DS1832U+T&R [MAXIM]

Power Supply Management Circuit, Fixed, 1 Channel, +2.55/2.88VV, CMOS, PDSO8, 0.118 INCH, ROHS COMPLIANT, MICRO, SOP-8;


型号：	DS1832U+T&R
厂家：	MAXIM INTEGRATED PRODUCTS
描述：	Power Supply Management Circuit, Fixed, 1 Channel, +2.55/2.88VV, CMOS, PDSO8, 0.118 INCH, ROHS COMPLIANT, MICRO, SOP-8 光电二极管
文件：	总7页 (文件大小：118K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

DS1832

3.3-Volt MicroMonitor Chip

www.dalsemi.com

FEATURES

PIN ASSIGNMENT

ꢀ Halts and restarts an out-of-control

microprocessor

V_CC

PBRST

ꢀ Holds microprocessor in check during power

transients

ꢀ Automatically restarts microprocessor after

power failure

TOL

RST

GND

DS1832 8-Pin DIP (300-mil)

See Mech. Drawings Section

ꢀ Monitors pushbutton for external override

ꢀ Accurate 10% or 20% microprocessor power

monitoring

ꢀ Eliminates need for discrete components

ꢀ 20% tolerance for use with 3.0-volt systems

ꢀ Pin-compatible with the DS1232

ꢀ Low cost 8-pin DIP, 8-pin SOIC, and space

saving µ-SOP packages available

ꢀ Industrial temperature range of -40°C to

+85°C

V_CC

PBRST

TOL

RST

GND

DS1832S 8-Pin SOIC (150-mil)

See Mech. Drawings Section

PBRST

TOL

GND

V_CC

RST

DS1832µ 8-Pin µ-SOP (118-mil)

See Mech. Drawings Section

PIN DESCRIPTION

PBRST

- Pushbutton Reset Input

- Time Delay Set

TOL

GND

RST

- Selects 10% or 20% V_CCDetect

- Ground

- Active High Reset Output

RST

- Active Low Reset Output

- Strobe Input

V_CC

- Power Supply

DESCRIPTION

The DS1832 3.3-Volt MicroMonitor monitors 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 resets to an active state. When V_CCreturns to an

in-tolerance condition, the reset signals are kept in the active state for a minimum of 250 ms to allow the

power supply and processor to stabilize.

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112099

DS1832

The second function the DS1832 performs is pushbutton reset control. The DS1832 debounces the

pushbutton input and guarantees an active reset pulse width of 250 ms minimum. The third function is a

watchdog timer. The DS1832 has an internal timer that forces the reset signals to the active state if the

strobe input is not driven low prior to timeout. The watchdog timer function can be set to operate on

timeout settings of approximately 150 ms, 600 ms, or 1.2 seconds.

OPERATION - POWER MONITOR

The DS1832 detects out-of-tolerance power supply conditions and warns a processor-based system of

impending power failure. When V_CCfalls below a preset level as defined by TOL, the V_CCcomparator

outputs the signals RST and RST . When TOL is connected to ground, the RST and RST signals become

active as V_CCfalls below 2.98 volts. When TOL is connected to V_CC, the RST and RST signals become

active as V_CCfalls below 2.64 volts. The RST and RST are excellent control signals for a microprocessor,

as processing is stopped at the last possible moments of valid V_CC. On power-up, RST and RST are kept

active for a minimum of 250 ms to allow the power supply and processor to stabilize.

OPERATION - PUSHBUTTON RESET

The DS1832 provides 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 RST and RST signals of at least 250 ms minimum are generated. The 250 ms delay commences as

the pushbutton reset input is released from the low level.

OPERATION - WATCHDOG TIMER

The watchdog timer function forces RST and RST signals active when the ST input is not clocked within

the predetermined time period. The timeout period is determined by the condition of the TD pin. If TD is

connected to ground the minimum watchdog timeout would be 62.5 ms, TD floating would yield a

minimum timeout of 250 ms, and TD connected to V_CCwould provide a timeout of 500 ms minimum.

Timeout of the watchdog starts when RST and RST become inactive. If a high-to-low transition occurs

on the ST input pin prior to timeout, the watchdog timer is reset and begins to timeout again. If the

watchdog timer is allowed to timeout, then the RST and RST signals are driven active for a minimum of

250 ms. The ST input can be derived from many microprocessor outputs. The most typical signals used

are the microprocessor address signals, data signals or control signals. When the microprocessor

functions normally, these signals would, as a matter of routine, cause the watchdog to be reset prior to

timeout. To guarantee that the watchdog timer does not timeout, a high-to-low transition must occur at or

less than the minimum times shown in Table 1. A typical circuit example is shown in Figure 4.

The DS1832 watchdog function cannot be disabled. The watchdog strobe input must be strobed to avoid

a watchdog timeout and reset.

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DS1832

MICROMONITOR BLOCK DIAGRAM Figure 1

PUSHBUTTON RESET Figure 2

TIMING DIAGRAM: PUSHBUTTON RESET Figure 3

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DS1832

WATCHDOG TIMER Figure 4

WATCHDOG TIMEOUTS Table 1

TIMEOUT

TYP

GND

Float

V_CC

MIN

MAX

250 ms

1000 ms

2000 ms

62.5 ms

250 ms

500 ms

150 ms

600 ms

1200 ms

TIMING DIAGRAM: STROBE INPUT Figure 5

TIMING DIAGRAM: POWER DOWN Figure 6

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DS1832

TIMING DIAGRAM: POWER-UP Figure 7

RST VALID TO 0 VOLTS V_CCFigure 8

OUTPUT VALID CONDITIONS

The RST output uses a push-pull output which can maintain a valid output down to 0.8 volts V_CC. To sink

current below 0.8 volts a resistor can be connected from RST to Ground (see Figure 8). This arrangement

will maintain a valid value on RST during both power-up and power-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 0 volts.

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DS1832

ABSOLUTE MAXIMUM RATINGS*

Voltage on any Pin 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

5.5

UNITS NOTES

Supply Voltage

V_CC

V_IH

1.0

2.0

V_CC+0.3

1, 3

1, 4

ST and PBRST Input High Level

ST and PBRST Input Low Level

V_CC

-0.4

-0.3

V_IL

0.5

DC ELECTRICAL CHARACTERISTICS

(-40°C to +85°C; V_CC=1.2V to 5.5V)

PARAMETER

SYMBOL MIN

TYP

2.88

2.55

MAX

2.97

2.64

+1.0

UNITS NOTES

V_CCTrip Point (TOL = GND)

V_CCTrip Point (TOL = V_CC)

Input Leakage

V_CCTP

I_IL

2.80

2.47

-1.0

µA

Output Current @ 2.4V

Output Current @ 0.4V

Output Voltage @ -500 uA

I_OH

350

I_OL

V_OH

V_CC

-0.3V -0.1V

Operating Current

I_CC

µA

CAPACITANCE

PARAMETER

(t_A=25°C)

UNITS NOTES

SYMBOL MIN

TYP

MAX

Input Capacitance

Output Capacitance

C_IN

C_OUT

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DS1832

AC ELECTRICAL CHARACTERISTICS

(-40°C to +85°C; V_CC=1.2V to 5.5V)

PARAMETER

SYMBOL MIN

TYP

610

MAX

1000

UNITS NOTES

t_PB

PBRST = V_IL

RESET Active Time

t_RST

t_ST

250

6, 7

ST Pulse Width

t_RPD

µs

V_CCDetect to RST and RST

V_CCSlew Rate

t_F

µs

t_RPU

250

610

1000

V_CCDetect to RST and RST

V_CCSlew Rate

t_R

t_PDLY

PBRST Stable Low to RST and RST

NOTES:

1. All voltages referenced to ground.

2. PBRST is internally pulled up to V_CCwith an internal impedance of 40 kΩ=typical.

3. Measured with V_CC≥ 2.7V.

4. Measured with V_CC< 2.7V.

5. Measured with outputs open, V_CC≤ 3.6 volts, and all inputs at V_CCor Ground.

6. Must not exceed t_TDminimum.

7. The Watchdog cannot be disabled it must be strobed to avoid resets.

8. Noise immunity - Pulses < 2 µs at V_CCTPminimum will not cause a reset.

9. t_R= 5 µs.

MARKING INFORMATION:

8-pin DIP - “DS1832”

8-pin SOIC - “DS1832”

8-pin - µ-SOP - “1832”

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