter of routine cause the watchdog to be reset prior to time-out. To guarantee that

the watchdog timer does not time out, a transition must occur at or less than 1.12 seconds. A typical

circuit example is shown in Figure 4. The DS1814/19 watchdog function can be disabled at any time by

tri-starting the strobe input. A sample circuit to disable the watchdog is shown in Figure 6.

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DS1814/DS1819

DS1814/DS1819 BLOCK DIAGRAM Figure 1

*Notes:

ST available on'A' and 'B' versions

PBRST available on 'A' and 'C' versions

RST available on 'B' and 'C' versions

PUSHBUTTON RESET Figure 2

TIMING DIAGRAM: PUSHBUTTON RESET Figure 3

3 of 8

DS1814/DS1819

WATCHDOG TIMER Figure 4

TIMING DIAGRAM: STROBE INPUT Figure 5

WATCHDOG DISABLE CIRCUIT Figure 6

TIMING DIAGRAM: POWER-DOWN Figure 7

4 of 8

DS1814/DS1819

TIMING DIAGRAM: POWER-UP Figure 8

RST VALID TO 0 VOLTS V_CCFigure 9

OUTPUT VALID CONDITIONS

The RST output uses a push-pull output which can maintain a valid output down to 1.0 volts V_CC. To sink

current below 1.0 volts a resistor can be connected form RST to Ground (see Figure 9.) This arrangement

will maintain a valid value on RST during both power-up and -down but will draw current when RST is

in the high state. A value of about 100 kΩ=should be adequate in most situations. The output with a

resistor pull-down can maintain a valid reset down to V_CCequal to 0V.

5 of 8

DS1814/DS1819

ABSOLUTE MAXIMUM RATINGS*

Voltage on V_CCPin Relative to Ground

Voltage on I/O Relative to Ground

Operating Temperature

-0.5V to +7.0V

-0.5V to V_CC+ 0.5V

-40°C to +85°C

Storage Temperature

Soldering Temperature

-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

TYP

MAX UNITS NOTES

Supply Voltage

V_CC

V_IH

1.0

5.5

0.8 V_CC

ST and PBRST Input High Level

ST and PBRST Input Low Level

V_IL

0.3 V_CC

DC ELECTRICAL CHARACTERISTICS

(-40°C to +85°C; V_CC=1.2V to 5.5V)

PARAMETER

SYMBOL MIN

TYP

MAX UNITS NOTES

V_CCTrip Point DS1814-5

V_CCTrip Point DS1814-10

V_CCTrip Point DS1819-5

V_CCTrip Point DS1819-10

V_CCTrip Point DS1819-20

Reset Trip Point Hysteresis (DS1814)

Reset Trip Point Hysteresis (DS1819)

Output Current @ 2.4V

V_CCTP

V_RH

4.50

4.25

3.00

2.85

2.55

4.75

4.50

3.15

3.00

2.70

µA

V_RH

I_OH

350

Output Current @ 0.4V

I_OL

3.2

V_OH

I_CC

V_CC*.8 V_CC*.9

Output Voltage @ -30 µA

Operating Current DS1814

Operating Current DS1819

µA

I_CC

120

160

ST Input Current

ST = V_CC, Time Averaged

ST Input Current

-20

-15

µA

ST = GND, Time Averaged

6 of 8

DS1814/DS1819

AC ELECTRICAL CHARACTERISTICS

(-40°C to +85°C; V_CC=1.2V to 5.5V)

PARAMETER

SYMBOL MIN

TYP

MAX UNITS NOTES

t_PB

µs

PBRST = V_IL

Reset Active Time

t_RST

t_ST

140

200

280

ST Pulse Width

Watchdog Time-out

t_TD

1.12

1.60

2.40

t_RPD

µs

V_CCDetect to RST and RST

V_CCSlew Rate (rising edge)

12.5

200

V/µs

t_RPU

140

280

V_CCDetect to RST and RST

t_PDLY

500

PBRST Stable Low to RST and RST

CAPACITANCE

PARAMETER

(t_A=25°C)

MAX UNITS NOTES

SYMBOL MIN

TYP

Input Capacitance

Output Capacitance

C_IN

C_OUT

NOTES:

1. All voltages are referenced to ground.

2. PBRST is internally pulled up to V_CCwith an internal impedance of 50 kΩ=typical.

3. Measured with V_CC=≥=2.7V.

4. Measured with outputs open, V_CC≤=5.5 volts, and all inputs at V_CCor Ground, except the ST input at

<10kHz duty cycle-square wave or ST input open.

5. Measured with outputs open, V_CC≤=3.6 volts, and all inputs at V_CCor Ground, except the ST input at

<10kHz duty cycle-square wave or ST input open.

6. The ST input current is defined as the average input current when ST is driven high or low. This input

must be driven high or low by an output that can source or sink at least 200 µA when active.

7. Noise immunity: pulses <100 ns at pushbutton input will not cause a reset.

8. Must not exceed t_TDminimum.

9. Noise immunity: pulses <2 µs at V_CCTPminimum will not cause a reset and V_CCTP-V_CC=100 mV.

7 of 8

DS1814/DS1819

PART MARKING CODES

SOT-23-5 PACKAGE

“A”, “B” and “C” represents the Device Type.

“D” represents the Device Tolerance.

14A

14B

14C

19A

19B

19D

DS1814A

DS1814B

DS1814C

DS1819A

DS1819B

DS1819C

10%

20%

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